You can find all info and schematic on Runoffgroove website here.
And a version with an added Notch Depth switch.
Showing posts with label Runoffgroove. Show all posts
Showing posts with label Runoffgroove. Show all posts
Sunday, 24 July 2016
Runoffgroove Condor Cab Sim
This was an old request.
You can find all info and schematic on Runoffgroove website here.
You can find all info and schematic on Runoffgroove website here.
Friday, 16 October 2015
Thursday, 11 September 2014
ROG Britannia
Here's a challenge for those who want theirs in 1590B. Should fit, but it'll be a challenge.
From ROG:
The English Channel was our first attempt to adapt the Vox AC-30 Top Boost amplifier for use as a guitar pedal. Released in 2004, the English Channel was a straightforward JFET implementation that was heavily based on the amp's schematic using the so-called "FET by numbers" approach. While this approach did certainly capture the amp character to certain degree, the overall sound of the resulting circuit was not as refined as its valve counterpart.
Through the years since the English Channel was released, we've been polishing the manner in which the different valve stages used in guitar amps are adapted to JFET-based circuits. This involves taking several aspects into account, such as the effective frequency response of the stage after considering parasitic capacitances, input and output impedances, gain and dynamic range, and clipping characteristics. Furthermore, in some cases we have taken the artistic license to replace certain portions the circuit with something that provides the intended function without necessarily looking like the original circuit.
Now we present Britannia, a fully redesigned adaptation of the AC-30 for use as a guitar pedal which has been optimized for playing into a clean solid-state amp. We hope that you will find this project a nice approach to the sound that was made famous by many artists, including The Beatles, Tom Petty, The Edge, and Brian May, to name a few, without having to invest in or carry around the real thing.
Here is the usual circuit walkthrough for those interested in the savory details: First, Q1 is our standard high impedance input stage, very "booster friendly" thanks to the two red LEDs at the Gate. Next, you will readily recognize a scaled version of the Gain control section, which together with Q2 form a treble booster. You will also notice that all JFET stages but Q2 are prevented from clipping hard by virtue of the back-to-back diodes present at each Gate. This helps retaining the sweetness and dynamics of the sound. However the original amp has some degree of grittiness in it when pushed hard, and this is achieved specifically by Q2, which is a high gain stage borrowed from the Omega booster. Apart from its higher gain, this stage is generous in 2nd order harmonics. Then comes Q3 as a voltage follower driving a slightly modified version of the original tonestack. Some additional gain is provided by Q4, then a cousin of the original Cut control, which in our case was wired backwards with respect to the original, and therefore labeled Brilliance. Next, the op-amp U1a provides the final touch of soft overdrive, followed by U1b that implements the ultimate toneshaping: a 200 Hz resonance characteristic of a 2x12" cabinet and some high frequency rounding.
Jon Patton's official demo:
Working voltages as posted by ξεναγός νεκρόπολης:
q1
d 6,05
s 0,89
g 0
q2
d 5,06
s 2,42
g 0
q3
c 8,55
b 5,62
e 5,43
q4
d 5,42
s 1,10
g 0
1 4,21
2 4,21
3 3,8
4 0
5 2,09
6 4,21
7 4,21
8 8,43
From ROG:
The English Channel was our first attempt to adapt the Vox AC-30 Top Boost amplifier for use as a guitar pedal. Released in 2004, the English Channel was a straightforward JFET implementation that was heavily based on the amp's schematic using the so-called "FET by numbers" approach. While this approach did certainly capture the amp character to certain degree, the overall sound of the resulting circuit was not as refined as its valve counterpart.
Through the years since the English Channel was released, we've been polishing the manner in which the different valve stages used in guitar amps are adapted to JFET-based circuits. This involves taking several aspects into account, such as the effective frequency response of the stage after considering parasitic capacitances, input and output impedances, gain and dynamic range, and clipping characteristics. Furthermore, in some cases we have taken the artistic license to replace certain portions the circuit with something that provides the intended function without necessarily looking like the original circuit.
Now we present Britannia, a fully redesigned adaptation of the AC-30 for use as a guitar pedal which has been optimized for playing into a clean solid-state amp. We hope that you will find this project a nice approach to the sound that was made famous by many artists, including The Beatles, Tom Petty, The Edge, and Brian May, to name a few, without having to invest in or carry around the real thing.
Here is the usual circuit walkthrough for those interested in the savory details: First, Q1 is our standard high impedance input stage, very "booster friendly" thanks to the two red LEDs at the Gate. Next, you will readily recognize a scaled version of the Gain control section, which together with Q2 form a treble booster. You will also notice that all JFET stages but Q2 are prevented from clipping hard by virtue of the back-to-back diodes present at each Gate. This helps retaining the sweetness and dynamics of the sound. However the original amp has some degree of grittiness in it when pushed hard, and this is achieved specifically by Q2, which is a high gain stage borrowed from the Omega booster. Apart from its higher gain, this stage is generous in 2nd order harmonics. Then comes Q3 as a voltage follower driving a slightly modified version of the original tonestack. Some additional gain is provided by Q4, then a cousin of the original Cut control, which in our case was wired backwards with respect to the original, and therefore labeled Brilliance. Next, the op-amp U1a provides the final touch of soft overdrive, followed by U1b that implements the ultimate toneshaping: a 200 Hz resonance characteristic of a 2x12" cabinet and some high frequency rounding.
Jon Patton's official demo:
Working voltages as posted by ξεναγός νεκρόπολης:
q1
d 6,05
s 0,89
g 0
q2
d 5,06
s 2,42
g 0
q3
c 8,55
b 5,62
e 5,43
q4
d 5,42
s 1,10
g 0
1 4,21
2 4,21
3 3,8
4 0
5 2,09
6 4,21
7 4,21
8 8,43
Tuesday, 1 April 2014
Runoffgroove Ginger
Info about the great ROG Ampeg emulation project:
The Flipster, runoffgroove.com's only circuit primarily intended for use with a bass guitar, was released in June 2004. It was another adaptation of a vintage tube amp for use as a distortion pedal, namely the Ampeg SB-12 Portaflex introduced in 1965. Several bass players in the DIY-fx community acted as beta testers during its development, and while the resulting circuit captured a good deal of the target sound, it had higher gain and the overall frequency response was inaccurate due to impedance differences.
In this "next generation" version named Ginger, the tonestack impedance has been scaled down 10x to reduce noise and overall frequency response has been further adjusted to cover a more suitable range with reduced insertion loss, as seen in this graph from Duncan's Tonestack Calculator.
Also, each stage has a pair of clipping diodes at the gate to avoid hard clipping in the JFET stages. Additionally, each stage has been adjusted to provide overall circuit gain more faithful to the Ampeg SB-12 Portaflex. While the circuit does not follow the original amp schematic, it has been tuned to approach the target sound. Finally, the low-pass filter at the output has been upgraded for improved attenuation of frequencies outside the original speaker range.
While the circuit is intended for use with a bass, it also provides excellent overdrive for a guitar and the flexible tone controls allow a great deal of fine-tuning.
The drain voltage of Q1 and Q2 should be adjusted close to 6.0V by tuning the corresponding trimpot. Once the optimum resistor value is determined, each trimpot may be optionally replaced by a fixed resistor for best noise performance.
More info can be seen here.
The Flipster, runoffgroove.com's only circuit primarily intended for use with a bass guitar, was released in June 2004. It was another adaptation of a vintage tube amp for use as a distortion pedal, namely the Ampeg SB-12 Portaflex introduced in 1965. Several bass players in the DIY-fx community acted as beta testers during its development, and while the resulting circuit captured a good deal of the target sound, it had higher gain and the overall frequency response was inaccurate due to impedance differences.
In this "next generation" version named Ginger, the tonestack impedance has been scaled down 10x to reduce noise and overall frequency response has been further adjusted to cover a more suitable range with reduced insertion loss, as seen in this graph from Duncan's Tonestack Calculator.
Also, each stage has a pair of clipping diodes at the gate to avoid hard clipping in the JFET stages. Additionally, each stage has been adjusted to provide overall circuit gain more faithful to the Ampeg SB-12 Portaflex. While the circuit does not follow the original amp schematic, it has been tuned to approach the target sound. Finally, the low-pass filter at the output has been upgraded for improved attenuation of frequencies outside the original speaker range.
While the circuit is intended for use with a bass, it also provides excellent overdrive for a guitar and the flexible tone controls allow a great deal of fine-tuning.
The drain voltage of Q1 and Q2 should be adjusted close to 6.0V by tuning the corresponding trimpot. Once the optimum resistor value is determined, each trimpot may be optionally replaced by a fixed resistor for best noise performance.
More info can be seen here.
Wednesday, 19 March 2014
Runoffgroove Tri-Vibe
Great layout here by John K and a very welcome addition.
Info about this great project from Runoffgroove:
The Tri-Vibe was born from the idea of developing a true vibrato pedal that could be built without resorting to parts matching and complex adjustment procedures. Various frequency modulation alternatives were analyzed to accomplish this goal.
There are numerous pseudo-vibrato implementations built around modified chorus and phaser pedals where the dry path is canceled, leaving only the wet signal. Several shortcomings to these approaches exist, such as: non-sinusoidal modulation (a sinusoidal LFO is a must for authentic vibrato), uneven frequency modulation across the audio band, poor noise performance, limited bandwidth, and intrinsic time delay.
Delay chips such as MN3007 or PT2399 were dismissed mainly due their limited bandwidth and the intrinsic delay associated with them. The Wurlitzer vibrato was also considered, however its implementation required a rather large number of components. This left the all-pass stage alternatives. We initially thought that at least four all-pass stages might be necessary to achieve the goal of true vibrato, but after further investigation we found that as few as two all-pass stages could be optimized for linear phase variation within the guitar frequency range. This explains the unusual 15:1 capacitor ratio that sets the frequency of each stage, as this arrangement can produce a quite flat +/- 90 degree phase shift variation for frequencies between 80 Hz and 6 kHz.
In order to implement the phase shift stages, the most common options were considered for the variable element: junction field-effect transistors (JFETs), light-dependent resistors (LDRs) and operational transconductance amplifiers (OTAs). JFETs and LDRs were discarded because they have wide production tolerances that would require precise matching and/or careful adjustments. On the other hand, OTAs are reasonably matched and predictable, so no parts selection or adjustments are necessary.
Different OTAs exist, such as CA3080, CA3094 and LM13600/LM13700. We decided in favor of the LM13600 device since it includes the output buffers and contains a pair of linearizing diodes that allow an improvement in the dynamic range and S/N ratio. In addition, we added corresponding pre and de-emphasis networks at the input and output buffers to further improve the S/N ratio.
The next challenge was to generate a suitable modulation signal. As a side note, in most phaser and chorus pedals adapted for vibrato mode, the lack of "proper" modulation vs. time produces an unappealing "motion sickness" characteristic. So, starting from a conventional triangle waveform generator with a predefined output level, a pseudo-sinusoidal signal is obtained by means of a 4k7 resistor, the 10k DEPTH pot, and two back-to-back diodes. The LFO is not finished yet, for the sinusoidal control signal needs to be exponentiated to obtain symmetric phase variation at each peak of the sinusoid. This final task is performed by the nonlinear arrangement of diodes and biasing resistor in the opamp stage U2b. Again, this section of the circuit requires no component matching or adjustments.
More info here
Info about this great project from Runoffgroove:
The Tri-Vibe was born from the idea of developing a true vibrato pedal that could be built without resorting to parts matching and complex adjustment procedures. Various frequency modulation alternatives were analyzed to accomplish this goal.
There are numerous pseudo-vibrato implementations built around modified chorus and phaser pedals where the dry path is canceled, leaving only the wet signal. Several shortcomings to these approaches exist, such as: non-sinusoidal modulation (a sinusoidal LFO is a must for authentic vibrato), uneven frequency modulation across the audio band, poor noise performance, limited bandwidth, and intrinsic time delay.
Delay chips such as MN3007 or PT2399 were dismissed mainly due their limited bandwidth and the intrinsic delay associated with them. The Wurlitzer vibrato was also considered, however its implementation required a rather large number of components. This left the all-pass stage alternatives. We initially thought that at least four all-pass stages might be necessary to achieve the goal of true vibrato, but after further investigation we found that as few as two all-pass stages could be optimized for linear phase variation within the guitar frequency range. This explains the unusual 15:1 capacitor ratio that sets the frequency of each stage, as this arrangement can produce a quite flat +/- 90 degree phase shift variation for frequencies between 80 Hz and 6 kHz.
In order to implement the phase shift stages, the most common options were considered for the variable element: junction field-effect transistors (JFETs), light-dependent resistors (LDRs) and operational transconductance amplifiers (OTAs). JFETs and LDRs were discarded because they have wide production tolerances that would require precise matching and/or careful adjustments. On the other hand, OTAs are reasonably matched and predictable, so no parts selection or adjustments are necessary.
Different OTAs exist, such as CA3080, CA3094 and LM13600/LM13700. We decided in favor of the LM13600 device since it includes the output buffers and contains a pair of linearizing diodes that allow an improvement in the dynamic range and S/N ratio. In addition, we added corresponding pre and de-emphasis networks at the input and output buffers to further improve the S/N ratio.
The next challenge was to generate a suitable modulation signal. As a side note, in most phaser and chorus pedals adapted for vibrato mode, the lack of "proper" modulation vs. time produces an unappealing "motion sickness" characteristic. So, starting from a conventional triangle waveform generator with a predefined output level, a pseudo-sinusoidal signal is obtained by means of a 4k7 resistor, the 10k DEPTH pot, and two back-to-back diodes. The LFO is not finished yet, for the sinusoidal control signal needs to be exponentiated to obtain symmetric phase variation at each peak of the sinusoid. This final task is performed by the nonlinear arrangement of diodes and biasing resistor in the opamp stage U2b. Again, this section of the circuit requires no component matching or adjustments.
More info here
Sunday, 19 May 2013
Runoffgroove Matchbox
Here's one more from the ROG archives. Apparently amazing sounding OD/dist. Should be doable in 1590B, if you feel brave enough with the rotary :)
From ROG: Back in the mid-90s, the Matchless DC/30 became one of the first boutique amps to hit the market. It excelled at clean tones, as well as thick Vox-like overdriven lead sounds.
There is good reason for the similarity in sound to a Vox amp. The lead channel of the DC/30 appears to be a modified Vox AC30/4. The AC30/4 amp featured the EF86 pentode preamp tube, just as the Matchless design.
runoffgroove.com set out to capture the lead sound of the Matchless DC/30 amp, using the technique developed by Doug Hammond for his excellent Meteor circuit.
We opted for a MOSFET to replace the EF86 tube. The MOSFET has better gain and fidelity attributes than the JFETs we normally use. We used J201 JFETs for the remaining two stages.
We've named this circuit the Matchbox.
An item of interest in this circuit is the odd-looking Tone control. This is in some ways similar to the FAC control on old Orange amplifiers. The sound is "thinnest" on setting A, and gets thicker as you progress through the settings. The Cut control acts as a simple Low Pass Filter. As you turn it counter clockwise, it will roll off some of the treble frequencies. We departed from the schematic a bit here. We used a 10n cap where the amp used only a 2n2. The reason for our deviation is to achieve a more dramatic effect.
NOTES:
-Try using a different MOSFET for the first stage. A 2N7000 sounded a bit "tighter" than a BS170. BS170 had a nice "loose" sound.
-Any N-channel MOSFET can be used, but as always, pay close attention to the pinout.
-Try to use all metal film caps in this circuit. It really seems to add to the smoothness of the sound. Ceramic caps or "greenies" will work fine, but you will probably notice a bit more "grainy" sound.
-A 12v Zener diode can be used in place of the LED used for static protection of the MOSFET.
-Philip Miller Tate (a.k.a. Ge_Whiz) found the Cut control to be quite subtle when using the stock values. He reports that substituting a 47nF capacitor and 50k-B pot provided a much more effective control.
-You can use other JFETs, but be warned! The middle stage may not bias correctly or have enough gain to distort. Try other transistors at your own risk. PLEASE do not post on Aron's Stompbox Forum with a complaint about the circuit does not working or sounding good when you do not use the specified components. You can always purchase J201 FETs from our friend, Steve Daniels at www.smallbearelec.com, who will ship to anywhere in the world.
From ROG: Back in the mid-90s, the Matchless DC/30 became one of the first boutique amps to hit the market. It excelled at clean tones, as well as thick Vox-like overdriven lead sounds.
There is good reason for the similarity in sound to a Vox amp. The lead channel of the DC/30 appears to be a modified Vox AC30/4. The AC30/4 amp featured the EF86 pentode preamp tube, just as the Matchless design.
runoffgroove.com set out to capture the lead sound of the Matchless DC/30 amp, using the technique developed by Doug Hammond for his excellent Meteor circuit.
We opted for a MOSFET to replace the EF86 tube. The MOSFET has better gain and fidelity attributes than the JFETs we normally use. We used J201 JFETs for the remaining two stages.
We've named this circuit the Matchbox.
An item of interest in this circuit is the odd-looking Tone control. This is in some ways similar to the FAC control on old Orange amplifiers. The sound is "thinnest" on setting A, and gets thicker as you progress through the settings. The Cut control acts as a simple Low Pass Filter. As you turn it counter clockwise, it will roll off some of the treble frequencies. We departed from the schematic a bit here. We used a 10n cap where the amp used only a 2n2. The reason for our deviation is to achieve a more dramatic effect.
NOTES:
-Try using a different MOSFET for the first stage. A 2N7000 sounded a bit "tighter" than a BS170. BS170 had a nice "loose" sound.
-Any N-channel MOSFET can be used, but as always, pay close attention to the pinout.
-Try to use all metal film caps in this circuit. It really seems to add to the smoothness of the sound. Ceramic caps or "greenies" will work fine, but you will probably notice a bit more "grainy" sound.
-A 12v Zener diode can be used in place of the LED used for static protection of the MOSFET.
-Philip Miller Tate (a.k.a. Ge_Whiz) found the Cut control to be quite subtle when using the stock values. He reports that substituting a 47nF capacitor and 50k-B pot provided a much more effective control.
-You can use other JFETs, but be warned! The middle stage may not bias correctly or have enough gain to distort. Try other transistors at your own risk. PLEASE do not post on Aron's Stompbox Forum with a complaint about the circuit does not working or sounding good when you do not use the specified components. You can always purchase J201 FETs from our friend, Steve Daniels at www.smallbearelec.com, who will ship to anywhere in the world.
Sunday, 31 March 2013
Runoffgroove Azabache
As requested. A long time ago. Size of the board tells you why it wasn't drawn up earlier....
From ROG:
More than a year ago we set out to revise and improve the Professor Tweed. Several approaches were pursued, but we were unsatisfied with the results. One of the downfalls was the high level of interaction between the tone and gain controls. Just as in the original Princeton amp, the tone control became ineffective when gain was set close to maximum. In addition, this arrangement was adequate only for a very specific type of sound.
We decided to step away from the inspiring amp's circuit and concentrate on developing a solution superior both in tone and usability. Builders may notice that the design does not correspond to any particular existing amp or pedal circuit. Though the use of a modified "Big Muff Pi" style tonestack is apparent, it is placed before the overdrive sections as opposed to its common location as a final tone shaping device.
The result is a circuit that is much more flexible and refined than its predecessor, and in our opinion it captures a wider variety of Fender-like tones. We have named this new circuit Azabache, which is the Spanish word for "black amber". The duality of its name recalls the Blackface and Tweed aesthetics.
This pedal has a very effective and flexible Tone control that varies the sound from fat and warm when set fully counterclockwise, to full at the center, to thin and bright at the clockwise end. In addition, two switches further expand the tonal possibilities: a Bright switch adds a glassy character to the sound, while a Scoop switch reduces the midrange around 400Hz to achieve more clarity. The different switch combinations produce several sounds which we have loosely named as follows:
Bright OFF / Scoop OFF: Blonde mode
Bright ON / Scoop OFF: Brown mode
Bright OFF / Scoop ON: Silver mode
Bright ON / Scoop ON: Black mode
As for the Gain knob, it can adjust the sound from almost clean, to a warmed-up light overdrive, to a medium overdrive, to a quite gainy overdrive. Each stage is set up to produce a moderate amount of gain while avoiding hard clipping in the JFET itself. The result is a refined overdrive with a natural note decay that reacts very well to the guitar's volume knob.
Finally, the tone shaping that takes place at the end is essentially modeled after the distinct frequency response of a Jensen P10R speaker, with its bright tone and deep 400 Hz notch. We think of this part of the circuit as a mini-Condor Cab Sim because the frequency response is akin to the Condor, however adapted to take into account that another amp and guitar speaker will follow afterwards.
Overall tone was optimized for solid-state amps that are moderately bright. If using a very bright guitar and/or amp it may be desirable to tame overall brightness a bit by changing the 1n capacitor between Q4 and Q5 to 1n5. Conversely, a bit more brightness could be achieved by replacing said capacitor with 680p. For best noise performance, it is recommended to use metal film resistors and replace the drain trimpots with fixed resistors once the necessary value is determined. Good wiring and shielding techniques are also encouraged.
Video of Geiri's build:
And according to discussion below (and the ROG post on DIYSB), the excessive treble content on the tone control can be cured by just lowering or shorting the 47K resistor at tone pot lug 1 connection. So here's a "fixed" version of the layout. I used 4K7 for this resistor, which should be low enough to achieve better tone control. But you can go even lower or replace that resistor with a link if you want to.
From ROG:
More than a year ago we set out to revise and improve the Professor Tweed. Several approaches were pursued, but we were unsatisfied with the results. One of the downfalls was the high level of interaction between the tone and gain controls. Just as in the original Princeton amp, the tone control became ineffective when gain was set close to maximum. In addition, this arrangement was adequate only for a very specific type of sound.
We decided to step away from the inspiring amp's circuit and concentrate on developing a solution superior both in tone and usability. Builders may notice that the design does not correspond to any particular existing amp or pedal circuit. Though the use of a modified "Big Muff Pi" style tonestack is apparent, it is placed before the overdrive sections as opposed to its common location as a final tone shaping device.
The result is a circuit that is much more flexible and refined than its predecessor, and in our opinion it captures a wider variety of Fender-like tones. We have named this new circuit Azabache, which is the Spanish word for "black amber". The duality of its name recalls the Blackface and Tweed aesthetics.
This pedal has a very effective and flexible Tone control that varies the sound from fat and warm when set fully counterclockwise, to full at the center, to thin and bright at the clockwise end. In addition, two switches further expand the tonal possibilities: a Bright switch adds a glassy character to the sound, while a Scoop switch reduces the midrange around 400Hz to achieve more clarity. The different switch combinations produce several sounds which we have loosely named as follows:
Bright OFF / Scoop OFF: Blonde mode
Bright ON / Scoop OFF: Brown mode
Bright OFF / Scoop ON: Silver mode
Bright ON / Scoop ON: Black mode
As for the Gain knob, it can adjust the sound from almost clean, to a warmed-up light overdrive, to a medium overdrive, to a quite gainy overdrive. Each stage is set up to produce a moderate amount of gain while avoiding hard clipping in the JFET itself. The result is a refined overdrive with a natural note decay that reacts very well to the guitar's volume knob.
Finally, the tone shaping that takes place at the end is essentially modeled after the distinct frequency response of a Jensen P10R speaker, with its bright tone and deep 400 Hz notch. We think of this part of the circuit as a mini-Condor Cab Sim because the frequency response is akin to the Condor, however adapted to take into account that another amp and guitar speaker will follow afterwards.
Overall tone was optimized for solid-state amps that are moderately bright. If using a very bright guitar and/or amp it may be desirable to tame overall brightness a bit by changing the 1n capacitor between Q4 and Q5 to 1n5. Conversely, a bit more brightness could be achieved by replacing said capacitor with 680p. For best noise performance, it is recommended to use metal film resistors and replace the drain trimpots with fixed resistors once the necessary value is determined. Good wiring and shielding techniques are also encouraged.
Video of Geiri's build:
And according to discussion below (and the ROG post on DIYSB), the excessive treble content on the tone control can be cured by just lowering or shorting the 47K resistor at tone pot lug 1 connection. So here's a "fixed" version of the layout. I used 4K7 for this resistor, which should be low enough to achieve better tone control. But you can go even lower or replace that resistor with a link if you want to.
Wednesday, 6 March 2013
Runoffgroove Professor Tweed
A request. Info from ROG:
One of the often overlooked Fender amps is the tweed-era Princeton. They are excellent guitar amps, especially for blues playing. The major drawback was the 4.5 watt output wasn't enough to keep up with a band. Again, using the technique pioneered by Doug Hammond, we decided to try to capture some of the sound of this little amp in pedal form so it can be used with a band.
The circuit we chose is the 5F2-A Princeton, one of the so-called "narrow panel" amps produced from 1955 to 1960. It was a very simple amp, using one 12AX7, one 6V6 power tube and a 5Y3 rectifier. Since we used 9V DC power, we left out the 5Y3. We used JFETs to replace the two halves of the 12AX7 and the 6V6 power stage.
We took the 5F2-A schematic and copied it part for part using MPF102 JFETs in place of each tube stage. Each tube Grid was replaced by a JFETs Gate. The tube Plates were analogous to a JFET Drain. Finally, a tube Cathode was replaced with a JFETs Source. We used a 100k trimmer for the plate resistors on the schematic due the fickle nature of JFETs and the much lower power supply involved.
Our "artistic license" is in the choice of the last JFETs output cap and the setting of the dual Low Pass Filters. Our goal was to produce the sound of a Jensen speaker. These are typically a little broader in frequency response than something like a Celestion.
Using all MPF102 JFETs, there is a great range of sounds available. No, you won't be playing "South of Heaven" with this pedal, but some classic blues, country, surf and rock sounds live here. The cleaner sounds are compressed and have an edge to them. As you wind up the Volume knob, you'll hear the dirt level increase. At full Volume, there is plenty of nice overdrive that never loses its dynamic feel. Even at full tilt, the circuit can clean up very well.
Possible mods:
Try using a J201 in the first stage. You'll notice the overall available gain increase and the sound will darken a bit. We preferred the sparkle of all MPF102s, but if you use sockets (as is always suggested) for the transistors, you can experiment until you find the combination you like best.
Socket the cap in the feedback loop. It is the 1uF cap connected to the output cap on one end and the 22k feedback resistor on the other. In this socket, try any value from 2n2 to 1uF. The sound will "open up" most around 10n and will "close up" as you get closer to 1uF. Try different values here to find the sound you like most.
Another possible area for modding would be the Tone control, specifically using different values for the 4n7 and 470p caps. The Tone control works well in its stock form, but you may find something interesting by substituting different values here.
Video of Geiri's build:
One of the often overlooked Fender amps is the tweed-era Princeton. They are excellent guitar amps, especially for blues playing. The major drawback was the 4.5 watt output wasn't enough to keep up with a band. Again, using the technique pioneered by Doug Hammond, we decided to try to capture some of the sound of this little amp in pedal form so it can be used with a band.
The circuit we chose is the 5F2-A Princeton, one of the so-called "narrow panel" amps produced from 1955 to 1960. It was a very simple amp, using one 12AX7, one 6V6 power tube and a 5Y3 rectifier. Since we used 9V DC power, we left out the 5Y3. We used JFETs to replace the two halves of the 12AX7 and the 6V6 power stage.
We took the 5F2-A schematic and copied it part for part using MPF102 JFETs in place of each tube stage. Each tube Grid was replaced by a JFETs Gate. The tube Plates were analogous to a JFET Drain. Finally, a tube Cathode was replaced with a JFETs Source. We used a 100k trimmer for the plate resistors on the schematic due the fickle nature of JFETs and the much lower power supply involved.
Our "artistic license" is in the choice of the last JFETs output cap and the setting of the dual Low Pass Filters. Our goal was to produce the sound of a Jensen speaker. These are typically a little broader in frequency response than something like a Celestion.
Using all MPF102 JFETs, there is a great range of sounds available. No, you won't be playing "South of Heaven" with this pedal, but some classic blues, country, surf and rock sounds live here. The cleaner sounds are compressed and have an edge to them. As you wind up the Volume knob, you'll hear the dirt level increase. At full Volume, there is plenty of nice overdrive that never loses its dynamic feel. Even at full tilt, the circuit can clean up very well.
Possible mods:
Try using a J201 in the first stage. You'll notice the overall available gain increase and the sound will darken a bit. We preferred the sparkle of all MPF102s, but if you use sockets (as is always suggested) for the transistors, you can experiment until you find the combination you like best.
Socket the cap in the feedback loop. It is the 1uF cap connected to the output cap on one end and the 22k feedback resistor on the other. In this socket, try any value from 2n2 to 1uF. The sound will "open up" most around 10n and will "close up" as you get closer to 1uF. Try different values here to find the sound you like most.
Another possible area for modding would be the Tone control, specifically using different values for the 4n7 and 470p caps. The Tone control works well in its stock form, but you may find something interesting by substituting different values here.
Video of Geiri's build:
Saturday, 19 January 2013
Runoffgroove Mockman
From ROG: This project has returned from beyond the grave for a tune-up. Compressed, harsh, and '80s sounding are fitting descriptions of its sonic character. Yes, it is a niche sound which is quite the opposite of some JFET-based distortions developed by the 'groove, however we feel it is a great time capsule of an era fondly remembered by many. Whether you are looking for a simple weekend project or willing to play a cover of an '80s hard rock anthem, the Mockman will suit your needs.
During the '80s, countless artists recorded directly to console using a Rockman amp. The Mockman sounds uncannily reminiscent of this sound as it is based on the Scholz Rockman's distortion section. Distortion is created by overdriving the op-amps, similar to the Sansamp units, but with strong equalization in each stage: a high-frequency emphasis combined with an aggressive low-frequency cut.
In this revision, the optional LEDs were completely removed, the high-end has been tamed to reduce hiss and some harshness, and gain was increased for additional sustain. Also, switch at the output sets the amount of bass for a biting '80s sound (Classic) or a heavier '90s sound (Modern).
The original op-amp was an RC1458, however you are encouraged to audition any dual opamp, as this component is an integral part of the sound. The JRC4558 opamp works quite well. Some faster/better op-amps like TL072 and NE5532 produce a slightly brighter sound. Modern rail-to-rail opamps like TLC2262 and TLC2272 sound a bit louder and better defined. In particular, our favorite op-amps were the JRC4558 and TLC2262.
The output filter capacitor can be set initially to 470pF, then tuned according to your preference and the op-amp in use.
During the '80s, countless artists recorded directly to console using a Rockman amp. The Mockman sounds uncannily reminiscent of this sound as it is based on the Scholz Rockman's distortion section. Distortion is created by overdriving the op-amps, similar to the Sansamp units, but with strong equalization in each stage: a high-frequency emphasis combined with an aggressive low-frequency cut.
In this revision, the optional LEDs were completely removed, the high-end has been tamed to reduce hiss and some harshness, and gain was increased for additional sustain. Also, switch at the output sets the amount of bass for a biting '80s sound (Classic) or a heavier '90s sound (Modern).
The original op-amp was an RC1458, however you are encouraged to audition any dual opamp, as this component is an integral part of the sound. The JRC4558 opamp works quite well. Some faster/better op-amps like TL072 and NE5532 produce a slightly brighter sound. Modern rail-to-rail opamps like TLC2262 and TLC2272 sound a bit louder and better defined. In particular, our favorite op-amps were the JRC4558 and TLC2262.
The output filter capacitor can be set initially to 470pF, then tuned according to your preference and the op-amp in use.
Friday, 18 January 2013
Runoffgroove Umble
As. Requested. Info from ROG: There has always been much talk about the mystical hand-built amps that a particular man sells for around $10,000 each. Some claim these are the greatest amplifiers known to man, while others maintain it's all hype. The runoffgroove.com team doesn't know for sure, because neither of us can plunk down 10 Gs on an amp! We've heard the Line 6 digital models of the amps. One of us owns the Behringer unit that has another digital model of these amps. Between the two of us, we also have several recordings of these elusive amps.
After some prodding by a member of Aron's Stompbox Forum, we decided to investigate and try to make a FET-based stompbox from one of these amps. There aren't many schematics available and those are subject to debate regarding their authenticity. Putting all that aside, we set out to distill the available information and come up with a circuit that was, at the very least, heavily influenced by the amps. We opted for the preamp section only, since the "precision power amp" is intended to be clean and not readily distort. We decided to omit that section for simplicity's sake.
We named our resulting circuit Umble. Looking closely, we can see what amounts to a few Fender-style gain stages and an odd looking Fender-style tone stack. There is nothing revolutionary about the cascaded gain stages, but the tone stack looks like it was mis-drawn. Maybe this was a "happy accident" by the designer, but this little variation from the Fender design has a larger impact on the sound and is perhaps key to the $10k sound. The controls become more effective and change the overall sound of the circuit in comparison to the standard Fender unit. One can also notice odd interactions of the three tones. In our research, we have read many accounts of the actual amps that back-up this effect.
A breakdown of the Umble circuit will reveal a conglomeration of several schematics available on the internet (see the Dumble Amps section of Schematic Heaven for a nice assortment). We used the gain stages from the '70s ODS model and the tone stack from the front section of the '97 ODS model. We eliminated many of the large resistors and small caps that didn't have much affect on the tone, but increased the noise level somewhat. We also left out all the complex switching options and hard-wired a straight-ahead sound.
We don't really know if it sounds like the amps SRV, Eric Johnson, Larry Carlton, etc. used. There are elements in the sound that are similar to some of these artists, though. We think the Umble sounds much smoother and more like the famous recordings than the Behringer or Line 6 models, but that may be personal preferences. There is some background hiss, but not an intolerable level.
With the real amps, it's hard to say what the definitive sound is supposed to be. Since each one is custom made, the amp sounds could be very different from unit to unit, even though they have the same model name. Our advice is to try the Umble as it is drawn. If you think you would like something a little different, "customize" this circuit after looking at the amp schematics.
Here's Geiri's demo with the build he finished using the layout below. Thanks Geiri for your work!
After some prodding by a member of Aron's Stompbox Forum, we decided to investigate and try to make a FET-based stompbox from one of these amps. There aren't many schematics available and those are subject to debate regarding their authenticity. Putting all that aside, we set out to distill the available information and come up with a circuit that was, at the very least, heavily influenced by the amps. We opted for the preamp section only, since the "precision power amp" is intended to be clean and not readily distort. We decided to omit that section for simplicity's sake.
We named our resulting circuit Umble. Looking closely, we can see what amounts to a few Fender-style gain stages and an odd looking Fender-style tone stack. There is nothing revolutionary about the cascaded gain stages, but the tone stack looks like it was mis-drawn. Maybe this was a "happy accident" by the designer, but this little variation from the Fender design has a larger impact on the sound and is perhaps key to the $10k sound. The controls become more effective and change the overall sound of the circuit in comparison to the standard Fender unit. One can also notice odd interactions of the three tones. In our research, we have read many accounts of the actual amps that back-up this effect.
A breakdown of the Umble circuit will reveal a conglomeration of several schematics available on the internet (see the Dumble Amps section of Schematic Heaven for a nice assortment). We used the gain stages from the '70s ODS model and the tone stack from the front section of the '97 ODS model. We eliminated many of the large resistors and small caps that didn't have much affect on the tone, but increased the noise level somewhat. We also left out all the complex switching options and hard-wired a straight-ahead sound.
We don't really know if it sounds like the amps SRV, Eric Johnson, Larry Carlton, etc. used. There are elements in the sound that are similar to some of these artists, though. We think the Umble sounds much smoother and more like the famous recordings than the Behringer or Line 6 models, but that may be personal preferences. There is some background hiss, but not an intolerable level.
With the real amps, it's hard to say what the definitive sound is supposed to be. Since each one is custom made, the amp sounds could be very different from unit to unit, even though they have the same model name. Our advice is to try the Umble as it is drawn. If you think you would like something a little different, "customize" this circuit after looking at the amp schematics.
Here's Geiri's demo with the build he finished using the layout below. Thanks Geiri for your work!
Friday, 11 January 2013
Runoffgroove "Big Grace"
Big Daddy and Grace circuits have this at the end of their document page: The two circuits are very similar and it may be possible to use a switching system to alternate between the buffer and the gain stage versions. (ROG)
Now did i really have a choice? :) Instead of using some monstrous 4PDT switch, i thought it would be just easier to accomodate both, the JFET buffer and JFET gain stages, on the same board and use 2PDT switch to switch between them. Takes more components, but i think you can build three of these circuits for the price of a single four poled switch.. So. I dubbed it, the "Big Grace".
Demo of his build by Madferret. Thanks mate :o)
Now did i really have a choice? :) Instead of using some monstrous 4PDT switch, i thought it would be just easier to accomodate both, the JFET buffer and JFET gain stages, on the same board and use 2PDT switch to switch between them. Takes more components, but i think you can build three of these circuits for the price of a single four poled switch.. So. I dubbed it, the "Big Grace".
Demo of his build by Madferret. Thanks mate :o)
New demos by Geiri.
Thursday, 10 January 2013
Runoffgroove Big Daddy
Continuing Grace Overdrive article at ROG: During the testing of this circuit design (meaning the Grace Overdrive), the thought occurred to try a Jfet gain stage before the 386, instead of the buffer. The impedance would still be high and the 386 would see more signal and clip harder. The result is a pleasing grind and responsive big amp-like distortion. The gain control functions in the same way, but the range is higher in gain. Pretty effective, considering that if you want to use a gain stage, you probably don't want the semi-clean settings of the buffered version.
So here's the Big Daddy. Basically, Grace with a gain stage instead of buffer at the input.
And a little clip with gain maxed:
So here's the Big Daddy. Basically, Grace with a gain stage instead of buffer at the input.
And a little clip with gain maxed:
Wednesday, 9 January 2013
Runoffgroove Grace Overdrive
From ROG: A few months ago, Aron Nelson released the Smash Drive. The circuit ingeniously used an LM386 audio power amp chip to produce great distortion sounds. Aron based his work on that of Tim Escobedo. Tim's Stupidity Box was another great sounding unit and beautifully simplistic. The Smokey Amp by Bruce Zinky was another design that used a 386 for some great sounds.
Depending on your personal tastes, there may be a potential down side to the 386 designs. The input impedance is listed at 50k, according to the datasheet. This is quite low and causes some loading of the guitar signal. There is some degree of high end signal loss. This may be a favorable thing, again depending on personal preference. I chose to try a high impedance buffer before the 386 to alleviate the loading effect.
A simple Jfet buffer was chosen, due to high input Z and minimal parts count. A high value of 4M7 was chosen as the gate resistor, which helps set the input Z. The J201 fet was used, but any N Channel Jfet could be used with similar results.
The result of the input buffer is easily noticeable. There is increased sparkle in the signal. The signal hits the 386 a little harder, due to more signal reaching the amplification stages of the 386. The buffer adds no gain, but there is a perceived increase. The gain control of the circuit is something else unseen this far with the 386 designs. It is simplistic, but functional. A simple 1k pot was chosen and wired as a variable resistor between pins 1 and 8 of the 386. Looking at the datasheet for the IC, you should notice an internal 1.35k resistor. By connecting the 1k pot between pins 1 and 8, you can effectively vary the gain from near the normal condition of 20X gain to the pins 1/8 connected setting of 200X gain with the 1k pot at minimum resistance.
Depending on your personal tastes, there may be a potential down side to the 386 designs. The input impedance is listed at 50k, according to the datasheet. This is quite low and causes some loading of the guitar signal. There is some degree of high end signal loss. This may be a favorable thing, again depending on personal preference. I chose to try a high impedance buffer before the 386 to alleviate the loading effect.
A simple Jfet buffer was chosen, due to high input Z and minimal parts count. A high value of 4M7 was chosen as the gate resistor, which helps set the input Z. The J201 fet was used, but any N Channel Jfet could be used with similar results.
The result of the input buffer is easily noticeable. There is increased sparkle in the signal. The signal hits the 386 a little harder, due to more signal reaching the amplification stages of the 386. The buffer adds no gain, but there is a perceived increase. The gain control of the circuit is something else unseen this far with the 386 designs. It is simplistic, but functional. A simple 1k pot was chosen and wired as a variable resistor between pins 1 and 8 of the 386. Looking at the datasheet for the IC, you should notice an internal 1.35k resistor. By connecting the 1k pot between pins 1 and 8, you can effectively vary the gain from near the normal condition of 20X gain to the pins 1/8 connected setting of 200X gain with the 1k pot at minimum resistance.
Thursday, 3 January 2013
Runoffgroove Thor
If i recall correctly, someone requested this a while ago. I think that's enough for today :)
Runoffgroove's current take on emulating the classic Marshall 100W Super Lead. Read the complete description and history of the circuit from ROG.
Runoffgroove's current take on emulating the classic Marshall 100W Super Lead. Read the complete description and history of the circuit from ROG.
Runoffgroove Tube Reamer
Simplified Tube Screamer workalike. ROG soundclips and info about the circuit:
The first incarnation of the Tube Reamer was developed as a stripped-down, yet edgier version of the classic Ibanez Tube Screamer. We removed the input and output buffers as well as the tone control stage, plus implemented a different gain control. Many builders enjoyed the circuit, but a number of them saw the circuit was ripe for modification. Since a majority of the popular mods dealt with the gain control and range, we decided to revisit the circuit in an effort to improve on it.
First, we reverted to the original Tube Screamer gain control. The type we used in the first Tube Reamer interacted with the bass content a bit too much for our liking and the range of available gain settings was quite narrow. We expanded the gain range and also adjusted the component values to keep more midrange frequencies in the signal. Finally, we added a second small gain stage to increase the output level of the circuit. Nearly any dual op-amp is suitable for use in this circuit, including the usual suspects: JRC4558, TL072, NE5532.
The first incarnation of the Tube Reamer was developed as a stripped-down, yet edgier version of the classic Ibanez Tube Screamer. We removed the input and output buffers as well as the tone control stage, plus implemented a different gain control. Many builders enjoyed the circuit, but a number of them saw the circuit was ripe for modification. Since a majority of the popular mods dealt with the gain control and range, we decided to revisit the circuit in an effort to improve on it.
First, we reverted to the original Tube Screamer gain control. The type we used in the first Tube Reamer interacted with the bass content a bit too much for our liking and the range of available gain settings was quite narrow. We expanded the gain range and also adjusted the component values to keep more midrange frequencies in the signal. Finally, we added a second small gain stage to increase the output level of the circuit. Nearly any dual op-amp is suitable for use in this circuit, including the usual suspects: JRC4558, TL072, NE5532.
Runoffgroove Omega
Continuing with the amazing Runoffgroove library, this time with Omega treble booster. The description below points out that this may be the last treble booster you'll need to build. ROG sound clip is here.
From ROG website:
This project began as a search for a FET treble booster similar to the well-known Dallas Rangemaster. We wanted to overcome several problems associated with building a Rangemaster clone, such as:
Getting a PNP or NPN Ge transistor with low leakage and proper hfe (50-100)
Bias variation with temperature
Poor noise performance (mainly hiss)
In addition, we wanted to retain several features of the original circuit, such as:
Guitar loading
Frequency response
Overall gain
Low output impedance
Non-linear behavior and soft clipping near collector cutoff
A variation of the Fetzer Valve, which we named the High Gain Fetzer Valve or HGFV, allows the accomplishment of all these goals. The HGFV uses a fixed high-valued drain resistor to increase the gain up to 30-35 dB (30-50 times). The drain bias voltage is adjusted by varying the source resistor, which is bypassed by a large capacitor.
During the development we found that varying the input impedance greatly affected the range of boosted frequencies, hence we named this control Range. For best results, the Omega should be driven directly by your guitar.
The output impedance of the HGFV is on the high side, so a MOSFET buffer takes care of driving hard whatever it follows. The gate of this MOSFET is fed from a voltage divider built on the drain resistor of the HGFV stage. This avoids clipping during the lower signal cycle in the output buffer.
The output control could have been named Level or Volume, but we preferred to call it Master to increase the mojo factor.
The resulting circuit is so flexible that it ranges from a treble boost with a slight amount of grit (in fact pretty faithful to a Rangemaster but with less hiss) to a fat overdriven boost (comparable to a gainy LPB-2). In between there are many sweet spots to be found that will correspond to your personal tastes and gear.
The drain bias voltage of the first stage plays a role in determining the character and grit added by the circuit. We encourage you to experiment and find the bias voltage that works best for you. A bias voltage of 7V proved to be faithful to the Rangemaster tones, while a lower drain voltage in the range of 4.5 to 5V was somewhat better for the fat sounds.
We thank Michael Klein who provided the name for this circuit. Omega is the last letter of the Greek alphabet, and we believe this is the ultimate booster. It is also the symbol used to represent ohms, the unit used to measure impedance, and it fits nicely into our circuit since the input impedance is strategically varied to alter the frequency response.
From ROG website:
This project began as a search for a FET treble booster similar to the well-known Dallas Rangemaster. We wanted to overcome several problems associated with building a Rangemaster clone, such as:
Getting a PNP or NPN Ge transistor with low leakage and proper hfe (50-100)
Bias variation with temperature
Poor noise performance (mainly hiss)
In addition, we wanted to retain several features of the original circuit, such as:
Guitar loading
Frequency response
Overall gain
Low output impedance
Non-linear behavior and soft clipping near collector cutoff
A variation of the Fetzer Valve, which we named the High Gain Fetzer Valve or HGFV, allows the accomplishment of all these goals. The HGFV uses a fixed high-valued drain resistor to increase the gain up to 30-35 dB (30-50 times). The drain bias voltage is adjusted by varying the source resistor, which is bypassed by a large capacitor.
During the development we found that varying the input impedance greatly affected the range of boosted frequencies, hence we named this control Range. For best results, the Omega should be driven directly by your guitar.
The output impedance of the HGFV is on the high side, so a MOSFET buffer takes care of driving hard whatever it follows. The gate of this MOSFET is fed from a voltage divider built on the drain resistor of the HGFV stage. This avoids clipping during the lower signal cycle in the output buffer.
The output control could have been named Level or Volume, but we preferred to call it Master to increase the mojo factor.
The resulting circuit is so flexible that it ranges from a treble boost with a slight amount of grit (in fact pretty faithful to a Rangemaster but with less hiss) to a fat overdriven boost (comparable to a gainy LPB-2). In between there are many sweet spots to be found that will correspond to your personal tastes and gear.
The drain bias voltage of the first stage plays a role in determining the character and grit added by the circuit. We encourage you to experiment and find the bias voltage that works best for you. A bias voltage of 7V proved to be faithful to the Rangemaster tones, while a lower drain voltage in the range of 4.5 to 5V was somewhat better for the fat sounds.
We thank Michael Klein who provided the name for this circuit. Omega is the last letter of the Greek alphabet, and we believe this is the ultimate booster. It is also the symbol used to represent ohms, the unit used to measure impedance, and it fits nicely into our circuit since the input impedance is strategically varied to alter the frequency response.
Tuesday, 1 January 2013
Runoffgroove Peppermill
Adding to the Runoffgroove library.
From ROG:
The idea behind this project is to create a natural sounding overdrive sound using minimal components. It should also be suitable for a booster for an already driven amp.
*snip*
Please take note of the transistor pin voltages shown below, specifically the source of the J201 JFET. It may be necessary to audition different J201 for the best sound. MPF102 and 2N3819 will not provide the desired sound in this circuit. Various J201 may have a range of source voltages, even when the drain voltage is set at 4.5 volts. Having a source voltage near 115mV should produce results that are very similar to the sound clips.
The LED serves as protection against potential damage to the MOSFET caused by static electricity (thanks to Joe Davisson for this idea). A 9.1v zener diode may be used as well (as seen in the Jack Orman's AMZ Mosfet Booster), with the same orientation. Jake Nagy's Blue Magic predates the Peppermill and exhibits a similar topology. However, the development of the Peppermill was not influenced by the Blue Magic design and any resemblance is coincidental.
From ROG:
The idea behind this project is to create a natural sounding overdrive sound using minimal components. It should also be suitable for a booster for an already driven amp.
*snip*
Please take note of the transistor pin voltages shown below, specifically the source of the J201 JFET. It may be necessary to audition different J201 for the best sound. MPF102 and 2N3819 will not provide the desired sound in this circuit. Various J201 may have a range of source voltages, even when the drain voltage is set at 4.5 volts. Having a source voltage near 115mV should produce results that are very similar to the sound clips.
The LED serves as protection against potential damage to the MOSFET caused by static electricity (thanks to Joe Davisson for this idea). A 9.1v zener diode may be used as well (as seen in the Jack Orman's AMZ Mosfet Booster), with the same orientation. Jake Nagy's Blue Magic predates the Peppermill and exhibits a similar topology. However, the development of the Peppermill was not influenced by the Blue Magic design and any resemblance is coincidental.
Saturday, 22 December 2012
Runoffgroove Tonemender
From ROG:The Tonemender is a very flexible, yet simple clean boost with a 3-knob tonestack that allows the user to re-create the classic Fender, Marshall and Vox responses.
We suggest using a TLC2272 for the dual op-amp. The TLC2272 is rated for low-noise and rail-to-rail output, which will offer the highest possible clean boost and dynamic range. The NE5532 is another good choice, but a TL072 can also be used with decent results.
The Mid Shift switch (SW1 on the schematic) selects the center frequency of the midrange dip in the response. The center frequency is moved from around 700Hz (Marshall/Vox) down to 400Hz (Fender) in the HI and LO settings, respectively.
For Fender-style curves, the Mid Shift is placed in the LO setting (closed). To replicate Marshall-style curves, switch the Mid Shift to the HI position (open). Set the Mid control between 12:00 and 5:00 for traditional Marshall settings, with lower settings providing additional flexibility. For a Vox-style response, keep the Mid Shift in the HI setting and set the Mids control fixed at 10:00 and move the Bass between 7:00 and 12:00.
A "flat" equalizer position is set with the Bass and Treble both at minimum, and the Mid control at its midpoint. When Bass and Treble are fully cut, the Mid knob acts as an additional Level control, which is a familiar characteristic of the Fender tonestack.
I've thrown out the previous version as this one is simply better. And definitely verified. There's quite a lot of gain coming from the circuit, so some squeels and noise from the unboxed circuits are expected.
We suggest using a TLC2272 for the dual op-amp. The TLC2272 is rated for low-noise and rail-to-rail output, which will offer the highest possible clean boost and dynamic range. The NE5532 is another good choice, but a TL072 can also be used with decent results.
The Mid Shift switch (SW1 on the schematic) selects the center frequency of the midrange dip in the response. The center frequency is moved from around 700Hz (Marshall/Vox) down to 400Hz (Fender) in the HI and LO settings, respectively.
For Fender-style curves, the Mid Shift is placed in the LO setting (closed). To replicate Marshall-style curves, switch the Mid Shift to the HI position (open). Set the Mid control between 12:00 and 5:00 for traditional Marshall settings, with lower settings providing additional flexibility. For a Vox-style response, keep the Mid Shift in the HI setting and set the Mids control fixed at 10:00 and move the Bass between 7:00 and 12:00.
A "flat" equalizer position is set with the Bass and Treble both at minimum, and the Mid control at its midpoint. When Bass and Treble are fully cut, the Mid knob acts as an additional Level control, which is a familiar characteristic of the Fender tonestack.
I've thrown out the previous version as this one is simply better. And definitely verified. There's quite a lot of gain coming from the circuit, so some squeels and noise from the unboxed circuits are expected.
Geiri's demo of his awesome Double Tonemender!
Friday, 14 December 2012
Runoffgroove 22/7
Phew. This board almost made me crazy. There is "only" 28 cuts and 11 links, but i got down to only one resistor over one strip. This one is quite interesting. CMOS Hex inverter based BMP adaptation.
A word about the circuit from ROG:
This circuit was born with the idea of making a CMOS workalike of the well known Electro-Harmonix Big Muff Pi (BMP). We chose the name Twenty-two Sevenths or 22/7 since it is a rational approximation of pi.
The gain and frequency response of each stage were adjusted to match the corresponding stage on a BMP. The result is a rich and full sounding pedal that evokes some of the fuzz sounds circa 1969, as well as some classic singing leads.
Through the years several variations on the tonestack have appeared, but after studying their variants we concluded that these differences correspond more to parts value availability rather than a significant difference in sound. So, the tonestack components were chosen to obtain an "average" BMP sound, which is referred to as CLASSIC mode in this implementation. In addition, a center-off DPDT switch was added in order to obtain two additional sought after sounds from the tonestack: a FLAT setting and a deeper SCOOP mode. In this way, the sonic palette of the 22/7 is greatly expanded.
The interstage coupling caps have been observed to vary between 100nF and 1uF in different versions of the BMP. In this implementation we chose 100n, which produces a more balanced bass/treble mix that works well for chords as well as soloing. If you want heavier and fuzzier bottom end as found in some BMP versions, you may want to replace the five 100nF caps with 1uF.
As this is a high gain circuit, good layout and cabling practices are critical for good performance. Apart from recommending shielded cable for input and output wiring, the entire circuit should be well shielded inside a metallic enclosure so as to reduce AC mains hum pickup to a minimum.
Sunday, 30 September 2012
Runoffgroove Odie
Short but sweet: "FET overdrive developed as a Tube Screamer alternative"
So there you go!
So there you go!
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