Sunday, 28 September 2014

Blade VSC Preamp, modified

Ran into a schematic of a preamp on-board circuit found in Blade brand guitars. The original called for LM4580 dual opamp, other channel unused. So i drew this layout for a single channel chip and added volume control, power filtering etc. You could try on a number of single opamps to see which sounds best to you. I'd also suggest trying linear taper for volume control. Should make a nice mids booster or a simple box that'll fatten your tone.

Monday, 22 September 2014

HBE Power Screamer

Haven't counted, but i believe we have fair number of Tubescreamers and derivatives listed here. And here's one more. Tweaked with couple of mods to low frequency response and gain. Switchable diodes etc. The boost switch is a stomp and with 2PDT you can use the second pole for a LED. I've omitted the 27K resistor from the output, but if you want yours verbatim, just solder 27K resistor between Level lugs 1 & 2.

The Power Screamer is our flagship pedal. Tonally wide ranging and transparent, The Power Screamer "oozes" vintage, tube like overdrive. Based on the JRC4558D The Power Screamer features: Adjustable Gain, Level and Tone controls, 3-Way Diode Select and footswitchable Boost.

Sunday, 21 September 2014

DOD FX56 American Metal

I think Mark would have squeezed this in a bit more compact size, but i got it "down" to 21x29. So super brave folk may aim for 1590B, but rest of us may want to give this a go with 125B or 1590BB instead. Layout is based on a schematic which was provided with the original units, along with stickers and other paperwork. Circuit has some similarities with Boss HM-2 Heavy Metal as the youtube demo below suggests. Sounds pretty mean.

Wednesday, 17 September 2014

EHX Germanium Overdrive

Thanks to Miro for the excellent trace job he did on this.

Hope you're stocked up on 470nF caps.  They were all polarised but I have shown poly for the caps with a 5mm pitch because I expect that is what most people will use.  I have shown electrolytics for the two with only a 2.5mm pitch just so people know the polarity if anyone would like to build it with electrolytics, but again I expect most would use poly or maybe 2.5mm multilayer ceramics for them.  Any PNP germanium can obviously be used an an alternative to the NKT275, and I suspect more people will have 2N3906's in stock than 2N5087's, so try those for Q2 and Q3.

Info about the original:
Classic '60s Germanium transistor overdrive and more. In addition to a Gain control, the Electro-Harmonix Germanium OD allows the user to control Bias for attack and the circuit Volts for that sweet spot found when a battery's voltage dips. Dial up that slightly torn speaker sound OR dial in total Germanium "Satisfaction."

Germanium is an element like carbon or gold. Germanium transistors were used extensively back in the 1950s and ‘60s. Eventually they were replaced by components that were considered “better.”  The EHX Germanium OD and Germanium 4 Big Muff Pi use these old school transistors. They have a distinctive sound, some say smoother or “spongier.” You be the judge, hear the Germanium OD here.

and the schematic

Thanks to ξεναγός νεκρόπολης for verifying and providing the following working voltages.

e 5,41
b 4,17
c 3,76

e 4.37
b 3,75
c 0

e 3,02
b 2,43
c 0

Monday, 15 September 2014

Ibanez BB9 Bottom Booster

Here we go with one of my personal favourites. To me, the sound is simply amazing. As Dirk's notes on the schematic suggest, you won't be saving any money by building this. New ones sell for pretty cheap and one should be able to score a used one for a very decent price. I still wanted to see how compact i could possibly get this and yes, i'm rather happy with the results. I did cut a few corners though. I omitted the six 100n power decoupling caps from each opamp as adding those would have made this way bigger (let's just hope this doesn't add to noise floor). The input resistor is 12k on this layout, but to make it verbatim, you should take 5k1 and 6k1 resistors in series in its place - or a value of 11k2. I also dropped the 100k resistor and 47p cap from the output. If you want to add those, just solder them between lugs 1 & 2 of the Level pot. I also made a couple of small changes to the power supply section input. I burned the LT1044 on my original unit, and that was way easy to do. So i added series protection and a zener+100R resistor after that. Should be pretty fool proof like this. Charge pump produces +9V/-9V swing, so you're safe with your 16V rated electrolythic caps. Should be a nice fit for 1590B.

Snippet for the marketing text:
Sometimes it's best to keep it simple. Which is why, in a world of dizzying often over-complex technology, the durable, dependable, and simple stomp box continues to be the most widely used and effective means to expand, color, distort, mutate, sustain, and twist tone. The Ibanez BB9 is a booster that provides a fat bottom end with a powerful sound, perfect for the player who wants to push their amp into overdrive without losing any of their low-end. This pedal is designed to help clean tones reverberate even more and bring more intensity to a player's sound. Combine it with a distortion pedal to create of a wide variety of tone colors.