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.



16 comments:

  1. A very good overdrive pedal for bass and for guitar.
    This monster pedal is a killer. I built this one off the Runoffgroove website and I use it all the time. stacked with another overdrive in front. It's got great crunch and very effective tone shaping controls.
    If you wanna read my post on FuzzQuest blog and listen to some riffs:

    http://fuzzquest.blogspot.com/2013/09/ginger-bread-bass-hot-from-oven.html

    BUILT IT !!!

    ReplyDelete
  2. Yeah! It was in my list, when i ll finish the sft this will be next!)

    ReplyDelete
  3. WOO HOO!
    I believe I was the one who first requested this, so many thanks to John for drawing this up, and to Mark for posting it.
    I've run out of PCBs for this, and need to build another one, so this has arrived just in time.
    As Doron says "a monster pedal".
    I've now got a week to build this up to take to a friend of mine in Iceland, so I'd better get building!

    ReplyDelete
  4. This comment has been removed by the author.

    ReplyDelete
  5. Hi there!
    What is the best substitute and easy-to-find transistor for 2n5457?
    It seems to be really difficult to have these trannies nowadays...
    Many thanks!

    ReplyDelete
  6. According to Frank NH you can use J202 as a direct replacement for 2N5457

    ReplyDelete
  7. maybe someone used a resistor in place trimpot?

    ReplyDelete
  8. Hey guys. Can this be added to the bass category? As always, thanks for all the bass goodies!

    ReplyDelete
  9. What diffrence does the voltage on the drain do to the sound? The vero layout says 4.5v with a 10k trimpot. And rog says 6v with a 5k trimpot.

    ReplyDelete
    Replies
    1. The trimpot value will not make a difference - 10k is preferred on here as it gives slightly more room to bias the JFETs correctly.
      With regard to the 4.5V versus 6V, JFETs usually bias best around 4.5V, which is why that figure is used here. ROG suggest 6V as this circuit may sound better biased slightly hotter. I suggest you bias to 4.5V and adjust the trimpots until it SOUNDS best to your ears. This is always best pracice with JFET builds anyway.
      Do yourself a HUGE favour, and put a voltage doubler in your build - two versions posted recently. You can then use a switch to select either 9V or 18V operation. Make sure you have 25V or over capacitors in your build first. 9V sounds great, but 18V sounds incredible - like an Ampeg SVT into a 8x10 running at full volume. Takk!

      Delete
    2. So if i bias at 4.5v and use a voltage doubler. Do i need to make any changes if my capacitors is 25v? Also, the layout for the voltage doubler says that the ic should be a 7660s but does it work with a icl7660 spca?

      Delete
    3. no you don't need to make any changes if you're caps are 25V. that means that they can handle 25V before they fail and will explode.

      no you don't want to use the 7660, you want the 7660s. the 7660 without the "s" will wine, and not work right.

      Delete
    4. I've built this and sounds great, but I'm getting a white noise from the pedal with the gain turned up.

      I get the same kind of noise when adjusting the bias trimmers, but the noise is more crackly during the adjusting.

      Anybody else getting white noise?

      Delete
  10. Hi, thank you again for another great pedal :)
    i'm gonna build this for bass guitar of course and i have a question: is here an easy way to to modify the schematic and add a balanced output for using the Ginger as a bass D.I.?

    ReplyDelete
  11. This is a great sounding pedal — many thanks.

    But my bass control goes from full cut to full boost in the first 25% of its rotation with A100k potentiometer. I've got no knowledge, other than how to solder! Should I try B100k? Which is Lin and which is Log (and are international conventions as inconsistent as they appear on the internet)?

    Or any other solution?

    ReplyDelete
  12. This comment has been removed by the author.

    ReplyDelete