Derailer gain mods

R

rickn2112

New member
Has anyone built the Derailer? I've just got mine working and am gobsmacked by the amount of gain and volume early in the knob rotation. It was also built using a TL072 instead of the OPA2134.
Would the OPA2134 have a noticeably different gain structure? Everything I've read suggests little difference in practice but practical experience may show something else.
Would I be better off using log/audio pots for Volume and Gain? And what of the HiCut?
 
I looked at mine and I used a pair of TLE2072 opamps in mine. Probably because they are what I had on hand, at the time. I'm going to look at a possible volume mod. It's super loud and little usable range in the rotation of the pot. I'm building a second one. I really like the pedal but it needs tamed a little. I have a bunch of good opamps (opa2134, opa2227, opa1642, opa1632, opa1678, etc). I could try but they won't make much difference with the volume. Sometimes, I prefer the "crappy" opamp.
 
Changing opamps won't change the gain or volume, at least not in a noticeable way. Switching VOL to A10K will move unity up higher on the dial. Changing GAIN to A10K will make it easier to dial in lower gain settings. If HICUT is too touchy at the bottom end of rotation, then change to A50K. Which taper works best for you depends on which end of the pot rotation you're using. A-taper spreads out the bottom end of rotation, C-taper spreads out the top end, B-taper does neither. The surrounding circuitry has a strong influence on the control feel as well.

Be careful you don't damage the board changing out the pots. Sometimes it's better to sacrifice the component to save the board. Pots are less than $1 each. A fully assembled board is worth $20 or more in parts, plus your time and effort to build it. If you're not good at disassembly, cut the pot leads and remove the remaining bits from the board one at a time.
 
Thanks Chuck.. that’s the effect I’m after.. I thought log pots would do the job, it’s a great pedal and I love the way it works with my Marshall Origin.. just so touchy when trying to dial it in! Thanks for the confirmation!
 
Just modded mine to A50k pots for Gain and Volume. Really helped open up the range on the Gain control. I'd call this a "must do" mod. With the linear pots this pedal is something of a one trick high gain monster whereas the logaritmic pots make the pedal more versatile as a boost and overdrive along with the stock distortion. On it's own it still doesn't really go from clean to mean with guitar volume even with single coils but we can't win them all.
 
jonoftheford said:
Just modded mine to A50k pots for Gain and Volume. Really helped open up the range on the Gain control. I'd call this a "must do" mod. With the linear pots this pedal is something of a one trick high gain monster whereas the logaritmic pots make the pedal more versatile as a boost and overdrive along with the stock distortion. On it's own it still doesn't really go from clean to mean with guitar volume even with single coils but we can't win them all.
Click to expand...
Hmmm, wish I had seen this thread before I gave mine to my brother. That sounds like exactly what this pedal needs to get out of the "one trick pony" mode. It does the high gain thing really well but I was definitely not able to get the cleaner side of the "From Clean to Scream" claim from Ethos.
 
Chuck D. Bones said:
Changing opamps won't change the gain or volume, at least not in a noticeable way. Switching VOL to A10K will move unity up higher on the dial. Changing GAIN to A10K will make it easier to dial in lower gain settings. If HICUT is too touchy at the bottom end of rotation, then change to A50K. Which taper works best for you depends on which end of the pot rotation you're using. A-taper spreads out the bottom end of rotation, C-taper spreads out the top end, B-taper does neither. The surrounding circuitry has a strong influence on the control feel as well.

Be careful you don't damage the board changing out the pots. Sometimes it's better to sacrifice the component to save the board. Pots are less than $1 each. A fully assembled board is worth $20 or more in parts, plus your time and effort to build it. If you're not good at disassembly, cut the pot leads and remove the remaining bits from the board one at a time.
Click to expand...
I just did the mod and am really happy with the results. Both the volume and the train are much more usable now. Thanks!
 
Ok, this pedal just came back to me from my brother.....it was too much gain for him too hahaha.

Bookmarking this to mod mine. I might actually like the pedal if I can get more usable gain range out of it.
 
MichaelW said:
Ok, this pedal just came back to me from my brother.....it was too much gain for him too hahaha.

Bookmarking this to mod mine. I might actually like the pedal if I can get more usable gain range out of it.
Click to expand...
With the mod it's a really nice overdrive pedal, that cleans up well. Yesterday after I modded it, I set the gain to be on the edge of breakup with the guitar volume rolled back, and used it as an always on pedal.
 
I think between the CowPoker and Mojito I have all the high gain I'm ever likely to need....hahah
 
Original gain and vol pots are B10k. I can see changing to A taper, but changing value is not so obvious. Does 50k really work better than 10k?
 
I started with the A50k, WAY too much gain. Then changed to a A10k. Not sure if it's better or not, but still too much gain. Looking at the schematic, all the pot does is increase/decrease the signal into the non-inverting op amp... which the gain for the op amp is fixed.
 
I started with the A50k, WAY too much gain. Then changed to a A10k. Even with the A10k gain pot, I am only using 1/4-1/2 the range. Not sure if it's better or not, but still too much gain. Playing with the guitar volume knobs is similar to the gain knob, just changing the gain into the IC2.

Looking at the schematic, all the gain pot does is increase/decrease the signal into the non-inverting op amp. The gain for the op amp is fixed at 1+(1M+100k)/(100k+3k3) = 10.6. Those C11 and C12 are filtering caps.

I wonder if I could reduce the gain any.

1705332039033.png
 
Changing the GAIN pot value affects the brightness. All six parts in IC1.2's feedback loop affect both the gain and the freq response. If you change one part, plan on changing most of them if you want to retain the freq response.
 
Chuck D. Bones said:
Changing the GAIN pot value affects the brightness. All six parts in IC1.2's feedback loop affect both the gain and the freq response. If you change one part, plan on changing most of them if you want to retain the freq response.
Click to expand...
Yeah, I have the gain pot as A10k. So I was wondering about changing R10-R14?
 
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