Deathklaw - Not at unity gain

[Ralfg]

Hey Guys,

I built a Deathklaw and I really like it, but when I tried it out in the band I noticed I wasn't hitting unity gain and had a pretty noticeable volume drop when I engaged the pedal.  I wired it true bypass.  I was thinking this would be a pretty easy problem to solve with a couple or even a single mod.  But I could use some help as to where.

I think, based on what I learned so far, if I increase R3 the whole thing should get louder, but I'm worried I would push too much through the delay circuit.  If I lower R4 I think I would increase the gain slightly for the dry signal, I was thinking 15 or 10K here.  If I increase R5 I think the whole thing would get louder?  Am I on the right track here?  Thanks in advance for any help.

[Ralfg]

Little more on this, it seems the problem only occurs when I use a loud high gain pedal in front of it, if I run it clean there is no noticeable volume difference.  I haven't had a chance to take it apart and experiment with swapping out components yet.  I'll post my results when I do.  If anyone has any thoughts on this I am all ears. 

[madbean]

If you are getting unity without the high gain pedal but it drops off with it then it might be an impedance issue. Here's what I would try: socket R2 and R3 and make them 470k. Now try the high gain pedal again. If you still have some volume drop, increase R3 to 680k or 1M. This combo will give you higher input impedance and a little more output with increasing R3 but not so much it will cause distortion.

[Ralfg]

Thanks for this. I will try that. Impedance is something I still have not quite wrapped my head around, but I'm doing research. This video helped a lot.

https://m.youtube.com/watch?v=o2TLng86djM

[Ralfg]

Just an update to this, I changed the impedance and it didn't solve the issue. I actually think the high gain pedal was a red herring, mainly because I was using this in conjunction with the high gain pedals for solos. I finally got around to messing with R5 and socketed it and went with 27k. Now there is a slight boost when I turn on the pedal. So I think 22k might be the right value for me. Thanks for the help! Consider this problem solved!

[Gristlepig]

I had the same issue with my Deathklaw build. So glad I found this thread!

Running a 200hz sine wave into it with the blend set to fully clean, unity gain was definitely at 22k.
Playing it with a few guitars and pickup types confirmed this--although the hottest pickups on any of my guitars are Seth Lover HB's. I think they are 7-8k. YMMV