SOLVED Boneyard circulator massive gain

C

comradehoser

Well-known member
So.... Finished this this evening complete with all boneyard mods, and it is phasering and doing what phasers should do, but

Besides being a tad dark, It has MASSIVE gain (and no gain/volume knob). Like I have to turn down my guitar volume to 2 for unity. 10 is like quadruple gain with heavy (not unpleasant, actually) clipping.

I'm guessing maybe something in the tl072 area. R6?

IMG_20250910_233430856.jpg

IMG_20250910_233450766.jpg
 
Last edited:
Sort by date Sort by votes
Hold the phone... Just double-checked against the screen print values and Chuck's notes, and it looks like C7 above the tl072s is 1uf, not 100nf.

[Edit: subbed it, it makes a difference. Reasonable range is now volume 4 on the guitar. Still super gainy and distorted and waaay above unity. What did I do wrong? ]
 
Last edited:
Upvote 0 Downvote
Thanks, Nostradoomus.

I tried searching for over-amplification/distortion on the circulator, but I couldn't find anything. The discussion referenced above is the opposite of my issue.

I just don't get why the gain is so out of spec. R6 is 10K, as required. Everything else checks out, including all phasing/vibrato/pot changes/what have you in the effect so far, except for the mistake on c7. It actually sounds like a pretty good phaser with the volume down. Not as nice as the duophase, but still good. That suggests that my chips are good, at least (Stomp box parts for the LM13700 and Mouser for the TL072IP).

I was thinking maybe something in my implementation of the mods, but it doesn't look like they are implicated in amplification anyway.

Guess I'll go match everything to the refdes again and take some readings. le sigh.
 
Upvote 0 Downvote
Well, so, anyway, and so forth, I checked the components against values and mods, and everything checked out in capacitors and resistors EXCEPT I had put 1m in instead of 2.2m for R2; I had meant to leave R27 at 27k (to see what this oscillation business was about) but subbed to 33k, and R23 was at 27k when I meant to sub for 33k, and drumrolllllll... R4 instead of 10K was at 2.2M. That one undoubtedly was the culprit as it was wildly off-spec, and is in the first TL072 in what looks like an amplification function. I'm sure I just remembered sub R3 and R4 to 2.2M instead of R2 and R3. Why? Who knows.

Swapped everything around and now everything is hunky dory and proper.

Let this be a lesson to not populate boards while watching decently enjoyable horror movies. Particularly if they involve heavy Chuck D Bones mods. I think it was Phantasm, but it could also have been Nope, both of which I really liked.
 
Upvote 0 Downvote
You must log in or register to reply here.
Back
Top