Odd Sunking Issue? Please help!

[tubeman]

Thanks in advance for any help I may receive via this forum.

I am currently making a dual sunking pedal with some switching options, relying on the original sunking (klon) layout and switching. The goal is to have two sunkings with the standard Klon type switching, controlled by a true bypass on/off switch and a true bypass switch that chooses which sunking will be in the signal chain. Each standard sunking circuit is wired exactly stock with the standard bypass circuit as designed by Klon, controlled by a DPDT toggle, which feeds the true bypass circuits, after passing through a TRS Channel Insert type effects loop for each sunking. This way, I can have two completely independant sunkings with a completely independant effects loop for each (also controlled by a true bypass wired DPDT toggle). Now that I have explained all the switching options, This should give an idea of what this pedal will be capable of. This is a very versatile design, giving the buffered bypass or true bypass in one box, for each sunking, with the ability to stab effects into each individual sunking.

Both sunkings sound absolutely wonderful and I am assuming they are very close to what they are supposed to sound like. At the moment, I am using TC7660SCPA pumps in each, TL072B opamps in one and JRC4558D's in the other. Both have matched clipping circuits, using BAT41's at the moment. Very impressive results here.

I have used 1% resistors throughout the build, with sockets for IC's and diode clippers so I can really tweak on thing. I have also opted for some serious pots. I am using military spec Centralab 10k linear pots and I was lucky enough to find two Allen Bradley Type J dual 100K linear pots for the Gain circuit. Some will say that 2 watt pots don't give any benefits to tone, but with my personal experience in tone benders , fuzz faces and rangemasters, the 2 watt heavy duty pots always drastically improve the pedals tone. Alpha seems to be the standard here, but I refuse to use them. They are junk and the only thing they are good for is repairing current production junk made by Dunlop and other types.

Seriously, on to the issue.

No matter where my output level or tone is set, I get a weird "hard clipping tremelo" effect when I max the Gain pot on either circuit. The tone is amazing until this starts to happen. This effect is even more present when doing lead runs that are about to start feeding back, which is what I want it to do, but without the inherent "tremelo" issue that is happening.

I have tried several charge pumps and opamps, including TC1044SCPA, TC7660SCPA, ICL7660SCPAZ, JRC4558D, JRC4558DD, TL072B, etc., 1n34A's, BAT41 and some other really nice germaniums that I have in my stock. Every setup has rendered the same problem... unwanted tremelo with Gain maxed!

Any ideas?

[tubeman]

  Issue has been resolved. I found a stock of great Metal Can diodes that did the trick and now I have even more gain than I had before. No motorboating and no issues! I currently have JRC4558DD in the clean socket and JRC4558D in the dirty socket with the ICL7660SCPAZ pumps running the board. Metal Can Regulator Diodes as clippers! It sounds awesome!

[bangerang101]

 That thing looks awesome!!! great job dude.

[bigmufffuzzwizz]

That's interesting. Many people have completed this build using regular diodes. I'm glad that you solved the issue. This is too cool of a pedal to sit in a box not working!! 

[tubeman]

I'll admit that with so much wiring in this pedal, there was some crosstalk goin' on. So I started sheilding input wires until that was resolved. I may still need to shield some more wires and that may solve the issue with regular diodes. I do plan to clean up a bit in there. There are some sires that I am not comfortable with at the moment and I'll bet they are the culprits.

Other than that, everything sounds incredible!!

[tubeman]

A fellow forum member helped bring an issue to my attention. It seems I had my diodes hooked up incorrectly all along. When I finally got a result that was acceptable, I was using LM313H Reference Diodes. I did not know that these are bipolar. After furthur investigation I was able to try other types like 34a's and Bat41's with impressive results, but they still didn't hold a candle to that of the LM313H. For now, the 313 stays. Way more headroom and Gain range!