Hot Silicon Fuzz oscillation

[Schappy]

I just used Doug Hammonds layout for the Hot Silicon Fuzz.

When I turn up the gain past 12noon I get crazy oscillation.

I cant seem to figure it out.

[jacobyjd]

Is your amp cranked pretty hard? I get a little of that if I am running into a hot amp. If my amp is clean, I get no oscillation. Mine has 2n5088s with gains over 500ish

[Schappy]

No my amp is on very low and Im getting some really crazy oscillation.

Im pretty new to this so not sure what would cause that type of noise.

Ive probed through the circuit with and audio probe and all the transistors sound fine until I increase the gain.

[davent]

If you were dealing with a high gain tube amp, lead dress can often be an issue causing oscillations, would the same thing apply to a high gain pedal? How is your wiring to and from the pots, does moving the leads/wiring around alter the ocsillation in any way?

Haven't noticed any such problems with my Hot Silicon but i do need to keep the volume pot turned way down due to the huge volume difference between bypassed and engaged.

dave

[Schappy]

No the wires are very short and it is obvious I need to debug but am at a loss.

[Quackzed]

i know the input wire of any fuzz, esp a high gain silicon deal, is very sensitive... take a look at the input wire, see if it is very close to the ouput wire anywhere ,or close to 9v or if it reduces noise by touching it... it may be helpfull to run an extra  wire connected at one end to ground and not connected on the other end and  wrap it around the input wire, just to provide a bit of shield...

[Gus]

Try a different battery first.  Some faulty batterys have high output resistance and because of this allow the gain stages in a effect like the Hot Si to interact via the supply.

Do you have a power supply bypass cap installed?

[Schappy]

Im using this layout.

Still cant get this figured out.

[John Lyons]

Pics?

[Schappy]

http://www.aronnelson.com/gallery/main.php/v/ulysses/ulysses_layouts/dh_hot_silicon/ulysses_dh_hot_silicon.gif.html

[jacobyjd]

That layout is verified for sure (fits perfectly into a 1590B!). Did you socket the transistors? I'd be curious to see the gains on those.

[Schappy]

Ive tried moving the wires every which way and no change in the oscillation.

Would a transistor with too high of a gain cause this.

[jacobyjd]

Ive tried moving the wires every which way and no change in the oscillation.

Would a transistor with too high of a gain cause this.

I've had problems in the past with transistor (read: no diode clipping) fuzzes oscillating--generally it's been because of gains that are a bit too high. I haven't had that problem with the HSF, but it could be part of the issue.

Have you checked for solder bridges? you could have some sort of accidental feedback loop going on.

[Schappy]

I didnt see any visable solder bridges so I just decided to run my soldering iron quickly across the tracks to clear any small pieces of metal or solder that might be in the way.

It worked.


Thanks for all your help.

[jacobyjd]

Fantastic! Glad you got it working I've had problems with solder bridges before that I've only been able to see with a powerful magnifier--it's a pain when it comes to that

[Schappy]

This is one great sounding circuit but does get noisy at higher gain levels.

Anything you can do to reduce the noise?

[jacobyjd]

This is one great sounding circuit but does get noisy at higher gain levels.

Anything you can do to reduce the noise?

Did you use 5088s or 5089s? 89s might help some. Other than that, there's not a whole lot you can do without hurting the overall sound--it's the nature of high-gain circuits

[Schappy]

I used 5089's

[Schappy]

Ive havent even boxed mine up yet so Im sure some of the noise will be taken care of there.

Would shielded wire help?

[kurtlives]

Ive havent even boxed mine up yet so Im sure some of the noise will be taken care of there.

Would shielded wire help?

Sure but imo it is not needed in this design.