Box of Rock Warble

[Chugs]

I built a Box of Rock. It works and sounds like it I expected but at maximum gain there seems to be a mild warble to the sound. I also bread boarded the circuit and got the same result. Is this typical for a Box of rock?

[alexradium]

Nope

[alexradium]

Is that a fuzzy bass frequency?
Because this circuit has a lot of bass, play it with tone at full setting bright and hear the sound

[Chugs]

No, it is not a fuzz bass frequency. It is very odd. Voltage readings are fine, the boost works great, all controls work how they should and it sounds like a Box of Rock it just warbles at full gain. What perplexes me is that I also bread boarded the circuit with all different parts and it does exactly the same thing.

I have listened to the output of each stage individually and all sound good but together, at full gain it warbles. I haven't boxed up the one I made. Maybe this is affecting it?

[alexradium]

do yo have flying leads to the pots?
if so,i recommend to leave them as short as possible,using shielded cables to the jacks can also help in case of oscillation.

[Chugs]

I do have long leads temporarily hooked up to test it on both the finished and breadboard version.

It could be some kind of oscillation but low frequency instead of high. That would explain why both the finish and breadboard version exhibit the same behaviour.

It is weird as I have built or bread boarded higher gain circuits and never experienced this type of low oscillation/warble before. I assumed I had built it wrong until I bread boarded and got the same result. Maybe I have made the same mistake twice but I can't find it. It is driving me a bit nuts!

[Jaicen_solo]

What do you mean by 'warble'

Is it some sort of low frequency intermodulation?? Or more a general wobbly vibrato effect?

[Chugs]

I would say some sort of frequency intermodulation. Not vibrato effect.

[Jaicen_solo]

Right that helps. Try reducing the values of the input caps, if that helps, drop the intersage coupling or bypass caps as well till it goes away.

[Chugs]

I tried changing caps but that didn't make a difference. The warble, for want of a better word is actually there at lower gains settings too just not as noticeable. I didn't realise that until I was able to turn up the volume a bit this afternoon.

Sounds like there is a ghost note under the sound too.

Here is a clip.

http://soundcloud.com/chugs74/box-of-rock

[Mike Burgundy]

I hear a fair amount of hum, could be intermodulating with that. Also, have you tried it with a different guitar? I've had high gain circuits sound crap on some guitars, which turned out to be the guitar sending out all kinds of subtle noises (resonating strings at headstock/behind bridge, stuff like that) that were lifted enough to annoy by the high gain circuit. How does it compare to a different circuit with the same riff and guitar? Other than the hum (fix that first) I'm not sure anythings actually wrong.

[Chugs]

It is humming quite a bit. The circuit is not boxed up yet though.

I tried another un boxed circuit with the same guitar and played the same chords and the different circuit sounded fine.

It is a weird one. The fact that the same thing occurs on the bread board version of the circuit too is what throws me.

I bread board high gain fuzz circuits quite a lot so I am familiar with the noise associated with gain in that situation but this seems like something different.

I will finish boxing up the finished circuit version and see what it sounds like. That way I can determine whether the noise is related to shielding or interference etc.

[Jaicen_solo]

Certainly sounds like some sort of inter modulation.
If you have a signal generator, you could try running a pure tone through to find the problem frequencies.

When you breadboard it, do you use the same components, not just same value, actual components??

[Chugs]

I don't have a signal generator unfortunately. Good suggestion though. I have it on the breadboard now with a completely different set of same value components and it has the same problem.

[pinkjimiphoton]

if you need a signal generator, on the cheap, google up

savihost by hermann seib, and get any of a gazillion freeware VST synths. if you load a vst (just drag it onto the executable) synth, you can find a relatively clear sine tone to test with... right click a note, and it will sustain indefinitely.

you can use the audio out from your computer to give you a signal to work with...just plug it into the effect's in.

works pretty good, i do it a lot.

hope that helps man!!

[Chugs]

Thanks, good tip. I have a bunch of software synths but never thought of using them for a sine wave.

[pinkjimiphoton]

cool! yah, they are useful little buggers.