Background noise with klon ??

[alltrax74]

These last days I built 4 Klon Centaur, which are not the first ones I build, far from it.
On 3 of them I have exactly the same issue.
The pedal seems to work fine, nice sound in buffer mode, nice drive in od mode, all the pots are behaving like expected, but I have this stupid crrrrrrrrr sound behind each note when the pedal is engaged.
I built the circuits extremely carefully, checking every step, each component value, solder joint, trace cut, component placement, grounds...well, all the usual suspects
I replaced the 3 ICs in the 3 units, with exactly the same issue.

I'm running out of ideas, don't know what to check. It's so easier to debug when the pedal is simply not working...

So guys, if you have any idea of what could be wrong, please share
I'll record a sound clip if you wish
Thanks !

[Jopn]

Any chance it`s the voltage doubler chip?  I remember something about the 7660 needing to have the "S" suffix otherwise they would whine a bit.

If not, then this sounds like a job for a signal probe and a lot of patience...

[alltrax74]

Thanks Jopn
No I tried 2 batches of 7660S with the same result.
I'm not sure a signal probe is the solution here, as the 3 pedals behave exactly the same.

This noise must be typical of something but I can't figure what

[Jopn]

But with a signal probe you could move your way through the schematic and see if you can locate the point where the offending sound is introduced.

[alltrax74]

Well, if it's post gain probably, if it's before it will be harder to locate it it.
Anyway, you're right I'll have to try

[alltrax74]

A customer returned me the 4th pedal of the batch, that started having the same issue after about a month. It was working absolutely fine when he received it and was very happy with the sound.

I tested it and like the others, I can hear this kind of "crrrr" noise in the background, which happens pedal engaged or not (it's louder when engaged).
So the problem also exists in buffered bypass mode.
I didn't take yet the time to probe it, but the symptoms accuse the pump charge part of the circuit.
As previously mentionned, I already tried 2 batches of 7660S whith the same result so I tend to think that IC3 is not the culprit.
The think that bogs me is that it was originally working fine, so could it be a deffective component (cap) ?

A link to the schematic

I'll check and post my voltages

[Dave]

Anyway you can get a soundclip up of the noise, is it high pitched or more like a motorboat engine?
Cheers
Dave

[alltrax74]

It's not high pitched at all, it has nothing to do with a hiss or whistle.
Not a motorboat engine either, sorry but my best description is crrrrrr in the backgound on each note
I'll post a soundclip

[Dave]

Ok, I think hearing it will help diagnose the problem. Not being high pitch or motorboat like probably rules out any sort of grounding or power issue.
Cheers
Dave

[alltrax74]

I just built a new one from scratch and bing, same problem again  
I recorded a short sound clip where you can ear the noise in the background :
http://9vzpn7.1fichier.com/en/index.html
And I checked my voltages :
Wall 8.96V
IC1 pin 1 to 8 :
4.5 / 4.5 / 1.12 / 0 / 4.45 / 4.5 / 4.5 / 8.96
IC2 :
4.45 / 4.5 / 4.45 / -8.85 / 4.45 / 4.5 / 4.55 / 17.4
IC3 :
8.96 / 3.78 / 0 / -5.1 / -8.85 / 4.42 / 3.73 / 8.96

If anyone has an idea that could help, it would be greatly appreciated

[alltrax74]

No one ?

[Geiri]

I've built so many Klons that I've lost count but I've never had a noise issue with them. Only issues I've had are faulty pots so far.

[alltrax74]

Yeah me too I built a lot without any issue, that's why i don't understand the problems i'm having with this last batch

[Surgeon]

I've built two using Madbean's pcb layout (which I etched) but never encountered noise issues either.

This is gonna sound quite simple and obvious (you probably thought of it but) which components (if any) did you get a new batch of for these builds? Anything you can think of?

[IvIark]

My bet is the charge pump.  If you bought a batch from one seller then they just may not be very good, or re-badged ICL7660 maybe so the noise is from the oscillator.  An oscillator is usually the source of motor boating and it's the only oscillator in the circuit.

Buy one ICL7660S from a trustworthy source even if it costs you a couple of dollars.  If that one is silent you know what the cause is, if not then your pedals are haunted

[alltrax74]

Thank you guys for your input, much appreciated !
I'm also thinking about the charge pump, the thing is I tested 2 different batches of ICL7660S, one from ebay China and the other one from Musikding, with the same result.
I'm gonna order a few from tayda to see, and even a few MAX. All the one I use are with the S, badged Intercil
Surgeon this is a question I asked myself a lot, and I can't see anything apart from the ICs
Next step will be to try with a battery to see if it changes anything, but im really running out of ideas

[IvIark]

Check the batch of electrolytic caps you're using around the charge pump too.  If one of those (or batch) is faulty then that would account for noise from the oscillator too potentially.  Measure them to see what actual range of values you're getting

[alltrax74]

Actually I check all the caps with a Peak device before soldering, and I reject any value out of 10% so at least the values where ok.
In order to save space I use 16v caps for both the 47µf, they seem to be out of the 17V network, could I be wrong there ? (I use 50V for all the others)
Thanks

[IvIark]

Yes there's no problem with 16V in those positions

[alltrax74]

Ah, too bad, I have to find something else then :)