It seems that the last few batches of ICL7660SCPAZ were either bad or fakes (so I believe) - I kept getting a high pitched whine/hum with the Tonebender Mk 3 circuits I was using them in. So I ordered some TC1044SCPA from Mouser, thinking that they would definitely be more reputable than an eBay seller.
Unfortunately, that didn't seem to help, either: the pedals were still making a high-pitched whine, more noticeable when not playing. I pulled the inverter out and ran it with positive ground through my test box, and behold! no whine.
So, in trying to figure out if there's a way to reduce the noise, I stumbled across this thread here:
- and I was wondering if that could be applied to the Negative Voltage Inverter layout here: layout
If so, what value of cap should I use, and where would I put it? The linked thread says:
Try adding a 100nf cap from the power output to ground (parallel with the filter cap) on the voltage inverter.
Sometimes a small cap in parallel with the regular 100uf filter cap helps remove high pitched whine.
- but since there's no 100u Filter cap, I'm not sure where it would go, or if that would work.
Any help or suggestions would be greatly appreciated. Thanks.
Re: Noisy Voltage Inverters - is there a fix/remedy?
I've been using charge pumps recently to get +/-9V supply voltages for bipolar overdrive designs. If you're using the barebones charge pump vero you linked to with two capacitors, I would modify it as follows:
(1) Add more columns so you can put a 100uF cap from the input 9V to ground. In parallel, add a ceramic 100nF cap for extra filtering.
(2) I always use a 1N5817 diode for polarity protection at the 9V input. This is optional but usually a good idea just in case.
I actually like using the LT1054 charge pump instead of the ICL7660. It's a little more expensive, but can handle more current. Anyhow, hopefully you can solve this with a few more capacitors. I just recently purchased some germanium transistors and plan to look at some PNP tone benders on my breadboard. I'll report back if I notice any whining.
My personal experience is that I have never built a Fuzz Face or TB circuit with a charge pump that I thought was usable, so I simply use batteries.
That's the weird thing: I've built a few for friends last year with inverters and haven't noticed any inverter noise at all in them: using a variety of transistors (AC125, Ru PNPs, etc.). It's just the last 4 that I have built have all had noise issues, whether I've used ICL7660SCPAZ or TC1044SCPA.
I actually like using the LT1054 charge pump instead of the ICL7660. It's a
little more expensive, but can handle more current. Anyhow, hopefully you
can solve this with a few more capacitors. I just recently purchased some
germanium transistors and plan to look at some PNP tone benders on my
breadboard. I'll report back if I notice any whining.