Whiny Distortion: Charge Pump?

[jposega]

I've got a Dunn Effects built Big Game CVLT preamp/ distortion and it's got a super high-pitched whine. The seller (who etched the enclosure) said it was noisy because of the charge pump (9v pumped up to 18v).

I haven't opened it up to see what kind of charge pump there is, or if it's soldered in, but are there different charge pump chips that could cut that noise, or some other simple mod? I could just put a noise gate after it, but I'd like to see if the pedal can be 'fixed' first.

It does this on an isolated outlet on my Truetone CS12 and a dedicated power supply.

[midwayfair]

Ask for a schematic, otherwise we're just guessing.

If it's an LT1054, it shouldn't whine. If it's a 1044 or 766x, it needs to have pins 1 and 8 connected or the clock will be in the audio band.

[reddesert]

I have an unbuilt PCB for the CVLT that I got from Ryan at Big Game Pedals. The effect circuit is essentially that of the preamp from an old Peavey Festival bass head, discussed in a talkbass thread, titled "Peavey Fuzz?". The charge pump is Ryan's addition, since the original preamp ran at 24 VDC. I'm not sure there was ever a released schematic or build doc as the PCBs were left overs from his run, but the schematic of the bass head is discussed and posted in the thread.

I can measure on my PCB to see if there is a boost connection between pins 1 and 8, but the other critical question is what charge pump chip was used in your pedal, because some of those chips have boost mode (typically "S" suffix) and some don't.

[reddesert]

Update: My Big Game CVLT board is silkscreened "ICL7706S" - typo for ICL7760S - and pins 1 and 8 are clearly connected.  So you need a charge pump IC that has the S boost mode.