GGG Stage center Reverb Squeeling Help Please!

[Evz]

Hello there! I made myself a stage center reverb unit from general guitar gadgets, but it seems to add a high pitch squeel to my line, i run it though a series FX loop in my amp, but the squeeling is coming just from the pedal. I built it with a charge pump. any ideas why it is doing so? what are some possible solutions? (i was thinking of a R-C low pass filter...)

Thank you!

[mth5044]

Did you try running it infront of your amp?

[Evz]

yep, same noise... seems to be higher pitch than the 21st fret... but less than 20khz because i can definately hear it, i believe it may be due to the charge pump

Edit: I've poked around and its the ocsilator pin on the ICL7660/MAX1044 which is making the noise, but the problem is that its not connected, yet its the one making noise - i found this because i touched it by accident with my DMM, and it killed the noise with a different popping noise... so it's the culprit but what do i do? because i dont think grounding works.. maybe use some cap to ground?

[mth5044]

Do you have pin 1 on the MAX1044 connected to the power supply? From GEOFEX

'If you connect pin 1 to the power supply (shown by the little open switch) then the oscillator frequency goes up by about 6:1. The oscillator then works well above the audio region. Any whine is then going to be inaudible.'

[Evz]

Yes, but I am trying to look for more issues, as I am using a 7660 counterpart from maxim instead of the 1044, but according to the data sheets they should be fairly similar

[fixr1984]

Try putting a buffer before it. I was having a similar issue to one that I built into a
valve junior amp. With a buffered pedal before it I had no squeel, but without it would make noises.
I ended up building a buffer and putting it in line before the reverb.

[mth5044]

If it makes you feel better, I never got mine to work 

[anchovie]

Yes, but I am trying to look for more issues, as I am using a 7660 counterpart from maxim instead of the 1044, but according to the data sheets they should be fairly similar

The standard ICL7660 does not have the Boost function on pin 1 (that's why there's a NC in parentheses on the combined Maxim datasheet), therefore the oscillator cannot be raised out of audio frequency. You need either a MAX1044 or the ICL7660S, which does have the Boost pin active.

[Evz]

Yes I realized that was the issue with the 7660 chip. Already requested a sample from maxim-ic for the max1044 chips... Will check if I can find it else where though. Seems my squeeling is at 10khz :p