Charge Pump Noise...

Big Monk

Well-known member
I’ve been troubleshooting some noise issues on my board. I was getting some digital “whine” from one of my non-isolated power supplies so I swapped it for a Mosky ISO-10. That squashed the whine for the most part but I was still get a high frequency noise out of the board.

Full disclosure: I tested my direct to amp connection and the pedalboard is certainly added some noise but I chalk that up to slight EM interference from the transformers in the Mosky. Definitely nothing crazy and I was happy to squelch most of the “whine”.

So I thought about returning the Mosky because I assumed it was another case of a cheap supply being non-isolated. Turns out, however, that it does in fact have complete ground and output isolation via 2 transformers in the unit.

I decided to to use process of elimination to isolate the noise. At first it appeared to be coming from my Strymon Flint but it was actually my Aion Ares EP Pre which is directly after the Flint in my chain. After migrating the Ares to my non-isolated Otraki Power brick with my other drive/fuzz pedals, the last bit of “whine” disappeared.

So, short story long, I’m thinking that it might have been the charge pump injecting noise into the supply it previously shared with my digital stuff. Since I have an IC Socket in the Ares, I may pull the charge pump and test it on a direct 18v feed.

My question is this: which pins on the IC socket need to be jumpered to bypass the charge pump circuit for 9v DC out?
 

benny_profane

Well-known member
it’s just a voltage doubler. You’ll want to short C9 anode to D4 cathode. You’ll need to bypass the zener and take care with that series resistor.

EDIT: Pull the IC just to be safe.
 
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Big Monk

Well-known member
it’s just a voltage doubler. You’ll want to short C9 anode to D4 cathode. You’ll need to bypass the zener and take care with that series resistor.

EDIT: Pull the IC just to be safe.

I think for now I can just move it over to my other supply and that should do it. I’m in the process of reorganizing the board and I’ll pay more attention to what’s near what and what is plugged into each supply.
 

cooder

Well-known member
It can also pay to try a few interchangeable charge pumps, like TC1044 and 7660spca and see if that makes a difference.

Just looking at the Aion schematic, it seems that on schematic there pin 1 and 8 are connected and a LT1054 charge pump is specified. The LT1054 AFAIK doesn't want to have pin 1 connected, only pin 8.
However for TC1044 or 7660spca you want pin 1 and 8 connected.
Pull the charge pump, see how the sound is without, then measure if pin1 and 8 are indeed connecte on board, in whcih case I think a TC1044 or 7660spca will be a better choice and might help.
 

cooder

Well-known member
If you pull out the charge pump the circuit should still work , just running on 9V. If the noise is gone then you know at least that it's the charge pump. And then try different pumps (TC1044 and 7660spca). Also try the LT1054 with pin 1 out of the socket, just bend it slightly so it sits outside and doesn't make connection.
 

Big Monk

Well-known member
If you pull out the charge pump the circuit should still work , just running on 9V. If the noise is gone then you know at least that it's the charge pump. And then try different pumps (TC1044 and 7660spca). Also try the LT1054 with pin 1 out of the socket, just bend it slightly so it sits outside and doesn't make connection.

I’ll check this out tomorrow and report back.
 

Big Monk

Well-known member
So after some extensive messing around today, it seems it is the new power supply i bought causing issues. It was meant to be an improvement over the daisy chain style power bricks I had, but it turns out that it is not. It certainly can't be isolated as advertised, no matter how much I wanted to believe it.

I had a spare, cheap O'traki supply and used it so isolate my digital pedals from the rest of the power supply. Most of not all of the noise disappeared. It's still not as quiet as plugging straight into the the amp, but I have 18 pedals on my board so that's understandable. I decided to return the Mosky ISO 10 and just buy 2 extra cheap O'traki supplies so that all my digital stuff can be isolated from the rest on it's own daisy chain brick.

I do have to chase down some nasty noise my Boss SD-1 is amplifying. It's a high pitched oscillation type noise that goes asway when I run the SD-1 solo outside the board. So it's obviously picking something up and amplifying it.
 
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