Buffer in front of a high gain pedal

[alltrax74]

I lately built the BE-OD which works great but suffers from a heavy high pitch whistle with the gain above noon.
So I built a Klon buffer and put it in front, and magically the pedal became dead silent (well I mean working as it should you get it :)
Then I decided to try the same with this tiny buffer that I plugged in my test box in front of the BE-OD

As for the Klon it did the trick so I decided to put it in the BE-OD enclosure : buffer input soldered to the switch in place of the main board input, and buffer output wire soldered to main board input wire, so that both circuits are in serie, buffer being first. I was pretty confident with the result.
But that didn't work, it sounded like before, as if I did nothing. I don't get it
Anyone has a clue of why it doesn't work ?

Thanks !

[balazs.bencs]

This noise issue comes from the power supply most likely, I had the same issue with the foxx tone machine. Try putting a 100R between the board and the power jack, or search for the Huminator in the forum and include that one. I use it in the problematic builds, solves a lot of issues.

[Boba7]

Had this exact same issue in a Pale Horse (VFE) build.

If I placed a Klon buffer in a different enclosure before it, not squealing, but when I put a Klon buffer directly in the box, the squealing came back. I just don't get it.

I'm not sure it could be a power supply issue.

[alltrax74]

There is already a CLR right after the power supply (ok, it's 10R).
And it's not a hum issue, it's a strident whistle (I use a high quality power supply)

Nevertheless, that huminator thread is interesting thanks

[scimitar]

Its probably radiated interference from the output being picked up at the input - if the buffer is outside the box the interference will not be picked up - I would guess that the different output impedance of the buffer (compared to the guitar) stops this but as soon as they are in the same box then the interference is picked up by the input to the buffer. Might be worth using shielded input wire (and possibly output as well).

[alltrax74]

Right, that might be my next try, the mainboard input wire (green) is long, it crosses the enclosure from the top down to the switch, running below the board (pic is before i added the buffer)

[Neil mcNasty]

95% of the time this issue comes from the power supply.
It does not matter if it is a "pro" power supply or not.
Because if you open it up, you very often discover that all (or many) of your +9v outlets shares the same regulator and is in fact daisy chained on the inside.
Making them function just as a regular one spot with a daisy chain.
Pro power supplies are very often the crem de la crem of snake oil in the pedal world, and you will be surprised by how little you find inside them when you open them up...
At the moment I have a Tortemann fuzz on my bench that squeels when I run it on "pro" power supply, but is ok when using a very cheap and crappy one-spot...

Notice the fact that putting a buffer in front (instead of "inside") of the pedal, removed the problem, and when you added the buffer inside, sharing the same power outlet, the problem reappeared.
This could be a hint towards power supply issues, since the problem does not appear when you run a separate power cable/outlet to the buffer, but only appears when they are sharing the same power cable/outlet...

My suggestion is to pay attention to which power outlet that you plug your pedals into (or have a look inside the power supply to see which ones are daisy chained) and then re-arrange your pedal's power wires on the power supply and see if that changes anything.

If not: raise the value of the 10R current limiting resistor as suggested above. I have a feeling that this will help...

If you do not get any changes, you could build yourself a Huminator and add it to the pedal that has the problem.
But notice that the Huminator II layout (here's a link) that I've posted in the forum section has a half wave rectifier via two diodes at the input.
This often helps remove any leftover ripple current from power supplies, and is often the cure when the circuit already has a small current limiting resistor.
Adding these two diodes inside the pedal instead of the whole Huminator circuit should be quite easy, as the resistor in the Huminator circuit lowers the voltage slightly, and the fact that your pedal already has a 10R resistor added there already, you might not need the whole Huminator circuit.
Also note that; the higher the mA your pedal draws, the higher the voltage drop becomes as a result of having a current limiting resistor.
But the advantage of having one, is that you "decouple" the pedal, and therefore you reduce the chance of power interference between pedals.
As we say: "They do not see each other anymore"

The other 5% of the time this problem appear, you could be dealing with a leaky/bad cap that does not block DC current properly, resulting in DC current passing into your audio path and creating high pitched whines. But this is more rare, but worth considering if none of the above help solve your problem...
This could be a bad cap inside the "issue pedal", or it could be the pedal before (or after) your problem pedal.

Good luck and happy problem hunting

[alltrax74]

Thanks Neil for this exhaustive reply !
I will definitaly consider trying that huminator
Hunting problems is where we learn

[alltrax74]

I added the huminator step by step : first with only both diodes (and links instead of resistors).
That didn't work
I removed the links and added the 100Rs. Didn't work
I added the capacitors for the full circuit and it didn't solve the problem.
I guess I'll just have to add the Klon buffer on the pedalboard at the beginning of the chain.
I removed the huminator, it could be usefull in another circuit