e-licktronic Forum

Has anyone have a (kind of) loud hum when the hi hat filter is in any position but off?

It's not very distinguishable when two or three other sounds are playing simultaneously but it's certainly loud enough when I have all but the hi-hat muted and the filter on.

Nava is otherwise fully working and the trimmers are set correctly (I'm on 3.2 so no resonance adjust)
When the filter is off the hum dissapears completely..it also goes away when I set the freq cutoff to zero.
Is this normal?

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I didn't bother matching the filter diodes or anything else really so I initially thought that what's you get when being lazy and it should a minor leakage or mismatch of some sort but it's pretty pronounced and I'm starting to think there's a fault somewhere.

Yes, I had the same and did the following: viewtopic.php?f=26&t=1546&start=10#p11811

I did the above but it's still there somehow..
I guess my problem is worse than yours since my filter stops being a filter after replacing r86_2 for 10k!!
I completely lost cuttoff frequency.
Which version of the PCB do you have?
I'm on 3.2.
I ask because R71 is already 10k on mine.
Do you happen to have a schematic of the filter?
Thanks!

I found the resistors values in temporarily replacing them by potentiometers.

Here is a part of the schematic with only the input and output stages (hope this is OK for the designer!).

Thanks!
I'll see what I can do; maybe the values vary with each circuit considering the different values and tolerances involved.

Also check this ! viewtopic.php?f=24&t=850&start=50#p11687

And my PCB is from the first run.

Hmmm, haven't checked that!
I use the 15vac supply which I think outputs a lot less AC than stated when loaded.
Measured about 13Vac which translates to about (16.something VDC) barely 1.5v higher DC value than the regulator output.
These are not low voltage drop regulators so they must be under stress.
Will check this asap and post back.

Yes, that can be a bit low. What I had was simply the regulator voltage constantly dropping so it made a sawtooth wave bleeding more or less slightly everywhere.

It was the power supply
And I've been checking and re-checking everything for the last couple of days..
So we can call that a success.
Thanks a lot mate!