Ampeg Scrambler Clone - issues

[phantombox]

Hi.
I just finished assembling an Ampeg Scrambler Clone. I got the schematic and PCB layout from "Tonepad FX projects - Ampeg Scrambler".

The components I used are the same as specified by Tonepad. For Q1, Q3 and Q4 I used MPSA13 (substitute to MPSA14), Q2 is a 2N3904, D1 and D2 are 1N4148, and I didn't use D3-D5 since (apparently) they also are not on the original Scrambler.
I tested the Scrambler with my bass guitar, so the result might not be the same as with an actual guitar.

Anyhow, contrary to what I read on the internet about this project, it did not knock my straight off my sox...

But the problem I have is that it works perfectly (no noise at all) with my regulable DC power supply (set to 9V), but not with a 9V/200mA wallwart that usually does work on "Boss" pedals but in this case induced a hellish background noise (it did however still work).

I did not put a receiver for a 9V battery in the circuit but went straight for a 9V power adapter jack (followed by a diode to protect against accidental inverse voltage polarity).

Are there some modifications that has to be made to the circuit in order to work with regular wallwarts and not produce noise?

BTW, the aluminum case and aluminum kobs for the pots are all connected to ground.

Thankx in advance,

Phantombox

[PRR]

Welcome!

> a hellish background noise

You mean "buzz"?

> wallwart that usually does work on "Boss" pedals but

Your wart makes junky DC.

Most BOSS have DC power filters.

The TonePad plan for Scrambler has no power filter. (Probably taken from original, which was probably battery-only.)

Try this add-on hack. Exact values not critical (use 150uFd, 470uFd, etc).

[phantombox]

I was also considering to add a 7809 regulator, since all the transformers I have do say 9VDC on the box but actually deliver a lot more when meassured without a load...

[PRR]

> say 9VDC on the box but actually deliver a lot more

If you are making fine audio, good power supplies are a worthy investment.

(OR do as BOSS did, make your audio-things pretty impervious to power supply crap.)

[phantombox]

What I meant is that the actual VDC output of the trafo is higher than the one specified on the casing.

Do you guys think that adding an LM7809 to the circuit would help with the noise?

[phantombox]

Thanks, PRR.

I added an 1N4739A (9.1V zener diode) to your suggestion and now the buzz is gone.