ABY Hum

[Kipper4]

i rehashed my ABY pedal after it developed a fault.
this time i made it with two buffers on the outputs rather than a single one on the input.
The only trouble is it hums when connected to the amp(s) now. which it didnt before.
Any suggestions as to what to do are appreciated.
Thanks

[R.G.]

Details matter. Schematic? How are the amps grounded? Do they have 3-wire cords? Are the outputs grounded to one another? Any possible floating of grounds? Jack bushings attached to chassis? Different house/venue? Powered from batteries/DC power supply the same both times? The list goes on.

[Kipper4]

Details matter. Schematic? How are the amps grounded? Do they have 3-wire cords? Are the outputs grounded to one another? Any possible floating of grounds? Jack bushings attached to chassis? Different house/venue? Powered from batteries/DC power supply the same both times? The list goes on.

1 schematic here
http://www.muzique.com/schem/mosfet.htm
i built two of  these on the same perf board the positive and grounds are common.

2
1 amp SS 30watter is 3 wire grounded. The others on a 9volt wallwart (homemade noisy cricket)
3
the ABYs outputs are grounded to one another.
metal jack plugs mean the chassis is grounded.



4
the circuit is powered by a 9volt wallwart all appliances in the same room on the same ring main.


Floating grounds. no idea mate if i knew what it meant i might be able to answer that one.

I'm still not sure i have given enough of a clue here but it might help narrow things down a little i'm hoping
regards
Rich

[familyortiz]

Transformer coupling of one of the channels will get rid of your hum, probably due to a ground loop situation.
RG's circuit, which uses a Xicon 42TM018 transformer, is an excellent way around this. Although the low end spec is at 300Hz, the opamp driven performance is very transparent.
It looks obsoleted at Mouser's website but I am sure it can be found. Cheers

[Kipper4]

Yer that would have been a good choice but i'm trying to fix what i have thanks anyway mate.
If i cant fix it this maybe a future project or go back to a single input buffer like i had before and hope that works too

[Kipper4]

I've got some plastic jack sockets on order maybe i'll try those to isolate the ground, I'm not hopeful but you never know.