Trying to get an ABY pop free

[remmy]

I have put together the below schematic for an ABY pedal which I am planning to build, it is based on the Jack Deville splitter, plus I have added RG Keen's polarity reverser and a transformer on the second output.

So far I have breadboarded it and it all seems to work well but I can foresee a problem as there is some DC on the isolated B output.  I plan to have a footswitches to select each output by shunting them to ground and I am concerned that the DC will introduce popping.  The DC on the transformer's output goes if I put a 1M pulldown resistor to the normal ground, doing it to the isolated ground doesn't help.  My question is will having the pulldown resistor to the normal ground stop the B output from being isolated?  And if yes is there another way around the issue?

Any other comments about the schematic would be great too, it works as I'd hoped but if there are any glaring mistakes or bad practice going on it would be good to hear.

Thanks, Remmy.

[ChanchoPancho]

Transformers actually block DC voltages so there's not supossed to be any DC level in output B. I assume that the purpose of the transformer is to isolate output b form the rest of the circuit, so if you don't need that isolation just remove it and get the B output from C6 just like the A output. I see that the transformer also inverts signal polarity, but that can be accomplished in other ways.

[electrosonic]

If you want a polarity switch, why don't you swap the transformer outputs with a DPDT. Then you can get rid of IC1B and use a TL072.

Andrew.

[remmy]

Transformers actually block DC voltages so there's not supossed to be any DC level in output B. I assume that the purpose of the transformer is to isolate output b form the rest of the circuit, so if you don't need that isolation just remove it and get the B output from C6 just like the A output. I see that the transformer also inverts signal polarity, but that can be accomplished in other ways.

I didn't realise that about transformers blocking DC, I'll take the measurements and post them tomorrow as I cannot remember what they were.  I will need the second output to be isolated as I get pretty bad ground loop hum when using both amps together 

[remmy]

If you want a polarity switch, why don't you swap the transformer outputs with a DPDT. Then you can get rid of IC1B and use a TL072.

Andrew.

I thought about it but the splitter circuit uses 3 amps (four on the original splitter circuit, one in, three out) and I fancied trying the reverse polarity trick out on one of them as I haven't used it before, thankfully that part is working 

[ChanchoPancho]

Transformers actually block DC voltages so there's not supossed to be any DC level in output B. I assume that the purpose of the transformer is to isolate output b form the rest of the circuit, so if you don't need that isolation just remove it and get the B output from C6 just like the A output. I see that the transformer also inverts signal polarity, but that can be accomplished in other ways.

I didn't realise that about transformers blocking DC, I'll take the measurements and post them tomorrow as I cannot remember what they were.  I will need the second output to be isolated as I get pretty bad ground loop hum when using both amps together 

Maybe the problem is not in the splitter circuit, i'd recomend that you check your amps groundings. Check this guy videos about ground loops.

Ground Loops:
http://www.youtube.com/watch?v=4YM1iwC6vhg

Noise Reduction:
http://www.youtube.com/watch?v=fCfa-I4SfiM
http://www.youtube.com/watch?v=FrgupGEXKNs

[Paul Marossy]

I highly recommend this video as well: http://www.youtube.com/watch?v=6ZGokkrsO_Y

Demonstrates quite well what happens when you defeat the ground on the power cord of an amplifier!