Fulltone A/B Switchbox mistake

[mikabodcrane]

I read in a much earlier post that there is a mistake in the way the diy fulltone A/B switchbox is wired which causes "Pops".  Does anyone know what the mistake is? I have the pop bad.  I have already tried the 1M ohm resistance between signals an grounds on the jacks.

[Alex C]

I don't know what else to suggest with the popping, but I did notice he misspelled "resistor" no less than 3 times ("resister").  

Alex

[Mike Burgundy]

well, it's not isolated as all these simple ones aren't, so it suffers from possible pops and groundloops, as all these do.
hih

[mikabodcrane]

What would be required to isolate it?

[Paul Marossy]

If you're using an A/B box to switch between two amps, the ground potential between the two amps is never the same 98% of the time. Thus you will always have a pop when switching or hum or both.

You should try building RG's hum free splitter A/B/Y circuit at geofex.com
That's about as good as it gets.

[mikabodcrane]

I'm using the A/B box to split to two seperate pedal effects chains, one for acoustic guitar and one for electric guitar.  Both chains end up in the same PA; different channels.  Also hum is not really a problem, just the pop.  I'll check out the A/B/Y box you suggest.  Also do the commericial units such as Morley A/B/Y suffer from the same hum  pops? I've never looked inside one of those units.

[Paul Marossy]

In my experience, that pop comes from a mismatch in signal levels. If in one loop you have a bunch of high gain pedals and in the other loop you don't, you get a loud pop. I am not totally sure why this happens, but it does, and sometimes in a big way.

AFAIK, the solution to that would be to use a flip-flop circuit or a fast switching relay to switch between the loops. Both of those can switch much faster than a standard stompbox footswitch can.

[mikabodcrane]

I looked at RG's hum free splitter; its looks much more involved that I want to getat this time.  I'm thinking about just getting a Morley A/B/Y selector.  Does anyone have experience with one of these relative to hum and pops?

[Jered]

Whirlwind makes a great selector box, it uses a CD4069UBE and four VTL5C9's for very quiet switching and hum free.
Jered

[The Tone God]

The Morely A/B/Y is nothing special. Its passive with no isolation too. You can check the schematic at the their site if you want.

I have modified a few Morely A/B/Ys to be active with isolated outputs for driving two amps at once. Laid out a board for it to make life easier when I get the requests. Its similar to the Super Y/ R.G.'s splitter. Opamps and isolation transformers.

Andrew

[mikabodcrane]

Yes, but does the Morley pop when switching channels like my DIY A/B box.

My question would be how much pop (or click) should one expect just from the mechanics of the switch and the fact that the signal passes through the switch for true bypass?  I think of it kind of like a microphone with on/off switch were one can here a slight click when turning the mic on and off.  The higher the amplification on the mic, the louder the click appears.

By the way, I'm using the Fulltone 3PDT switch.

[Paul Marossy]

Any passive A/B box whether it be DIY or commercially manufactured can have a pop when switching. Switching a chain of pedals or between amps is a totally different matter than a switch on a microphone.

The Fulltone 3PDT switch is the exact same switch as the ones Aron offers for sale. His are just molded in a different color so he can charge more for his "special" switches.

[mikabodcrane]

These switches have an audible click just due to the mechanics of the switch.  Should one expect any of this to be picked up in the signal when the switch is connected in a stompbox?

[Paul Marossy]

The pop of the switch itself due to mechanics is not what causes the pop when switching. The pop occurs for other reasons.