Sending a guitar signal to two amps

Rocker · February 2021

I have a simple Pedalboard with an Orchid Transformer Isolator in circuit. To use a second amp, I connected the balanced output from my Peterson StroboStomp tuner. Worked nicely. But now I find that the balanced output refuses to output so what problem(s) will I create if I fit two Jack sockets in a box, both in parallel and soldered to a short guitar lead? The plug to the tuner output and one Jack to each amp (one is through the isolator).

Will this work or is there a better way? Thanks.

maltingsaudio · February 2021

Not quite seeing your signal path can you rough out a diagram, however the simple splitter you describe should work.
A bespoke splitter here https://www.thomann.de/gb/jhs_pedals_buffered_splitter.htm

prowla · February 2021

You could get a mini mixer - I was thinking about this the other day.

Another option is if the amps or a pedal has an effects loop or tuner output.

Danny1969 · February 2021

You need to buffer the signals so one amps input isn't loaded by the other and visa versa. You can do this with a very simple opamp circuit, use a dual one like a TLO72 or similar, feed the signal to both non inverting inputs, short both outputs to the inverting inputs for unity gain .... the only additional components needed would be blocking caps on the ins and outs and a couple of resistors to bias the non inverting inputs at half your supply. Maybe a lowish 470R or so in series with the outs to guard against accidental direct short of output.

ICBM · February 2021

Danny1969 said:

You need to buffer the signals so one amps input isn't loaded by the other and visa versa.

Not necessary given the very high impedance of guitar amp inputs - a passive split will work fine.

I'm puzzled by why it doesn't work with the balanced output though - is there a TRS connection on one piece of equipment but not the other, and the wrong pin is used as hot, so then grounded by whatever it's connected to?

Rocker · February 2021

You are not the only one puzzled by the no sound from the balanced output on the StroboStomp @ICBM. It worked fine last week, it might be the cable [which is an unused microphone cable with a standard ¼" jack at the guitar amp end]. I hope to go through the testing again today or tomorrow. For some reason or other, the StroboStomp does not work with a PP3 battery but it does work with a Boss PSU. Recently I got a Rockboard Power LT/XL (mainly to eliminate hum which originates in a mini Reverb pedal when that pedal is powered by a mains PSU), so the possibility is that the StroboStomp is sulking as it is being battery powered and not mains PSU. There is also the possibility of a fault in the microphone cable.

All will be revealed in the next few days.

maltingsaudio · February 2021

Rocker said:b

Recently I got a Rockboard Power LT/XL (mainly to eliminate hum which originates in a mini Reverb pedal when that pedal is powered by a mains PSU), so the possibility is that the StroboStomp is sulking as it is being battery powered and not mains PSU. There is also the possibility of a fault in the microphone cable.

All will be revealed in the next few days.

Dodgy cables would be my guess on this, but the stroboscop on battery power would also be a suitable suspect, I would also check you didn’t knock the internal dip switch in the battery compartment which may effect the function

andy_k · February 2021

When I was allowed out to play live, I had no problems using a cheap Fender A/B/Y passive split, into a Marshall Code and a Katana. I dont use a powered FX board, so never ran into excess noise problems, which I think are caused by earth loops (electricity is magic to me )
I have recently discovered that my MXR KFK 10 band is true bypass, so I am using that as a splitter at home, it has 1 in and 2 outs, and works unpowered as a simple split.
I think any stereo pedal would do the same, if it is true bypass, and have recently been experimenting with signal loss through unpowered pedals. My board has 6 pedals, all analogue kits, and the first one in the line is a Klone with a buffer, this has to be powered in bypass, but the other 5 all pass signal with no appreciable loss of tone when unpowered in bypass.
I don't think I am being fooled by the buffer, but it was a revelation when I started to use it.
My only other stereo pedal to try, is a HOF mini, which has a dip switch for selecting buffer, and I think I wouldn't be using it with batteries as it is quite juicy.
There are more expensive isolated splitters available, which probably use the principles Danny describes above, and they will also be adding the benefits of a buffer, and I do believe most Boss pedals will not work as true bypass.
I like it when I can understand why my equipment works, but that is not always the case.

Rocker · February 2021

I went through all the connections, I checked the dip switches in the StroboStomp ( thanks @maltingsaudio) and when I powered everything up. It worked as before. Using the Rockboard power unit!

I made up a rough and ready splitter box, three old Jack sockets in a plastic box with all three sockets wired in parallel, and this worked as @ICBM said it would. There was some hum from the amps, two mains powered and one battery powered, this was reduced slightly when the two mains powered amps were powered from the same extension strip. Workable. I like using one mains powered amp and the battery powered amp as it gives a less boxy sound in our room than when a single amp is used.

I now know it can be done. More importantly my preferred two amp setup now works.

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Sending a guitar signal to two amps

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