the tuner output from a volume pedal *should* be unaffected by the setting of the volume pedal and should see the full signal at all times. so with a two-amp setup, that's a great way to have, for example, one amp that's more focused on being clean or delivering the low end and it's always on, and then a second amp which is more sharp or more distorted, and then you can use the volume pedal to control how much of that amp is in the mix.

the cheapest way to use two amps would be to use some pedal you already own that has two outputs, like a volume pedal or a tuner or stereo chorus or delay or something. if you have nothing with two outs, then the cheapest way is going to be to use a Y cable (or some cables with a Y-adaptor).

A vs B wrote:The only issue is that you'll get ground loops which will give you an audible and obnoxious hum, especially with distortion.

This is a good point. It might be fine with some amps, and unusable with others.

otisroom wrote:I bought a Radial Bigshot for this purpose. It's actually a true-bypass amp switcher but it has a split output with a ground lift, phase switch and iso transformer switch. I use it sometimes as an A/B box but mostly to split a signal out of a bass guitar into an amp and into the avalon DI or Summit DI I use for bass direct injection. This box was only $80 and it works well. I like the radial product line I plan to buy more of their stuff in the future. They gots the fancy stuffs.

I second this product. I love the radial bigshot

This might be the cheapest, non-used a/b/y box I've seen. It usually runs at about $30-$35 from most online dealers (Musician's Friend), but I've seen it for as much as $50 (Sweetwater - so much for free shipping in this case). I think it might absolutely require a 9-volt though.

steve wrote:If you need to isolate one amp from the other to prevent ground loops, here's a trick: Use an active DI box in-line with amp #1 to send a balanced. low-impedance signal to a transformer (passive) DI box (connect to the "output" or low-impedance side of the transformer), then connect the high impedance side of the transformer (the "input") to amp #2.

Make sure the ground is lifted on one or both of the DI boxes. You often get a few dB of gain from this setup as well.

Why is it necessary to use an Active DI box ? Can't we use 2 passive di box ?

thank you

nobody wants to answer me ? please....