OK so the build is done and testing is on-going. So far I want to make few minor changes. The impedance pot as suggest by Jensen is a nice tone shaper! But a pot may not as repeatable as switched resistors. The OPAMP drivers sound very clean, but I want to add an attenuator before them. I am wondering at this point if the gain pot is needed? Do I really want to overdrive the input of the amps? So far so good.

Neat project, Link.

What are you driving the op-amp outputs of the device into - are they feeding the guitar amps? The gain controls you have on the op-amps can be set to unity, so there is little point in stripping them out. I can understand that the raw output of the interface is too much for the inputs of the guitar amps. You might be better off wiring in a fixed pad of 20dB or more in the amp channels and then using the gain adjust if needed. Most re-amp boxes I have used offer attenuations going up to at least 40dB.

Thanks Boswell!

Here is where this started from
http://www.jensentransformers.com

Yes a Pad would be a good idea. Rev 1 here we come ;) Last night I changed where I tapped the op-amps from pin one of the pot to the wiper, and that gives a bit of a divider to the input of the opa2134's. Which helps.... I am running these op-amps straight into different guitar amps.

I saw another circuit where they used a inductor to feed the guitar amplifier, to simulate a guitar output. Personally I like the tone not dragged down, Maybe for a distortion sound this would sound smoother.

I am happy with this prototype now, but if I get back to it I will lower available gain to the op-amps, add a few switchable pads and simplify the ground lift switches.