Output of preamp is very likely to be of Low Impedance in all situations, this due to the design constraints of analog amplifier chips, which are typically High Impedance at Input to chip and Low Impedance at output.

That's a Good Thing, as the Low Impedance output is powered and at Audio Frequencies we can always easily drive any High Impedance input with a Low Impedance powered source like this one without fear of losing or altering any frequencies. (The reverse, High Impedance driving into Low Impedance, does not work like that and should be avoided.)

Sounds like John has already discovered how much output gain the Fishman preamp can provide, by design, in order to be able to drive the many differing inputs that might be encountered. But some amp systems may not need that much gain and the answer is simply to back off the output gain fader on the guitar preamp until your ear tells you that you have a good clear sound. From there it may be necessary to then use the Volume fader(s) on the ampolifier itself to adjust things in. Depending on the input gain of whatever the Fishman preamp is plugged into, it may result in having a Fader on the guitar that cannot be used its full range without overdriving the amp input. The simple answer is to govern your use of that fader on the guitar accordingly.

**You might find better situation using a LINE INPUT instead of a MIC Level input.**

If no Line Level is available:

John, if you still find there is more gain than you would like to deal with in live performance, or that you simply desire to have more fader travel available in a live performance situation, use your ham radio/electronics knowledge to construct a simple Y or L pad across the preamp output. This could be as simple as a 10 to 20K pot that has its outside pins wired directly across the preamp output + and ground, with the wiper going to the input of the amp, sharing the ground pin for shield. The pot would be a set and forget item, used as an attenuator such that you could move the guitar's fader to full and not overdrive your amp input. I would recommend placing this pot right at the amp input side and not on the guitar itself, such that you still enjoy all that line level voltage coming from the guitar preamp, for lowered noise figure among other things.

Turning the guitar fader down to an accomodating level should work as well, it should not be detrimental to the sound quality, but might be a situation where you can't really use the fader easily live onstage due to the short amount of area that is okay before distortion begins. The attenuator can solve that if you're into a bit of soldering, though.


--Mac

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