[Guitar Amp] Preamp Output - In phase or not?

Guitar preamps usually have 1, 2, 3 or 4 inverting stages, so I expect those that have a pre-amp out are not consistent regarding phase.
Since the signal is an unbalanced one (i.e. all signals are relative to ground), I think the only option to make the pre-amp output in phase with the guitar input, if you have an odd number of stages, is to use a signal transformer. I've never heard of that being done.
There is always a debate about whether the overall polarity of a guitar amp and speaker matters or not, but the 'convention' (if there is one) is that a positive going input signal should push the speakers forward (towards the front of the cab.)
 
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rohatkilic

Member
2015-02-03 2:26 pm
Thank you for your replies.

The reason that I'm asking this question is that most of guitar amp schematics I've seen have preamp output in phase with guitar input, but only Soldano's SLO-100 has not. And this is the one that has the tone I'm in love with and inspired by to make my own high gain amp. Maybe the secret behind this awesome tone is forcing the output to be out of phase :)

By the way, I've never thought about feedback issue. This should be a very important point.
 
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Phase really only matters when you use more than one amplifier or you are mixing signals. If you use the preamp out to drive a slave amp, you want the result in the slave to be in phase with your main rig speakers, otherwise they cancel.

If you use the preamp out to go to an effect unit, and then return through a power amp in jack, phase becomes irrelevant.