got asked to build a reamper - well, not one, but two.
the idea is that in a studio environment, it can be a lot of fun to run just about anything from your DAW through a pedal+amp setup again.
even more fun is the possibility to run everything in a nice wide stereo.
so, what we decided on:build two mono reampers in a single box, for convenience.
more convenience is provided by Neutrik Combo Jacks.
we want the possibility to run just one input to both outputs (mono in, stereo out), to use two different amps on one guitar at the same time, for example. or to layer two effect chains - you name it.
that does require the extra possibility to flip the phase, if you want it done right.
i thought about having 'master' functionality where one set of controls would control both paths at the same time, but since the whole idea of this setup is mostly to be able to use two different chains, they will probably require their own settings anyway. so that idea got scrapped.
a little google session gave me a couple of interesting links.
i used the same Edcor brand xformers as they do here, which basically uses a variation on the classic Jensen schematic. no need to reinvent the wheel there.
while Jensen proposes a 10K:10K, some schematics use a different ratio xformer, like 10k:600. terminating the secondary with a resistor closest in value (680R). i tried both varieties, and i must say the 10K:600 doesn't quite cut it for me, levelwise. it just doesn't provide the punch of the original signal to my ears.
the 10K:10K, on the other hand, provides ample level and will play very well with dynamic recording levels in your DAW.. read: if you're not pushing up against 0dB all the time it's about plug-and-play without too much fiddling with the level control. so that'll be the transformer of choice here.
as for phase switching, i found several people hinting at just swapping the wires of the (isolated) output jack. while that might do the trick in a standalone mono box, it didn't seem to play nice in the dual box i was building. so i flipped phase right at the secondary, before going into the level pot. that works well.
one thing i was sort of worried about, was feeding two transformers with a single signal, without a buffer of sorts. worried about impedance issues and whatnot.
testing with my own soundcard, there was no problem at all - no audible difference on the outputs while feeding one or two chains. no problem, no problem solved. hah.
here's the full schematic of the build.
who knows, someone might have a use for it.