so, i finally got my Ampeg Gemini I home and it sounds incredible. i took it to practice friday and it was amazing. it was breaking up pretty early, which is a known "feature" of this amp, but i decided to check out the original speaker anyway. turns out the voice coil was rubbing, so even though it sounded really good, it was terribly inefficient and breaking up way too early. i dropped a vintage 30 in there (16 ohm though) and bam. now its got plenty of headroom for me (breaks up around 2 o'clock on the volume) and it sounds more present. hooray!
so, now the ugly. for one, there is a hum that i am pretty certain is tied to the reverb circuit that i need to science out. any tips or pointers from experienced ampeg dudes before i go spelunking appreciated. i know that i will need to replace the filtering caps soon, but thats not an issue. a little worried about that cap can with multiple caps, but i think JJ has a solution.
okay, now the weird! there is a pot on the rear of the chassis that is wired up to the tagboard and the reverb pot on the front. when i first got the amp, i figured the last owner had just modded it. it seems to add brightness to the reverb while adding dwell time maybe? in the extreme setting it starts to feed back. i keep it either all the way down or halfway up to keep it from feeding back. the weird part is that the pot date code matches all the other pots in the amp, and the wiring is the same shielded wiring used throughout the amp! factory modification upon customer request? there is like, no info online i can find! arrgghhh. here are photos of that mod:
heres the pot on the rear of the chassis
wide shot, reverb mod on bottom right hand corner, you can see the grey wiring going over to the tagboard then behind the baxandall board to the reverb pot
closeup of the reverb pot thats on the front of the chassis
okay! who wants to see more pics of the guts? yeah you all do. here we go!
heres the mysterious "afterbeat" module
sorry for all the pics! i figured you dudes would like seeing this amp. with the exception of the three prong cord and a single power resistor, it looks like this amp hasnt been screwed with at all. everything works wonderfully, which leads me to believe that this particular amp is kinda rare. theres tons of Gemini I's out there, but they either dont have reverb or dont have trem. its like they never work.
and like i said, if anyone has any tips or pointers for making sure this baby is tip top, please lemme know.
