Friday, March 13, 2015

Alamo Fiesta! 3/13/15

 Today we have an Alamo Fiesta. I re-capped this amp last year and also modified the tremolo to play slower. Today it was in for a simple re-tube. Output tube was making horrible howling sounds and the main preamp tube was microphonic. These use a 50L6 tetrode for power yielding about 4 watts. Easy to find NOS examples on the cheap. Nobody makes them any more. For the preamp tube I installed an RCA 12AU6. I'm usually not a fan of amps with these tubes, they have a cheap arrangement for the filaments. They really are kinda crappy when you put them up next to a Fender but, this little amp kicks. Plenty of volume.

  I recommended the customer buy my personal favorite 8" speaker, an old Jensen C8R, one of the brown ones you see pulled from an old organ where they were usually used as midrange drivers. I find these on a regular basis in great condition since they weren't being abused in a guitar amp. And they are usually obtained at a good price. And of course, they just have a lovely sound. Better than anything being made today.

This amp also boast a lovely tremolo. Very rich sounding amp overall, more of a darker sound which I like. Warm like a tube amp should be.

It's always helpful to have a schematic handy. Thanks to whoever drew this one and I hope it's okay to feature it here!

To slow the tremolo down I simply increased the value of the 3 in series tremolo capacitors. The bigger the caps, the slower the trem. Experiment! Start with the one on the plate of the 12AV6 first. Try a .047 or a .1 and proceed from there.


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