Sometimes it takes almost nothing to mod an amp for better. In this amp I have designed and built last year, the tone was not exactly what I was expecting. Today, I had the chance to tweak it a little more : just replacing the 12ax7 cathodes r & c values did the job. This preamp tube is the only one and it is hooked up in cascade. Before: first stage 25uF / 1k5 , second stage: 25 uF / 820 . Result: round and warm tone, but lack of voltage at the plates, perfect for jazzy tone ( i am not a jazzman, I think this is not a secret ). After the change: first stage 2k7 / .68 uF second stage 1k5 / 22 uF. Marshall type tone, more rock and agressive. General specs: class A, one output tube ( 6550 ), one 12ax7, GZ34 rectifier, 330V at the plate of output tube drawing 104mA through a 240 OHM 10w resistor bypassed with a 60mF 63V. 230V at the first plate of the 12 ax7, 200V at the second. Power section: PI filter, 50uF reservoir cap, 10uF cap for the preamp tube. Big huge trannies from HEYBOER. awesome tone. I play my all original 1973 Gibson SG ( mini humbuckers ) through it, direct, no pedal, straight into the amp and this thing REALLY ROCKS. Beautiful rock tone at 6, past six, heavy rock and very nice not harsh distortion. It's been built into a BOGEN Challenger amplifier but none of the parts have been used.
Hers's some pics. I will try this time to record a soundclip and put it on youtube, as I promised last year...... ( promises, promises, like my wife ( new girl friend, rather ) would say : no, I am not going into that, wives, girlfriends, kisses and more don't count on me okay ????
Colas Coca
Topic: New build from last year modified (Read 1820 times)