Ampeg Super Echo Twin - Model ET-1
Serial No. 305507 (1963)
2 original Jenson Chicago special design (blue label) 12" speakers (C12Q)
Two separate 15 watt (loud) amplifiers (in one) that work as stereo or mono.
This amp has two rectifier tubes (two independent power supplies), each amp has a pair of push pull 6V6 cathode biased output tubes and two 6SL7 preamp/driver tubes.
Top view shows the 4 inputs, the controls for each channel, and the channel switch in the middle. The original foot switch for reverb and tremelo is also shown.
With the back removed, the inside wireing is shown. All capacitors and most resistors had to be replaced to make the amp stable and playable. The 'Blue Lable' Jenson speakers are shown.
- Re-capped most coupling capacitors
- Bundled electrolytics to replace bad canned filter capacitors
- Replaced the old line chord with 3 wire ground
- Reduced B+ (from +410 vdc) due to increase in line voltage (from 1963 levels - 110VAC to 117+VAC today), to +390 vdc using 25 watt 100 ohm sag resistors on each of the two power supplies
- Added 47K ohm screen grid resistors toall four 6V6's on both amps. This action, with the lowered B+, reduced tube current to 27 ma at idle and put the output tubes into more of a pentode mode
- Increased cathode resistors both channels, because 6V6s were running way to hot (over 40 ma each)
- Added a optional fan and switch for heat dissapation
- Added a switch to switch in/out the bypass caps on the output tube cathode resistors both amps to gives a more rounded sound when out of circuit