SET Asylum

Posted by Unison845 (A) on August 06, 2002 at 20:11:38

In Reply to: Schematics? posted by korneluk on August 06, 2002 at 13:29:07:

I never actually draw the SE833A schematic when I builded it. Here is a description:
Input stage: 12AY7/6072 SRPP capacitor coupled to the input of the driver stage.
Driver stage: KT66 as cathode follower using the primary of Electra-Print 3033 interstage transformer. With about 300V on the plate of the KT66 the cathode will be biased about 20V. The cathode of the KT66 is directly coupled to the Grid of the 833A. Other tube like KT77/KT88 can be substituted here but will make the 833A draw more current. It can be compensated by inserting bias resistor to the cathode of 833A.
Output stage: 833SE @ 1300V, 250ma, it will put out 135 watts when clipped . At this voltage the tube dissipate about 325 watts, the plate turn orange color. Force air cooling is a must. You can also use 800v - 1000V on the plate with bias current of 250ma to get 45 watts - 70 watts. The output transformer used is the EP CU5KB. It will take up to 300ma. I am running withe the cathode of the 833A directly to ground. If the 833A draw more current (depending of driver tube used) cathode bias resistor can be added to decrease bias current.

The EP 3033 will not work as an interstage transformer in Shishido circuit since it is a 1:1 and will not drive the grid 833A deep enough to get significant power.

There you have the circuit description of the 833SE. Use every caution if you want to build an amp using this high voltage.

This amp sounded much better than the 845SE (Tamura 2013 output) and 845PP (Tamura 2012 output). In fact this amp sounded better than any 845 amp that I have builded so far ( I still have to build another 845 PSE using CU5KB and 3033 to compare with). It does have the "big stage sound"of the 845, and more "neutral". The mid and high is very sweet.