L'Amp: A simple SIT Amp

[juanitox]

The heat will also affect the gate leakage

if the gate leakage is very important for the sit bias what about using a Grid choke for the gate so we could have a very big AC loading and a very low DC resistance ?

[Michael Rothacher]

Nah, 1uA is typical when used at proper temp. Easily manageable.

[nicoch58]

On tube when driving the grid positive on peaks that charge the coupling caps,the grid choke speeds up the recovery from overload ...

[Salas]

Maybe a bit OT, maybe not given this kind of amp's power supply range. There are $200 double and $130 single linear high current regulated bench supplies about. I have a double 30V 5A unit for series linking up to 60V high or up to +/-30V symmetric. Also because I could find one of the fan-less variety in doubles. Maybe good for checking out such amps fast, listening, and then deciding to keep and build them their own costly supplies. And for a number of other projects of course. For Matching MOSFETS, SiC JFETS, SITS, also. But don't use it as a circuit's CCS, you remember it did not work correctly for member Protos amp. It takes to fit an NTC primary side not to trip 10A breakers (I put one there). That trafo is 500VA easily. Construction is so-so, but OK for the price. Its meters look set true. Setting the scope's trigger for single shot, I captured the power on event. Looks smooth, no over voltage or ringing. That one's a 5V/Div 100mS/Div ramp up.

[nicoch58]

Nick look like a "creative" fullrange array ;D

[Salas]

NP used one such PSU for testing Nemesis?

[Michael Rothacher]

I found a few more family photos this morning. The bench PSUs in the first photo are very similar. They work well. I do believe Obi-Wan has used something similar.

[juanitox]

hi michael , today i decide to try negative bias with no source degeneration , first i make a big error in wiring and turn on my sit with no bias and a great 5amp on one side .. rewired turn on and Ouf! my 2sk82 is not dead .. i now got a great 22V and 2amp on each side.. for the sound i'v got a mixed feelling . first the gain of the amp is far bigger , low level details seems better now ,sounds cleaner too. i found it to be very dependant of the 10uf input cap , with a epcos MKTS it sounds very fast and a little dry sometimes, and with a Clarity cap Esa it sounds more refined and warm. do you think your hand made inductors will sounds different than the Hammond too ?

[Salas]

Originally Posted by nicoch58

Nick look like a "creative" fullrange array ;D

Cheap array full Chinese, but decent help if you know how to use well. Agilent and Tek in next life.

[Salas]

Originally Posted by Michael Rothacher

I found a few more family photos this morning. The bench PSUs in the first photo are very similar. They work well. I do believe Obi-Wan has used something similar.

Handy. Do you link the middle +/- or just the series button mode takes it well with 1-2A+?
Edsyn iron in mid photo, sweet.