Is the Toshiba 2SJ201/2SK1530 pair (Mosfet) suitable for output stage ?

[Mark Hedges]

Should anyone by sufficiently interested in building one of these amplifiers I still have circuit boards and power transformers available.

Part of the design work for this amplifier was to pulse test it into a 0.1 ohm resistor at full power repeatably with a pulse train. I cannot remember how long the pulse train was. Pulses were supplied by HP pulse generator and set to a width of 10ms. Supply voltage to the MOSFES runs about +/- 52 Volts. It is likely that you cannot do this with an amplifier that uses a minimal amount of MOSFETS in the output stage.

There may also be better OPAMPS available now but finding some that can run on the original +/- 24 Supplies can be difficult. Thus the supply voltages were dropped to +/- 18vdc. To drive the MOSFETS to full power does not require a lot of AC drive voltage but at higher frequencies does require considerable current since each MOSFET gate input has considerable input capacitance.

Do you have any pictures of a completed amp? What is the power rating?

 

[qusp]

do you still have the PCBs? its a beast! should the fets be matched? because finding that many matched k1530/j201 these days will be a tall order

 

[h_a]

I had a short look at the amp design; mosfets should be matched to ensure reliable turn-on (Nelson typically recommends a tolerance of 100mV or so).

However, 10R as gate stopper is an incredibly low value - are you sure you're not running into local oscillation? Also I'm surprised you're not using different values for the N's and P's to reflect their different input capacitances. With equal gate stoppers you'll have different roll-offs. Not that this is a problem, it's just a remark.

Hannes

 

[viki_v2]

Hello Friends,
I have 2 pairs of 2sk1530/2sj201 Mosfets, can they be used as replacements for 2sk1058/2sj162.