Many question about Threshold S/** supply rails

[ANADIGIT]

I need to know how many voltage supply rails of these model, also current each channel :-)

S/550E
SA 3.9E
SA 4E
SA 12E

Thanks
Anadigit

[Nelson Pass]

I'm sorry to say that I don't have that data. You can calculate it
fairly easily knowing the rated power of each amplifier and adding
about 10 volts to the voltage required to reach a peak wattage of
twice that power.

There was no current limiting to those amplifiers as I recall, so the
current was pretty high.

[ANADIGIT]

My S/550E was +/- 70 VDC, I need to change it to SA/4E.
Is it posible ?

Thanks
Anadigit

[Nelson Pass]

I recall the SA4E as being 100 watts. You want to take the supply
down to 45-50 volts.

[ANADIGIT]

I seen 2N5566 in the front end of S/550E, could I use 2N3958 instead of 2N5566 ? (also 2SK170, 2SK389, 2SK129A)

Thanks for advance
Anadigit

[Nelson Pass]

Yes, I expect so.

[ANADIGIT]

I never heard Threshold have SA/3.9E in line production !

Could anyone show it schematic ?

MPS-U10 and MPS-U60 are hard to obtain parts, Did someone have idea for substitute them ?

Thanks
Anadigit

[Nelson Pass]

The SA3.9e was one of my favorites.

I have the schematics up on passdiy, but we changed the server
and I don't recall the new passwords, so I'll check tomorrow at work.

I have the U10's and U60's if you need them desperately, email me.

[ANADIGIT]

Hi,
Thanks PAPA but I can find them in my local shop already.
I decide to build 125W version, How do I select correct supply voltage rails ?

Also bias adjustment

Thanks
Anadigit

[Nelson Pass]

Originally posted by ANADIGIT
Hi,
Thanks PAPA but I can find them in my local shop already.
I decide to build 125W version, How do I select correct supply voltage rails ? Also bias adjustment

125 W = 250 watt peak.

V^2 / 8 =250

V^2 = 2000

V peak = 45V

Add 10 volts or so, V supply = +/-55V

Bias it for heat sinks at 50-55 deg C.