Step 5: Bias Setting
Now is the time to set up the pro-bias module.
• Prepare a multimeter, set into DC volts.
• Turn VR1 on the pro-bias module counter clockwise till you reach a stop.
• Place the red probe of the multimeter at the test point, and the black probe at the ground/chassis.
• Turn on the amplifier
• Turn VR1 clockwise until the multimeter shows 580V (for Stax Pro bias)
• Wait until the amplifier has reached operating temperature, then re-check the voltage at the test point, and re-adjust VR1 if necessary.
• For Koss ESP950 you can set the voltage to 620V.
Step 6: Testing
If the bias has been properly set, then you can test using the headphone connected.
The modded SRM-1/Mk2 now has a normal bias and a pro bias socket.
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Thanks to Psychaudio for sharing this modification technique.
M H
Would this design work with SRD-6/7?
Mike
Aren’t the SRD transformer boxes?
M H
Yes.
Mike
I think you should be able to, it’s based on the same principles and basically you just want to up the bias voltage right? However I’m not quite an expert in this and so I can’t make any guarantees.
M H
That’s what I think as well, though I am not an expert on the issue either.
Mai Buhaul
Doesnt the srd already have a board? Would you just need to add a resistor?