This is what I did.
Disclaimer - I am a DIY stat amp n00b. So take what I say here with the proverbial grain
(or 50 pound sack) of salt. I will not be held responsible if you blow up your amp or headphones.
I know that I am preaching to the choir here, but all the regular B.S. about following safe build
and test procedures without electrocuting yourself apply here too.
1) The psu is to be burned-in for eight hours at 125% of rated power output.
[with a dummy load attached - simulating the load of both amp boards]
After burn-in, ensure that both the high voltage and low voltage +/- rails are outputting the correct voltages and are stable.
2) Short the signal inputs on the amp board to ground, or if already hooked to an attenuator, set it to zero (volume).
No source input signal should be applied at this time.
3) Initially, only hook-up and test/calibrate one amp board at a time.
Important: Ensure that the +/- 15VDC and +/- 450VDC* output voltages from the psu along with ground are connected
to the amp board before powering on. (*make that +/-500VDC in your case)
If any of the LEDs do not light, or are very dim or are blinking upon power-up, something is wrong!
Remove power immediately, then troubleshoot.
4) Assuming that all LEDs are glowing uniformly, perform the following calibration procedure to the amp board(s):
[note: this is copied from KG's HeadWize article on the KGSS. Same stuff applies here.]
"The two pots balance the output voltages to 0V referenced to ground.
Begin the adjustment by putting a voltmeter between + output and - output and setting the first pot for zero volts.
Then put a voltmeter between the + output and ground, and set the second pot for 0V.
After the amplifier warms up for 30 minutes, adjust the pots again.
I adjusted my unit once, and keep checking it every so often.
The output voltages on my unit are less than ±200mV.
Compared to the 580 volt bias, that is close enough to 0V. And that is over a 1-month period."
5) Repeat steps two through four when the unit is cased with both amp boards connected
along with the input and output jacks.
This time, final test & calibrate the output voltages through the Stax jack(s). [without headphones connected]
6) Hookup a source and your headphones and enjoy!
At first, I recommend using a "cheap" set of cans for a while. Sure would hate to fry them 009's!