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kevin gilmore

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I have found in photos on other DIY Stax amps that the Stax jack has Grey, White, Orange, Yellow and Blue wires soldered to its pins. The photos are none too clear and cannot see which goes with which.

Is there a L+, L-, B, R+, R- convention to the color code that is used? Like to keep things as standardized if possible.

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I must chip in here  There is no official convention.  I have a sort of mnemonic way of doing it.  Bias is always white.  Left channel has two colours with L in such as blue and yellow. The brighter being the more positive so yellow is the + output.


The right channel has at least one colour with an R in such as grey, and the brighter one is pink or similar.  This aids in checking you have it connected up correctly.


It's pretty too. 

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So I finally received my transformers.  I've built 2 KGST PSUs and all of the measured DC voltages seem to be within a few volts of what's expected. However, the -350V line is off on both PSUs.  One PSU stabalizes at around -366.6VDC and the other PSU stabalizes at around -360.2VDC after about 10/15 minutes .  The +350V lines are +353VDC and +356VDC.  The transformers I have measure around 320VAC with no load on the HT lines.


Is this something to be concerned about?  Anything I can do to bring it down a bit?

Edited by chiguy
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Thanks for the advice!


It was pointed out to me that with 5% zeners, 350 x 1.05 = 367.5 and yup, I am using 5% zeners.  I guess I got unlucky.  =\


What I'm currently using:




I guess I can order some more zeners test for the best ones.  I can't find anything that are better than 5% at 1.5W. 

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Thanks everyone!  I've ordered some zeners. 


I didn't think having +/- 350VDC on the dot was terribly important, I wasn't expecting such a difference in range however.  While testing last night, part of me was thinking "just plug the amp boards in, what's the worse that can happen?"


On that note, what would happen if I ran the amp boards with my power supplies as they are now?

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Got my amp and PS boards stuffed and soldered. Got my transformer 2 days ago and case yesterday. Everything in the photo is only trial fit and not screwed down.

Getting ready to test the different power sections, and wonder if I can test the +/-15VDC circuit on the amp boards without +/-350VDC active.

Thanks again to Kevin and Birgir for all the fun.


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Thanks Kerry and Birgir.

Did not want to try powering everything up at once, even with a variac. I don't like bright flashes, loud BANGs, and letting the smoke out of the transistors (along with tripping home circuit breakers). Trying to take a systematic approach to powering up for the first time. At least powering up the LV first should get the front end CCS LEDs to light. HV to be added in time..... I have a healthy respect for that.

Yeah, the case will eventually have lots-o-holes. Thinking both top and bottom plates to have them above and below the heatsinks and tubes. Also a heat isolator if needed between the PS and amp boards. Going to have to get it up and running first and then decide on what it will take. A lot more work to do.

Edited by Laowei
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