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The ultimate DIY? A Stax SRM-T2!


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The file is in a place i can't get to from here at the moment, but i'm pretty sure

i can convert it to dxf format and send it to you... Tomorrow, first thing.

Ah, so it's not completely flat. I wondered how they did it.

You do know that nothing in this world is ever perfectly flat :D

Edited by kevin gilmore
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This DIY design is fantastic and Mr. Gilmore is doing an astonishing work.

I know that it is very impolite to give opinions when you are a layman and not proficient to suggest alternatives, but I would like to ask a few questions regarding air circulation.

More holes are needed for dissipating tube heat or resistors heat?

If they are required to dissipate heat deriving from resistors, should those holes be placed near/around the tube sockets in the DIY SRM-T2?

Justin could explain why he decided to do BHSE holes this way:


Regarding the DIY SRM-T2 chassis and PCB integration, are those resistors placed at the tube sockets PCB side (above side) or at the internal PCB side (below side)?

Correct me if I am wrong, but I think there was surface mount resistors below the PCB in the original SRM-T2. BHSE too:


If the DIY SRM-T2 has them placed below, how the heat can raise to the above side (tube sockets side)?

Again, correct me if I am wrong, but I have not seen wholes provided at the DIY SRM-T2 PCB (like BHSE) to do that task besides those at the outer limits where the semiconductors are soldered. Are those pcb outer holes sufficient to let air circulating?

If hot air is arising, shouldn’t be good to have holes above the chassis to let cold air entering the chassis? Or XLR, RCA, IEC and other connectors already let air enter the chassis interior?

Last but not least. I have been reading that a faraday’s cage is very difficult to achieve. Once you have one hole, EMI or RFI is entering the case. Is that somehow frequency dependent (refraction)? If not, more holes would not be prejudicial, would them? Should 6DJ8 be shielded like they were at the original SRM-T2 to accomplish that purpose?


Jose Luis

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So on the original T2, there are a lot of .5 watt resistors on the bottom of the board,

lots of holes, lots of internal heatsinks, tubes completely inside, no ground plane of

any kind, and the exterior gets to 55C. The inside gets to more like 75+C.

On my T2, everything that generates more than .5 watt (with 2 resistor exceptions)

is mounted directly to the heatsink. While more holes in the board is probably

going to be a good idea, the tubes generate thermal flow that will pull air thru

the unit. A thermal design program i'm playing with basically indicates that more holes

is not always a good thing as it reduces air flow.

I gave the board layout to the master (justin) and he will do some cleanup. Otherwise

in less than 2 weeks i'm going to send the boards out.

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That's a very good price. No word on the TKD's yet but I'm hopeful they will offer us a cheap alternative. :)

I ended up at the tail end of this enquiry. The factory wont sell direct, which means cherry picking a retailer locally or online. All the ones I tried don't list the CP2500, nor any pots from TKD, so it means contacting them and hoping whatever monkey gets the enquiry wont throw on a stupidly massive markup. Half the retailers are pro-audio or sound-engineer-type pro-audio ("You want what?") and the rest are the odd electronic parts retailers. The latter with online stores will hopefully price them reasonably.

I have the day off tomorrow so I'll see what I can find out. Now to find out WTF a 4-pot attenuator is called in Japanese. :D

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