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The ultimate DIY? A Stax SRM-T2!


spritzer

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Does anyone have the part number for the testpoint connectors? I did a search and couldn't find them.

Thx

Kerry, just noticed this question. I used Mouser 534-11012-R (and presumably 534-11012-B). I like them, my only complaint is that they are hard to get exactly centered with respect to each other, as the hole in the PCB is rather large and they sorta float around in the hole... but, that's a minor complaint.

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nice!

With your loop, won't you have the input RC filter from the amp transferred to the other input? I would think this would have some unintended consequences...

I think it's worthwhile to move the feedback resistor like Craig did. I noticed Kevin did this in the second board revision, so I'd assume that he would agree. If you don't have a scope, I'd also add the additional 5pF/1kV caps across the 100K resistors as well (IIRC, Craig ended up omitting these caps and the 2.2pF caps, but I wouldn't do this unless you can verify the results, including transient response). I'm not sure if Craig ever posted picture of the modification, but it's not too hard to imagine what he did.

Also, has anyone else done the mod outlined below? If so, I'd be curious to see what your thoughts are.

https://picasaweb.google.com/inuponken/T2#5566996623938911634

Edited by luvdunhill
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ok, one more question that probably nobody cares about, but hey...

Would it have been possible to locate the Stax jack and the hole for the volume shaft at the same vertical position? If the jack is about 1.125" tall and the RK50 is 27mm off the PCB, this looks like it should be possible. I'm trying to figure out why this wasn't done... to potentially avoid a mistake cutting my front panel :) I'm staring at the missing front panel on mine and it looks doable, but I'm not sure if I'm missing something.

Edited by luvdunhill
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I've recently bought myself some 2SK216 and 2SJ79 from pacific semi. I'm wondering if these are real or counterfeit since it is lacking the round dimple on the front that most genuine devices seem to have. The edge of the plastic casing is also sharp, not smooth. What do you guys think?

5824786502_902514d767_z.jpg

5824786522_b353aeeff6_z.jpg

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Some progress today, now I just need to finish wiring the PSU and it is ready for testing:

p1010100s.th.jpg

I also dared to mess with the one off titanium knob Kevin gave me. I needed some indicator on it so it took about 10 minutes of very careful drilling to come up with this:

p1010105im.th.jpg

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Some progress today, now I just need to finish wiring the PSU and it is ready for testing:

p1010100s.th.jpg

I also dared to mess with the one off titanium knob Kevin gave me. I needed some indicator on it so it took about 10 minutes of very careful drilling to come up with this:

p1010105im.th.jpg

nice! what's that massive green with yellow stripe wire for? Have you flipped it on yet? :)

Edited by luvdunhill
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Looking good.

I got the amp board soldered up and de-fluxed before I mounted anything to the top. I centered all the POTs before soldering them in.

Just about to put in the 9 pin sockets. Should they be seated all the way down? If I do that they will sit at a lower height than the octal sockets. I vaguely remember something early in the thread about this, but couldn't find it.

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I enlarged the center hole for the input tube sockets to improve the fit. In looking at various pics, not everyone did this (did anyone?), so it's probably a personal preference. Regardless of what you do, they sit at a lower height than the output tubes. Don't forget to really tighten the center pin before soldering to make sure the two halves of the socket are firmly connected together.

Edited by luvdunhill
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nice! what's that massive green with yellow stripe wire for? Have you flipped it on yet? :)

Those are the chassis ground wires, one per umbilical. Better safe than sorry so it is 16AWG. Craig might recognize the wire since it comes from a Russ Andrews cable I was given.

If I have time today then I'll finish the PSU and start testing.

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There is at least 2 different kinds of the input tube sockets.

On the ones i used, the center pin had no bushing, and fit thru

the board completely just fine.

You put the 8 pin sockets in as far as they can go. On the

9 pin sockets you align them so that they barely fit thru

the circuit board. Then the top of the octals and the 9 pins

are close to the same height.

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Getting there :prettyprincess:

Here's a couple of shots of the Amp. I'm going to solder the XLR connectors after I mount them in the chassis. I'll likely do the same with the POT.

Here's the underside. Lots of red drops...

t2amp002.jpg

Here's the top...

t2amp010.jpg

and here's the 5pF bypass caps on the 100K feedback resistors...

t2amp008.jpg

That was a bit of a marathon :) Next up all the power connections and umbilical cords.

Edited by Kerry
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