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The ultimate DIY? A Stax SRM-T2!


spritzer
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Why did actually the T2 end up using a 50k pot and not like the other KG designs, BHSE, etc a 10k? I think at 2012 time frame the RK50 was available in 10k so the DACT (which still is). 

Edited by starcat
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4 hours ago, Craig Sawyers said:

Then there is this http://www.tkd-corp.com/products/att/pdf/p65cs-e.pdf which is what Curl used in the Blowtorch. He used a stereo one, not four channel, because Blowtorch was not inherently a balanced preamp.

It is available in four channel, I have no idea of the price, but expect it to be substantial.

Then there is the Seiden 74005, 58 position 4 channel switch. You need to add resistors of course. That switch is Y47,000 direct from Seiden ($430, shipping, taxes etc on top). Depending on the resistor choice you could be back in RK50 territory or beyond.

Although the Seiden price list is 2012, that is the one that Seiden sent me in Feb 2020.

I have not tried either the TKD nor the Seiden, but at least considered the Seiden for another project (pending) that needs a really weird attenuation law.

SEIDEN.pdf 531.84 kB · 4 downloads PRICE_LIST_2012.10.pdf 315.56 kB · 4 downloads

That TKD pot (2-gang) is also used in the Audio Note M7 preamp.
I looked up its price at Michael Percy’s site many years ago. I don’t remember the exact number, it was expensive but I did not choke on it. 

Edited by mwl168
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Had to use tricks 🙂 to hold the 10PPSG washer in place on the K216 as it rotates awfully during tightening.

IMG_2052.JPG

Lifted the 6DJ8 teflon socket as much as possible as they are lower than the 6CA7. Resistors are all Xicon 273 series and raised 1.5mm from the board.

IMG_2056.PNG

Edited by starcat
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Would like to test the J79 and C3381 prior soldering them. Anyone can help? Every other component I have tested on its own prior soldering.

Decided to use the KSA1156 on the heatsinks instead of 1486, despite having them. From what I've read it shouldn't matter at all. Everywhere else using 1486. No other mods whatsoever. Curious to hear what Dr. Gilmore thoughts are regarding this. @kevin gilmore

Thank you, highly appreciated. 

Edited by starcat
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Good NOS (heh) 6922s are probably rare as hell anymore. When I used to have a tube preamp (Counterpoint SA5.1) 10 years ago, I had a pair of Amperex PQ white label 6922s in it, which I really liked. The EH 6922 gold pins are quite good. If you can manage to find some vintage, you will pay out the nose for them, and possibly get ripped off.

Some seemingly decent recommendations for dealers here: https://www.thegearpage.net/board/index.php?threads/online-tube-dealer-sticky.1197164/

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Thanks, guys!

Found this here as well https://www.head-fi.org/threads/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes.761078/

Looks like the Valvo E88CC CCa Herleen white imprint and gold pins is a best buy for around 90/pair here in Europe.

Interesting the list above is headed by a Russian REFLECTOR make with silver shields specifically from 1975, even in front of Telefunken or Siemens. They are talking "solid state fast and precise, but with tube liquidity and warmth". 

Edited by starcat
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  • 5 weeks later...

I've been trying to understand what should I measure to be sure that a transistor is genuine, for example in case of 2SK246-GR. But what if I will replace it with 2SK208?

It is still in production and it is just a SMT version of 2SK246, with lower max power dissipation (100 mW vs 300 mW).

But in the original scheme of active battery power dissipation of the JFET is around 1-2 mW. So... It would be ok to use 2sk208. 

Am I right ? 

Thanks and I hope it would help someone else 🙂 

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I've definitely helped someone, who had immediately bought all 2sk208-GR from digikey 😄. There is only an R-grade on mouser/digikey with very low Idss now ((

Did someone try to buy something at arrow.com ? They have 2sk208-GR at japanese warehouse and FQP8N80C. 

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I think I know who that was. And it is not someone on this list or associated with it. I mentioned the 2sk208-GR to him by email, and he told me he had previously bought 3,000 of them, before I even mailed him.

By the way, TI have just introduced a low-noise n-channel JFET, the JFE150 (0.8nV/root Hz, and 1/f corner at 10Hz) https://www.ti.com/product/JFE150 . Apparently this is just the first in a series they are planning, with n-channel monolithic duals (apparently imminent), and possible p-channel versions.

They are quite serious about the audio market, with a superb and growing portfolio of audio op-amps.

Unlike On-Semi; don't start me on that soap box....

Edited by Craig Sawyers
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