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The ultimate DIY? A Stax SRM-T2!

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7 hours ago, Craig Sawyers said:

A question for the few who might have an original fried-egg-temperature-case original Stax T2 - is there a problem with the battery trimmers in that?

Not that I've heard but then again...they have so many issues (and noise) that it might just be lost in the haze. 

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I finished my fourth original DIY T2 a couple of weeks ago. All with Xicon resistors. No elevation above PCB of components except for power resistors. Initial settings of batteries have been straight forward and the three first amplifiers have been silent, no audible hum or noise to my ears. But this last one has some low “static noise” from power-on which disappears after approximately 10 minutes.

 

Now I’ve replaced all four trimmers on left channel with resistors and it didn’t change the noise behavior at all. Than I thought maybe I’m eventually punished for not elevating components - so desoldered all left channel battery resistors and put them on the other side with no ground plane and… no change on noise. But as it vanish within 10 minutes I maybe should accept Birgir's view of the T2 and be satisfied. Just grabbed a bottle of red wine and enjoying

Cliburn-album-cover.thumb.jpg.8746a8742bb66b1a635d5cd2e6c9242c.jpg

this.

Edited by JoaMat

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Try looking at a scope to see if the noise is on the + or - leg of the channel. This helps to identify where to put your attention. 
 

Good luck and above all, enjoy :) 

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Well, by accident I found Head-Case and “The ultimate DIY? A Stax SRM-T2!” on internet in 2011. Read that thread back and forth several times and I became kind of absorbed by the clone Stax T2. So it’s actually you Craig and Kevin, Birgir, Kerry, INU, et. al. that dragged me into this – I’m very grateful for what you all did to get the DIY T2 possible for armatures like me to build.

 

After managing to build a KGSShv successfully I felt ready for the real thing - DIY T2. Bought boards from Tran and I actually succeeded with this monstrous project and had a working amplifier - at least for a while. Then all kind of problem popped up. Somehow I did fix them but eventually I found it meaningless to continue with that amplifier. Reason for the problems was probably myself (Builder Induced Failure) but it gave me a lot practice.

 

My impression was that the quality of the boards Tran sent me was a the lower end. So I order five high quality amplifier boards. Desolder all the expensive sands including c3381 and used them on a new board. Believe it or not but it succeeded despite reused sands - no popping up failures. Then I started to make some modifications (don’t ask me why – just a bad habit) most of them worked. As I thought I needed an unmodified as reference I built the third T2. Now it felt like - just put the right component in the right position, power on, adjust batteries and you are set. But of course I started to fiddle with the new one as well.

 

After a long hike with my wife this summer. 820 km/ 510 miles in 31 days I felt it is most  appropriate to have an original DIY T2 again (I still had three amp boards left).

 

That’s why four.:)

Edited by JoaMat
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The new T2 has behaved in a good manner for a whole month. Now qualified for old good tubes...

BZ8A0289.thumb.jpg.c202112abe5f9a890324937577b94796.jpg

...Amperex Bugle Boy to the left and Brimar to the right.

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23 hours ago, JoaMat said:

The new T2 has behaved in a good manner for a whole month. Now qualified for old good tubes...

BZ8A0289.thumb.jpg.c202112abe5f9a890324937577b94796.jpg

...Amperex Bugle Boy to the left and Brimar to the right.

Is that a custom chassis of your own crafting?

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Yes, heat sinks and front/rear panels are from modushop.biz. Brackets and aluminum plates for top/bottom covers from local shops. Drilling, tapping and other crafting done in kitchen.

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