The ultimate DIY? A Stax SRM-T2!

[mortal_fiend]

Managed to get a hold of a set of blue boards.  I've got most of the basic stuff in them already (caps and resistors), however I'm not really having much luck finding the sand I need.

[Craig Sawyers]

Just about every useful piece of audio silicon is obsolete.  Low noise bipolar (at lease those with sensible noise specs like contours and rbb' spec) are dead, such as 2SB737.  Low noise FETs - although LSK170 are now easily available LSJ74 are only sporadically available.  Original 2SK170 and 2SJ74 are like hen's teeth.  A shed load of silicon for the T2 is now obsolete, as with original Blue Hawaii.  Low noise dual FETs 2SK389 and 2SJ109 long dead, although at least LSK389 is now available.

 

This often happens when companies merge or are acquired, and product ranges are "rationalised".  A prime example is one of the lowest phase noise SC-cut ovenised clocks on the planet was made by Oscilloquartz - the BVA.  Lower phase noise than rubidium and deployed in space missions.  Also used by high end digital audio nuts with deep pockets.  Taken over 2014 by ADVA a year after the highest spec ever BVA-C was introduced.  The BVA has now been discontinued. http://www.oscilloquartz.com/textes-history-563.  For the comfort and convenience of - er - the shareholders or private equity piranhas. 

 

Boy oh boy does this grind my gears.

[mortal_fiend]

Bdent seems to have most of what is needed (at an exorbitant price, but hey, beggars can't be choosers).  Do they offer a matching service or is just luck of the draw with them?

[nopants]

what needs to be matched in the T2? The quantities in their stock probably make matching prohibitive

[GeorgeP]

Pretty sure no matching is needed tor the T2. 

[spritzer]

Yup, no matching needed. 

[mortal_fiend]

That's good news as far as my wallet is concerned.

[G600]

Dr Gilmore said that the LED must be 2.1V.

I've ordered the recommended Lite-On, and they appear to be 1.9V on my cheap chinese tester.

I presume it's alright ?

 

Another question regarding the 3W resistor.

The old BOM says 3W, some PCB say 1W.

The 5.11k one is stocked at 2W (Vishay/Dale), not 3. And could be obtained at 5.1k (Vishay/BC)...

This has already been discussed, but I can't find that info.

 

Thanks

[GeorgeP]

Your LEDs sounds fine.

 

My recollection was that 3W was not mandatory, but I cannot recall for certain. Pretty sure some successfully used 1W in place of 3W (a search with "1W" should show you who).

[samsie]

I know it is  a long shot.  any one have a spare set of boards available.

 

 I'd  love to buy it  from you. ;-)

[nopants]

900 USD

 

I kid, but someone is selling the Lil' Knight version on headfi

Edited May 27, 2015 by nopants

[GeorgeP]

900 USD

 

I kid, but someone is selling the Lil' Knight version on headfi

 

That fellow is also selling an "almost finished" T2 that appears to be from Lil Knight. If you do a search you will this was one of the chassis he had made (prior to stealing a bunch of peoples' money).

[nopants]

yeah I guess that's the line we walk in DIY, also why I'll never accept money upfront for a commission

 

the price for that chassis and that much completion isn't actually ludicrous, always an option for someone who wants one

[GeorgeP]

yeah I guess that's the line we walk in DIY, also why I'll never accept money upfront for a commission

 

the price for that chassis and that much completion isn't actually ludicrous, always an option for someone who wants one

 

No, assuming everything is perfect and no fakes and proper resistors in the batteries. My view is that in the case of a T2 it is worth less partially assembled than the parts alone... troubleshooting could potentially take as long as the entire build if something is amiss... and I am guessing that almost complete chassis isn't plug'n play.

[samsie]

made me wonder why the builder did not finish the job.

[nopants]

george implied the builder is lil' knight, whose history has been chronicled around the internet

 

you probably just need to fab the boards yourself, the gerbers are available. Make of 5 boards for the amp and psu and sell the other ones

[G600]

Thank you GeorgeP.

[DefQon]

Oh wait for Michael to do a gb run of the T2 boards I suggested to him.

[samsie]

Is it possible to build one in a single chassis instead of separate power supply and amp?

 

The amp and power supply share the same heat sinks.

 

Of course the height of the case will be increased and heat sinks even bigger.

 

any pros and cons?

[nopants]

nothing stopping you from making whatever case you feel like

[GeorgeP]

Is it possible to build one in a single chassis instead of separate power supply and amp?

 

The amp and power supply share the same heat sinks.

 

Of course the height of the case will be increased and heat sinks even bigger.

 

any pros and cons?

Sure it's possible, but I would expect it would make the build significantly more difficult. Plus if you are maintaining the same footprint you would have transformers and power supply mounted under the amp board - a great way to collect even more heat and keep it in the chassis.

[samsie]

I am considering putting 2 of the transformers on the top planels. I think there's sufficient space between the el34 and the driver's tube

[G600]

Big children are happy with weired toys... At least no Lenesas here !

(always crappy pictures with me)

 

[G600]

While going very slowly, I inspected my blue board PS and have a question.

It looks there is a mistake on it at filament relay.

Are the 3 lower rows of pads supposed to be connected together ? I have continuity from a row to another (except the upper row obviously).

[GeorgeP]

That sounds right - not a board error. If you want further assurance, the schematic and board pictures will show the same thing.