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stax mafia circuit boards


kevin gilmore
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All the T2 amp boards are a single monolithic slab (except the version I modified). The non shrunk versions are more than 400mm deep and will not fit into most diy chassis like the disapante 400mm. Also they have solder pads for a very expensive and now not easily available volume pot.

Original T2 uses almost completely obsolete transistors which are both very very expensive (if you can even find them) and almost all the sellers e.g. ebay etc are selling fake parts anyway.

t2schem.PDF

So if you have not got the transistors already from known good sources you are looking at probably looking at 10-30+ dollars PER transistor and there are a lot of transistors.... The original T2 amp board was massive... too large to fit into a 400mm deep case! so there was also various attempts to make it smaller:

t2shrunk.zip

Hence the number of different T2 gerber zip files. 

I would very roughly guestimate budget $1000 just for the transistors for the amp board. If you make a build error and the magic smoke comes out things can get real expensive real quick. Building an original T2 is going to be fraught with danger and failure unless you can find a reliable source of non fake parts or have them already for a know good source. You also need resistors that can handle the high voltages without the insulation breaking down. Xicon 273 series worked for me and KOA mf1/2 seem ok. PRP appear to fail.

Joamat plus others worked on a version of the T2 which used mostly still in manufacture transistors but still requires 12 obsolete resistors:

staxt2nc3fdh7.zip   t2schemmodified.PDF

shrunk version 398mm deep: 

t2shrunk2.zip

shrunk version but with solder points for an alps potentiometer

t2shrinkedv10.zip

This is the version I built. Fortunately I purchased the obsolete transistors from a very well known forum member who purchased them from a known good supplier when they were still available. There is no known version of the full T2 that only uses modern parts....

independent of this there are also three versions of the power supply, (the golden reference power supply series is not suitable because it can't handle the high voltages required for a DIT T2).

Joamat et al created a fully regulated version using the lt10 voltage reference: 

   t2250kgsshv.zip   t2hvandlvpsukgsshv2.zip

(the same reference that is in the golden reference LV and HV boards so I went with this). The other designs use a ref102.

 t2schempower-2.PDF t2250.zip  t2hv2.zip

joamat told me the lt10 had lower noise and since I bulk purchased lt10 references I went with his psu boards.

I posted the modified gerbers I made and a circuit diagram for the joamat T2 plus power supplies in this thread a short time ago in the diy t2 thread https://www.head-case.org/forums/topic/6837-the-ultimate-diy-a-stax-srm-t2/page/190/. The modifications to joamats gerbers documented in the post to fit my build style (one pcb per channel, no solder points for a pot etc), a few silk screen error corrections and placed a missing track in one of the psu boards and some more ventilation space for the 3W resistors in the psu boards etc etc. 

 

 

Edited by jamesmking
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On 1/23/2021 at 6:15 PM, jamesmking said:

(the golden reference power supply series is not suitable because it can't handle the high voltages required for a DIT T2).

I have a reworked board layout of t2hvandlvpsukgsshv2 to a golden reference style T2 power supply.

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James, JoeMat, thank you very much. I will be building the original T2 in the black Dr. Gilmore case with the RK50. A valuable forum member was kind enough to provide the bulk of the transistors, some are coming from BDent. Ordered everything else from mouser, custom transformers from mueller-rondo. Some parts already showed up. Will be posting in the T2 thread how everything goes. 

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  • 4 months later...

If anyone needs Carbon or Dynalo PCB's, I have a few left. All very high quality with 2oZ copper.

Carbon in either SMD version being built by myself or standard TH version "kgsshvcarbon6ground2".

Also SMD version Dynalo with GRLV and kits of PCB's with genuine matched MPSW56/06. I have enough from my own needs to put together a few kits.

https://i.ibb.co/fQ6bxth/IMG-2854.jpg
https://i.ibb.co/r3rdDBf/IMG-2855.jpg
https://i.ibb.co/bRQXk9c/IMG-2856.jpg
https://i.ibb.co/qjRfZWx/IMG-2857.jpg
https://i.ibb.co/wMQTjRm/IMG-2859.jpg
https://i.ibb.co/fYHX3Bg/IMG-2860.jpg
https://i.ibb.co/mBQQQhx/IMG-2861.jpg
https://i.ibb.co/py0v4CW/IMG-2862.jpg

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