The ultimate DIY? A Stax SRM-T2!

[kevin gilmore]

You're the main man - hats off sir! Helluva job - how you find the time *and* hold down a 9 to 5 beats me!

I multitask very well.

If i was just 21 years old again, the whole thing would have taken only 2 months.

(subject to availability of parts)

[grawk]

when you were 21, transistors were easy to get :b

[kevin gilmore]

when i was 21, a lot of stuff was still tubes.

power fets did not exist. Things like 2sc3675 and 2sa1486 did not exist.

Capacitors of equivalent value were 4 times the current size.

[Inu]

...and STAX did not exist.

[mypasswordis]

...and STAX did not exist.

Before Christ = BC. Before Stax = BS.

[kevin gilmore]

...and STAX did not exist.

Wrong you are... Stax's first commercial product was made in 1950.

4 years before i was born.

[Craig Sawyers]

i added an extra battery to the schematic, output a bom, multiplied everything by two

and this should be the right number of resistors and values

http://gilmore.chem.northwestern.edu/t2schem.txt

someone please verify.

Checked line by line, with minor differences on capacitors at board level:

0.47u, 12 off required - 2 extra are used on U8 decoupling both channels

0.1u, 4 off required - 2 extra used for U8 decoupling both channels

High voltage power line decoupling not on schematic (and hence not on schematic BOM printout)

But that's it. Exceptionally close. Resistors and semiconductors all A-OK.

Craig

Decoupling on

[Craig Sawyers]

Checked line by line

Forgot to mention that the checking process also found a couple of errors in my version of the BOM; I'll do another check through and then get it across to KG.

Craig

[kevin gilmore]

updated schematic with all decoupling caps.

http://gilmore.chem.northwestern.edu/t2schem.pdf

text list of parts for power supply

http://gilmore.chem.northwestern.edu/t2schempower.txt

[n_maher]

Just an FYI - neither of those links works for me, Kevin.

[kevin gilmore]

Massive connectivity problems between NWU and the rest of the world for about 30 minutes.

Everything should be OK now.

[n_maher]

Yup, everything's 5x5 now.

[Craig Sawyers]

when you were 21, transistors were easy to get :b

When I was 21, IC's were difficult to get and the 4040 was a shiney new thing. Pass the walking frame.

[spritzer]

When I was 21... never mind, it wasn't that long ago. I did have a SR-007 though.

[kevin gilmore]

For those doing the DACT instead of the RK50, here is the howto

mouser part number 517-647-07-36

unsolder the pins from the DACT.

cut the above pins into 3 pin pieces

bend the above pins approprately to fit.

Use 2 bars of metal (or whatever) .280 inches to space

the thing off the board, then solder.

http://gilmore.chem.northwestern.edu/dactmtg.jpg

[swt61]

When I was 21 Yamaha introduced the YH-1000 Orthodynamic headphone. And I bought one.

[spritzer]

I've got confirmation that my TKD 4CP-2508 (special HQ version of the 2500 line) will be shipping soon so expect a how to fit one to the T2.

[kevin gilmore]

The idea on the DACT is to make an aluminum angle bracket, and secure it to the hole provided

in the circuit board.

[Craig Sawyers]

The idea on the DACT is to make an aluminum angle bracket, and secure it to the hole provided

in the circuit board.

This all looks great Kevin - thanks for looking at this!

[spritzer]

The idea on the DACT is to make an aluminum angle bracket, and secure it to the hole provided

in the circuit board.

Yup, same deal with the TKD as they don't have PCB terminals.

[Craig Sawyers]

Yup, same deal with the TKD as they don't have PCB terminals.

I had some problems with TKD. In fact I'm looking at the part now - 2CP-2511, a 100k stereo unit. There is no good and solid electrical connection between the metal shaft and the grounded fixing bush, so you get a really irritating whoosh or crackle as you turn the pot. I though it was faulty, so I returned it (HiFi Collective - they are a good bunch) and they cheerfully replaced it. The replacement did precisely the same thing - so it looks like a generic "feature". Just replaced it with a DACT, which is a source of joy (and a bunch more expensive than TKD).

Could certainly be overcome with a spring leaf bearing on the shaft and connected to ground - I've seen this done in Tektronix 7000 series plugins before, presumably for the same sort of reason - and there is certainly room in the T2 to fudge this in if it turns out to be a problem.

Craig

[Pars]

I had a problem like this with one from Michael Percy. He suggests conductive grease (the silver bearing stuff). Did the trick, though I would agree, TKD should do something about this.

[spritzer]

That's a strange design choice for sure since this line of TKD's are made for the Japanese broadcasting industry. A spring leaf would certainly work and it would be easy enough to fit it to the L-bracket holding the attenuator in place.

I would use the DACT if I could stand steppers but sadly I can't. I've even gone so far as to custom order a production run of 4-gang 50k pots (should get the first sample soon) and scoured the earth looking for more alternatives. Now if I could fit a 4-gang, 64 step Shallco in the T2 then I might stop looking for pots...

As for the price, a DACT should cost about the same as the TKD. I'm paying roughly 20KYen for a 4CP-2508 and a 4 gang DACT is 230$ from Justin.

[Craig Sawyers]

That's a strange design choice for sure since this line of TKD's are made for the Japanese broadcasting industry.

Yeah - I was surprised too. And suprised that being Japanese they haven't fixed it.

As for the price, a DACT should cost about the same as the TKD. I'm paying roughly 20KYen for a 4CP-2508 and a 4 gang DACT is 230$ from Justin.

I can't seem to find it now - but earlier today I found a Japanese high end retailer who had them on for 11KYen - hence my comment about cheaper. But for some inexplicable reason, it is significantly cheaper to buy a DACT from Justin, and get it shipped across the pond than it is to buy it in the UK. The damned things come from Denmark - so Denmark - US - UK is cheaper than Denmark - UK. Go figure, and good on Justin.

The four-gang DACT sits in front of me, accusing me of not getting on and populating the T2 boards.....

[spritzer]

Yeah - I was surprised too. And suprised that being Japanese they haven't fixed it.

Well Stax are still shipping the "broken" SR-007Mk2/A...

I can't seem to find it now - but earlier today I found a Japanese high end retailer who had them on for 11KYen - hence my comment about cheaper. But for some inexplicable reason, it is significantly cheaper to buy a DACT from Justin, and get it shipped across the pond than it is to buy it in the UK. The damned things come from Denmark - so Denmark - US - UK is cheaper than Denmark - UK. Go figure, and good on Justin.

The four-gang DACT sits in front of me, accusing me of not getting on and populating the T2 boards.....

11K for the basic version would be about right but I factored in all the fees etc. The 2508 is about 14K at the store all in.

This might belong in the Stax thread, but did you catch the newest issue of Hi-fi news? They are doing some tests on a Quad ESL as a part of their vintage roundup...