The ultimate DIY? A Stax SRM-T2!

[kevin gilmore]

use these for the fast diodes

DSEP12-12B Ixys Rectifiers

turns out the answer was actually in the kgsshv thread

make absolutely sure you get the teflon tube sockets. unlikely that anything else will fit.

use these for the octal sockets and i have extras of these if you want them, but ebay is cheaper

CONNEX Socket 8-pin, Octal (KT88, 6550, EL34, etc.)

and like this

http://cgi.ebay.com/Machine-made-Teflon-tube-socket-8Pin-KT88-EL34-6SN7-/220565777104?pt=LH_DefaultDomain_0&hash=item335abeaad0

use these for the 9 pin sockets

CONNEX Socket 9-pin, (12AX7, 12AU7, 12AT7, 6DJ8, etc.)

i don't have any extras of these.

http://cgi.ebay.com/Machine-made-Teflon-tube-socket-9Pin-12AX7-6922-6H3-/220565777143?pt=LH_DefaultDomain_0&hash=item335abeaaf7

will try to locate the other parts tomorrow.

Resistance is Futile. See kgsshv thread.

Edited November 13, 2010 by kevin gilmore

[blubliss]

Thanks, I already ordered the sockets from DIYhifisupply. I was referring to something on the BOM under hardware (line 5) which says 2 - 8 pin sockets. A mistake?

[kevin gilmore]

those are the 8 pin dip sockets. you need two for the amp board and 9 for the power supply board.

808-AG11D-ESL-LF Tyco Electronics / AMP IC & Component Sockets

another version of the bom with additional part numbers

http://gilmore.chem.northwestern.edu/t2parts3.xls

Edited November 13, 2010 by kevin gilmore

[Pars]

<snip>

And I can't find these:

100/3W 71-CPF3100R00FKE14 CPF3100R00FKE14

These should work:

CPF3100R00FKB14

100K/3W 71-CPF3100K00FHE14 CPF3100K00FHE14

CPF3100K00FKE14, 6 in stock, 100ppm instead of 50ppm tempco

100uf/50v 647-ups1h101mpd ups1h101mpd

8 pin socket ??

I found the FKE14 at Newark but the shipping is not nice and wanted to see if i could combine.

Thanks for any help.

And Colin/Nebby, watch the wallets

Caps, not sure, would probably look at panasonic.

[spritzer]

100uf/50V: 667-EEU-FC1H101

These should fit as I even manged to cram Elna SilmicII's in there...

[blubliss]

Thanks guys, just screws and wire to go now.

[n3rdling]

Very nice Andy!

[kevin gilmore]

There is still one complete chassis set with boards available.

[MASantos]

If only I had the money!

[pedefede]

There is still one complete chassis set with boards available.

hmm ... looking for the ultimate amp for my stax, and this seems to be the winner for a lot of years to come, so ...

my wife will hate me but.... i would like to buy the chassis+boards, if its still available.

peter

[Nebby]

Woot! Thank goodness for my wallet. I was going to ask if payment plans were possible

[kevin gilmore]

I'm sure there are payment plans. There will be one extra chassis in the final batch, which

i won't have polished or anodized till the beginning of january.

Its really nothing compared to the pile of parts.

[header]

Hmm .. is it possible to use other (less awsome, less ambitious) cabinets? For those that doesnt catch the chassis-run?

Perhaps you could even stack the amplifier board above the PSU, in a taller cabinet?

[spritzer]

If there were extra boards then sure, you can do something like that but it would be a lot of work. The modushop boxes are also very poor compared to the custom made unit. Since there aren't any extra boards this is a moot point really...

[pedefede]

hmm, got to select/source parts now ... As I mainly have my experience from normal pure tube speaker-amps, I would really appreciate some hints/comments, to my current ideas:

(SS - decition seems easy, "just" have to find the piece (bdent, future, allied, ebay) ). By the way - does any of the transistors need to be matched? (or just find close pairs for +/- part of the circuit)

caps - not a lot. Silver mica on small, PP on the rest - except PSU. Anyone tried bypassing the 680uF with say 1uF film caps?

Resistors .. wow, a lot. Of cause i can do like Spitzers suggestion (mainly good bang/bucks PRP). But i would like to add GOOOOD resistors (whipe drooling) to the critical positions - but where is that?

- My guess: is around the input/output parts, i.e. mainly the tubes. Like R 94/95, 7/8, 78/79, 96/97 ??!

(anybody know the voltage limit of tantalium resistors (Shinkoh, Audionote)

btw ... Partsconnexion has 20% discount for the rest of the week ... (damn, more drool)

Peter

1/2W PRP's can handle 500v and are relatively cheap so they make up the majority of the resistor with a few Rikens thrown in where PRP's weren't available. The 5W resistors are Mills. The only resistors I'm a bit worried about are the 5.1k/1W output units which will see the full fury of this beast... \

[jgazal]

Resistors .. wow, a lot. Of cause i can do like Spitzers suggestion (mainly good bang/bucks PRP). But i would like to add GOOOOD resistors (whipe drooling) to the critical positions - but where is that?

- My guess: is around the input/output parts, i.e. mainly the tubes. Like R 94/95, 7/8, 78/79, 96/97 ??!

Perhaps those on the schematics of the critical signal path (R9/R10 - R78/R79):

Bored and twiddling my thumbs waiting for semiconductors to arrive to fix the zapped T2, I thought I'd try to get a grip on what the actual signal level circuit was doing.

I've replaced all the current sources and 740V battery with ideal symbols. I've also left out compensation components, and some of the details of one or two current sources which I think are error handling, to prevent the thing blowing up if a tube goes down badly. I think the result shows the rather neat symmetry of the design, and the clever way in which DC voltage shifts are generated using the FETs and batteries to move the ground referenced input signal to -500V.

File is here http://www.tech-enterprise.com/tekstuff/T2deconstruct.pdf

And output resistors:

1/2W PRP's can handle 500v and are relatively cheap so they make up the majority of the resistor with a few Rikens thrown in where PRP's weren't available. The 5W resistors are Mills. The only resistors I'm a bit worried about are the 5.1k/1W output units which will see the full fury of this beast... \

Right?

I am using those on the BOM:

uploaded struts spreadsheet.

http://gilmore.chem.northwestern.edu/t2parts3as.xlsx

[nattonrice]

I vote for PRP.

Red is naturally superior to everything else.

[spritzer]

PRP is a solid choice and they continue to work fine in the BH amps I've built. I'm on a bit of a carbon film binge these days but you really have to match them as most are 5-10%.

[nattonrice]

Indeed! The nice thing is that they will cater to small orders for none-pcx stocked values.

For what it's worth the takman carbons I've used hold on average closer to 1%tol than the spec'd 2%.

[pedefede]

I vote for PRP.

Red is naturally superior to everything else.

The original T2 har xicon resistors - however quite a few have chosen other/better parts. It would be quite interesting to hear other peoples sound review/feedback/impressions, of their new amp - combined with their choice of combonents.

[luvdunhill]

You might want to take some time and convince yourself whether or not the Xicon resistors are magnetic... That would be the main reason not to use them in my opinion.

[Craig Sawyers]

You might want to take some time and convince yourself whether or not the Xicon resistors are magnetic... That would be the main reason not to use them in my opinion.

You'd be surprised how few resistor types are non magnetic. Vishay bulk foil, old fashioned Allen Bradley carbon composition, original Holco, and Dale mil-spec are all non-magnetic. Highly thought of and expensive resistors like Shinkoh and Audio Note tantalum, and RC55 precision film are all magnetic. As are all regular film types I have tried, like the Xicon. I'm not convinced that the magnetic characteristic is a determining factor in sound quality - there are many other resistor parameters that are more likely to influence sound quality.

[kevin gilmore]

whether or not the material is magnetic is only part of the equation. Any precision resistor that is spiral

cut to set the resistance is going to act like a coil. Way back when when i was designing stuff i had

a list of the military resitors that now reside in my basement, that listed the approximate number

of turns for each of the resistors in the stack. I would usually design for minimum inductance.

Or build in the inductance coupled with the capacitance to make filters out of single components.

Stax did this with one of the servo feedback loops.

[blubliss]

Progress

[ATTACH=CONFIG]3967[/ATTACH]

[ATTACH=CONFIG]3966[/ATTACH]

[Kerry]

Looking good.