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The ultimate DIY? A Stax SRM-T2!


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Nod, thanks spritzer. I may reach out in PM when I'm in a position to start really getting my shit together. Thanks in advance and hope Iceland is good :) My friends keep visiting and I keep trying to steer them to visiting your bakery :)

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Finished...   Back plates before I mounted them...

I finally got the last plate machined.  I had to replace the spindle on my CNC and also made a mistake on the CAD so had to redo this plate, but it's looking great now.  

Been busy at work, but managed to pull a new version of the T2 amp board together. I've added separate modules for the active batteries, balance servo, pre-CCS feeding the output CCS and the opto

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No capacitors or resistor issues that I'm aware of.  These are generic parts so there are always subs.

Some of the xicon resistors in the batteries are no longer available. I recall there were some other brands that people had success with, but that for the most part if xicon's weren't used in the batteries you would end up with a noisy t2. For someone like icarium he needs to make sure the large caps are short enough to safely fit in the case without being accidentally hit by a case screw. The one in the original bom is no longer available, though alternatives are probably out there.

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Thanks Spritzer. Any advice on 2SA1486 or is bdent the spot? I'm probably going to hit the 200 quantity price break.

You just need 34 1486 and 34 3675 per amp, if you are going with "all original" parts, so 200 is a lot more than you would need.

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Some of the xicon resistors in the batteries are no longer available. I recall there were some other brands that people had success with, but that for the most part if xicon's weren't used in the batteries you would end up with a noisy t2. For someone like icarium he needs to make sure the large caps are short enough to safely fit in the case without being accidentally hit by a case screw. The one in the original bom is no longer available, though alternatives are probably out there.

 

Use Vishay's and lift them off the board which does the same thing.  :) 

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You just need 34 1486 and 34 3675 per amp, if you are going with "all original" parts, so 200 is a lot more than you would need.

 

Oh yah I know. I'm an inveterate parts/gear hoarder so I want to keep some around just for the who knows what. And also in case they are used in other designs. I don't ever want to pay 6 dollars+ a piece if I had a chance to pay 3 dollars :) It seems like they will appreciate for sure so if I can afford it now.

 

Also who knows what I might need to trade for in the future :)

Edited by Icarium
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Almost all of the sand in the T2 can be replaced by modern parts. Look into JoaMat's updated T2 a few pages back. I plan to build something similar but fully solid state at some point, since there are now 1000V+ FETs with low enough capacitance available.

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I populated my build with fake 3675's.  Generated frightening cracking sounds and sparks.  Took out a bunch of FETS as collateral damage. With good parts it hasn't missed a beat.  I also got some fake FET's too that did not make the build. All from Dalbani in the UK - be warned.

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Good to see you posting here again!

I found all your bad experiences very helpful in building my t2 - I am sure it helped many others as well.

Any way to repost son of your photos of the fakes again as they are not working any longer.

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I believe under the JIS system that Sanyo had exclusive use of the 2SC3675 numbering. The right side transistor is obviously not Sanyo.

 

The one on the left looks like a perfect copy or genuine. If the numbering is not etched below the surface and printed instead or the tab and leads are not all copper, completely non-magnetic it's a fake.

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The one on the left is real but the one on the right... yeah... 

 

Even though I have more than 1000 2SC3675's in stock I don't think there is any sense to use them with the 2SC4686A available.  Having the main CCS short to the chassis isn't fun... 

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I do prefer isolated tabs. Does make mounting easier.

 

It goes without saying that isolated heatsinks are a solution. But if it's a clone amplifier or a repair then that may not be how the original was designed.

 

The data sheet device parameter curves are interesting to me to their differences given that both are stated as being Triple Diffused Planar types.

Edited by CraigBuckingham
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No good way to do that with our boards.  Going this way and using KSA1156 for the front end CCS means only the fets are non isolated.  That plus the new batteries will make the amp far easier to deal with. 

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Is it more important for the 3675's in the batteries to have matching hfe's, or for that hfe to be of higher value? Aside from three 3675's (which are 41x2 and 46) the rest of mine have a hfe between 50-70.

Edited by s_r
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Thanks Kerry.

 

Figured I may as well show my progress with the build:

 

post-3922-0-29960200-1423973404_thumb.jp

 

Still missing a number of xicons (as per the ad I posted) though. Unless someone has a chunk of them they're willing to spare I might pick up carbon takmans instead. Maybe just for the batteries in case vishays are fine outside of there.

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The resistors in the batteries were the ones that were leaking.  Make sure whatever you use are well insulated and are lifted off of the board. 

 

I originally used the red PRP and had them lifted, but they still caused problems.

 

EDIT:  Looks nice so far :)

Edited by Kerry
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