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The ultimate DIY? A Stax SRM-T2!


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Here is our work shed.


The amp is making music. I did say a serious prayer before I turned it on smile.gif

Hi, i'm a new user.

Congratulation for this perfect work!!!!!

I'm starting to make my first project, and i want to know were i can buy a case amp like that you have used in this project. Maybe a little bit higher.

Thanks and best regards.


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Good thing to see some vendor info in this thread. I am looking for some IRF230s for my brother's amp, and here is what UTsource sent as far as a device picture:


The markings on this don't look like any IRF I've seen... do these ring a bell with anyone else? I guess I'll have to go with Newark.

Just as a follow up.

UTsource kept sending me an email reminding me to order these, so I replied back. Here is their reply:

ok, thanks!




UTSOURCE.NET power by UTSOURCE International(S) Pte.Ltd.

Singapore Service Line : TEL : 0065-315-631-17

Email: [email protected]

USA Service Line : TEL : 001-818-698-1878

Email: [email protected]

&nb sp;

China Service Line : TEL : 0086-755-23959113

Fax : 0086-755-23959192

Email: [email protected]


发件人:Chris Young

发送时间:2011-11-10 21:10:31

收件人:[email protected]


主题:Re: Please place order to us for IRF230

Devices do not look genuine. No thanks.

Edited by Pars
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  • 2 weeks later...

Are these things good enough to measure (and match) small signal devices for hFe? Might need one for my Christmas list...

It depends. First, how linear is the device being tested with respect to hfe versus Ib? If it's linear, then perhaps it would work. If not, or you like to match at the actual circuit conditions, then you'll be out of luck.

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I have a test fixture that I use with 2 DMMs and a bench supply now, but it is time consuming (I'm sure you both know all about that smile.png). I just saw that this thing had at least 3 Ib ranges (10uA, 1mA and 10mA) and thought it might do the trick for all but critical matches. Probably something worth having anyhow, particularly given the price.

Intended devices would be stuff like 2SA970/SC2240, 2SA1016 and it's complement, etc.

Edited by Pars
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The 10uA should be useful. Was setting up my test fixture (if you can call it that) last night, and going thru some previous measurements. I'm using 24uA Ib and Ic is ~12-15mA. 10mA is probably my Ic target in general. On a BL device, the 10uA would get me to between 3.5 and 7mA Ic which is probably close enough.

I have no idea what the POS Centras or whatever that Harbor Freight DMM uses for hFe... probably much less than 10uA though.

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So I was in a local electronic shop the other, shopping for some test rig material. There I found that they have a small collection of japanese transistors, and I found these stuffed into a tiny compartment:


Looks like some real units are mixed with other very questionable quality units. They also have 2SK246GR, some 2SK216, K170, and apparently they are waiting for LSJ74 to appear. Quite surprised at what they offer locally.

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Black sheep has been finished (almost):

http://dl.dropbox.co...phone%20326.jpg (quick iphone pic in the dark)

Noise issue solved - Replaced shinkohs 390K, 820K, 100R in one of the batteries for xicons.

There is NO noise now, even at full volumen. Feels a bit wierd actually, to put the beast to full volumen, and to be unsure wether it has been turned on ... (I allmost blew my ears, when i accidently left the volumen at 100%, and put on a 1 KHz sinus signal ...death.gif )

You can measure the 50Hz noise from the unregulated heaters on the batteries ... but during to the balanced nature of the beast - it is canceled at output smile.png

It plays fantastic ...

I still have some to-do stuff

(balanced volumen attenuater with fixed resistors, optimizing balance by switching tubes, trying with current-stock.tubes, eventually replacing more resistors for Xicons)

(During measuring - i discoverd a small volumen-dependent oscillation (200KHz, 30mV pp at 100% volumen) . Too small to cure for now.

- but that can wait ... now i really just wanna listen to the sweet, sweet music - and improve my signal sources, to match this thing ....!


Edited by pedefede
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