Jump to content

The ultimate DIY? A Stax SRM-T2!


spritzer
 Share

Recommended Posts

42 minutes ago, Kerry said:

I have some 2SA156 that I got from BDent way back when that are green.  The 2SA1486 were all black.

Not sure what the different color represents.

I have a few from both with the same color as yours they came from Dalbani I think.

Link to comment
Share on other sites

1 hour ago, JoaMat said:

Back in 2011 I bought 50 2SA1486 from www.utsource.net.  Price 0.30USD each plus 28USD for FedEx, a few days from China to Sweden.

They were green and I haven’t used them at all, but they measure same on DCA75 and DY294 as 2SA1486 from bdent.

 Anyone tried www.utsource.net ?

A few pieces a few times from eBay I do not remember fakes but I am not sure I checked them all. Usually when I could not get from mouser what I wanted.

Link to comment
Share on other sites

I've measured 62s of mine 2sa1413 from bdent: 

https://docs.google.com/spreadsheets/d/1sadOLdhxStUQfL94wJkuKEtn7qOEWFBdP0m-BNzwVw0/edit?usp=sharing

It is interesting that green transistors were worse than black. 

And thanks to Helium - I've found that 2sa1413 has a twisted pinout - BCE instead of ECB for 2sa1486. 

Edited by Rinat
Link to comment
Share on other sites

6 minutes ago, Craig Sawyers said:

For a transistor mounted on a heatsink there 6 possible lead orderings, 3!. For a small signal transistor that you can insert either way round, that reduces to 3 effective orderings. 3!/2.

I'll get my coat...

It’s even easier for the ones not mounted on the heatsink. 😉

Link to comment
Share on other sites

  • 2 weeks later...
  • 3 weeks later...
3 hours ago, kevin gilmore said:

DO NOT ROLL TUBES on a T2.

Definitely do not roll fake siemens tubes as they cause the amp to blow up many expensive parts.

1000%. I have seen people do this with unfortunate results. Even what some consider to be drop in replacements for the el34, like kt77, should not be used. 

Link to comment
Share on other sites

52 minutes ago, GeorgeP said:

1000%. I have seen people do this with unfortunate results. Even what some consider to be drop in replacements for the el34, like kt77, should not be used. 

 

4 hours ago, kevin gilmore said:

DO NOT ROLL TUBES on a T2.

Definitely do not roll fake siemens tubes as they cause the amp to blow up many expensive parts.

by do not roll tubes meaning don't stray from the recommended 6922 and el34s? i do roll different el34s and 6922s sometimes.

Link to comment
Share on other sites

3 hours ago, kevin gilmore said:

6922 and el34 only.

the pinched waist siemens tubes on ebay for stupid amounts of money are all fakes that blow up as soon as you put 75 volts on the grid.

Thanks for the clarity Kevin! definitely not playing around with such a stern guideline!

  • Like 1
Link to comment
Share on other sites

6 hours ago, GeorgeP said:

1000%. I have seen people do this with unfortunate results. Even what some consider to be drop in replacements for the el34, like kt77, should not be used. 

I know a man who replaced EL34 by KT77 successfully, with slighly changed sound. These tubes was not from JJ and I know that JJ's KT-77 are not suited for T2. 

15 hours ago, rayofsi said:

would the diy t2 circuit handle something like the e288cc tubes for the preamp section?

I would'nt be so adamant as Kevin - In my opinion you can change anything, but only with a really careful recalculation of the scheme. If you are not sure that you can handle it yourself, don't do it. 

I am going to try 6N23P-EV, but only because it is a direct replacenment for 6922 and I've measured every tube with good results. And am going to check all again, maybe even twice. 

Edited by Rinat
Link to comment
Share on other sites

On 12/3/2021 at 4:12 PM, bbest said:

I tried to buy 2SK216 here:

wehavethatitem

https://www.ebay.com/itm/283871974560

also fake, seller agree on refund

Hi, I read Kevin mentioned in the past that KSA2690AYS (160V capacity) works fine as substitute for K216 except pin layout.  They are cheap on Mouser.  BTW KSA1220A can be used as J79 replacement, but it's not available.    Then I learned that J78/K215 (180 V capacity) or J77/K214 (160 V capacity) should work as well, and they are pin compatible with J79/K216.   Do I understand anything wrong?   They also aren't popular, but maybe easier to find and slightly cheaper than J79/K216.

Link to comment
Share on other sites

15 hours ago, Rinat said:

I would'nt be so adamant as Kevin - In my opinion you can change anything, but only with a really careful recalculation of the scheme. If you are not sure that you can handle it yourself, don't do it. 

Kevin is talking about his amplifier, the DIY T2. Of course you can design another one and change everything.

Link to comment
Share on other sites

NO, the incident with the T2 was a real original T2. The fake siemens tube made on RFT equipment arcs over when you use it in the cascode position. Then it shorts out the gain tube and puts 200 volts on just about everything in the front end including the volume pot. Lots of damage. 

I've never tested with lower voltage rated parts. probably they will eventually blow up as the 2sk216 definitely sees about 200 volts on it.

  • Like 1
Link to comment
Share on other sites

1 hour ago, kevin gilmore said:

I've never tested with lower voltage rated parts. probably they will eventually blow up as the 2sk216 definitely sees about 200 volts on it.

Sorry, I found that compatibility discussion on GG thread.  "in the original kgbh, the 2sj79 can be replaced with a ksa1220A".    I wasn't aware the difference of requirements between GG, BH and T2.  JoaMat also confirmed that Ksa1220A worked for his BH and DIY T2, but probably with lower voltage setting.

BTH I found a guy selling tk7a90e cheap.  It's 900 V 45W Nch MOSFET.  Does this work in the place of K216?  or it's not that simple?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.