Amek M2500 transistors

[Bill Wilson]

The original transistors in the Neotek & Allison mike pres were MPS4403; they are no longer available.
A good substitute would be 2N5087's. They were not specd. as low noise but when 2 or more are in parallel
they become very low noise. My recreation of the original Neotek Series 3 console mike pre are extremely quiet.

 

[gar381]

BC560C works very well to replace the ZTX214s
in my Angela mic-pre which is almost the same as the M2500 mic-pre.
Been there ...done that

GARY

 

[MidnightArrakis]

It's actually a very straightforward circuit but it's drawn in a rather confusing way.

[it's drawn in a rather confusing way] -- I did not find this schematic to be "drawn in a rather confusing way" necessarily, but I was wondering that if Pins 3 & 4 were swapped, so the ( + ) sign was at the top and the ( - ) sign was on the bottom, would doing so make any difference? The circuit seems to be nearly "identically parallel" all along its path, so I am only guessing that the output signal polarity might be reversed. Any comment?

/

 

[abbey road d enfer]

I am only guessing that the output signal polarity might be reversed. Any comment?

The return of the living thread...
Q7-10 invert the + signal, then U2A reverts it, which makes it positive, and it goes to the positive input of U1.

 

[glbaudio]

If you find, 2SB737 is a great substitute option.

 

[abbey road d enfer]

If you find, 2SB737 is a great substitute option.

They are now as rare as hen's teeth. Beware of fakes.
I'd use those ZTX951, you may use just one per side instead of four.
https://www.proaudiodesignforum.com/forum/php/viewtopic.php?p=17282&hilit=ztx951#p17282

 

[zzzzz]

not sure if even relevant anymore, but I've used both KSA992 and 2SA970 in this circuit with good results. 2SA970 is no longer available but I have a decent backstock. KSA992 had better noise performance iirc and is cheaper.

 

[user 133392]

They are now as rare as hen's teeth. Beware of fakes.
I'd use those ZTX951, you may use just one per side instead of four.
https://www.proaudiodesignforum.com/forum/php/viewtopic.php?p=17282&hilit=ztx951#p17282

+1 on the ZTX951.
I have them in stock as well as the 2SB737's I got from JR.

 

[Whoops]

Guys just to let you know this thread is from 2016,
the op last reply to this thread was in Jun 10, 2016, and he doens't even login into this forum for more than 1 year.

I have no problems in threads getting revived when a new related subject appears, but it was just to let you know that the original poster is not looking for answers to this for a long time. He is not looking for these transistors for 7 years already

 

[user 133392]

Guys just to let you know this thread is from 2016,
the op last reply to this thread was in Jun 10, 2016, and he doens't even login into this forum for more than 1 year.

I have no problems in threads getting revived when a new related subject appears, but it was just to let you know that the original poster is not looking for answers to this for a long time. He is not looking for these transistors for 7 years already

Yes, understood, but the response is relevant to the general readership today and search indices.