Customized Stax SRA 12s vrs Non Customized Stax SRA 12s

[Scottsmrnyc]

I have both of these amps and I am not satisfied with the customized one.  Is there anyone out there in Headfi land that has a good customized SRA 12s?  How is it set up and what headphones are you using.  I use my Stax Sigma Non Pro 6 pins on the non customized 12s.  It is an amazing sound.  Not so good when I switch the Sigmas to the customized 12s?  Any and all comments are welcome.

 

[kevin gilmore]

we need to know what was customized.
 
That one is old enough that the original output transistors are
not and have not been available for some time. So if parts
were replaced its just not going to sound the same.

 

[spritzer]

Customized is meaningless to us as what was changed?  I have two of these amps here, the original Japan only SRA-10S and the later multi voltage SRA-12S and while they are supposed to be identical they are very, very different.  Input and phono boards are completely different, different input transistors on the amp channels and extensive changes done to the PSU.  These were just normal production changes but I've never seen any official work done on these amps by Stax.  Some might have been altered for use in studios as they were supposed to be used with the SR-X phones and thus for monitoring. 

 

[Scottsmrnyc]

Thanks for the responses so far.  I honestly don't know what was changed internally.  Externally the front panel has a new volume nob that is worse.  It clicks and you can't set the volume as exactly as on the normal one.  Additionally, One of the selections of Reverse and or Stereo doesn't work.  The rear panel looks the same on both units.  All I know is that the sound is so so.  It is as if the customized one is working in mono with no definition. 

 

[spritzer]

If you can open it up and take pics of both the interior and the plug in cards we might be able to solve this mystery.