[spaghetticode]

Hello everybody,
 
I own those old Stax SR40 phones since when I was a child in the late 80s, I'd been using them for a few years for listening to classical music till mid 90s, then put them away. Yesterday I decided to put them back use again, so I connected all the hardware and tested them with some music. 
 
Unfortunately the phones don't seem to be working fine, and I doubt the problem is the amp: the music comes out very low, and the worst thing is that if I pump up the volume to the max the sound gets to a normal level, but it gets really crappy, it seems like the music is frying. 
 
I tried to look around the forum for similar issues on the same Stax model but could not find anything similar. Is there anything that I can do to fix them?
 
Thanks In advance
 
Andrea

 

[NA Blur]

Are you using the SRD-4 with the SR40 headphones?
 
Is there a bias adjustement on the amp?  I think they take a while to come up to full charge, but not more than a minute or two.
 
What input source are you using at what is its volume level ( i.e. what DAC )?
 
From what I remember you go:
Source to Speaker Amp ( non E-stat )
Amp output to SRD-4 energizer
Energizer to STAX headphone
 
Please explain your exact setup a bit more and we should be able to help.

 

[spaghetticode]

My setup is the same as in the 80s, so I was expecting everything to work (almost) exactly as back in the days.
 
Yes, of course the adapter is a Stax SRD-4. I used both a Philips table CD player and the computer soundcard as sources, the amp (Kenwood, but I can't tell you the exact model as I won't be home until saturday) works fine with dynamic headphones and loudspeakers, so I'm quite positive the problem is the Stax setup.
 
I left them playing all night long and there was little improvement, if any. 
 
Yesterday evening while googling  I found an Italian source that said those elecrets in time loose the factory "prepolarization" and eventually become inoperable. (see here http://forum.videohifi.com/discussion/132164/stax-sr-40-le-cuffie-ad-electret-si-esauriscono/p1).
 I could find no other source in the web that reported the same issue with electrets so I don't know if the information is reliable or not, but it may explain my problem. 
 
This is rather sad as I remember the cans sounded quite decently and I'd rather avoid spending some hundred bucks on new decent headphones, if I can.

 

[nick n]

Assuming wires are correct on the speaker terminals, and nothing appears amiss inside the adapter box itself, that may be the only thing left to consider.
Unless they were stored in detrimental conditions, or were over-volumized at some point by mistake the electrets can last a long time. I have a 40 year old pair out of the box that work perfectly, though I also have experienced some ones with imbalances and symptoms like you describe but am not sure why they are that way having no background on those sets' history.
 
Nothing in the way of odd switchings on the Kenwood that might interfere, 2 things on at once?
 
At any rate here will get you more traffic ( or should ) on this post if you transfer it over
http://www.head-fi.org/t/588716/vintage-stax-repair-and-maintenance

 

[spaghetticode]

Thanks for the hints. Right now I'm away from home and I won't be back home to check the equipment until saturday. As soon as I can I will check more thoroughly the hardware, hoping to find the reason for the weird behavior.