• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Stax SR-3

E

elektronror

Well-Known Member
I may soon have a pair of Stax Sr-3 headphones with the ''preamp'' in my collection and after reading some reviews on them i could not be more excited!

Only thing is, since there are dangerous voltages in the ''preamp'', are there anything i should do before i test them? I know there are 2 capacitors that could not hurt to change but should i do something with it before i use it?

Would also be nice to hear what people here think about them. :)
 
Register to hide this ad
Hm. Silence. Well, let's start with nomenclature. What you're calling a "'preamp'" is nothing more than a metal box with step-up transformers plus a DC circuit to put a steady charge on the diaphragms.

The only truly dangerous voltage inside the box comes from your wall outlet. The 250 or so volts DC for the diaphragms is all volts, no current, so you might get a small poke from it but no harm would result. It's static electricity.

What to do with it before you use it...? Admire it. It was arguably the most advanced headphone of its day, so far ahead that we can still enjoy it today. That's about it. But there is a one-time-only procedure for bringing long-stored electrostatic headphones back to life:

Plug the SRD-5 into some mains power and connect the headphone to either of the SRD-5's headphone output connectors and let it all sit overnight to let the diaphragms charge back up, especially if the headphone hasn't been used for decades (it was probably made around or even before 1970). Don't play music through it until the next day.

Once the diaphragms are charged, they'll stay charged and the headphones will be ready to use the moment you put them on.

I think you'll be pleasantly surprised.
 
Okay, so once i get them i should plug them in over night before i start using them. But , how is it with the components in the actual metal box, are they good quality? Dont want to blow anything since its hard to find the box.

There was actually two headphones (both are the ''new'' SR-3) in the bag that was left for me at the radiomuseum but the metal box was gone! Someone had brought it home to throw it away, strange thing to do? Yes... But he will return it on friday so hopefully i can listen to them this weekend.

Both of the headphones seems to be in good shape. Nice and clean but one thing worries me. There is a sort of plastic film on each of the ''speakers'' and one of them is a bit slack, dont know if it does anything since i dont think it has anything to do with the actual sound, maybe a dust protector?

When i get the things working i may have to buy or build an amplifier since my Yamaha Cr-2020 doesnt sound to good with headphones, doesnt have any bass at all. Will probably be a tube amplifier but first i need to check that they actually work.
 
[ When i get the things working i may have to buy or build an amplifier since my Yamaha Cr-2020 doesnt sound to good with headphones, doesnt have any bass at all. Will probably be a tube amplifier but first i need to check that they actually work. ][/QUOTE]

You won't need another amp as the stax connect to your speaker output terminals bypassing any internal headphone amp.
 
Radioactive, the amplifier it self is the ''problem''. The Yamaha gives more punch than ''hearable'' bass. You can really feel it but you cant really hear it- just as i love it. :) So when you use headphones you cant hear the punch so there arent any bass.

Au01, i have read it a dozen of times before but thanks.

Okay, i finaly have the metall box to. But, it is not like any you find on the internet. It is 100% passive. It has a whole other design after the transformers. 4 diodes, 4 capacitors and a couple of resistors. No power required!
This creates a problem, only way to ''charge'' them up is to play music that isnt something many people recommend doing. At the lowest volume i can play the voltages are around 30v so ill guess i will have to charge them up this weekend before i can really use them.

They sound really good from the start but the volume is less on left than right but i guess it needs charging up.
 
After some investigation about the metal box it seems to be a special model. Instead of the white front there is a brushed metal plate over the original front that says SRD-5sb instead of SRD-5. Still cant find any information about it so im hoping someone here can tell me something about it.
 
Enjoy those headphones. My SR-5NBs(not much more advanced than your model) out performed the $600 pair of Ultrasones I had before, and not by a small margin. Dynamic headphones are better in some respects(more musical and let you feel the music more) but stats are the best for detail retrieval.

As for the box, the SB series get the bias charge for the phones from the music playing rather than from the wall as the normal SRDs do. The SBs only charge the headphones when you're playing music through them. This is why your headphones are weak in one channel(mine do the same thing). To solve the problem turn your amp up loud (with the headphones off of course) and play some music for 10-15 seconds. You'll then be good to go. With the age of these phones they tend to lose their charge when they haven't been used for a few hours. Another solution would be to get a non-SB(self biasing) SRD box or a dedicated Stat amp; both of these will charge up the headphones whenever as long as they are plugged in as they are not reliant on your speaker amp to do so.

As for servicing the box, I wouldn't bother. With a dedicated Stax amp it is good practice to swap out the power supply caps(and these do carry lethal voltage!) but with the SRD boxes you are good to go.
 
Last edited:
I can say that im gladly enjoying them, atleast one pair. Im amazed how nice the bass sounds, just the right amount and with the right sound. The middle and treble is also very good but the detail in the sound? Need to find the words first. :D

Okay, so SB can be easy translated to passive. It would be nice to use a none SB and compare if there are any diffrent but to find one in sweden, i would say impossible.
With the ''headphones off'' you mean take it of your head but still have it connected to the box? Seems a bit brutal to me but i guess the headphones can handle it.

Does anyone know how much these usally sell for? Not that im gonna sell them but it would be nice to know since people compare them with expensive headphones.
 
The 'leader of the STAX mafia' over on head-fi(don't ask :p ) says that the SB boxes and the regular SRDs are indistinguishable in sound quality. And I've compared by SRD-6SB(w/ Sherwood S6000 amp) to the STAX T1 and returned to the transformer box solution. The dedicated amp gave more detail but it lost some dynamics/bass and seemed overly colored to my ears. Of course I felt the same way hooking my SRD up to a Pioneer SX780.

When I say to turn the headphones up loud I don't mean to max them out, just turn them up a bit louder than you usually listen. You may want to experiment with it a little to see how loud you have to get it to get the channels in balance. When I'm feeling a bit lazy I do it with the headphones on my head. Not loud enough that it hurts to do so but certainly louder than I'd want to listen for an extended period of time.

If I were go guess on price I'd say $150-250. I got my SR5s with the SRD6SB for about $350.
 
Good that they say there is no big diffrent, but it would still be intressting to test them all.

Just as i thought then.
I did try it and it went really bad but very good. I raised the volume alittle a time over 15 mins but suddenly one channel popped and it died. I wasnt playing that high, i could still listen to one song before my ears would give up. Luckely the amplifier itself didnt brake, ''just'' the box to the headphones. Removed almost everything so that i could measure all the things but nothing was broken. Hmm, put it all back togheter and it works! Even the headphones that had a ''permanent'' weak channel is now charging up. I have no idea what hapend but i will never play that loud again.

150-250$ isnt so bad for headphones that beats 600$ headphones. Shame its hard to find any at all here in Sweden.
 
Both of the headphones are now working just like they should!
The one with the weak channel was lying in the basement for a couple of days and now it works just as good as the other one. I would say the humidity fixed it but i have no idea how that would make any sense at all.

Now it's time to change the fake leather for the real deal. I find it strange that they used fake leather for these headphones. I also need to make a headphone stand for them.
 
Very glad to hear you now have two working SR-3ns.

When 'stats have been sitting unpowered for many years, their diaphragms lose their charge, and the left and right channels don't always charge back up together. One side will often seem weaker than the other, but that usually means they're not fully charged yet, as you found out.

Europe seemed to get the SB versions of the Stax transformer boxes, and I'm not sure why, since it wasn't difficult for Stax to make my SRD-7 box accept 100-240vAC. Having mains-powered bias certainly makes it easier to maintain the charge on the diaphragms, but once charged, the diaphragms normally retain their charge for days or even weeks. The two types of boxes are otherwise identical, as the Stax Mafia says.

Having said that, I've owned other headphones with SB boxes (Superex, thought to be made by Stax, and the Koss ESP.9), and personally I prefer the mains-powered-bias boxes. See if you can find an SRD-7 that accepts a wide range of world voltages. They're out there, but they tend not to be cheap any more.

Humidity is the enemy of any electrostatic device!
 
I would think that the reason Stax didn't make transformers for the Europe market would be that we had harder electrical rules. Was the same with many old 30-40 and 50s radios.

Here in Sweden there haven't been any Stax stuff for sale for the last 7-8 years but i am looking for a non SB transformer. Ebay is one option but it takes a lot of money to get a non SB transformer.

So humidity is bad for them? No more basement for them then.
 
Stax and other makers of electrostatic headphones usually enclosed their drivers in loose bags of ultrathin plastic to ward off moisture from the air, but it's best not to tempt fate. Besides, humidity is bad for everything else, including switch contacts.
 
I've done a couple of things to the SRD-5sb. First of all, i skipped the selector switch so the cables from the amplifier goes direct to the PCB. The second thing is that i have change all the cables in it. The originals were ''standard toy cables''. They are now change to something a little more ''heavy duty''.

There aren't a big different in the sound but there is some. The treble is quiet a bit cleaner and the bass has a more punchy texture. Overall the sound is cleaner and has more depth. Well worth it! I'm planning on changing the 4 capacitors in it since one of them has leaked some gue.
 
Hello Electronror

Any SRD5, 6 , 7 or SRA3S , SRA7S, SRA14S will work with your SR3 .
STAX did produce " box " with transformers inside for Europe , YES !
STAX is really famous here but it is difficult to find somebody who knows very well STAX products like I do .
I have refixed so many during years....If I can help you it will be with pleasure !
 
clinic-audio said:
Hello Electronror

Any SRD5, 6 , 7 or SRA3S , SRA7S, SRA14S will work with your SR3 .
STAX did produce " box " with transformers inside for Europe , YES !
STAX is really famous here but it is difficult to find somebody who knows very well STAX products like I do .
I have refixed so many during years....If I can help you it will be with pleasure !
Click to expand...

Very good to know.
At the moment there isn't anything wrong that i can't handle but there is one thing that i am looking for and that is a transformer box that isn't passive (sb). Impossible to find here in Sweden and Ebay is a little bit pricey.
 
No luck on the SRD but my passive one still works. So does one of the headphones but the other one needs a very long time to charge. 6-7 hours is often minimum. Is there any way at all to fix this?
 
You must log in or register to reply here.
Back
Top Bottom