- 1,932 Posts. Joined 11/2002
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The Stax Thread III - Page 29
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Yeah as Currawong likes to put it, stay on topic or steel capped boot to the rear end.
Anyone here have the schematics to the SRM-1 amp? I do wonder what Stax headphone Stax originally sold it with the SRM-1 amp. I know the SRM1 MK2 and SRD-7sbmk2 was sold with the Lambda Pro's, SRD-(n) energizers with the other SR-(n) headphones, but I wonder what the original earspeaker was sold with the Mk1's as a complete package.
@Spritzer: What diodes did you replace the originals ones in your SRA-3S rebuild? Can the 1N4007 be a suitable drop in replacement? It is nearby 4x0.47uf 600v Toshie axial supply caps besides the two dual section 350v ELNA's .
Even though I've replied at the other place, for future reference the 1N4007 works just fine. Also always change out the output capacitors on these and it would be a good idea to add the proper output resistors for safety.
In vintage Stax news I just scored a SRA-7S which will need complete refurbishment. Should be fun to have with my SR-1's.
- 119 Posts. Joined 10/2012
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SRM-T1 is best for the Lamdas and has both bias outputs normal and pro!
SRM1 MK2 for the Lambdas. Cleaner and more refined sounding than the T1 which is still pretty good, the MK2 provides more output powah as well.
SRM 323S for the 303/404.
@Paradoxper: If those trans are EOL vintage stuff Steve from ceitron can hook you up with bulk orders and his prices are sometimes better than Bdents for the same stuff. Feel free to PM me if you need more info or can't find the site.
Edited by DefQon - 9/24/13 at 5:47am
Time for a bit of a history lesson. As we all know this all started with the Stax SR-1 set back in 1960. Now I've owned three of these and while all were a bit different from one another, they were also pretty similar to the later SR-3. Until this arrived:
First off that nameplate, it's completely different. Rubber used for the strain relief (hence it being so perished) but the biggest difference is the housing. Not only is it a bit smaller but the material is very different. It's almost like nylon as it is slightly soft and can bend a bit. Also notice how rough the finish is where the cups meet the earpads. Then we have the metal grills inside the capsules, one painted red and the other one gray to show the channels. Headband is pretty much the same as the SR-3 but the plastic on the top is deep brown and not black.
This plug is the same as the first SR-1's so this one is very, very old. The biggest clue for the vintage are the earpads though as the normal doughnut pads aren't supposed to be used with this set. The first SR-1's used round foam pads which Stax dropped in the early 60's.
Here they are next to a younger sibling. Roughly 10 years between them as I know the date when those SR-3's were bought new. Best thing about the SR-1 is that all the holes under the pads are still covered up so they have never been opened in these 50+ years. Now this does mean they need to be refurbished but that was a given thing. Now what would you use to drive one of these?
Something like this naturally, the first full size Stax transformer box introduced in 1965. I also have a SRA-7S incoming from ca. 1966 which will work well once it's been completely rebuilt.
And do they work? Well yes and both channels powered up immediately and to the same level. Not bad for a 50+ year old headphone which haven't been opened since they were built. Some intermittent distortion in the right hand driver but it's probably a connection issue. The Stax midrange is all there but not a whole lot of bass under 200Hz. Given how all my other SR-1's were made then the baffle seals are gone so one they are replaced, there will be some bass. Not a whole lot of it but it is also very controlled.