The Headcase Stax thread

[spritzer]

Well here is the super rare SR-2:

 

 

Stock earpads were probably from PWB and perished all to hell. 

 

 

That baffle looks very much out of place but identical to the link above.  Some of the SR-1's were made in that color though. 

 

 

Standard late model SR-1 driver.  Notice how much smaller the stators are compared to say the SR-X Mk3 units.  That adhesive ring is found on all the very early models and just falls off now.  The baffle needs to be resealed somehow though or the lack of bass will become quite overwhelming. 

Edited November 6, 2013 by spritzer

[DefQon]

Been waiting for those pictures for a long time

 

The stator looks a bit dirty inside like some sort of rust build-up? 

 

Any serial sticker inside the cups? I know my SR-3 and SR-5 has them.

 

Very curious as to how many SR-2's were produced in 1968...maybe it was used for prototyping the SR-3?

Edited November 8, 2013 by DefQon

[spritzer]

The stators are brass so they oxidize a bit but all the old units do that.  No crazy/stupid enough to try and fix that... 

 

No S/N on the set but the original box has one, nr. 170.

[spritzer]

Here something funny, an upgrade service for Stax tube amps...

 

T1 and variants

 

007t and variants

 

Not so sure about this clusterfuck...

[nopants]

Well at least they let you know in advance you can't revert it once they perform the upgrade. Maybe you should shoot them a question and see if they cough up anything of value 

[faust3d]

Well here is the super rare SR-2:

 

 

Stock earpads were probably from PWB and perished all to hell. 

 

 

That baffle looks very much out of place but identical to the link above.  Some of the SR-1's were made in that color though. 

 

 

Standard late model SR-1 driver.  Notice how much smaller the stators are compared to say the SR-X Mk3 units.  That adhesive ring is found on all the very early models and just falls off now.  The baffle needs to be resealed somehow though or the lack of bass will become quite overwhelming. 

 

Very interesting stuff right here.

[spritzer]

That's pretty much as rare as they come. 

 

Well at least they let you know in advance you can't revert it once they perform the upgrade. Maybe you should shoot them a question and see if they cough up anything of value 

 

There is nothing there but a fire hazard.  The person doing that has zero clue as can be seen from the axial power caps haphazardly mounted or the local PSU film bypass caps in the amp stage replaced with some audiophile crap. 

[faust3d]

I have a general question about SRM-313. How many version of the amp are out there and are they all the same from the topology standpoint?

Edited November 19, 2013 by faust3d

[spritzer]

There are at least two main versions, the one with the normal bias and the one that is Pro bias only.  Both have the side mounted PCB but there were some small changes to the chassis such as went holes on the back.

 

There are also some that look a lot like the 323 inside (pcb sitting on the bottom of the chassis) but I've never seen one up close to know if it's really a 323 in an old style chassis or just the first redesign to get around the discontinued dual jfets at the time. 

 

This is Stax though so there could be other revisions that nobody knows about.  The SR-2 above doesn't exist officially yet, there is one. 

[faust3d]

There are at least two main versions, the one with the normal bias and the one that is Pro bias only.  Both have the side mounted PCB but there were some small changes to the chassis such as went holes on the back.

 

There are also some that look a lot like the 323 inside (pcb sitting on the bottom of the chassis) but I've never seen one up close to know if it's really a 323 in an old style chassis or just the first redesign to get around the discontinued dual jfets at the time. 

 

This is Stax though so there could be other revisions that nobody knows about.  The SR-2 above doesn't exist officially yet, there is one. 

 

Interesting. Was the first verion with jfets? What were they replaced with?

Edited November 19, 2013 by faust3d

[spritzer]

All the Stax amps have used Jfet inputs since the early 70's.  The 313 used the J109 dual fet until it was discontinued and replaced with matched pairs of J74's (which is just what a J109 was, matched J74's) thermally coupled. 

[faust3d]

All the Stax amps have used Jfet inputs since the early 70's.  The 313 used the J109 dual fet until it was discontinued and replaced with matched pairs of J74's (which is just what a J109 was, matched J74's) thermally coupled. 

 

Interesting I just picked one up in champagne color with sideways PCB. How is this amp different from SRM-1/ mk2 in terms of topology? I seems to be running much less hot that I remember SRM-1 did.

[DefQon]

Quote from the other site:

 

 

By KG:

 

The 727 is a local feedback version of the 717. The 727 has a current source, the 717 has a resistor. Otherwise virtually identical.

The 727 runs the output stage at higher power.

 

The kgss and the 717 are similar amplifiers. (4 stage amplifiers)

 

The kgsshv and the 727 are similar amplifiers except the kgsshv uses global feedback. (4 stage amplifiers)

 

If people want it, the next revision of the kgsshv boards will have the local/global feedback option.

 

Personally i like the sound of the global feedback version better.

 

The 313 and 323 are 3 stage amplifiers. Same or similar to all the transportables (srmXh,srm151,srm252)

 

There are the 2 ac coupled single power supply amps, sr-001 and srm300

 

the srm-t1, t1s and 006t are virtually identical. (solid state/tube hybrid)

 

the 007 has twice the number of output tubes and runs the output stage at twice the power. (solid state/tube hybrid)

 

The T2 is a tube/solid state/tube hybrid.

 

The BH and BHSE are essentially the T2 output stage with the kgss input stage configured for 800 volts.

 

For stuff older than the srm-t1, things get complicated. spritzer has more of the really old schematics.

 

 

By spritzer:

While we are on the subject, Stax amp history lesson. 

 

First SRA1-8 amps were all classic tube units of varying complexity made in the 60's. 

 

SRA-3S was the first deviation from this with a transistor front end and AC coupled tube output stage.  Preamp and phono amp on plug in cards similar to the old ISA units used in PC's. 

 

SRA-10S/12S were the first SS amps with a push pull front end and AC coupled outputstage.  Run fully in Class A they get stinking hot and feature a nice regulated PSU for the low voltage circuit and a stacked PSU for the +640VDC B+. Similar plug in system as on the SRA-3S but now everything except the basic PSU is on plug in cards and the build quality is far better. 

 

SRD-X was the first portable Stax amp and features an automotive chip amp driving a pair of transformers.  Think Darkstar but with much better specs done in 1979.... 

 

SRM-1 Mk1 was pretty much the same circuit as the SRA-12S but turned on its head.  Similar AC coupled output stage.  I recently refurbished one of these and it is a nice little amp but the SRA-12S is better over all. 

 

SRM-1 Mk2 is where things get tricky since there are so many variations of it.  The first ones were some weird Mk1/Mk2 hybrid though fully DC coupled but later units are much more similar to the current crop of Stax amps like the 313.  Now the amps are fully balanced from input to output though most only have RCA inputs. 

 

SRA-14S is pretty much the SRM-1 Mk2 circuit but turned on its head.  Better parts and some tweaks but most of the price difference is spent on the preamp capability. 

 

SRM-3 is just a SRM-Xh with a full size power supply.  It even uses the same circuit boards. 

 

SRM-600LTD is the same basic circuit as the T1/006t but modified to take the ECC99 tube. 

Edited November 21, 2013 by DefQon

[spritzer]

The SRM-1 Mk2 has only 4 output devices so the current sources are resistors.  Even on the SRA-14S (released 3 years later) this was still the case (though the circuit is far more complicated as a whole) and it wasn't until the SRM-X that they moved to transistors.  They did progressively turn down the bias current though so the amps run cooler. 

[faust3d]

The SRM-1 Mk2 has only 4 output devices so the current sources are resistors.  Even on the SRA-14S (released 3 years later) this was still the case (though the circuit is far more complicated as a whole) and it wasn't until the SRM-X that they moved to transistors.  They did progressively turn down the bias current though so the amps run cooler.

This explains what I am seeing inside. Thanks a lot. Now to try it out with SR-5, O2 and Sigma and whatever I can dig out from my closet.

[s1rrah]

So recently my re introduction to Stax ended ... it was via a set of SR-307 phones and a vintage (circa 94ish I think) SRM-T1W driver unit.

 

I bought the T1W on a whim and with very little research and decided to quickly put it back up for sale just a few days after I got it as I want to source something with a bit more longevity (even though the particular amp was pretty damn cosmetically pristine inside and out). Thankfully, it sold for 800+ US, within the first hour of posting pics/listing on Ebay this morning (a bit more than I invested; I feel lucky).

 

Anyway, I retain the 307 cans but have been thinking about selling them too as, like I'd read re: this particular ear speaker, I did in fact detect a little of what I've heard described as "etch" (though otherwise, I thought the amp sounded pretty good). The whole etch thing wasn't too bad, could be lived with, but since I'm considering a little time to save some more cash and read a bit more about amps, I thought I'd ask if anyone had experience with the 407's or 507's and if they all share that peculiar attribute. Or, if some other decent ear speaker might be preferred over those variants?

 

Oddly, my first Stax system, some four years ago, a Stax SRM-323II and SR-303, to my memory anyway, didn't have this quality. It's been a bit, though and it was a solid state amp and so who knows?

 

RE: amps, the KGSS variants are simply far too big for my listening space, the Woo WES would fit fairly well (and I haven't read too much about it) and so I've still been considering hunting down something from the typical, more slim Stax driver units (have read some good things about the rather affordable 323s). 

 

Anyway ... back to the drawing board.

 

 

 

[livewire]

You sound like a good candidate for a Koss ESP-950 system.

Have you tried that yet? No etch, just abundant midrange and pretty good bass for a stat.

The newer Stax Lambdas are all tilted toward the treble end of things.

I happen to like the Stax Lambda treble and dont perceive it as "etch". To each their own...

Or if you got the big bucks, try a SR-007. You're also gonna need a real good amp like a KGSS to make it play well.

Figure around $4000 total for that rig.

[HeadphoneAddict]

s1rrah, I did not like the 507 at all, as they had a nasally sounding upper mids/lower treble that was way worse than the usual mild upper mids etch I heard on vintage Lambda Signature and Lambda Pro. I very much prefer my Lambda Nova Signature (LNS) over the 507, and I think the LNS are among the best of the Lambda Series (although SR-404LE were pretty good but hard to find).

Livewire mentioned the Koss. My current LNS sounded better than my old ESP-950 which I sold; but I preferred those recabled ESP-950 over my older Lambda Pro and Lambda Signature (but my ESP-950 were using an SR-007 cable and Stax amp). However, my LNS via KGSS sound a lot like my HE-500 via ZDT amp, and the SR-007 are a noticeable upgrade over any Lambda series phone.

Sometimes I've considered downsizing things and selling the KGBH/SR-009 and just enjoying the KGSS/007. It's a very nice combo, and my DIY KGSS is a bit smaller than my old WES. The KGSS reminds me of the SRM-717 with a little more spacious soundstage but a little less warmth and bloom. So, if you can find an SR-007 and SRM-717 or KGSS I think you will be pretty happy. A KGBH will be even better for 007 but harder to find.

Note - my KBGH is noticeably more powerful, punchier, warmer, and smoother sounding than my KGSS; but it's circuit has been tweaked and I think it's better than a few other KGBH out there (such as the one Namaan built and brought to my house in 2009 for a meet.)

[Dusty Chalk]

IIRC, the trick with the Koss amp is to replace the power supply.  Yes?

[s1rrah]

s1rrah, I did not like the 507 at all, as they had a nasally sounding upper mids/lower treble that was way worse than the usual mild upper mids etch I heard on vintage Lambda Signature and Lambda Pro. I very much prefer my Lambda Nova Signature (LNS) over the 507, and I think the LNS are among the best of the Lambda Series (although SR-404LE were pretty good but hard to find).

Livewire mentioned the Koss. My current LNS sounded better than my old ESP-950 which I sold; but I preferred those recabled ESP-950 over my older Lambda Pro and Lambda Signature (but my ESP-950 were using an SR-007 cable and Stax amp). However, my LNS via KGSS sound a lot like my HE-500 via ZDT amp, and the SR-007 are a noticeable upgrade over any Lambda series phone.

 

 

Well I can certainly live with my current 307's ... really, the "etch" I mention is getting near the splitting of hairs as I found the cans to be quite enjoyable (though I remember the SR-303's being more smooth); but while I amass my small fortune to re invest in a proper amp, I figured I'd really check out the ear speaker landscape as well. Good comments on the Lambdas ...

 

I've found some used Lambda Nova Signatures but not sure I want to spend the money (about $550 US); I've also found some other variants like the SR-407 SR and the Lambda Nova Classic on ebay and for comparable money (perhaps a bit less, give or take) but I have no clue about those.

 

RE: the Koss system... I'm intrigued by this but being a tinkerer/hobbyist to a certain degree, I'd enjoy having something a bit more extensible (easily change amps/cans on a whim and without to much scrounging for adapters/hacks/etc.). I like what I've read about it, though. And there's something to be said for a lifetime warranty (I love my Koss Portapros!). Just not sure if it's what I'd want to replace my current, dynamic rig with ... but It would certainly make for a nice supplement, I'm sure. 

 

Also, regarding the Koss system ... is it an easy thing to source an adapter so the headphones will work with typical Stax amps?

 

Re: amps. Have you heard the SR-600LE amp? Haven't found this online currently for sale but I'm intrigued by the use of ECC99 tubes and really want to hear it. For now, the SRM-323S is leading in the personal polls, though I'm a good month or so away from purchasing anything.

 

Thanks for the word.

Edited November 22, 2013 by s1rrah

[The Expanding Man]

Rearrange your listening space, buy a BHSE and end the upgrade itch.

[padam]

Also, regarding the Koss system ... is it an easy thing to source an adapter so the headphones will work with typical Stax amps?

 

Re: amps. Have you heard the SR-600LE amp? Haven't found this online currently for sale but I'm intrigued by the use of ECC99 tubes and really want to hear it. For now, the SRM-323S is leading in the personal polls, though I'm a good month or so away from purchasing anything.

 

Thanks for the word.

 

You can have the supplied extension cable modified to be an adapter, no biggie.

But being in the minority I found them to be not that great sounding (not as smooth FR) despite only using Stax amps, plus you might experience the squealing caused by dust sooner or later the dust covers are - shall we say - not very sophisticated. But at least they will fix it no questions asked.

 

ECC99 tubes are a bit better if you have a 006t or T1 to mod but really not that different to a stock one so I wouldn't pay that much more for a factory unit.

It is might not actually be better than the 323S more like a different flavor tube vs ss (in that sense the LNS is probably more different to your 307 than an amp change) I guess if you are patient enough you can have a 717 for the same money which is what I would choose.

[spritzer]

I'd stay away from the SRM-600 given the very high failure rate.  It's always the plate resistors that die so they could just be replaced but that's pretty much the amount of work needed to change a T1/006t to use ECC99's so hardly worth the price difference. 

 

The Koss isn't a bad choice.  Simply upgrading the wall wart for the E/90 amp won't make a dramatic difference so your best bet is always a Stax amp.  Even cheaper is the Stax SRS-2170 which is pretty much untouchable at that price.  Sounds far better than the 307 too and the Japanese units are easy to use with a domestic 12VDC psu modified for the correct pinout. 

 

Any of the Lambda Nova units would also be a good choice but many of them aren't aging all that well.  The adhesive used is acting up and the pleather parts are flaking or even worse.  Some of my favorite headphones ever though and my main set these days is pretty much a Nova Signature. 

[faust3d]

The SRD-313 with SR-303 sounds plenty good to me, no surprising that they sold this as a system. I was also surprised how nice SR-5NB sounds when compared to SR-X that I had, much more comfortable to boot.

Edited November 22, 2013 by faust3d

[s1rrah]

The SRD-313 with SR-303 sounds plenty good to me, no surprising that they sold this as a system. I was also surprised how nice SR-5NB sounds when compared to SR-X that I had, much more comfortable to boot.

 

That exact system was my first introduction to Stax about four years ago; I agree ... super sweet. I've been hunting for SR-303's today but have had no luck... 

Edited November 22, 2013 by s1rrah