[Svperstar]

He also says it is 1150Vppss on his website. The SRM-717 is 1200vpp per Justin/HeadAmp on that other forum.

Yeah don't ask me. I am not an electronic engineer. I know the 717 was specifically made for the 007, people seem to agree it was the best amp Stax made. I was able to get one used for less then $1,000.

Figured it probably doesn't drive estats as well as a Carbon CC but hey the law of diminishing returns and all.

 

[SolarCetacean]

For an electrostatic headphone, the amp needs to push current to charge/discharge the stators in order to swing voltage. I think Kevin Gilmore himself chimed in a few hundred pages ago saying that less than 1 mW of power actually goes into the headphones, but the current from the amp is used to overcome the capacitance in the driver. The Vppss value is a measure of the power supply voltage, but not of how well it can swing that voltage across a given capacitive load. For a given output voltage, differences in the output current result in different ability to drive that voltage swing in a more demanding load. It's probably the case that the 717 has just a little more output voltage, but much higher output current, resulting in 2x power at the amp outputs and increased ability to drive that voltage into a difficult load.

 

[kevin gilmore]

The srm717, srm727, 500S and 500T are all the same voltage power supplies, and roughly the same current in the output stage. 500t is a slightly lower voltage swing.

a srm727 with the global feedback modification is a better amplifier than the srm717.

 

[Svperstar]

a srm727 with the global feedback modification is a better amplifier than the srm717.

Why is it better?

 

[VandyMan]

For an electrostatic headphone, the amp needs to push current to charge/discharge the stators in order to swing voltage. I think Kevin Gilmore himself chimed in a few hundred pages ago saying that less than 1 mW of power actually goes into the headphones, but the current from the amp is used to overcome the capacitance in the driver. The Vppss value is a measure of the power supply voltage, but not of how well it can swing that voltage across a given capacitive load. For a given output voltage, differences in the output current result in different ability to drive that voltage swing in a more demanding load. It's probably the case that the 717 has just a little more output voltage, but much higher output current, resulting in 2x power at the amp outputs and increased ability to drive that voltage into a difficult load.

Thanks. That is an excellent explanation.

 

[Firschi]

The max output voltage is a measure of power.

It is not, as power in general is the product of voltage and current. The previous post roughly outlines their relationship in the STAX context.

 

[kevin gilmore]

Why is it better?

real current sources in the 727 at the top of the 3rd stage. as opposed to just resistors.

real power is voltage * current * cosine( phase between voltage and current)
since the load is a pure capacitor, the phase is 90 degrees.

its actually a bit more complicated than that because there is some inductance in the cable.

 

[Chefguru]

Why is it better?

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 / The kgsshv and the 727 are similar amplifiers except the kgsshv uses global feedback and both ver of kgss typically use higher v power supplies (4 stage amplifiers)

When people are telling you the 717 is the best amp Stax made, they likely are saying in terms of stock. The T2 is the best amp they ever made but it had engineering issues (that KG eventually solved for with his DIY ver), and the 727 stock requires the feedback mod to be returned to 717 default.

 

[Svperstar]

T2 is the best amp they ever made but it had engineering issues

Yeah I view the T2 kinda like a concept car. Good luck buying one that isn't going to burn itself alive.

 

[tameral]

Hey everyone! I'm interested in trying out some Stax headphones. Considering either the 007 or 009 models, or perhaps starting off with an L300 or L700. I've heard great things about Dukei and Soren as builders, but I'm wondering if there are any builders in the USA who specialize in the major KG designs (aside from Blue Hawaii)? Thanks for any insights!

 

[myheadHz]

Since starting my Stax journey, the Sigma, was an enigma that I thought I would never see in the flesh, let alone listen to. However, after a chance encounter with a very resonably priced ebay BIN listing, ambiguously titled "Vintage stax headphone"... one impulsive jump later... I am the proud owner of an iconic Stax OG NB Sigma serial #02109 ... and another SRD 6 for the enigiser pile!

Given the state of the headphones in the images, I wasn't holding too much hope (one cup hanging off the arc, cups R/L reversed, one of which was also upside down half connected to the yoke) and was anticipating this being parts for a restoration of some description, however after an intial scare of a rattle coming from the right side and some careful removal of the obviously degraded ear pad cover, they are now working a treat.

In one way it's a shame it's in such good working condition as part of me was hoping to be able to put in newer lambda drivers, but I guess I wouldn't have a baseline to reference against, and it is nice to hear (the prized) NB lambda transducer.... albeit not in a lambda

One side, the ear covering disintergrated and decided to embed the contents of this process into the the wool dampening itself which is incredibly annoying since as well as being the culprit of the initial rattle, still happens occasionally, and so is a bit of an ongoing process to get the tweezers out every now and then and with a steady hand, grab rogue earpad 'particles' and pry them from various seems/gaps around the pad and driver .

Panelling of one of the cups is the lovely grey it should be, the other, seems like it has a sun faded or smoke discoloured yellow tint (although they don't smell or feel greasy) to the back panels, which I really want to clean if I can.

The arc is a mixture of apparently very sturdy/solid plastic coupled with an impending feeling of snapping or collapsing under the weight of the cups, so probably needs addressing if I am to feel more comfortable wearing these for longer sessions.

It certainly is an iconic monstrosity, however sounds really nice and smooth like butter (with lovely bass, albeit not as extended). Soundstage is certainly unique, positioned in front of the face divided into it's respective channels (rather than eminating from inside the head), however my L500 seems as wide, (if not slightly wider sometimes) which is surprising. Seperation is also is not as good as the Lambda, but overall sound certainly not as harsh as the Lambda. Very easy listening.

Some questions for other Sigma users if I may...

1. Pads are in surprisingly great condition, and possibly not too far removed from their birth condition but I might get some thicker ones (for comfort) and new earpad covers. How well do angled lambda pads work (if at all)? Or is it better to keep flat-ish ones?

2. The dampening wool seems complete, although quite fragile. Does the dampening wool material have much of an impact on the sound if removed entrely? I'm guessing yes for the Sigma (as there is so much of it), but it has also been mentioned this stuff on the early Lambda's is a bit irrelevant? Anyone tried them without the wool?

3. Is there a modern replacement for this particular wool with similar sonic characteristics? It's currently in good condition, but feel it could be something that needs attention in the future and I don't fancy genetically engineering Japanese sheep from the 70's (if that is indeed where it comes from).

4. The pins on the yokes have smaller diameter than modern Lambda yokes (Ideally I want to replace with a new arc assembly, preferably mk2 metal yoke version), are these the same as older Lambda yoke pins? Is there an alternative place to get correct fitting yokes with correct dia for Sigma?

5. Are there any disassembly instructions?

6. Whats a good way to clean the plastics?

7. Whats a good way to clear the erroneous fluff off the drivers? I presume the drivers have dust covers like the new Lambda ones?

I think I would like to upgrade to 404 drivers, however since the Sigma's are getting increasingly hard to find (in general, and NB especially), is it worth it? I love the smooth sound currently but would like something with a bit more extension as a daily (like my L500 [blu-tacked]) while retaining the unique soundstage these offer. I am even temped to get an ES labs kit now that I have heard what it can do, and put 404's in there, then I can keep NB Sigma as is. But ya know... monies'n'all.

 

[John Buchanan]

Some answers:
1. Leave the pads alone. Yes the netting is gone.
2. Don't remove the damping wool. This is part of the sound (reflection, refraction, damping and sealing the front of the driver from the back.
3. See 2
4. Leave the headband alone.
The Sigma NB has roll off at the bass and treble end of the frequency response, but what's left is the best headphone of all time. And even that can be improved - either buy a Stax Sigma Pro or Sigma/404. Both have extended the usable frequency response to a superlative headphone. AFAIK, the only people who do transplants now are ES Labs. Mjolnir Audio modifies them for sale, not as a service to customers.

 

[Schelp san]

Since starting my Stax journey, the Sigma, was an enigma that I thought I would never see in the flesh, let alone listen to. However, after a chance encounter with a very resonably priced ebay BIN listing, ambiguously titled "Vintage stax headphone"... one impulsive jump later... I am the proud owner of an iconic Stax OG NB Sigma serial #02109 ... and another SRD 6 for the enigiser pile!



Given the state of the headphones in the images, I wasn't holding too much hope (one cup hanging off the arc, cups R/L reversed, one of which was also upside down half connected to the yoke) and was anticipating this being parts for a restoration of some description, however after an intial scare of a rattle coming from the right side and some careful removal of the obviously degraded ear pad cover, they are now working a treat.

In one way it's a shame it's in such good working condition as part of me was hoping to be able to put in newer lambda drivers, but I guess I wouldn't have a baseline to reference against, and it is nice to hear (the prized) NB lambda transducer.... albeit not in a lambda

One side, the ear covering disintergrated and decided to embed the contents of this process into the the wool dampening itself which is incredibly annoying since as well as being the culprit of the initial rattle, still happens occasionally, and so is a bit of an ongoing process to get the tweezers out every now and then and with a steady hand, grab rogue earpad 'particles' and pry them from various seems/gaps around the pad and driver .

Panelling of one of the cups is the lovely grey it should be, the other, seems like it has a sun faded or smoke discoloured yellow tint (although they don't smell or feel greasy) to the back panels, which I really want to clean if I can.

The arc is a mixture of apparently very sturdy/solid plastic coupled with an impending feeling of snapping or collapsing under the weight of the cups, so probably needs addressing if I am to feel more comfortable wearing these for longer sessions.

It certainly is an iconic monstrosity, however sounds really nice and smooth like butter (with lovely bass, albeit not as extended). Soundstage is certainly unique, positioned in front of the face divided into it's respective channels (rather than eminating from inside the head), however my L500 seems as wide, (if not slightly wider sometimes) which is surprising. Seperation is also is not as good as the Lambda, but overall sound certainly not as harsh as the Lambda. Very easy listening.

Some questions for other Sigma users if I may...

1. Pads are in surprisingly great condition, and possibly not too far removed from their birth condition but I might get some thicker ones (for comfort) and new earpad covers. How well do angled lambda pads work (if at all)? Or is it better to keep flat-ish ones?

2. The dampening wool seems complete, although quite fragile. Does the dampening wool material have much of an impact on the sound if removed entrely? I'm guessing yes for the Sigma (as there is so much of it), but it has also been mentioned this stuff on the early Lambda's is a bit irrelevant? Anyone tried them without the wool?

3. Is there a modern replacement for this particular wool with similar sonic characteristics? It's currently in good condition, but feel it could be something that needs attention in the future and I don't fancy genetically engineering Japanese sheep from the 70's (if that is indeed where it comes from).

4. The pins on the yokes have smaller diameter than modern Lambda yokes (Ideally I want to replace with a new arc assembly, preferably mk2 metal yoke version), are these the same as older Lambda yoke pins? Is there an alternative place to get correct fitting yokes with correct dia for Sigma?

5. Are there any disassembly instructions?

6. Whats a good way to clean the plastics?

7. Whats a good way to clear the erroneous fluff off the drivers? I presume the drivers have dust covers like the new Lambda ones?

I think I would like to upgrade to 404 drivers, however since the Sigma's are getting increasingly hard to find (in general, and NB especially), is it worth it? I love the smooth sound currently but would like something with a bit more extension as a daily (like my L500 [blu-tacked]) while retaining the unique soundstage these offer. I am even temped to get an ES labs kit now that I have heard what it can do, and put 404's in there, then I can keep NB Sigma as is. But ya know... monies'n'all.

Recently I also wanted to have a Sigma/404, so I got a Lambda 404 and a Sigma NB and changed the drivers. Now there is a Lambda NB and a Sigma 404. Also the 404 cable is now with the Sigma. Swapping the drivers is not difficult, however I only recommend doing it if you have a little bit of fine mechanical skills. I found the conversion kind of self explaning once both headphones were disassembled. Only tricky thing is to remove the Sigma NB drivers with a sharp cutter knive without damaging something. Tools is only screw drivers, glue, knive and a soldering iron plus a bit of patience.

 

[arielext]

I know Stax energizers don't get a lot of love and especially the newer ones, but I'm still in awe of what the SRM-700S brings to the table combined with the SR-007A (port modded). I have owned the 353X (recent) and KGSSHV (longer time ago) before.
I paid about half the new-price for a like-new 700S which is a good price IMO compared to the 353X and KGSSHV. At full price I would have not opted for the 700S.

 

[NCUS]

I know Stax energizers don't get a lot of love and especially the newer ones, but I'm still in awe of what the SRM-700S brings to the table combined with the SR-007A (port modded). I have owned the 353X (recent) and KGSSHV (longer time ago) before.
I paid about half the new-price for a like-new 700S which is a good price IMO compared to the 353X and KGSSHV. At full price I would have not opted for the 700S.

All that matters is you enjoy what you have. Once you are at that point, just ignore the noise.