[astrostar59]

  The SRM-727 has a power rating of 450V r.m.s./1kHz compared with 400V r.m.s/1kHz for the SRM-353X and 300V for the SRM-006t, but I don't really understand voltage swing.

The specs are a guide to what a particular amplifier can output. But the sound quality you get is not always pro-rata. My 717 was supped to be 450v but it sounded more like half the power and dynamics of my KGSShv. My amp also sits on 10mA power supply, so probably a reason it sounds so fast and alive compared to the more restricted Stax amps.
 
I would try and get to hear a good KG amplifier before you spend on another Stax amp.

 

[soren_brix]

 
Electrostatic headphones mainly require voltage to work, and barely any amperes (current). Obviously, there must still be a small current, but I do not know how these relate to amp or headphone performance.

 
The current required to drive a phone depends on the phones capacitance (incl cable), the frequency and the volume.
The higher the volume the higher the current is needed.
 
As KG pointed out in the post I quoted a few posts back, the KGSS ~ 717, and the KGSShv ~ 727.
 
The difference between KGSShv and KGSS is mainly the addition of current sources.
Comparing a 717 to a KGSShv is more or less comparing the amp without/with current sources not to speak about the PSUs being very different.
Spritzer has mentioned several times that the Stax amps are equipped with mediocre PSU's , I guess that covers the 717 and 727 as well.
 
I'd say that current is equal as important as voltage swing, although people tend to focus on the latter.
 
That said, doing the math considering 007 and 009, it sort of end up very much the same place, but the 007 is so much harder to drive ... so there are much more to it than just looking at voltage swing and current.
As for my own experience the 007 never really came to life using either 323 nor 006t. Using a KGSS sort of made the 007 sing. Same experience using the Sigmas.
The KGSShv is better in comparison to the KGSS ... and one could continue  .... although it will mainly be reports from the land of diminish returns ...
 
For someone buying a new pair of 007s and wants to get the most of it I guess the only option is 727 or some 2nd hand 717/KGSS or similar (some also like Cavalli's)

 

[astrostar59]

Not sure if that is all correct.
 
Here is the specs via Kevin Gilmour:
 
3000 volts peak to peak stator to stator (+/-750 power supplies)
KG TOGTE
 
2400 volts peak to peak stator to stator (+/-600 power supplies)
koss esp950
 
2300 volts peak to peak stator to stator (+/-575 power supplies)
KG’s new Silicon Carbide jfet based space heater.
 
2000 volts peak to peak stator to stator  (+/-500 power supplies)
Stax T2, DIY T2, KGSSHV (ixys parts)
 
1800 volts peak to peak stator to stator (+/-450 power supplies)
KGSSHV (sanyo parts)
craig has said his new electra amp does 1800 volts, power supply unknown
Ergo Jecklin
 
1600 volts peak to peak stator to stator (+/-400 power supplies)
BH, BHSE, singlepower ES1,ESX (after being modified to remove the 100V offset)
Cavalli Audio Liquid Lightning
 
1400 volts peak to peak stator to stator  (+/-350 power supplies)
KGSS,Stax T1,T1s,T1W,313,323,717,727,sra-14s,srm-1 mk2,srm-monitor
woo audio wes
 
1300 volts peak to peak  stator to stator
stax sra-10s/12s
 
1200 volts peak to peak (+/-300 power supplies, and +600 capacitively coupled)
KG tube #1,aristaeus,HEV70,HEV90,RSA A10,srm300,Exstata
Egmont,Cirolan,SRM-1,srm-3,woo audio ges,srm310
 
1100 volts peak to peak stator to stator
stax sra-3s
stax srm-001 (when the batterys are at full power)
 
1000 volts peak to peak (+/-260 volt power supplies)
Rudistor Egmont
 
960 volts peak to peak stator to stator
Stax srmXh, srm212
 
540 volts peak to peak stator to stator
Very early HEV70  (+525 volt power supply and tubes biased at 390 volts)
 
I can say categorically the Stax 727/717 is way behind my KGSShv, I know I had the 717 at the same time on my 007As and the 009s. It is also not just the specs or voltage, the design of the power supply and the output is key here. The 717 sounds thin, strained and flat with a constricted soundstage and a cold unnatural treble. So listening is the key here, the specs try to say they are close which is afar from the truth.

 

[martyn73]

 
Not sure if that is all correct.
 
Here is the specs via Kevin Gilmour:
 
3000 volts peak to peak stator to stator (+/-750 power supplies)
KG TOGTE
 
2400 volts peak to peak stator to stator (+/-600 power supplies)
koss esp950
 
2300 volts peak to peak stator to stator (+/-575 power supplies)
KG’s new Silicon Carbide jfet based space heater.
 
2000 volts peak to peak stator to stator  (+/-500 power supplies)
Stax T2, DIY T2, KGSSHV (ixys parts)
 
1800 volts peak to peak stator to stator (+/-450 power supplies)
KGSSHV (sanyo parts)
craig has said his new electra amp does 1800 volts, power supply unknown
Ergo Jecklin
 
1600 volts peak to peak stator to stator (+/-400 power supplies)
BH, BHSE, singlepower ES1,ESX (after being modified to remove the 100V offset)
Cavalli Audio Liquid Lightning
 
1400 volts peak to peak stator to stator  (+/-350 power supplies)
KGSS,Stax T1,T1s,T1W,313,323,717,727,sra-14s,srm-1 mk2,srm-monitor
woo audio wes
 
1300 volts peak to peak  stator to stator
stax sra-10s/12s
 
1200 volts peak to peak (+/-300 power supplies, and +600 capacitively coupled)
KG tube #1,aristaeus,HEV70,HEV90,RSA A10,srm300,Exstata
Egmont,Cirolan,SRM-1,srm-3,woo audio ges,srm310
 
1100 volts peak to peak stator to stator
stax sra-3s
stax srm-001 (when the batterys are at full power)
 
1000 volts peak to peak (+/-260 volt power supplies)
Rudistor Egmont
 
960 volts peak to peak stator to stator
Stax srmXh, srm212
 
540 volts peak to peak stator to stator
Very early HEV70  (+525 volt power supply and tubes biased at 390 volts)
 
I can say categorically the Stax 727/717 is way behind my KGSShv, I know I had the 717 at the same time on my 007As and the 009s. It is also not just the specs or voltage, the design of the power supply and the output is key here. The 717 sounds thin, strained and flat with a constricted soundstage and a cold unnatural treble. So listening is the key here, the specs try to say they are close which is afar from the truth.

Thanks, how does the Nezzar amp compare with Stax amps?

 

[Michgelsen]

  I can say categorically the Stax 727/717 is way behind my KGSShv, I know I had the 717 at the same time on my 007As and the 009s. It is also not just the specs or voltage, the design of the power supply and the output is key here. The 717 sounds thin, strained and flat with a constricted soundstage and a cold unnatural treble. So listening is the key here, the specs try to say they are close which is afar from the truth.

 
I know you're very fond of the KG amps, but which Stax amps do you like best?

 

[astrostar59]

   
I know you're very fond of the KG amps, but which Stax amps do you like best?

 
I have heard the 007t and it was quite nice at low volume or classical material, but ran out of juice quickly on my 007s and sounded stained and compressed. The bass was also loose and lacked drive and depth.
 
I had a 323 which was ok, but the last amp I had was the 717, much better. With the 007s it was on the limit I think, and the cold treble and thinness of the sound was irritating to me. It was clearly the best of those amps though. The 727 is not quite as good as they messed up the feedback stage. It can be reversed but why hack a new amp? Better buy a KG amp instead.

 

[soren_brix]

   
The 727 is not quite as good as they messed up the feedback stage.

what does that mean?

 

[astrostar59]

  what does that mean?

This is common knowledge on this forum. Google 727 mod.

 

[soren_brix]

 
This is common knowledge on this forum. Google 727 mod.

so you haven't really compared a stock 727 with a modded 727, but rather concluded that since you don't like the stock 727 and have read that some says that Stax messed up the feedback loop this is the reason to your disliking ... 

 

[Ali-Pacha]

I own a 727 (+lots of different Staxens) and had the mod done few months ago.
 
Stock 727 is not a bad amp since it has a lot of power, but it does have some weaknesses :
- bass is a bit bloated. Pleasing on some genre, because it brings some meat around the bone and fights e-stat trend to sound ethereal, but not very tight / precise
- dynamic is a bit compressed. 
- not very linear, you get some harshness in the high-mids when you push the volume
- to sum up, I've always struggled to find the "right" volume with the stock unit. You push up the volume because you want more dynamics / engagement, and after several minutes you lower it because it sounds harsh and oddly compressed
 
Stock SRM-727 is perfect for those looking for extra warmth at low volume listening. You'll lose this loudness / romantic presentation with the mod, but you're much closer to wire with gain.
 
2 cents.

Ali

 

[zolkis]

Thanks, how does the Nezzar amp compare with Stax amps?

 
Very well. IMHO it sounds smoother and more musical than the 007t II. In my books that beats all stock Stax amps.
But that is only one opinion, and I haven't seen others on this forum. The same amp was favorably reviewed by a local famous and very picky reviewer, but I haven't seen other reviews.
 
Anyway the sound was very good, and it drives the 007 fine -- of course, probably less volume than the Carbon, but dynamic range is fine as I tested with various classical and jazz recordings. A lot of options are also negotiable with the designer (input switcher, balance, etc). The Nezzar is my highest recommendation for the L700, but works well with the 007 and 009 as well. For the price it's unbeatable, but the high end Stax mafia amps probably have more dynamic headroom. If it matters to you. The dynamic range of a concert is very big, so in principle the higher the useful dynamic range, the better. Yet very, very few people listen to high dynamic range musical content, most of contemporary music and regular instruments have way less dynamics and are well covered. Myself I am listening to high dynamics concerts at a pretty low volumes, and normal music at moderate volumes. I have used the Nezzar volume control around 12pm (middle) position during testing and didn't have any problems with dynamic headroom - that is only to gauge my evaluation of the Nezzar.

 

[astrostar59]

  I own a 727 (+lots of different Staxens) and had the mod done few months ago.
 
Stock 727 is not a bad amp since it has a lot of power, but it does have some weaknesses :
- bass is a bit bloated. Pleasing on some genre, because it brings some meat around the bone and fights e-stat trend to sound ethereal, but not very tight / precise
- dynamic is a bit compressed. 
- not very linear, you get some harshness in the high-mids when you push the volume
- to sum up, I've always struggled to find the "right" volume with the stock unit. You push up the volume because you want more dynamics / engagement, and after several minutes you lower it because it sounds harsh and oddly compressed
 
Stock SRM-727 is perfect for those looking for extra warmth at low volume listening. You'll lose this loudness / romantic presentation with the mod, but you're much closer to wire with gain.
 
2 cents.

Ali

I agree 100% with this. There is a well documented report on the 717 v 727 and how to do the mod. IMO though, the 717 or the 727 even with the mod is still well behind the KGSShv or any other of the KG designs. I listen fairly loud and like a dynamic and realistic presentation i.e. wide soundstage and uncompressed dynamics. It is what the 007 and 009 are create at. But to get that magic you have to drive them with a great amp. Even though the b009 is more efficient it still sounds too bright and edgy out of the 007t or 727 to me, and quite a bit flatter and 2D.

 

[Ali-Pacha]

 
I agree 100% with this. There is a well documented report on the 717 v 727 and how to do the mod. IMO though, the 717 or the 727 even with the mod is still well behind the KGSShv or any other of the KG designs. I listen fairly loud and like a dynamic and realistic presentation i.e. wide soundstage and uncompressed dynamics. It is what the 007 and 009 are create at. But to get that magic you have to drive them with a great amp. Even though the b009 is more efficient it still sounds too bright and edgy out of the 007t or 727 to me, and quite a bit flatter and 2D.

There are technical insights from KG, such as current sources on 727/KGSSHV vs. resistors on 717/KGSS. And of course unregulated PSU. Measurements from my SRM-727 showed bias and Vmax RMS slightly above specs (600 V / 500 V vs. 580 V / 450 V), guess because of that. But I don't know personnaly where 717/727 modded sit against KGSS(HV) because I've never had a listen to the latters.
 
Anyway, final payment for my BHSE 2 months ago, it should be here soon...by Justin's standards 

 So I don't care about those lesser amps 

Ali

 

[Quixote79]

 
I agree 100% with this. There is a well documented report on the 717 v 727 and how to do the mod. IMO though, the 717 or the 727 even with the mod is still well behind the KGSShv or any other of the KG designs. I listen fairly loud and like a dynamic and realistic presentation i.e. wide soundstage and uncompressed dynamics. It is what the 007 and 009 are create at. But to get that magic you have to drive them with a great amp. Even though the b009 is more efficient it still sounds too bright and edgy out of the 007t or 727 to me, and quite a bit flatter and 2D.

 
Totally agree.
I would try and find a used 717, as that will sound better, in fact give you a taste of what a better amp will sound like. The 717 is the bast sounding Stax amp bar the T2 IMO.
The 323/727 IMO are not good. I would also say using a step up transformer will have even more negative effects on the sound.

 

[oogabooga]

   
Totally agree.
I would try and find a used 717, as that will sound better, in fact give you a taste of what a better amp will sound like. The 717 is the bast sounding Stax amp bar the T2 IMO.
The 323/727 IMO are not good. I would also say using a step up transformer will have even more negative effects on the sound.

 
I use the 323 with my SR-007 and would disagree with the statement that it's "not good". I find the sound quite enjoyable. I'm not saying there aren't *better* options, mind you.