The Stax Thread III

[padam]

Anyone here messed around with collecting multiple LNS and heard a difference between different serial numbers the way there is with the 007?

Yes. I do have one with a suspicious Airbow-like SN (yes, on an original headband) that seems to be better than others (more clarity and 'liveliness' without loosing anything in smoothness) even though I have not seen them operating before the 404, so not sure if that was a custom one-off or what's up with that.

Otherwise, differences can also be attributed to how well the process of re-gluing the drivers went.
Because pretty much every single pair I have or had suffered from this problem, and if dust gets in during the process...it's not good.
I have started to see this appear on some 202/303/404 sets as well.

 

[573531]

srm212,252 etc are 6 volts 1 amp. So 6 watts
koss is 9 volts 1 amp. So 9 watts.
topping is 15 volts 1 amp. So 15 watts
.............
carbon cc is 125 watts
T2 is 225 watts
megatronxxl is 325 watts

no way an opamp driving transformers is going to be able to do .0008% thd

amir (incorrectly) measured koss at .01%
i (correctly) measured koss at .005% which is the limit of my equipment.
(i'm waiting on the new quantasylum qa404)

i do have a problem with the quoted noise figures. Likely they are measured with the attenuator in place.
That is clearly not correct.

What does input power have to do with output power? Especially if a big chunk of that is used just for heating the tubes and the regulators, wish you could quote output power instead because that’s what matters

 

[aokman]

Anything with tubes will waste a crapload of power on filament heaters and such. Anything class A will also waste a ton of power as heat. You cannot use input power as any sign of performance. If anything you can draw conclusions that anything with tubes will have more distortion, more susceptible to microphonics and a higher noise floor. Thats not to say they don’t sound good though…

 

[573531]

If an electrostatic headphone has an impedance of about 150 Kilo ohms like they typically do, even if you feed it 1000 Volts rms Which I doubt any headphone amp in the world is doing, except maybe an SRD7 setup, it will be sucking only 7 Milli amps which calculates to 7watts, VA to be precise.

 

[mulveling]

Enjoy your 10 Watt *total* power consumption amps -- I'm sure they're just fine
The difficult part of high quality electrostatic amplification is not in pushing raw power into the headphones - they don't use that much. It's in keeping the output devices biased into class A at rail voltages of 400V+, even regardless of tube heaters. That's why so much heat is burned up relative to the raw output power. And that's why people keep get tempted to use step-up transformers to avoid that issue.

 

[573531]

Enjoy your 10 Watt *total* power consumption amps -- I'm sure they're just fine
The difficult part of high quality electrostatic amplification is not in pushing raw power into the headphones - they don't use that much. It's in keeping the output devices biased into class A at rail voltages of 400V+, even regardless of tube heaters. That's why so much heat is burned up relative to the raw output power. And that's why people keep get tempted to use step-up transformers to avoid that issue.

quoting input power as a ranking system though is one heck of a stretch, all a manufacturer has to do is build in a short circuit and say mine is the best.

 

[mulveling]

quoting input power as a ranking system though is one heck of a stretch, all a manufacturer has to do is build in a short circuit and say mine is the best.

He didn’t advertise it as a black and white ranking system, but it does convey useful
information given the application and the disparities involved.

 

[573531]

He didn’t advertise it as a black and white ranking system, but it does convey useful
information given the application and the disparities involved.

There may be use for calculating the power bill but I don’t see much use, in predicting the end sound quality from the input power.

 

[mulveling]

Maybe use for calculating the power bill but I don’t see much use, in predicting the end sound quality from the input power.

Maybe you should be in basement-fi rather than summit-fi

 

[aokman]

On the topic, I can finally share some data from testing my Lundahl LL1630 setup and limited testing with all the gear I have available... It's fascinating to see it all plotted out and compare STAX gear to transformer setup. The STAX SRM-1 surprised me with its low end performance but also how quickly it falls off, also interesting was its behaviour changing quite dramatically based on the load used. Even a 2 wire reading from my oscilloscope (1mOhm) would drag down its output significantly...

In contrast the Lundahl LL1630 just doesn't give a crap really, it will deliver consistent results regardless of what load I put on it and is basically flawless across the FR (voltage output), its only limitation seems to be its fall off at 20hz and lower (270Vrms limit when the core saturates) it may be possible to work around this with a different winding configuration or possibly series them???

Out of the amplifiers used, the Topping LA90 was the most linear, clean and consistent from what I saw and 2 of them fit nicely on a desk with balanced inputs used. Also threw in some random testing with different amplifiers to see how it impacts the response and also a 1960s Encel tube amplifier for the LOLs of "tube sound"

Tried various loads from 120pF capacitor to 150kOhm resistor with capacitor in series / parallel and ended up settling on the 120pF capacitor alone with a single wire reading off my scope and multimeter (10mOhm) to give the SRM-1 a fair chance. I chose 150Vrms as the reference based on my listening levels.

What was used:

STAX SRM-1 mk2 (Fully restored and calibrated)
STAX SRD-7 modified with 4.7ohm resistors and switching removed (performed the best compared to my other SRDs)
Lundahl LL1630 - Driven by Topping LA90 Monoblocks (Roughly 90Wpc)
Lundahl LL1630 - Driven by Sony TA-N9000ES (Roughly 200Wpc)
Lundahl LL1630 - Driven by Luxman LV103 Tube / MOSFET Hybrid (Roughly 75Wpc)
Lundahl LL1630 - Driven by Encel CSM-40 OT Tube (Roughly 18Wpc)

 

[573531]

Maybe you should be in basement-fi rather than summit-fi

Is there where your man cave is at? Now I understand how amps with more heat dissipation would rank better. My bad.

 

[DougD]

On the topic, I can finally share some data from testing my Lundahl LL1630 setup and limited testing with all the gear I have available... It's fascinating to see it all plotted out and compare STAX gear to transformer setup. The STAX SRM-1 surprised me with its low end performance but also how quickly it falls off, also interesting was its behaviour changing quite dramatically based on the load used. Even a 2 wire reading from my oscilloscope (1mOhm) would drag down its output significantly...

<< snip snip >>

What was used:

STAX SRM-1 mk2 (Fully restored and calibrated)
STAX SRD-7 modified with 4.7ohm resistors and switching removed (performed the best compared to my other SRDs)
Lundahl LL1630 - Driven by Topping LA90 Monoblocks (Roughly 90Wpc)
Lundahl LL1630 - Driven by Sony TA-N9000ES (Roughly 200Wpc)
Lundahl LL1630 - Driven by Luxman LV103 Tube / MOSFET Hybrid (Roughly 75Wpc)
Lundahl LL1630 - Driven by Encel CSM-40 OT Tube (Roughly 18Wpc)

I know less about electronics than fish know about bicycles, but this really shows some very different stuff. INTERESTING!

You said the STAX SRM-1 mk2 is "fully restored and calibrated" ... so no CC mod (?constant current) ?

Same amp I'm using to drive pre-Lxxx lambdas. Mine is probably not well-calibrated. My hearing cuts off at 14.5k so I don't detect much of the high freq dropoff. Guess I know why the Stax almost never sound too bright and edgy to me.

Did I mention Very Interesting? Thanks for sharing.

 

[aokman]

I know less about electronics than fish know about bicycles, but this really shows some very different stuff. INTERESTING!

You said the STAX SRM-1 mk2 is "fully restored and calibrated" ... so no CC mod (?constant current) ?

Same amp I'm using to drive pre-Lxxx lambdas. Mine is probably not well-calibrated. My hearing cuts off at 14.5k so I don't detect much of the high freq dropoff. Guess I know why the Stax almost never sound too bright and edgy to me.

Did I mention Very Interesting? Thanks for sharing.

Not aware of any mods for the SRM-1mk2 only the SRM-T1? The restoration included new trimpots, diodes and all new capacitors except the polystyrenes. Outputs were removed and reseated with new thermal paste.

I was going to experiment with further improvements on it but abandoned it once I found out about the Lundahl Transformers and put all my efforts into that and a modern pro bias setup.

 

[oneguy]

Is there where your man cave is at? Now I understand how amps with more heat dissipation would rank better. My bad.

Whoa whoa whoa, let’s not put down basement man caves. I’ve seen some good ones and I’ll be rocking one eventually. Any dedicated space that can be carved out is a win

 

[HifiXMen]

On the topic, I can finally share some data from testing my Lundahl LL1630 setup and limited testing with all the gear I have available... It's fascinating to see it all plotted out and compare STAX gear to transformer setup. The STAX SRM-1 surprised me with its low end performance but also how quickly it falls off, also interesting was its behaviour changing quite dramatically based on the load used. Even a 2 wire reading from my oscilloscope (1mOhm) would drag down its output significantly...

In contrast the Lundahl LL1630 just doesn't give a crap really, it will deliver consistent results regardless of what load I put on it and is basically flawless across the FR (voltage output), its only limitation seems to be its fall off at 20hz and lower (270Vrms limit when the core saturates) it may be possible to work around this with a different winding configuration or possibly series them???

Out of the amplifiers used, the Topping LA90 was the most linear, clean and consistent from what I saw and 2 of them fit nicely on a desk with balanced inputs used. Also threw in some random testing with different amplifiers to see how it impacts the response and also a 1960s Encel tube amplifier for the LOLs of "tube sound"

Tried various loads from 120pF capacitor to 150kOhm resistor with capacitor in series / parallel and ended up settling on the 120pF capacitor alone with a single wire reading off my scope and multimeter (10mOhm) to give the SRM-1 a fair chance. I chose 150Vrms as the reference based on my listening levels.

What was used:

STAX SRM-1 mk2 (Fully restored and calibrated)
STAX SRD-7 modified with 4.7ohm resistors and switching removed (performed the best compared to my other SRDs)
Lundahl LL1630 - Driven by Topping LA90 Monoblocks (Roughly 90Wpc)
Lundahl LL1630 - Driven by Sony TA-N9000ES (Roughly 200Wpc)
Lundahl LL1630 - Driven by Luxman LV103 Tube / MOSFET Hybrid (Roughly 75Wpc)
Lundahl LL1630 - Driven by Encel CSM-40 OT Tube (Roughly 18Wpc)

it's simply awesome, thank you for sharing such valuable data