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The Stax Thread III - Page 125

post #1861 of 2800

Slew rates DO matter. Most amplifiers have such high slew rates that they are thought not to matter- and certainly I doubt whether anyone could hear the difference in two amplifiers, one with a slew rate of 200 V/uSec and one with a slew rate of 20 V/uSec - all other things being equal.  But if you had an amplifier with a 1 V/sec slew rate, do you really think it would sound OK?

 

When driving the reactive load presented by the 007, most electrostatic amplifiers tend to start showing power bandwidth and slew rate problems at their max voltage output levels.  

 

I'll post some 'scope pictures if I get around to it. Square waves even as low as 1 kHz don't really look all that great from the output of a T1 driving an 007 at ~90 dB SPL, while the DIY T2 is close to flawless.  

 

You CAN hear the difference.  Be sure you have actually tried listening to a 007 mk I on both a DIY T2 and a T1  (or 727 etc)  before you claim  that these things don't matter.

 

I suspect that IM also increases from the T1 and other amps at high-ish drive levels into an 007.  With a steady-state test signal (sine wave etc) the amp's negative feedback will reduce IM and THD levels rather quickly, but music is NOT a steady state signal, and I think that the lesser amps are introducing IM into short-duration signals.  This is just a guess. I have no way to measure this.  My distortion analyzer relies on sine wave test signals, as they all pretty much do.

 

The DIY T2  is extremely linear even at high output voltage levels, even without negative feedback.  So is the BHSE.  


Edited by milosz - 3/26/14 at 3:35pm
post #1862 of 2800
Quote:
Originally Posted by 3X0 View Post
 

I'll be the first to admit that I have a fairly limited understanding of what such factors mean in practical applications (i.e. outside of circuit topology theory and conversation topics for electrical engineers).

 

In particular I'm unsure of the implications of damping factor and slew rate in the electrostatic realm.

 

That's why I'm genuinely curious as to how and when the theoretical limits of electrostatic amplification might be breached, particularly from individuals who have first-hand experience with such audible distortion/clipping. This is not just for something like a SRM-252S or SRM-323S or SRM-T1, but also for justifying the increments from a KGSS to a KGSSHV to a BHSE to a SRM-T2.

 

I have the money for just about anything short of a SRM-T2/DIY-T2, but I just can't justify the outlay. Let me say that my first-hand experience with the KGSSHV was less than revelatory.

 

The slew rate is how fast the output voltage can change. If you ever hit the slew rate limit, there is substantial distortion because the output can't "keep up" with the input. You shouldn't actually ever be breaching this if the amplifier is properly built for the load it drives. I measured my Blue Hawaii's unloaded slew rate at about 125V/uS (it is entirely possible the BHSE has superior slew rate, I didn't spend a whole lot of time tuning my DIY BH for slew rate, and the published schematic has typos so every DIY BH is going to be a little different). This means that at full 800Vp-p output, there is no slew rate distortion up to 50kHz. I always forget to measure it with headphone load when I have it in the shop, but it is safe to say it's going to be quite a bit lower. 


Basically, since the slew rate limit is caused by the amplifiers inability to provide sufficient current to the load to slew its voltage. Since the current required to slew a capacitor is proportional to the capacitance, adding more capacitance will directly decrease the slew rate of the system.

 

 

I think it was stated that slew rate doesn't matter, because it actually doesn't unless you're hitting the wall. At reasonable volume levels with a reasonably quality amp, you're just not hitting the slew rate limit. But the thing is, if you start adding long cables and multiple headphones, you might. Now, that's not to say there aren't other forms of distortion caused by increasing the capacitive load. But calling any of those slew rate limitations is an incorrect use of terminology.

 

It blows my mind that industry standard is to put two output jacks on electrostatic amplifiers. It is completely absurd to listen to an amplifier with two headphones attached. Sure, this might not matter on a T2, but just about everything else including the Blue Hawaii does not have enough power to recklessly be throwing away slew rate and capacitive loading distortion. I believe it started as amps having two jacks, one pro bias and one standard bias, and now it just kind of stuck because your amplifier would look worse with only one jack. But in fact, the second jack should NEVER be used if you care about sound quality. Those of us who build electrostatic headphones have noticed that etching away even one or two square inches of unnecessary stator area affects the sound produced, especially in the trebles where the slew rate is much higher. Now add a second pair of headphones...

post #1863 of 2800
Quote:
Originally Posted by dripf View Post

Although, if you do transpose the formula into SR = current / capacitance, things aren't looking so great for my hot air.

By this I mean that I've proven milosz's point. rolleyes.gif
Good conclusion 😄
post #1864 of 2800
Quote:
Originally Posted by milosz View Post

Slew rates DO matter. Most amplifiers have such high slew rates that they are thought not to matter- and certainly I doubt whether anyone could hear the difference in two amplifiers, one with a slew rate of 200 V/uSec and one with a slew rate of 20 V/uSec - all other things being equal.  But if you had an amplifier with a 1 V/sec slew rate, do you really think it would sound OK?

When driving the reactive load presented by the 007, most electrostatic amplifiers tend to start showing power bandwidth and slew rate problems at their max voltage output levels.  

I'll post some 'scope pictures if I get around to it. Square waves even as low as 1 kHz don't really look all that great from the output of a T1 driving an 007 at ~90 dB SPL, while the DIY T2 is close to flawless.  

You CAN hear the difference.  Be sure you have actually tried listening to a 007 mk I on both a DIY T2 and a T1  (or 727 etc)  before you claim  that these things don't matter.

I suspect that IM also increases from the T1 and other amps at high-ish drive levels into an 007.  With a steady-state test signal (sine wave etc) the amp's negative feedback will reduce IM and THD levels rather quickly, but music is NOT a steady state signal, and I think that the lesser amps are introducing IM into short-duration signals.  This is just a guess. I have no way to measure this.  My distortion analyzer relies on sine wave test signals, as they all pretty much do.

The DIY T2  is extremely linear even at high output voltage levels, even without negative feedback.  So is the BHSE.  

Milosz, by any chance would you happen to have any square wave measurements at lower dB SPL, like 50dB or less. I have not done any listening comparisons between my DIY-T2 and other electrostatic amps i have had, but am curious, particularly since I tend to listen at very low volume levels.

Dude, regarding the 2 output jacks issue, I had been under the impression from comments made by Kevin Gilmore that there was little to no difference in running two headphones at the same time - but I could be mistaken on this. Maybe a BHSE, Liquid Lightning, Electra or WES owner could ask their respective makers the question.
post #1865 of 2800

I think the KG statement about 2 ES headphones driven from a stat amp concurrently from the two outputs is not a problem since the Z load is very different on electrostats to that of conventional dynamic transducers. My memory is vague here as it was in the old Stax thread and on the other site but I could be wrong.

post #1866 of 2800
Quote:
Originally Posted by georgep View Post


Milosz, by any chance would you happen to have any square wave measurements at lower dB SPL, like 50dB or less. I have not done any listening comparisons between my DIY-T2 and other electrostatic amps i have had, but am curious, particularly since I tend to listen at very low volume levels.
 

 

My DIY T2 is back apart now, boards and so on being fit into the casework.  No measurements possible for a while yet.

post #1867 of 2800
This has me curious to measure various step responses on the 007 and 009 through my 727 amp and bhse when it gets (any day or week or month now smily_headphones1.gif ).
post #1868 of 2800
Quote:
Originally Posted by arnaud View Post

This has me curious to measure various step responses on the 007 and 009 through my 727 amp and bhse when it gets (any day or week or month now smily_headphones1.gif ).

I'd be interested to see what the signal output from the amp itself looks like, the acoustic output of the 007 and 009 are of interest too but I'd be curious to see if you can see any difference in the voltage from the amp.  CAUTION:  use isolated 'scope! High voltages!

post #1869 of 2800

Milos what's your scope/gear that you'll be using to measure your T2 when completed?

post #1870 of 2800

Hi,

 

I'm trying out the Stax 4170 system and can't detect any 'etching' in the mid-range. I'm not sure exactly what an etched mid range is supposed to sound like but the SR-407 headphones are clearly a step change from dynamic headphones. Compared to my previous Sennheiser HD 700 there's no excruciating emphasis of the treble so sibilance is not artificially emphasised. The SR-407 seems to produce a warm sound compared to my old Stax Basic system with no fatiguing treble issues. 

 

However, for financial reasons I may end up buying a SRM-323S and SR-407 instead (after selling my HD 650 and Graham Slee stuff). Is there a very noticeable difference in the sound quality of the SRM-323S compared with the SRM-006TS? I've searched the forum without luck. Due to size of these amplifiers (compared to my tiny Stax Basic system) the SRM-006TS has to sit on top of my PC tower. I know class A valve amplifiers run hot but the SRM-006TS is like a radiator.

 

Thanks

post #1871 of 2800
Quote:
Originally Posted by martyn73 View Post
 

Hi,

 

I'm trying out the Stax 4170 system and can't detect any 'etching' in the mid-range. I'm not sure exactly what an etched mid range is supposed to sound like but the SR-407 headphones are clearly a step change from dynamic headphones. Compared to my previous Sennheiser HD 700 there's no excruciating emphasis of the treble so sibilance is not artificially emphasised. The SR-407 seems to produce a warm sound compared to my old Stax Basic system with no fatiguing treble issues. 

 

However, for financial reasons I may end up buying a SRM-323S and SR-407 instead (after selling my HD 650 and Graham Slee stuff). Is there a very noticeable difference in the sound quality of the SRM-323S compared with the SRM-006TS? I've searched the forum without luck. Due to size of these amplifiers (compared to my tiny Stax Basic system) the SRM-006TS has to sit on top of my PC tower. I know class A valve amplifiers run hot but the SRM-006TS is like a radiator.

 

Thanks

 

I can't speak towards comparing the two amps but I've read a lot from some pretty damned on-top-of-it Stax aficionados and from what I've read, the SRM-323S is considered by many to be one of the best (if not the best, considering the money) Stax amps currently available ... also, one of the most powerful.

 

You could probably expect a slightly more detailed image with the SRM-323S ... I use one currently (with 404LE's and Koss 950's) and love it. Had a SRM-T1 before and the 323S blows it away (for my preferences, anyway) ...


Edited by s1rrah - 3/29/14 at 12:43pm
post #1872 of 2800

Hello all. As you see, a newbie (few posts!) but a long time owner of Stax headphones. I currently own the 20 years old SR-5 (driven with either SRD-6/SB or with the portable unit SRD-X) and the SR-001(the baby Stax).

 

I have been a bit away from Hi-end music gear in the last years partly due to the attraction to mobile devices such as iPod Classic (which I also own). But having discovered the new generation portable players (such as Fiio X3) I am back to being interested in the Stax headphones.

 

Through ebay, I have bought from Japan a SRM-T1S (Japan version, 100v only). I have connected my Fiio X3 to it through the line out and it sounds great.

 

My questions are two:

 

1) I was sourced by the seller a 220V to 100 V converter but the Power is too low, it overheats and disconnects. I have bought a 220V to 110V converter. Works fine with it, and since I have seen that there is a fuse inside the amplifier connected to the main current plug, I assume that I run no risk (otherwise, the fuse would blow out). I understand that having a 100V converter would be better but they are extremely hard to source. So…. what are the risks, if any, I am running by doing this?

 

2) Thinking in replacing the SR-5, does it make sense to buy the 507?

 

Thanks!

post #1873 of 2800
Quote:
Originally Posted by martyn73 View Post
 

Hi,

 

I'm trying out the Stax 4170 system and can't detect any 'etching' in the mid-range. I'm not sure exactly what an etched mid range is supposed to sound like but the SR-407 headphones are clearly a step change from dynamic headphones. Compared to my previous Sennheiser HD 700 there's no excruciating emphasis of the treble so sibilance is not artificially emphasised. The SR-407 seems to produce a warm sound compared to my old Stax Basic system with no fatiguing treble issues. 

 

However, for financial reasons I may end up buying a SRM-323S and SR-407 instead (after selling my HD 650 and Graham Slee stuff). Is there a very noticeable difference in the sound quality of the SRM-323S compared with the SRM-006TS? I've searched the forum without luck. Due to size of these amplifiers (compared to my tiny Stax Basic system) the SRM-006TS has to sit on top of my PC tower. I know class A valve amplifiers run hot but the SRM-006TS is like a radiator.

 

Thanks

My Stax 007t/ii runs fairly cool for a tube amp with no significant heat build-up with 3 inches of clearance on top.

post #1874 of 2800
Quote:
Originally Posted by angeche View Post

 

Through ebay, I have bought from Japan a SRM-T1S (Japan version, 100v only). I have connected my Fiio X3 to it through the line out and it sounds great.

 

My questions are two:

 

1) I was sourced by the seller a 220V to 100 V converter but the Power is too low, it overheats and disconnects. I have bought a 220V to 110V converter. Works fine with it, and since I have seen that there is a fuse inside the amplifier connected to the main current plug, I assume that I run no risk (otherwise, the fuse would blow out). I understand that having a 100V converter would be better but they are extremely hard to source. So…. what are the risks, if any, I am running by doing this?

 

2) Thinking in replacing the SR-5, does it make sense to buy the 507?

 

Thanks!

Did you buy yours from buyjapan from ebay?  A 507 would be a substantial step up from the SR-5 except the mids. The SR-5 is all about voicing and mids.

post #1875 of 2800

Yeah, mids on SR-5 are soooooooo lovely.

When I want to hear voices at their best, I drop my SR-009 and take my SR-5 :p

 

Ali

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