The Stax Thread III

[soren_brix]

BHSE bias current is 18mA afaik (Kevin's input), maybe differences between the commercial version and some diy builds?

Believe you are right. The original Blue Hawaii was set at 25mA ...but I guess that current has been lowered due to heat problems.

 

[joseph69]

BHSE batch #4 (current)
 
SPECIFICATIONS

Device Type	Solid State with Vacuum Tube Output
Frequency Response
Signal-to-Noise Ratio
Total Harmonic Distortion
Gain	500x / 54dB
Input Impedance	50K ohms
Output Voltage	1600V peak-to-peak
Inputs	2 RCA, 1 XLR
Outputs	1 RCA and 1 XLR loop output, 2 headphone jacks
Bias Voltage	580V (adjustable)
Operating Voltage	100VAC, 120VAC, or 230VAC
Power Consumption	200 Watts
Chassis Dimensions (Amp)
Chassis Dimensions (PSU)
Weight (Amp)
Weight (PSU)

 

[soren_brix]

 


Here are the schematics for my 845 electrostatic amp. Sorry for the hand drawings, but it's the way I've done this stuff for 40 years so it's a little late in the game to change
 
Electrically it's a pretty basic design. A simple 3 stage zero feedback single-ended design with a phase-splitting 1:1-1  1kV rated interstage transformer as the output device. Only things slightly unusual are the use of "fixed" bias on the output tube, the interstage transformer driving the 845, and perhaps the CCS/LED set up of the first stage.
 
The power supply is a little more complex. The HV is solid-state rectified but passes through cascaded series tube regulators. The bias supply passes through a relay that powers the B+ supply transformer. If the bias fails, the relay drops out and shuts down the amp. The 845 filament voltage comes from a simple "brute force" CLCLCRC supply. Haven't had much luck with regulated filament supplies at these (6.6A) current levels. First and second stage filament voltage is sourced from a small Pete Millett regulated supply.
 
In subsequent posts I'll discuss construction details and the reasons behind design and component choices.

Doesn't this deserve a thread on its own? Thanks for sharing.

 

[bmichels]

Can we consider that With A SR009, the KGSSHV Carbon can be better than a BHSE ?  
 
(it is easier to get and cheaper, but... is it at least as good as the BHSE ?)

 

[astrostar59]

  Can we consider that With A SR009, the KGSSHV Carbon can be better than a BHSE ?  
 
(it is easier to get and cheaper, but... is it at least as good as the BHSE ?)

Only way to know is get to hear both for yourself. Understand that is almost impossible however. Thing is, comparing a SS amp with a tube amp, they are so different. The tubes in the BHSE impart a sonic character that you will probably never get from a SS design, even though the BHSE only has the tubes on the 4th final stage. And having those tubes can help balance the system, whereas an SS amp is fixed, take it as is.
 
My guess (probably wrong) but the BHSE would be more transparent and organic, the Carbon more punchy and have more bass output. That seems logical to me. Maybe wait for more Carbon users to post here and at the 'other place'. Some will buy the Carbon and already have the BHSE so that will help. Having said that though, even if they use the 009s on both amps, the DAC they use will also change the sound i.e. if the DAC is a bit bright, the Carbon may be the better sounding amp in that particular system.
 
Regardless, I bet the Carbon will be superb. I would buy one for sure if my wallet could stretch....

 

[Tinkerer]

BHSE bias current is 18mA afaik (Kevin's input), maybe differences between the commercial version and some diy builds?

Also a link for MusicAlchemist before we beat yet another dead horse: http://www.head-fi.org/t/223263/the-stax-thread-new/18570_30#post_8458789

 
The amount of current you can push through is usually limited by what heat you can dissipate from the sand or the triodes. Like on the KGSSHV, the current would be about 5.5ma x2 per amp card with the normal onboard, but the heatsinks handle a little more just fine. And the offboard handles even more.

 

[jgazal]

...and how useful would that be to anyone speculating on this?

So forgive me. Not useful. Just genuine curiosity. Would like to grasp what designers can do to improve electrostatic transducers.

 

[kevin gilmore]

somewhere here there was a part of a thread where a couple of people did calculations
of how much current you need at the voltage swing you desire into a standard electrostatic load (120pf)
etc. (someone else can probably find the links)
 
But the result is roughly 20ma for full voltage swing with +/-400v power supplies at 20khz.
 
Every solid state or solid state/tube hybrid that's fully dc coupled (i.e no output transformers)
has to be a pure class A device, and while balanced, is not push pull.
 
My circlotron is a version of push pull, 25ma of bias, capable of 100ma or more current delivery.
(for those people that want full voltage swing at 50khz)
 
you can do push pull at lower voltages to reduce power and maintain frequency response
(likely the sure kse1500 does this because it gets way better battery life than the srm001)
 
recently I have received samples of "P" type devices rated at 1200V that are going to make
a standard complementary bridged amplifier possible.
 
Please thank the Solar and Wind industries for generating the need for these new devices.
(and the demand for these devices is going only one way, at least until cold fusion happens)

 

[rgs9200m]

  Can anyone tell me if the 007 ear pads are thicker than the 009 are pads…also are they compatable?
Thank you.

In terms of comfort only, I find the 007 Mk 2 to be significantly more comfortable than the 009; the 007 Mk2 pads feel more cushy and pillowy, whereas the 009 pads are spartan and basic, with sharper edges and just barely thick enough for me.
Personally, I would love a thicker more rounded pad on the 009, but it is what it is. I put up with it because of the great sound (KGSSHV-mini driven).
(In contrast, the original 007 Mk 1 that I owned starting in 1999 had pads so thin they just collapsed and felt unacceptable to me. Just my experience here. I actually sold them because of this discomfort.)

 

[joseph69]

  In terms of comfort only, I find the 007 Mk 2 to be significantly more comfortable than the 009; the 007 Mk2 pads feel more cushy and pillowy, whereas the 009 pads are spartan and basic, with sharper edges and just barely thick enough for me.
Personally, I would love a thicker more rounded pad on the 009, but it is what it is. I put up with it because of the great sound (KGSSHV-mini driven).
(In contrast, the original 007 Mk 1 that I owned starting in 1999 had pads so thin they just collapsed and felt unacceptable to me. Just my experience here. I actually sold them because of this discomfort.)

Thanks for the input.
I find the 009 pads extremely comfortable…no issues.
I was asking because when I pull the 009 cups ever so slightly away from my ears (without blocking the grills with my hands) the bass response/warmth is tremendously increased. I was just wondering if there were thicker pads available to move the drivers away from my ears to hear how it would sound. I may look into the pad mod #2 (HERE) and hear because it seems to describe what I'm hearing when pull the cups away from my ears and see how I like it. 
also by all means, I'm not complaining about the sound in any way…at all.

 

[Music Alchemist]

  Now I'm using it with my modified SR-007Mk2 which have pretty much outshone all my other cans.  Nothing can touch the bass these dish out or the sheer control over the entire sound spectrum.  The Carbon just adds to this as the detail they dig out is simply astounding, placing instruments in their own fixed place in the soundstage which the 009 can't really do as well. "

 
Wow, thanks for sharing that. I had no idea he liked his modified SR-007MK2 more than the original SR-007. Great news for me, since the SR-007MK2 is the only headphone I have nothing to complain about in terms of aesthetics.
 
Do you know if he did mods other than the port mod and springs? (Looked up the post and found those were the only mods involved.)
 

BHSE bias current is 18mA afaik (Kevin's input), maybe differences between the commercial version and some diy builds?

Also a link for MusicAlchemist before we beat yet another dead horse: http://www.head-fi.org/t/223263/the-stax-thread-new/18570_30#post_8458789

 
Well, I was aware of some of the figures (such as from this thread), but just didn't have a technical understanding of how electrostats benefit from current. All I know is that they need high voltage.

 

[Ali-Pacha]

You know, for as much as STAX amps get hammered, I'd still say things like an old 10S/12S do just fine for what they are. Better than even the 727A modded or the 717. Something like the KGSSHV is better, and noticeably so, but it's a game of inches past a certain point. Even Spritzer said how much he loved his rebuilt 10S with the SR-009 way back.

Also, pretty sure all the older KG amps were designed with the 007 in mind. The KGBHSE dates back to the Mk I and even the version 1 KGSSHV was something like 6 months before the 009 was announced, and that was mostly a higher voltage/current KGSS with a new power supply based on the one for BHSE if I remember right. The DIY T2 is basically a T2 (designed for the Omega).

I can't really think of a non-stax estat amp designed specifically for the SR-009. It's more like they piggyback off stuff made for hungrier phones.

I'm not the kind of guy who will slam Stax amp's. I own two lovely units (SRM-1/mk2 pro rev. C and modded 727II, both black), and they are maybe the best you can get for the (japanese) price, considering enclosure, regulations, reliability, performances, etc... We have to praise them, considering how much overpriced crap you may find in this hobby. I won't give brand names, but you know what I mean 

 
Birgir is obviously one of the most skilled guy out there regarding Stax / e-stats technology, with his Doppelgänger Herr Gilmore. Their technological statements won't give them any diplomatic awards, but as rude as the mafia could be, it has been (and still is) one of the most useful community to this hobby.
Considering Birgir's personal statements about sound, they are his, and I'm not always on the same wavelength, so I won't argue...let's say I do love 009, and won't be as hyperbolic (to say the least) on differences beetween amps.
 
From my experience, Lambdas do pretty well out of any Stax amp, but large Omegas drivers do benefit from extra current, whatever the sensitivity. So BHSE/T2 class are a good way to go when you want ultimate dynamics and tight response, not only beautiful tones. Sigmas are somewhere in the middle...easy to drive, but enclosure's damping has to be taken into account.
 
Obviously, Frank's pieces of art / madness are out of this world, and my only feeling about his work would be
(And that's what Jude did, indeed)
 
Maybe I should stop parroting myself for a while, now 

 
Ali

 

[Ali-Pacha]

  In terms of comfort only, I find the 007 Mk 2 to be significantly more comfortable than the 009; the 007 Mk2 pads feel more cushy and pillowy, whereas the 009 pads are spartan and basic, with sharper edges and just barely thick enough for me.
Personally, I would love a thicker more rounded pad on the 009, but it is what it is. I put up with it because of the great sound (KGSSHV-mini driven).
(In contrast, the original 007 Mk 1 that I owned starting in 1999 had pads so thin they just collapsed and felt unacceptable to me. Just my experience here. I actually sold them because of this discomfort.)

Metal springs within 007 pads, no springs in 009 pads.
Brown pleather on 007mk1, black lambskin leather on 007mk1 BL, 007mk2/A and 009.
Looks like springs were gone on your 007mk1....?

Ali

 

[Jones Bob]

Wow, thanks for sharing that. I had no idea he liked his modified SR-007MK2 more than the original SR-007. Great news for me, since the SR-007MK2 is the only headphone I have nothing to complain about in terms of aesthetics. Do you know if he did mods other than the port mod and bending the metal frame?


Well, I was aware of some of the figures (such as from this thread), but just didn't have a technical understanding of how electrostats benefit from current. All I know is that they need high voltage.

Electrostatic headphone present a load to the amp of a large plate capacitor, and will have a decreasing impedance at increasing frequency. Means that more current is required to fully drive them out to to 20kHz (or beyond).

 

[Jones Bob]

Thanks for the input.
I find the 009 pads extremely comfortable…no issues.
I was asking because when I pull the 009 cups ever so slightly away from my ears (without blocking the grills with my hands) the bass response/warmth is tremendously increased. I was just wondering if there were thicker pads available to move the drivers away from my ears to hear how it would sound. I may look into the pad mod #2 [COLOR=FF0000](HERE)[/COLOR] and hear because it seems to describe what I'm hearing when pull the cups away from my ears and see how I like it. 
also by all means, I'm not complaining about the sound in any way…at all.

I have gently bent/modified the arc of my SR-009 to:
1) Better fit with less clamping on my pumpkin sized head.
2) Get the most natural and deep bass response. In my case, there is very little clamping force now. An almost sloppy fit .

One can try this easily while slowly pulling the earspeakers out (relieving clamping force) while playing music. For me there was a location window of within 3mm where SQ just came together. I bent the arc and retest/rebend to make sure the SQ results are set at optimum.