The Stax Thread III
Nov 1, 2015 at 2:12 PM Post #7,007 of 25,142
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.

The KGST was an attempt to design an amp for the 009 specifically.

Also, according to spritzer's store the KGSSHV Carbon was designed/tweaked for the SR-009 specifically.
Nov 1, 2015 at 2:51 PM Post #7,009 of 25,142
  I'am leaving the comparison for now and let other Head-fier to compare it with "better" amps

Even though I just started my journey into estats and have never heard another amp than the 
KGSSHV (spritzer build) I have to say that my 009 sounds amazing to me…but like I said, I have nothing to compare it to and ignorance is bliss. I'm waiting for my BHSE to arrive so then I'll compare both amps.
Nov 1, 2015 at 3:03 PM Post #7,010 of 25,142

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.
Nov 1, 2015 at 3:08 PM Post #7,011 of 25,142
Considering how rigid the 009 construction is, and bigger diaphragm of the 009, the L700 seems to be less solid build and have the usual Lambda diaphragm size, it is a bit surprising that the sound is "frightening close" ... might it be that what you actually hear is that your amps is just not up for the task?

Stax considers 009 as their greatest achievement to date. OK, they are far more sensitive than previous Omegas, but large drivers do need powerful amp with lots of current to really shine. So they began to work on a TOTL T2/BHSE/Carbon like amp.
So Stax's choice through L700 looks the most effective one for Q/P ratio and company's health. Unless Stax reveals their TOTL amps pretty soon, tough times are coming for 009 (and moreover 007).

Considering Stax portfolio evolution, what would be next step?

An improved SR-007 adopting the 009/L700/L500 metal arc and multi layer electrodes, while retaining the current SR-007 ear cups, ear pads and its peculiarities, such as rotating ear cups, unperforated stator edges and thicker spacers?

So in order to unleash full performance of such hypothetical new headphone, does Stax need first to develop the high power amplifier you mentioned?
Nov 1, 2015 at 3:14 PM Post #7,012 of 25,142
  Not as far as I know.
"Sound wise they are very similar but the KGST is warmer and more forgiving making it a better match to the SR-009", taken from Spritzer own website

You were reading the description of the KGST vs the BHSE.  For the KGSSHV Carbon he says:
 The original design concept for this amp was born to tame the rough top end of the SR-009 but it grew from there to become the best solid state amplifier we have designed.

Nov 1, 2015 at 4:03 PM Post #7,014 of 25,142
I dread to think how much you will be posting after you hear the higher models.
You might want to start your own thread.

LOL at the reputation comment about starting my own forum. XD
I've actually been considering starting one of those blog/journal threads for some time. Believe it or not, I have a rather large "fan club".
  large drivers do need powerful amp with lots of current to really shine.

Which reminds does this "lots of current" thing work? Most technical sources say that electrostats require high voltage, but barely any current. But I also hear about how they generally sound better with a better power supply. Does this only involve the power supply, or other aspects as well?
  Can anyone tell me if the 007 ear pads are thicker than the 009 are pads…also are they compatable?
Thank you.

Check this out:
Nov 1, 2015 at 4:30 PM Post #7,016 of 25,142
  Check this out:

  That info should be in the SR-007 ear pad mod thread, but IIRC the 009 are a slightly larger diameter meaning you can put them on the SR-007 but not vice versa

Thank you for the information, I appreciate it.

Nov 1, 2015 at 4:41 PM Post #7,017 of 25,142
You were reading the description of the KGST vs the BHSE.  For the KGSSHV Carbon he says:

Spritzer quotes from the other site:
May 2014:
"I haven't had enough time with this version yet but the design offers a nice middle ground between the BH and the KGSSHV.  That's also why we picked it as a starting point to do a 009 amp...  
May 2015:
"Now with it sitting in my main rack for a couple of hours it's time for some impressions.  
  The basic concept of this amp came from me wanting to tame the SR-009 artificial top end and doing it in a cool way.  End result is the continued refinement of older circuits but the changes here will no doubt migrate to the older circuits at some point.  As better SiC units became available and the new SR-009 showed up it rendered this amp unnecessary but then it became clear that it could melt together the superb technical nature of the KGSSHV and the musicality of the KGST into one package.  So we basically have a lot of power, with plenty of detail and a tube like sound from a solid state amp. 

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"
If you have a look at the schematics of the KGST and the Carbon you'll see that it's a the Caron is a KGST with silicon carbide output devices in place of the triode...sort of ....where as the KGST runs at 10mA at the output stage the Carbon runs at 20mA ...pretty close to the 25mA the BHSE runs ...
Nov 1, 2015 at 4:48 PM Post #7,019 of 25,142
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:

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