Stax Interview and Factory tour 12/12/12

[CDWMcInSpots]

(The front of) Stax x 2:
 
Stax Ltd.
 

 
Stax Records
 

 

[bcschmerker4]

Quote:

(The front of) Stax x 2:
 
Stax Ltd.
 

 
Stax Records
 

  Anybody listened to Booker T. and the M. G.'s, e.g.:
 
GREEN ONIONS (Stax 701, Track 1)
(Al Jackson Jr./Booker T. Jones/Lewis Steinberg/Steve Cropper) Irving Music, BMI
 
through SR-Omegas?

 

[YoengJyh]

 

[Currawong]

I shall inform Mr. Sasaki that the readership thinks that the factory needs more hot, scantily clad women. It may, however, leave the male workers too embarrassed to leave their workstations, however. 

 

[Magick Man]

I can imagine the looks on the faces of those honorable (and very conservative) older gentlemen and can't help but chuckle.

 

[Hutnicks]

Quote:

  Anybody listened to Booker T. and the M. G.'s, e.g.:
 
GREEN ONIONS (Stax 701, Track 1)
(Al Jackson Jr./Booker T. Jones/Lewis Steinberg/Steve Cropper) Irving Music, BMI
 
through SR-Omegas?

The other Stax rears it's (sic) head here Green onions rocks!  But that's Isaak (Shaft) Hayes in the Lincoln there. Given the proportions of the girl that somehow seems appropriate.
 
Now if they could just get all binaural over this girl (Most consecutive top 10 singles in Japanese history) They'd make enough to build that new amp

 

[Donnyhifi]

Thanks guys, very nice work, it was an enjoyable read. I'm curious about this new amp that may be released hopefully not too long from now.

 

[qusp]

Before I run off with some semi OT rambling, I also must thank you guys for a great article, as has been said it looks as if STAX are a well rounded company, with typically humble Japanese front men and it gives some welcome encouragement to makers of short run high quality 'hand made' boutique audio products. Longevity is possible too, if you have the right attitude and can garner the support and respect of your customers.

Cruel facts: power supply voltages for a VERY dedicated ESL speaker all tube amp:

+ - 275 V DC input stage
+ - 650 V DC driver stage
+ 6.5 kV DC output stage ( EL 519 tubes, 4pcs/ch ) > 10 kVpp output into load
bias as per requirement of the speaker used

I still have this schematics somewhere - needless to say, stay well clear if you do not know exactly what you are doing. Will stretch best available electronic components to the max .
Finding someone capable of making safe power transformer(s) is just the first hurdle to pass.

It does apply to earspeakers, there were transformer boxes with BB suffix - but no amplifiers for earspeakers with BB/batteries for polarizing voltage/bias.

Forgot the non pro voltage for earspeakers ( it is lower ), but pro bias for Stax is 580 VDC ( NOT Vpp - that applies to drive signal - peak -to-peak amplitude PO ). The output of Stax amps is approx 1500 Vpp - so that output devices with rating of approx 800-900 V can be used. Unfortunately, since TVs became pancakes, no large scale need for semiconductors with this voltage rating and ever scarcer availability of solid state devices that can be used.

By Vpp I meant DC Plate voltage (for the vacuum-tube supply) rather than peak-to-peak AC volts.  Vb=+580VDC looks more manageable from a components point of view.  Beam power tubes are available that can withstand 1kVDC across cathode and plate at cutoff; but such tubes can be dangerous to tune due to the exposed plate leads.  Readily-available beam power tubes for audio, such as the 6L6GC's, 6V6's, and EL34's, work at the same +250VDC  as the 7025A and its 12A?7 twin-triode cousins (spec sheets have 300VDC, plate to cathode, as design maximum).  In any case, some sort of multistage power supply is likely a necessity for providing +250VDC to the audio-tube plates and +600VDC for electrostat field bias.

A few of years ago that may have been true and they are still not really prevalent, but since the advent of Silicon Carbide (SiC) dies, more and more discrete solid state devices with these kind of ratings are coming to market. Especially the last 12 months or so. its being driven by High Voltage/Power RF amplifiers/satellite Coms and Solar/EV development.

Parts from Infineon, IXYS, CREE, Semelab, Transic, Semisouth (recently chapter 11 struck with them, but they sold their remaining Dies to Semelab) are all running to247/to3 and larger parts at 1200-1800VDC.

Silicone Carbide (SiC) Devices

CREE has Mosfets and Zero Recovery Schottky rectifier diodes/bridges

Semisouth was making fantastic Power Jfets (such as the R100 and R125 Enhancement mode parts of Pass Labs fame), Static Induction Transistors (SITs) and rectifiers

Transic is making hirel Bipolars and rectifiers

Infineon
Is making Schottky Diodes and Mosfets (not sure if they have any Sic yet but over 1kV parts anyway

Semelab has repackaged the dies from the Semisouth labs into Hi-Rel packaging (and upped the price 500%) as well as some crazy Mil/RF and Hi-rel solar spec parts of their own (semelab are one of the largest fabs of audio spec Lateral fets and bipolars on the planet right now).

IXYS is making Schottky rectifiers, Mosfets (I think) and what look to be jfet based high voltage programmable Current sources

Some of these are very useful for audio indeed and lately one of the Co-founders of Semisouth has joined DIYAUDIO and become interested in Class A amps (hes building a Pass F2J with completely unobtainium exotice SITs), with some interesting murmurs.

It seems not all hope is lost for lovers of linear audio parts, there is also a burgeoning newly growing AM radio interest in China that is driving some production of nice low noise jfets and current mirrors (albeit in small SMD packages)

so dont count out some more development of fully solid state class A Stat amps, if the market will have it and of course hybrids

/OT

 

[brat]

Quote:

[Mr. Meguro] Until recently, we used the SRM-T1 as the base. It is a product with a long history. It started as the T1, then the T1S and the 006t. Currently, we are using 2 production models as references, the SRM-727A solid-state and SRM-007tA tube amps.

That explains why the 727 has never made my omegas sound decently but people say it's good with SR-009.

 

[dukeskd]

Quote:

That explains why the 727 has never made my omegas sound decently but people say it's good with SR-009.

It's really good for me, I feel there is a good synergy however I haven't heard other TOTL electrostatic amps so I can only wonder. But many others here like the pairing.

 

[wink]

Quote:

Quote:

By Vpp I meant DC Plate voltage (for the vacuum-tube supply) rather than peak-to-peak AC volts.  Vb=+580VDC looks more manageable from a components point of view.  Beam power tubes are available that can withstand 1kVDC across cathode and plate at cutoff; but such tubes can be dangerous to tune due to the exposed plate leads.  Readily-available beam power tubes for audio, such as the 6L6GC's, 6V6's, and EL34's, work at the same +250VDC  as the 7025A and its 12A?7 twin-triode cousins (spec sheets have 300VDC, plate to cathode, as design maximum).  In any case, some sort of multistage power supply is likely a necessity for providing +250VDC to the audio-tube plates and +600VDC for electrostat field bias.

A few of years ago that may have been true and they are still not really prevalent, but since the advent of Silicon Carbide (SiC) dies, more and more discrete solid state devices with these kind of ratings are coming to market. Especially the last 12 months or so. its being driven by High Voltage/Power RF amplifiers/satellite Coms and Solar/EV development.

Parts from Infineon, IXYS, CREE, Semelab, Transic, Semisouth (recently chapter 11 struck with them, but they sold their remaining Dies to Semelab) are all running to247/to3 and larger parts at 1200-1800VDC.

According to Kevin GIlmore the problem, if I remember correctly, is that the new devices don't have the same low internal capacitance as the old devices.

 

[padam]

Quote:

That explains why the 727 has never made my omegas sound decently but people say it's good with SR-009.

 
Yes the SR007 is really not a good match with it.
I would say there may be some synergy going on with the SR009 but the annoying bland and soft character of the 727 is very much still there so I don't really like that either.
 
Both the 717 and KGSS sound much more like a solid state amp should.
There is a mod that is supposed to fix the NFB design but I've yet to hear it.

And I am not sure if I get the reason why Stax made to sound like this in its stock form.

 

[spritzer]

Quote:

According to Kevin GIlmore the problem, if I remember correctly, is that the new devices don't have the same low internal capacitance as the old devices.

 
That is indeed the problem.  There are plenty of high voltage mos-fets out there but they are useless for this role due to the internal capacitance.  Output capacitance should be as low as is possible unless one wants nasty artifacts such as high top end distortion. 
 
I do wonder what part Stax will use now as the 2SC5466 is EOL... 

 

[Scottsmrnyc]

I like both Stax Companies- But now that I am almost 60 years old, I might like the Stax Electrostatic Earspeaker Company more.  Did I just say that!

 

[Scottsmrnyc]

I am tentatively thinking of a return visit to Japan in the Fall or Winter of 2013.  Not exactly sure yet.  Can you tell me again when the Big Headphone Bash takes place at The Tokyo Forum?