Stax Interview and Factory tour 12/12/12 - Page 9

I have just read the article and would like to thank you all.

Very nice interview. I personally own 2 Staxs (507 and Omega II MkII) and now seriously thinking about 009 now after finished my KGSSHV and borrowed my friend 009 to try on.

Very nice read, thank you.

Continued thanks for you feedback about our project. 

Quote:

Originally Posted by analogsurviver 

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.

 

Yes, the most rational amplifier for driving ESL is something along your lines - tubes, step up transformer with the minimum step up ratio that achieves

full drive for the ESLs - done. It is perhaps the best compromise reagarding performance, cost, and above all, safety. High voltage "direct drive" amps are lethal and are getting ever more illegal in various parts of the world....

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.

Quote:

Originally Posted by bcschmerker4 

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.

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.

I've spotted one error in the article now that my work craziness has settled down.  The SR-Omega did sell for 180K Yen but the SRM-T2 was never that cheap.  The earliest price I found (in a 1994 brochure) was 460.000Yen but it later rose to 468.000Yen. 

Quote:

Originally Posted by MrViolin 

:) 

 

I've just thought about it, but why didn't they go back to making the SR-Omega when the company was revived? Sorry if this is me w/ random information that may not be true, but I remember seeing it somewhere. Would it have been costs, like in the cases of the R10 and the Orpheus? 

The answer I've gotten was due to cost as the housing and mesh drivers were very costly to make.  There were also some problems with the design that were never resolved.  I've spotted these fixes as I open up more and more Omegas. The SR-007 OTOH is a far more mature product so no tiny clip on bias connectors or faux center taps to try and make the headphones safe. 

Quote:

Originally Posted by spritzer 

I've spotted one error in the article now that my work craziness has settled down.  The SR-Omega did sell for 180K Yen but the SRM-T2 was never that cheap.  The earliest price I found (in a 1994 brochure) was 460.000Yen but it later rose to 468.000Yen. 

 

 

 

The answer I've gotten was due to cost as the housing and mesh drivers were very costly to make.  There were also some problems with the design that were never resolved.  I've spotted these fixes as I open up more and more Omegas. The SR-007 OTOH is a far more mature product so no tiny clip on bias connectors or faux center taps to try and make the headphones safe. 

Gotcha. Thanks spritzer. Is it me, or do you appear in all of the stax threads?  As a lurker 2 years ago, I remember seeing that same picture of the packaging quite a bit when I searched up the omega ii

Same brochure that's been on sale on ebay for the past 3 years. lol

Quote:

Originally Posted by MrViolin 

Gotcha. Thanks spritzer. Is it me, or do you appear in all of the stax threads?  As a lurker 2 years ago, I remember seeing that same picture of the packaging quite a bit when I searched up the omega ii

I'm required by law to participate... either that or somebody asks a question that I'm the only one who can answer. 

Quote:

Originally Posted by Currawong 

 

Good spotting about the price. The article translates what Mr Meguro said though, so I can't change it. 

 

I tend to think of the 009s as the new Omega I, but that may be due to the physical resemblance more than anything, if not some of the sonic resemblance as well.

Perhaps some footnotes are in order then? 

The 009 and SR-Omega are similar in many ways and their sound signature isn't that far off.  The SR-Omega is richer though and with a better top end.  The key to the SR-Omega is to get the earpads right as they are all 20 years old now and the black replacements are atrocious. 

Oh, noes... I was *so* hoping to see some news on the successors to the 4070... :( :( :(

I don't have anything to add that hasn't been said already but excellent work to all 3 of you. It's really interesting to see this side of such a legendary company. The article is definitely print-worthy.

I know there was demand for a more open top in the headphones which was mostly caused by the amplification not being up to snuff.  The SR-007 made some drastic changes to get rid of the ever present "etch" but most of the SR-Omega troubles are not due to the open nature of the drivers but the crap build quality.  The SR-009 does address just that but then Stax goes on yet another "new toy" tantrum with the new diaphragm material and we'll have to wait some years until they bounce back. 

As they stated in the interview Stax has specific design goals but they have got lost a few times in the last 50 years, embracing new technology over good sound.  The move from the SR-3 to the SR-3N was the first of these moves from a very good transducer to a mehhh replacement.  This is repeated time and time again, always with the promise of "moar clarity" or something like that.  SR-Lambda to Lambda Pro, SR-Sigma to SR-Sigma Pro, Lambda Nova to the numbered series for instance. 

My ideal headphone would be the SR-009 but with the SR-Omega diaphragm material...