The Headcase Stax thread

[spritzer]

Have the KingSounds here on loan right now.  Pin out appears to be the same as Stax pro bias.  Running from the normal bias jack of my SRM-T1. 

 

Spent some time at the dealer's place with the KS amps for about an hour.  The SS amp sounded better to me.  More control, blacker background, etc.  The tube amp sounded wimpier.  SS amp got really hot near the top...I think they're gonna have to look at more adequate heatsinking.  Both amps were RCA input only (SS had a loop out as well).  He popped the top off the tube amp to change the tubes, so I got a peak at that at least.  2x 12AX7, 4x EL84, and 1x dunno.  I'm pretty sure it was some kind of rectifier tube. 6-something-something-L I believe. 

 

Looks-wise, the headphones scream MADE IN CHINA.  The plastic is really cheap toy stuff and I wouldn't try to bend them much.  The positive to that is they're super light and quite comfortable on my head.  I don't know if somebody with a bigger head can wear these without snapping the headband though.  Pad material feels decent (better than ESP950), and they're rather large in diameter so my ears don't really touch anything.  Again, comfy.  Cups don't have much travel to move up and down, but can swivel from side to side freely so you can fold them flat if needed (think Grado pizza box).  Cups don't really seem to be able to tilt much...it looks like they should but I don't want to break them.  Cable and connector both pretty nice. 

 

You can't really see the stator design unless you hold it up to a pretty bright light.  Looks to be standard perforated metal, hole diameter about 60% size of those on the grill.  They're also using pinwheel/spoke bracing as found on the SR-Omega/SR-009.  Think 009 brace but with a quarter-size hole in the middle and 12 spokes.

 

I'll post impressions of the sound when I have some more time with them.

 

I missed your PM by about 10 min or I would have taken you up on it.  Not sure when that other set arrives... 

 

I'll be sure to test that headband to destruction too. 

 

ECC83's and EL84's... are they high?  Pretty similar to this then:

 

http://en.dubieltubeamps.pl/102/eurydice-stereophonic-tube-amp-dedicated-to-electrostatic-high-class-headphones/

 

Which I just sent Kevin a link about laughing about it.  At least the Kingsound isn't 3K+$ like the Polish one.  Both will have very limited voltage swing in common... severely limited.

Edited August 3, 2013 by spritzer

[spritzer]

 

On other hand

 

Golden 12S?

 

http://www.ebay.com.au/itm/ULTRA-RARE-Mint-STAX-SRA-12S-Golden-PRO-bias-NORM-bias-Modified-by-STAX-/200942962215?pt=UK_AudioTVElectronics_HomeAudioHiFi_Amplifiers&hash=item2ec9224627&_uhb=1

 

Doesn't mean anything past the usual upgrades Stax made to their long running designs.  The SRA-10/12S went through at least 4 different power supply layouts though they are all pretty much the same.  Two preamp revisions too but it was mostly change of parts. 

 

Which brings me to your issue, just sub that part with some modern Jfet.  Stax moved to the 2SK30A in the SRA-12S so that might work (too lazy to compare the data sheets), K117, K170 and all the Fairchild Jfets.  Just find one that's close and the right Idss and try it.  Just watch out for the pinout. 

[complin]

Just means that the front of the unit is champagne colour which was in vogue at that time rather than the usual silver or black

 

On other hand.

 

Golden 12S?

 

http://www.ebay.com.au/itm/ULTRA-RARE-Mint-STAX-SRA-12S-Golden-PRO-bias-NORM-bias-Modified-by-STAX-/200942962215?pt=UK_AudioTVElectronics_HomeAudioHiFi_Amplifiers&hash=item2ec9224627&_uhb=1

 

[DefQon]

Doesn't mean anything past the usual upgrades Stax made to their long running designs.  The SRA-10/12S went through at least 4 different power supply layouts though they are all pretty much the same.  Two preamp revisions too but it was mostly change of parts. 

 

Which brings me to your issue, just sub that part with some modern Jfet.  Stax moved to the 2SK30A in the SRA-12S so that might work (too lazy to compare the data sheets), K117, K170 and all the Fairchild Jfets.  Just find one that's close and the right Idss and try it.  Just watch out for the pinout. 

Thanks for that, I was looking at the 2Sk117 (BL version) which has a max idss at 14mA. Just checked the 2SK170 (BL version as well) and it's rated at max 20mA. Guess it works, I'll order some of each kind. From here onwards it's pretty much shotgun troubleshooting.

[spritzer]

Anybody want to bet that this is the basis of the M-20 amp?

 

[mypasswordis]

Wtf am I looking at... but I see 12AT7 and 6FQ7 on the bottom so the top schematic is also a Stax design? Must be the first one they ever made...

[spritzer]

It's the first of the two designs they published in 1968 for DIY use.  The second, which is at the bottom of the page (you can just make out the tube types), is the SRX. 

 

This design fits with just one rectifier and the low voltage rating of the tubes used.  They could have used a voltage doubler after the rectifier but it makes little sense since the EL84's really don't like 300V or more.  There are also just 8 tube sections in those 6 tubes and only two ways to go about it.  Either you use this setup with a two stage phase splitter into the output tubes or a diffamp on the input which provides enough gain and uses one tube for each channel.  The small amp I built with the Ikea bowl over the transformer is essentially just that, this circuit with a differential amp input to make it fully balanced  but run at +300/+600V. 

[spritzer]

So, who wants to see the Russian Blue Hawaii? 

 

http://fluxlab-acoustics.com/Products/11

 

Looks kinda nice but they are using the old parts so sourcing them must be an utter pain. 

[complin]

Not anything to do with the first three letters being

KGBH Hybrid amplifier for electrostatic headphones Kevin Gilmore  

 

Must be sponsored by the Russian government

Looks 80's retro with all that wood but construction looks good but no pricing

 

So, who wants to see the Russian Blue Hawaii? 

 

http://fluxlab-acoustics.com/Products/11

 

Looks kinda nice but they are using the old parts so sourcing them must be an utter pain. 

[Torpedo]

Nice enough, however I wonder if with just those heatsinks under the hood it'll dissipate heat properly. Making the twin umbilical must be a PITA.

[livewire]

Moozt zound vunderbar!

[Dusty Chalk]

Uh, that's German, dude.  I believe the word you're looking for is замечательно.

[spritzer]

I'd rather have gone with "in Russia, amp listens to you"...

[tkam]

I actually kinda like the wood look, but really the best part about that build is the company name: Flux Lab!

[spritzer]

There is a newer version too with a full size PSU so they can be stacked.  So pretty much a WES which isn't terrible... 

[wink]

спасибо

[DefQon]

Any recommendations for a dual volume control stereo 50k pot? (One's used on SRM1 MK2's etc)

[luvdunhill]

No compensation caps? Seems unlikely that it would be stable.

[spritzer]

The blue caps are probably the WIMA FKP's so that could be 470pf/2000V.  Still, those are kinda important... 

 

I'm also wondering what's lurking underneath the boards.  Could be the missing resistors from the board as thick films bonded to the sinks. 

[n3rdling]

I've spent some time comparing the KingSounds to a LNS, both driven from a T1S.  As the hours passed I definitely preferred the LNS.  My biggest complaint with the KS is that they sound super laid back.  I noticed this the first time I auditioned them, and ended up having to play them a lot louder than I normally listen.  At these higher levels, I noticed quite a bit of compression on loud passages...the drivers didn't seem to like being pushed that much.  I actually don't mind laid back phones at all, but these took it a little too far for me.  There's also a large difference in soundstaging between the two: the LNS has the typical Lambda soundstage, with decent size and really 'tall' imaging; the KS has a very natural soundstage with smaller but more believable sized instruments/sounds.  The KS are quite bass shy, with even less sub bass impact than the Stax which is saying something.  The KS also emphasize hissing/pops/ticks on the recording.  Comparing the mids of the headphones, the Stax is preferred once again.  The KS don't stray too far off neutral, but have a sort of echo'ey sound to the mids if that makes any sense.  Strings sound much more right on the LNS especially.  The KS are also one of the most veiled sounding electrostats I've heard.

 

I'm sure most people haven't heard the LNS before (plus it's OOP), so I'll try to compare the KS to my 207's later.  Note that the LNS is easily one of my favorite Lambdas.  I would say the KS actually sound somewhat like a less neutral ESP950 (more treble, less mids), with a slightly bigger soundstage and a bit less detail.

 

Also note that I was running the KS from normal bias voltage so there might be a little change in sound once I put the recommended voltage, though going by past experience it won't change much.

Edited August 8, 2013 by n3rdling

[livewire]

Interesting read, one of the first. No KS amp on hand?

Bump da bias dude!

[n3rdling]

Nah I didn't want the amp so I just bought the HPs.  I heard the KS amps for about 1 or 2 hours and preferred the SS amp.

[spritzer]

Try them on Pro bias and report back.  They should be just fine unless you given them the full volume of the BH. 

[chinsettawong]

I had a chance to listen to KS with its tube amp earlier this week. The overall sound wasn't that bad, but I didn't quite like its bass. There's bass but it's different from Stax or mine DIY phones. It's rather difficult for me to describe it. But, I think the open area at the back side of the drivers is not enough or there is too much damping material. The bass just doesn't sound as "open".

I also don't like its headband. It's just too small for my head.

[mypasswordis]

Try them on Pro bias and report back.  They should be just fine unless you given them the full volume of the BH. 

 

^ This, listening to pro bias Stax out of a normal bias socket is less than optimal though I don't know what the Kingsounds are supposed to run at.