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The Headcase Stax thread


thrice
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Let us know if it turns out to be a good design or not and whether or not it can be fixed easily if it's bad, did a currency conversion and a $600 KGSS is a pretty bargain.

 

Despite the dim view my organization takes on IP theft, I too am interested...

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Also Stax related.  I ordered a second set of Lambda pads from Amazon USA this time and kinda got screwed but not too bad at least at $49.  I ordered for the 404LE and did not get the black leather pads but rather the 407 brown pads after 3 weeks :(  Smarter to go through Amazon.co.jp and use forwarding service if you want the 404LE/507 pads.

 

I have KuboTen order them from Ippinkan.  Stax refused to sell me some 009 pads though claiming they aren't user replaceable.  ::)

 

You mean that loud start up sound isn't a good thing?  ;D I found it quite funny actually...what other manufacturer comes to market with a product like that and says: "we meant to do that"?

 

"That's not a flaw, it's a feature...." 

 

what is this scream that you guys are mentioning? I remember reading he had a switching supply for DHT's, and it would be amusing if that noise was the ps ramping up in frequency

 

The tubes starting to conduct would be my guess which is why output relays would be a good idea. 

 

Despite the dim view my organization takes on IP theft, I too am interested...

 

We've wanted somebody in China to make a KGSS for years so that is all good.  Some recognition would be nice but mostly so people know what they are buying.  The price is certainly attractive and the build quality seems good enough:

 

0BYcHPW.jpg

 

Cheap pot but at just over 700$ shipped to the US it isn't all that bad.  The one I bought shipped yesterday so we'll soon know what Kevin thinks. 

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They could be hid next to the output devices but since the original article doesn't have them I think you are right.  Justin's version didn't have them either

 

As for the sound, it does depend on what output device is used. 

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So are you referring to the Electra, or the so called "God Amp" for dynamics based on '45s?

 

Well naturally since somebody could possibly have dissed that piece of shit 45 amp that he's peddling for Eddie Current.  You know the one that screams at you when you power it on.  Pure quality there...

 

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Some good news as we can all expect some more measurements of electrostatic headphones.  Kevin and I weren't happy with the lack of a good amp for Tyll to measure on so being a bit loopy we decided to build one for him and donate to the cause.  :)  It fell to me to build it and it had to be something special, with some unique features but also a known standard.  A souped up KGSS felt like the best choice as it's a well known design and probably the most popular high end Stax amp out there.  Justin built a pile of them, it's been a popular DIY project, I'vv and the Stax SRM-717 is pretty much a KGSS so an easy reference point.  I've also built a dozen or so of them so plenty of parts in stock. 

 

xB3uL3sh.jpg

 

Here it is sitting on top of it's younger sibling.  It is clear that this isn't a bog standard KGSS since Tyll as a reviewer needs flexibility.  All the outputs are driven off the same amp section but the three major bias voltages are taken care off via their dedicated sockets.  The bias supplies are all either generated by fully regulated power supplies or derived via a voltage divider off a fully regulated line.  Now the fourth output is a bit special as it is a small variable DC supply driving an EMCO DC-DC converter and goes up to 1kV.  There are jacks on the side to plug in multimeter probes and the pot to adjust it.  The ballast resistor can also easily be swapped out for any value required by what ever unit is up for testing.  I'll ship it with a 4M7 unit rated to 2000V which works just fine for most sets.  The LED's for power indication are mounted underneath the chassis to make the front a bit cleaner.  I looked into transparent feet but found nothing that I liked.  :)

 

z9oBoZDh.jpg

 

So here are the guts.  The PSU is a design derived from the KGSSHV but simplified and limited to single 500V caps.  I run it at +/-415V which is about as high as that Edcor transformer will give me.  On the KGSS amp board the 2SA1156's are replaced with 2SA1486's and it uses 2SC4686A's as output/gain devices.  I had to back the current off a bit as the sinks were reaching 95°C at the stock KGSS setup but even at 8.5mA it is a very powerful amplifier.  Vanishingly low output capacitance  and no protection resistors means a very linear output.  I left the 5k1 output resistors off as they might interfere with a non Stax based design.  Other than that it is a pretty standard fair for my builds, XLR inputs and loopouts, quad Alpha pot which is easy enough to bypass by simply maxing it out.  The AC input also features a voltage selector which made hooking up three transformers a bit easier. 

 

Needless to say this amp sounds awesome and has no problem driving even the tricky SR-007A (SZ2) to perfection.  Tyll is happy and and so are we. 

 

So are you referring to the Electra, or the so called "God Amp" for dynamics based on '45s?

 

The "God amp".  Who comes up with this shit as it is a pretty lackluster piece of engineering.  Same with the Electra which nobody cares about any more.  How come nobody can build an all tube electrostatic amp properly?

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you mean how come a commercial builder can't build an all tube electrostatic amp.

Because they don't have a fucking clue, thats why. Craig got lucky with the Balancing Act,

and everything after it has been a disaster. But hey, the balanced input is done right, or

so he says.

megatron is all tubes... and easy to build.

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Spritzer is it possible for you to explain why the WES is considered not as good as the BHSE and the KGSSHV?

I am using a GES at the moment, and is considering upgrading. I have read in multiple places that the WES is not as good, and from what I gather it is the DC bias, headroom and phase shifter being some factors.

I mostly listen to LNS, LS and O2 at low volume. In this case is the differences between the amps large?

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Yes, you wrote the issues yourself, you can just stay where you are especially for lower volumes where the differences are less apparent.

 

Upgraditis is a disease, but a BHSE should cure it reasonably well. Or you can also try a 717/modified 727 for a slightly different flavor.

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This looks fantastic Birgir/Kevin I bet Tyll is like a dog with two tails  :dan:

I understood Craig bought in some industry expertise from outside to help with the design of the stat amp? 

 

Some good news as we can all expect some more measurements of electrostatic headphones.  Kevin and I weren't happy with the lack of a good amp for Tyll to measure on so being a bit loopy we decided to build one for him and donate to the cause.  :)  It fell to me to build it and it had to be something special, with some unique features but also a known standard.  A souped up KGSS felt like the best choice as it's a well known design and probably the most popular high end Stax amp out there.  

 

 

The "God amp".  Who comes up with this shit as it is a pretty lackluster piece of engineering.  Same with the Electra which nobody cares about any more.  How come nobody can build an all tube electrostatic amp properly?

Edited by complin
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and that guy had absolutely no clue.

both the wes and the electra share the same problem.

the output inductor/transformer is WAY undersized to get

decent voltage swing and wide frequency response.

think 4 times that size for decent performance. and likely

4 times the cost.

and then there are the 6sn7's craig seems to have shoved firmly

up his ass. not enough voltage gain, so a tricked out input and bias

circuit that is unstable. resulting in clipping and other forms of

distortion.

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Glad to know reliable gatekeepers have appropriate tools. In the coverage of latest Chesky binaural disk, Innerfidelity provides much deeper understanding than others. If I only had this level of information when I first tried to record my own binaural files...

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Spritzer is it possible for you to explain why the WES is considered not as good as the BHSE and the KGSSHV?

I am using a GES at the moment, and is considering upgrading. I have read in multiple places that the WES is not as good, and from what I gather it is the DC bias, headroom and phase shifter being some factors.

I mostly listen to LNS, LS and O2 at low volume. In this case is the differences between the amps large?

 

The simplest answer is that the WES and BHSE have nothing in common, at all.  Sure they both drive electrostatic phones and have similar tubes but it ends there, same with the Electra.  The goal of both Woo and EC is to price their amps at the same level or higher to fool people to think they might be in the same class which they clearly aren't.  Let's just view what a WES with all the upgrades and updates looks like:

 

WVOrG7Xh.jpg

uSdAO0gh.jpg

 

This is what 8000$ will buy you.  Now for some impressions of the design, the PSU in this thing is the usual Woo joke.  Utterly overloaded tube rectifiers which don't matter due to the bridge present.  No regulation what so ever except for the circuit which powers the LED's and front end heaters.  This power supply is very similar to what Stax do so why would anybody pay a premium for this? 

 

Now for the amp section, here is where it gets from bad to "we will kill your headphones".  First off, a HE90 should never be used with a WES or a WEE.  Never in a million years should the twain meet as both will destroy the phones.  It's easy to see in the amp pic, see the small PCB next to the output sockets?  Yeah, those aren't close to be the correct values though for Stax they are closer so not as big of a deal.  So with actual amp the worst idea are those output chokes as there should be only two of them.  Simply connecting them as a single push-pull unit doesn't work, they need to be on the same core.  Inductors for Stax are bad idea though given the electrostatic load and its behaviour but a push-pull choke at least works.  This doesn't which is why the amp sounds like shit, hell it sounds like it is broken.  You can also clearly see that there are four isolated amp sections here with no adjustment so how can one phase know what the other one is doing?  It can't so the natural drift found in all circuits is , quite literally, out of control.  The amp should also be wired differently to use the benefits of matched triodes within the same envelope.  The phase splitter is also an absolute dog and should never have been there.  How come the ESX uses all the same tubes, far less components and doesn't need one?  Other stuff such as series connected heaters for the EL34's are a problem.  These are not computer/TV tubes and were never designed to be series connected. 

 

So the bottom line is this, it's an 8K$ amp that measures and sounds worse than a SRM-323S and has less power.  Also worse components and build quality.  My initial reaction to hearing a WES at CJ'10 was to ask Jack if it war broken.  That sums it up nicely enough...

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Thank you Spritzer, you have explain it very clearly.

 

Then clearly my decision for upgrade will come down to BHSE or KGSSHV. I don't mind the GES and the SRM-1MK2 PP I got at the moment, the best is probably to wait and take it slowly.

 

Would be very interested in your impression on the cheap Chinese KGSSHV, maybe that is the way to go.

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The Chinese one is a KGSS, not a KGSSHV.  It runs at +/-350V when a KGSSHV runs 400V or higher.  Not the sole distinction though...  Going by the pics the Chinese amp will need some mods to perform better than a nice little desktop unit. 

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Wow, that's a great amount of nothing special and a waste of Vcap's. 

 

After popping up a WA5LE and hearing it, it concluded what I think of Woo Audio, quality and fancy enclosure and case work, but mediocre sound. At least Spritzer thinks the WA6 and WA2 are ok sounding, I think the entire lineup is a fad. Without the Woo Audio "brand" just another lineup of cheap sounding amplifiers. 

 

Now if Woo Audio changed the pricing on the WA2 or WA5 to $900-1200, then I think it's ok but not "great".

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Interesting.... I thought the WA5 was supposed to be fantastic with Sennheiser HH800's? 300b's and all that!

 

Wow, that's a great amount of nothing special and a waste of Vcap's. 

 

After popping up a WA5LE and hearing it, it concluded what I think of Woo Audio, quality and fancy enclosure and case work, but mediocre sound. At least Spritzer thinks the WA6 and WA2 are ok sounding, I think the entire lineup is a fad. Without the Woo Audio "brand" just another lineup of cheap sounding amplifiers. 

 

Now if Woo Audio changed the pricing on the WA2 or WA5 to $900-1200, then I think it's ok but not "great".

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Thanks Kevin

I heard that on its first outing it sounded so poor against the competition (BHSE, DIY T2) that there was need of some redesign and swapping of parts to up performance.

Been claimed it sounds more like the Aristaeus or the EC "house sound" 

 

 

and that guy had absolutely no clue.

both the wes and the electra share the same problem. the output inductor/transformer is WAY undersized to get decent voltage swing and wide frequency response.
think 4 times that size for decent performance. and likely 4 times the cost.

and then there are the 6sn7's craig seems to have shoved firmly up his ass. not enough voltage gain, so a tricked out input and bias circuit that is unstable. resulting in clipping and other forms of
distortion.

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Thanks Kevin

I heard that on its first outing it sounded so poor against the competition (BHSE, DIY T2) that there was need of some redesign and swapping of parts to up performance.

Been claimed it sounds more like the Aristaeus or the EC "house sound" 

 

Poor or simply broken.  Chewing up tubes might just be a design choice...

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Interesting.... I thought the WA5 was supposed to be fantastic with Sennheiser HH800's? 300b's and all that!

 

It sounded ok when I listened to them through my HD600/800's I tried at the time, my Crack sounded better with the HD600's and was about on par with the WA5 with the 800's. But neither amp was the optimum solution with the HD800's which I thought sounded better through the Stratus (apparantly also frowned here due to bad design or cheap parts used).

 

Speaking of the SRD-7, there was a listing on YJ a while ago with some tricked out SRD-6 or something with extra output transformers mounted and 2 triode tubes, any idea what it was?

Edited by DefQon
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Given how big a factor the output impedance is to the HD800 sound then that should be compensated for when comparing amps.  Then again I'm a crazy purist...  :)  Sticking the HD800 on a WA5 is a bit like sticking the SR-009 on the Liquid Lightning, having a highly resolving transducer dumbed down by a highly colored amplifier. 

 

Didn't catch that SRD box.  Do you have a link?  Funny thing though, I recently found a box I'd put into storage years ago with a pile of SRD-7 transformers.  No idea I had that so I'll have to find some use for them.  Perhaps show Woo how the WEE should have been down with a regulated PSU and relay switching?  :) 

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