The Headcase Stax thread

[spritzer]

Well I bought it because it looked like it used the KGSS design without permission.  Kevin gets so happy when I send him something to tear apart...    The amp is a clear copy of the KGSS but doesn't work out of the box unless you count 1mm of volume control travel as a sufficient adjustment range. 

 

That repair work is mild compared to the Cavalli Liquid Lightning and it didn't cost less than 1k$.... 

[rx79ez08]

Spritzer can you list the part numbers for the resistors you have changed and what you have changed them to?

 

I am not very familiar to the KGSS circuit and have some difficulty following what you done.

[kevin gilmore]

I'm waiting for birgir to send me a liquid gold 

[spritzer]

 

Spritzer can you list the part numbers for the resistors you have changed and what you have changed them to?

 

I am not very familiar to the KGSS circuit and have some difficulty following what you done.

 

Here goes...

 

R17 and R55 changed to 150K/2W

R7, R8, R49 and R50 changed to 300K/2W

R14 and R52 changed to 350K/0.5W

R35, R36, R38, R39, R73, R74, R75 and R76 all changed to 100K/0.25W

 

Also R37 and R42 changed to 0 ohm jumpers (or just jumpered by some wire) for the RCA/XLR switch rewiring. 

 

To fix the input section in general (you can leave the pot in place) do the following.  Remove the RCA wiring and connect the wires directly to the XLR jacks.  The XLR pinout is 1: ground, 2: + or hot and 3: is - or cold.  You can see the numbers in the back if the socket and the pins go straight through and into the PCB.  Ground goes to ground and the center conductor goes to + or hot. 

 

Now next step is to cut all the traces which lead from the XLR sockets to the pot, also all traces from the pot to the amplifier.  Leave the ground all alone as it works just fine as it is.  When the amps is shipped then the input goes to the center row (which is the wiper) and that will never work.  You want the input for each phase to go to the row on one side which isn't grounded.  Then take the output from the center row and feed it to the series resistors right next to the pot. 

 

Now the tricky bit about the RCA/XLR selector is how it is wired.  It takes half of the traces off the pot and feeds it through the switch which means all those traces have to be cut (except those which lead to R37 and R42).  Run a jumper wire from 500K resistor to each one of the input fets to replace the long trace running on the edge of the board. 

 

For the switch you take the - or cold legs off the XLR sockets (or the input to the pot) and run them to the center of the switch.  Then the RCA side is grounded but the XLR side is left empty, not connected to anything.  That way the switch does nothing in XLR mode but switch to RCA and the - side of the input is grounded.  Easy as pie... 

[rx79ez08]

Thank you spritzer.

Project for a Sunday afternoon.

[DefQon]

Scam or what?

 

http://www.ebay.com.au/itm/Stax-electrostatic-headphone-step-up-transformer-/171397731627?pt=Kopfh%C3%B6rer&hash=item27e819d52b&_uhb=1

 

SRD-7 Pro with some nicer grade components for a whopping price. 

[spritzer]

Here's the thing, I don't think it uses better parts than the SRD-7.  Transformers for electrostatics are the height of this particular black art and I doubt Audio Valve are sourcing properly made ones.  The SRD-7 units are small but made for electrostatic loads with low parasitic C. 

 

I'm sure this will be shilled like the second coming by that half-wit eric65 but then again he ran the SR-009 single ended and claimed it sounded awesome!!!!! 

[kevin gilmore]

this thing has a real problem. self powered bias.

so you get to listen to music for maybe 30 minutes

before the bias caps charge up, and before the headphones

charge up. major stupid. anyone with a koss esp6 would

know what i'm talking about.

and yes eric65 is a fucking shill, but mainly an incompetent

moron that cannot think and believes anything on the web.

like the fact that the rkv has .01 ohm output impedance.

see BHSE thread over there.

[DefQon]

French audiophiles like there sound coloured. 

 

That blind test shootout with the 009+Wee+RKV vs 007t, 717 and T2 was interesting. 

 

Wasn't he the same poster who linked about some crazy diy e-stat designed amp from a Russian diy'er that cost about $30k and without hearing one or the BHSE or a DIYT2 claimed it is the bestest amp in the world because of its price? (The pic in the Stax thread on the other site with the big ass 845 tubes or someshit and big NOS caps).

Edited July 26, 2014 by DefQon

[Ali-Pacha]

French audiophiles like there sound coloured. 

I'm french, so...

 

Anyway, could the "transformer path" be an interesting low-cost option for an entry-level Stax amp ? Something like the old SRD-X/P with a class-d chip, more powerful than automotive audio-chips used in SRD-X/P. Or maybe would it be totally irrelevant versus a brave SRM-252s ?

 

Ali

[kevin gilmore]

so take a look at the 2 scope graphs here

http://www.head-fi.org/t/439657/headamp-blue-hawaii-special-edition/5685#post_10741753

 

First one has no vertical scale.  My guess is that it is no more than 20 volts peak to peak.

And look at the very rounded edges of the triangle wave.

 

If you did the first one at 100vpp it would look absolutely grim with lots of ringing. And

really horrible slew rates.

 

I pulled some lundhall transformers, and a few other things this morning, drove them

with a krell ksa50 and got nothing even close to acceptable. Same with a srd7 and srd5.

 

Serious amounts of deliberate fudging of the specs here.  But the worst one is the

Ri of .01 ohm.

 

Not even the biggest of the atmaspheres can come close to this number. Off by at

least a factor of  20.

 

Adding transformers just fucks things up. Same with the electra.

 

Now if you were gaku-on and were able to wind the transformers correctly

(like quad does for its esl63) then things would be different. And the price would

be more than building a solid state amp.

 

No free lunch.

[spritzer]

Wasn't he the same poster who linked about some crazy diy e-stat designed amp from a Russian diy'er that cost about $30k and without hearing one or the BHSE or a DIYT2 claimed it is the bestest amp in the world because of its price? (The pic in the Stax thread on the other site with the big ass 845 tubes or someshit and big NOS caps).

 

He did post that Demograf amp at some time claiming it was awesome.  I can't say I'm impressed as it is just a glorified take on a Western Electric design and far removed from what we would call state of the art.  I like reading the Russian forums as even though there is a company building Blue Hawaii's without permission most of the design work is with tube amps that could have been built in the 50's.  One of the latest ones even uses an Eimac tube for the output but not a CCS in sight ever even *gasp* regulated power supplies.  Each to his own and all that but things have moved on from 20% tolerance resistors and AC coupling. 

[DefQon]

He did post that Demograf amp at some time claiming it was awesome.  I can't say I'm impressed as it is just a glorified take on a Western Electric design and far removed from what we would call state of the art.  I like reading the Russian forums as even though there is a company building Blue Hawaii's without permission most of the design work is with tube amps that could have been built in the 50's.  One of the latest ones even uses an Eimac tube for the output but not a CCS in sight ever even *gasp* regulated power supplies.  Each to his own and all that but things have moved on from 20% tolerance resistors and AC coupling. 

 

That's the one, sufficed to say was not really impressed with the very rough diy'esh prototype build approach of the Demograf amp (though supposedly still in the works) the price did not reflect a $25-30k (after Russian euro to usd exchange) product. But I'm all in for the diy approach people are doing out there but when people start judging something to be the best solely on price and not even hearing one....that's when we all go hmm.

 

The RKV looks like a simple tube amp that can be diy'd, any floating schematics around the RKV is based off? 

 

I'm still trying to find the listing for that custom SRD-6 tube loaded adaptor from YJ Auctions late last year. 

Edited July 26, 2014 by DefQon

[kevin gilmore]

http://www.jogis-roehrenbude.de/Verstaerker/PCL805-KH-Amp/Schaltung.jpg

 

by the way there is a cap in series with the grid that is missing on the bottom output tube

its a futterman design with a lf351 solid state front end.
would be much better if you build it with 6as7

Edited July 26, 2014 by kevin gilmore

[astrostar59]

Bit off topic, but here goes. I have a DAC with single stereo XLR and single stereo RCA outs to feed my KGSShv.

The problem is I also use this same DAC to feed my speaker amp inc a sub.

 

So, (might be a dumb question) will my DAC see a bigger load as all 3 items being 50K input impedance,

or will it not affect it so much? I would have either my KGSShv switched on, or my power amp, not both at the

same time.

 

My KGSShv doesn't have 2 x pairs of RCA to do the usual in - out loop through in in many Stax amps.

 

Any ideas on the best way to do this? I could retro fit a loop though set of RCA on the KGSShv, or

fit an Elna selector switch on the DAC as there is room in the case and then select the output RCA set.

I would rather have them all connected at once, no switch at all, but not if it affects the sonics. 

[kevin gilmore]

whether it has a loop output makes no difference unless you have installed extra switching

relays etc. So if the pot is 50K and turned to zero, then the impedance is 50k from the headphone amp.

If the speaker amp and sub amp are also 50k then the dac see's about 16.6k.

But some amps may short the input, or open the input when not powered.

 

build a set of loop thru cables.

[luvdunhill]

Agreed. The best way to do this is cabling.

[spritzer]

That's the one, sufficed to say was not really impressed with the very rough diy'esh prototype build approach of the Demograf amp (though supposedly still in the works) the price did not reflect a $25-30k (after Russian euro to usd exchange) product. But I'm all in for the diy approach people are doing out there but when people start judging something to be the best solely on price and not even hearing one....that's when we all go hmm.

 

The RKV looks like a simple tube amp that can be diy'd, any floating schematics around the RKV is based off? 

 

I'm still trying to find the listing for that custom SRD-6 tube loaded adaptor from YJ Auctions late last year. 

 

That amp has a few 1k$ silver caps and the not so cheap Sowter transformer volume control but polishing a turd comes to mind.  For that amount of money you could easily build a T2 with dual power supplies and teflon PCB's. 

 

You can get the RKV pcb off ebay as a fully assembled kit.  Not worth it though...

[kevin gilmore]

so I did some playing around with a lundahl ll9202 transformer.

setup to drive electrostatics. Using all the lundahl specifications,

and what I get on the scope looks almost identical to this simulation.

top graph is frequency and phase 20hz to 20khz, the bottom graph

is 1khz square wave. Using a full synthesis of the rkv amplifer.

 

synthesis by the way of the rkv indicates a real impedance of about 800 ohms.

 

http://gilmore.chem.northwestern.edu/rkv.jpg

 

while not exactly the same transformers that are in the verto, my guess

is that the verto looks like this or worse.

 

this is not a minor aberration to the frequency response.

This is a complete fucking of everything.

 

The graphs on the rkv website as well as everything out of eric65's

mouth seem to be a complete fabrication.

Edited July 29, 2014 by kevin gilmore

[spritzer]

Proven yet again that transformers and electrostatics don't mix. 

[eggil]

If anything is mentioned at head-fi, the moderator police will show up in force

[kevin gilmore]

its been posted already.

since rkv is not a sponsor there, they probably don't give a shit.

clone board now available, usual place.

 

if you read the French forum, the manufacturer has already decided

that 1:5 transformers cause all sorts of grief, and now they are making

1:14 and 1:20 transformers.

 

Between a rock and a hard place they are.

 

The amp may be just ok, and only for high impedance dynamic headphones.

The transformer box is a clusterfuck for electrostatics.

[spritzer]

If you are a sponsor over there anything negative about you will be removed but if you won't pay, nobody gives a fuck. 

[nemomec]

Some users here with any experience with the very old stax headphones like SR1, SR2 or SR-3?

 

I have here a SR-3 New and after some problems with channel imbalance and long charge up time it works now fine and i replaced also the pads with new ones. Now i´m very surprised that they sounds on my SRA-12S so good with a clear/transparent sound, huge soundstage and nice mids, the only big issue that i found is the lack of deep bass. I heard 90% of all models after this SR-3 New to SR-009 and i think what a amazing headphone quality was made by stax in 1971. 

 

How is the quality of the other very old Stax models and there are any other experience with this nice SR-3 New?

[Sherwood]

A few of us have heard the older Stax... 

 

I remember being impressed by the SR-5NB (A.k.a. SR-5 Gold) when i last heard them.  Same drivers as the SR-X mk.3.  Slightly newer than the SR-3, but excellent nonethtless.