Need help from the STAX experts
Dec 31, 2009 at 10:08 AM Thread Starter Post #1 of 35

DaveBSC

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I just bought a pair of STAX O2 Mk1s, and I'm trying to decide on amps. I'm not interested in tubes, so I'm looking for suggestions on the best SS electrostatic amps available. It seems like the currently available choices are just the KGSS and SRM-727II. Does anyone have experience comparing the two, or the 727II to the 717? From what I've been reading on various headphone forums, it seems like the reaction to the new 727II over the 717 has been pretty negative.

My source is coaxial digital out from my PC, into a Cambridge DAC Magic. I listen to mostly metal (Opeth, Eternal Tears of Sorrow, Arch Enemy, Noumena, Insomnium, that sort of stuff) and also a mix of William Orbit, Boards of Canada, and Stereolab. I'm looking for a sound slightly on the warm side of neutral, with plenty of dynamics and detail, but without any harshness or aggressive treble. More Mark Levinson than Krell as it were.

Any recommendations for running balanced or single ended from DAC to amp? I believe the DAC Magic uses pin 2 as positive, but it can reverse polarity so that shouldn't be an issue with the STAX amps. I'm new to electrostats, so I appreciate all the help I can get.
 
Dec 31, 2009 at 10:30 AM Post #3 of 35

plaidplatypus

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I've owned both the STAX and HeadAmp. The SRM-727II is dull. The KGSS is just great for the SR-007. There is a new DIY amp being developed that's been getting positive comments but I haven't had a chance to try one. If you want a new HeadAmp KGSS I would suggest ordering one as soon as possible.
 
Dec 31, 2009 at 2:42 PM Post #5 of 35

DaveBSC

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Additional question: the guy I bought those phones from on Audiogon is Lobster_king, who apparently has a bit of a bad history around here? The price was fair and he has perfect Agon feedback though. Should I be concerned that they will show up in rough condition?
 
Dec 31, 2009 at 2:48 PM Post #6 of 35

Dinan

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If your source component is balanced and the input stage of the KGSS is balanced (should be) as is the 717, there will certainly be an improvement.

As Spritzer points out, the 717 is superior to the 727. STAX was forced to retire the 717 due to a design infringement. If it weren't for this, we would have likely not seen a redesign of that product, probably just some very minor changes in a Mk2 version to keep things "fresh".
 
Dec 31, 2009 at 3:41 PM Post #7 of 35

spritzer

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Quote:

Originally Posted by DaveBSC /img/forum/go_quote.gif
Thanks for the suggestions. Are there any mods available for the KGSS? V-caps, Bybee, things like that? Any advantage to running in balanced?


All electrostatic amps are balanced and running the KGSS with a SE input will only give you less ultimate voltage swing with no effect on the amps performance. The quality of the output stage is far more important then type of connection used.

The KGSS is DC coupled so no coupling caps to upgrade. You can put in "better" psu caps but anything short of gigantic film caps would be a waste and there are far better ways to spend the cash. Some people just need V-caps everywhere even though they will not make any difference. I've seen a picture of a SRM-007t where every cap had been replaced even though none of them are in the signal path.
rolleyes.gif


Now there are some real mods that can be done to the KGSS. Redesign the output stage and equip the second to last stage with a real constant current source. Put in a new tracking PSU with higher voltage rails (+/-450V should work), a better low voltage PSU (Sigma22 would work well here) and increase the standing power of the amp dramatically. Since you are only limited by the transistors available (with true HV models on the extinction list) you can push to new voltage heights (+/-900V is in the realm of possibility) which will leave the tube amps in the dust.
 
Dec 31, 2009 at 4:40 PM Post #8 of 35

DaveBSC

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Yet another question - is there anything about Stax phones that makes them difficult or impossible to recable? It seems like pretty much any dynamic phone can be recabled, but I've never seen an Omega or any Stax phone with a Jena Labs cable.
 
Dec 31, 2009 at 5:17 PM Post #9 of 35

Duggeh

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Lobster-King is a flipper. He scoops stuff then sits with it at a very high price until he can pass it on. He isn't going anything illegal, just very disagreeable.

The best cable that can be put on a Stax headphone is made by Stax.

You could try using a Jenalabs cable, but in addition to how heavy, unweildy and astonishingly ugly the jena cable is, you'd also destroy the sound of the headphones.

Think of it like upgrading the lens in your microscope, but installing a telescope lens. The application is ill-fit for purpose.
 
Dec 31, 2009 at 6:06 PM Post #11 of 35

DaveBSC

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When my wallet recovers a bit after ordering the KGSS, the next step will most likely be a DAC upgrade. I was just curious as to why nobody has done a Stax recable since pretty much all of the top Dynamics (HD800, D7000, UE9 etc.) benefit from stock cable upgrades. I have a pair of balanced Wireworld Gold Eclipse 5 Squared, which I think should work well between my current DAC and the KGSS. Better interconnects than the GE 5.2s like the Platinum Eclipse, Tesla Apex, Indras etc are 4X the cost so they are out for awhile.
 
Dec 31, 2009 at 6:54 PM Post #12 of 35

spritzer

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Stax have used upgraded cables since 1987 and the wire used is far better then the crap Jena uses. The cable is also crucial to the performance of the electrostatic drivers as any capacitance the cable has is added to the load the drivers present to the amplifier. The cable has to be a ribbon and have the proper arrangement of the conductors.

I'd also not look at all this recabling/burn-in stuff as fact as it couldn't be further from it. It's mostly driven by people that know nothing about electronics and believe cables have some magical properties. If it is really expensive then it must be moar better...
 
Jan 1, 2010 at 8:53 PM Post #13 of 35

plaidplatypus

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Quote:

Originally Posted by DaveBSC /img/forum/go_quote.gif
Yet another question - is there anything about Stax phones that makes them difficult or impossible to recable? It seems like pretty much any dynamic phone can be recabled, but I've never seen an Omega or any Stax phone with a Jena Labs cable.


I owned a SR-Lambda that Germania had recabled, it did not stop them from sounding like a Lambda should. Isn't Jena Labs the company that really messed up that R-10 recable?

The KGSS will work fine with either RCA or XLR input. I wouldn't let the lack of one type be the determining factor for phono pre or digital player. That being said, I remeber the KGSS sounding best with avcable.com XLR cables running from my SACD player.
 
Jan 1, 2010 at 9:30 PM Post #14 of 35

El_Doug

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Quote:

Originally Posted by spritzer /img/forum/go_quote.gif
Now there are some real mods that can be done to the KGSS. Redesign the output stage and equip the second to last stage with a real constant current source. Put in a new tracking PSU with higher voltage rails (+/-450V should work), a better low voltage PSU (Sigma22 would work well here) and increase the standing power of the amp dramatically. Since you are only limited by the transistors available (with true HV models on the extinction list) you can push to new voltage heights (+/-900V is in the realm of possibility) which will leave the tube amps in the dust.


...why haven't we done this yet? why bother with the DIY upgraded T2, when this would seemingly be much less similar to the BHSE?

I for one would be extremely interested in such a powerful, dc-coupled stat amp, especially if I could avoid using tubes!
 
Jan 1, 2010 at 9:57 PM Post #15 of 35

spritzer

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The simple fact is, tubes are just easier to work with in the long term. EL34's will be here in 30 years time but semiconductors discontinued two years ago can be very hard to find. High voltage parts are also being killed off fast and putting out a design that will be dead in two years makes no sense. Just look at the Dynahi, great design but the parts are hard to find and have to be substituted for which most DIY'ers won't do for some reason.

The DIYT2 is different though, it's more of a homage to the engineering talent that has brought us electrostatics for the last 50 years rather then a step forward in amp design. Same can be said about the SRX redesign.
 

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