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The Headcase Stax thread


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10 hours ago, Laowei said:

Not many houses have the the square footage for the circlotron. :rolleyes:

IMG_2208.JPG

Actually, that's just a Cockroft-Walton generator/voltage multiplier.  Same principle as the voltage multiplier in the Stax bias supplies, except MUCH higher voltages, e.g. 1-3 megavolts out, albeit with a fair amount of ripple.   Walton and Cockroft used it to accelerate charged nuclei to bombard atoms and transmute them into heavier elements, for which they won a Nobel Prize in physics.  Currently, used to give charged particles a starting kick before they enter the circlotron.

Edited by JimL
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Isn't everybody glad that I'm crazy enough to buy this stuff and have Kevin rip it apart?   

I have compared the 009 and 009S running from the same amp (T8000) today. The room was somewhat quiet, but I had only two source options: my iPhone (connected through Apple's lightning adapter direc

Look what just showed up.  I decided to treat myself for my birthday...    Sounds brilliant with the HE90 and is pretty much required to use them.  Also the build quality is nothing short o

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... and, not only that, you learn lotsa spurious stuff from them.....  :wub:

 

Yep, it turns a dedicated thread into an eclectic mish-mash of triviality..   what's not to like...?   :P

Edited by wink
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11 hours ago, spritzer said:

Not sure, I bought a pile of them from Japan back in the day.  Stax USA had them but yeah...dead now. 

Speaking of such, anyone has update on the new Stax USA distributor?

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I'm not sure if they're any more than a warehouse that Stax has contracted

But we've been receiving dealer shipments

Currently repairs get shipped overseas

Edited by justin
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Try emailing Douglas Ip: [email protected] 

He's the one still in the process of setting up new US STAX distribution in Fort Worth. I went thru him to get a cable replacement for my SR-009 several months ago. He arranged my purchase from STAX HQ and their export shippers in Japan. Lots of archaic bureaucracy dealing with STAX. Douglas helped.

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Stax are firmly stuck in a 70's business mindset so yeah... it is to be expected that they are difficult. 

It seems a lot of theJapanese companies are this way. TKD anyone?


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4 minutes ago, Pars said:


It seems a lot of theJapanese companies are this way. TKD anyone?


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Older workforce, more financially conservative. FAX machines and bank transfers still the norm with long established homegrown Japanese companies. 

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Hi folks, long time lurker, first time poster. Fantastic forum this, lots of good info!

I've been wanting a Stax setup for some time and I finally took the plunge and got a 007mk1 (71xxx) in what seems to be very good condition.
To drive it I decided to build the KGST, and have ordered boards and parts (thanks, Spritzer!). I want to take my time building this and not rush anything, and I couldn't let the 007 sit unused in the box.. so I bought a chinese KGSS clone, the famous MT-F1, to use temporarily. And I thought some pictures of the "new and improved?" version might be interesting, so here goes:

http://imgur.com/a/6wRct

Case is pretty nice, has a power LED, 230V/110V switch, Neutrik connectors, teflon socket.

 

The problem with the amp as documented by spritzer some years ago:

R17 and R55 changed to 150K/2W.
These are now marked with Dale rn60c 3243F 9720J. Can someone help me identify the value of these?

R7, R8, R49 and R50 changed to 300K/2W
Seems to be 200k, should probably be changed.

R14 and R52 changed to 350K/0.5W
330k. Might be OK?

R35, R36, R38, R39, R73, R74, R75 and R76 all changed to 100K/0.25W
Seems these are all 100k now, not bad.
 

I have not taken the PCB out, but I will at a later time, to check the input stage.

Turned it on, adjusted bias to 580V (checked R1 on PSU side, to ground, assume this is correct?), adjusted the 4 trimpots to get within 500mv on all 4 outputs.

Plugged in source, connected phones, it plays :)

Channels are reversed, no biggie. Some white noise/high frequency when turned all the way up, also no big deal.
Was some slight noises when turning the volume pot, seems to be gone now.
If I turn the volume way up the left channel starts to crap out, should problably not be listening at these levels anyway.

At minimum volume the right channel gives out before the left, balances out after turning the pot ca 2mm. Also not completely silent at lowest setting. Volume is operational across the whole pot, though.

All in all, I'm happy with it. SQ seems awesome to me, but this beeing the first Stax I ever hear I can't compare to anything else yet :) (Went from 15 year old grado sr-80's)

 

 

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I had a brief look over the pics and this amp is still a clusterfuck...  :rolleyes:  A lot of wrong values and quite frankly odd ones.  So first thing to tackle is the input section, that pot is garbage so I would swap it out and make sure that the - side of the input is grounded when using the switch.  It was the + on my amp which makes no sense... 

Dale rn60c 3243F 9720J = 324K.  3243 means 324 with 3 zero's after it.  That resistor is way too small though for the heat this part of the circuit dissipates. 

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Thanks for looking. Hehe, I thought it might be. He did fix some of the original problems, though, so maybe it will be all good in another 3 years. 

I have ordered parts based on your original fix and will swap all resistors accordingly (except the 100k's as they seem OK to me).

Input section will be fixed too, I might swap the pot but it seems a tight fit. Any (not too expensive) pots that you know would fit? 

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The pot looks kinda like this one: http://www.ebay.com/itm/2x-12mm-Alpha-C100K-100K-Reverse-Audio-Taper-Potentiometer-4-Gang-20mm-D-Shaft-/261215523097

If they're similar then check the dimensions and see what fits, or if there's enough space to mount on the front panel you can put whatever new pot there and airwire

Edit: I like how they went through the trouble of doing the shaft extender to minimize wiring but the shaft and pot are way too close to the heatsinks, not sure how reliable that will be over time. 

Edited by mypasswordis
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