The Stax I thread

Discussion in 'Headphones' started by knerian, Mar 28, 2016.

  1. Audiophile

    Audiophile New

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    Is there any news on the new stax flagship headphone ?
     
  2. %20 Oddity

    %20 Oddity Friend

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    Nothing yet! Really, the last press release from Stax suggested more that the new flagship (that people like to call SR-011 for the time being) is still under development, as opposed to the T8000 which had its finishing touches put together at the time. So expect a 2018 release, maybe.
     
  3. 9suns

    9suns [insert unearned title here]

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    It should be called SR-010, because 007 was the 7th flagship, 007 mk2 the 8th and 009 the 9th flagship.
    EDIT: I prefer the 007 mk1 or the port modded 007 MK2 to the 009 (more natural sounding to me out of a good amp), I hope they make the new flagship more natural sounding than 009.

    I don't have big hopes because in the 2012 head-fi interview, they said that the new flagship amp had to be better than the T2, and well...it's a lot worst than T2.
     
    Last edited: Aug 25, 2017
  4. Audiophile

    Audiophile New

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    It looks like that the majority of people prefer Stax 007 over 009.
     
  5. JimL

    JimL Tongues KG's hairy starfish for fun

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    I wouldn't necessarily say that. At a recent Albuquerque meet, six persons listened to both the 007 Mk II with port mod and the 009, both driven by the BHSE. Three preferred the 007 and three preferred the 009. I happen to prefer the 007 Mk II with port mod, but for example @Arnaud and @Ali-Pacha prefer the 009. It's very difficult to tell from internet postings which is preferred overall, since the number of people who post is a small fraction of owners, and may or may not be representative.
     
  6. GanGreinke

    GanGreinke Friend

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    There is also the complication of there being several versions of the 007 (Mk 1, Mk 2, Mk 2.5).
     
  7. JimL

    JimL Tongues KG's hairy starfish for fun

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    True. To me, the Mk i is somewhat on the soft, euphonic side, the 009 is somewhat on the bright side, and the so-called Mk 2.9 ( current version since 2015) with port mod fits between them.
     
  8. JK47

    JK47 Guest

    I've been toying with Stax for a little while now, and holy shit, I enjoy them. 009 too much $$$, 007 too fussy when it come to amps, Lambda Pro with SR7 Pro... yes sir, nice. Can it get better for a little, not a lot more cash, f**k yaaaaa.

    Enter the SRM-T1S and Airbow SC-1 (404 LE). I splurged and spent $600 for the pair shipped to the USA from my buddy in Japan, expecting to dick around with the power transformer ala head case, to get 117volts. Guess what... when I opened up the case to change the tubes. The presto change plug for 100v, 117v, 220v, and 240v was hidden in the bottom, under the plate, not like the older models with the plug directly on the back.

    I changed the tubes to el-cheapo Electreo Harmonix, recapped it for $50, and holy shit Batman, Superman, and a the rest of the Justice League, this combo is devastatingly good for the money.
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    I'm letting the amp marinate on power overnight before I set the balance and offset. Hopefully without burning the apartment down.

    I've had a bunch of time on my hands lately while I wait for my new "Union" job to start. So lots of little projects are getting done.

    This post was brought to you by Makers Mark, the Icebirg ice ball maker, and the Flashdance soundtrack.
     
  9. JimL

    JimL Tongues KG's hairy starfish for fun

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    So, a couple other changes you could make to better protect the headphones. These are safety resistors that are in all the modern Stax amps but not in the T1 (don't know about the T1S).

    First, check and see if the output socket terminals have 5.1 kilohm resistors in line from the tube output. To do this is (with the amp disconnected from the power line), with an ohm meter, put one probe in the output tube terminals 1 or 6, and the other probe in the appropriate output socket terminal (if you're not sure, just move it around all the terminals until you get either 5.1 kilohms or zero). If you get zero ohms, then the easy way to fix this is to desolder each wire going to the output socket at the circuit board (the yellow, green, red and blue wires going from the board to the output socket next to the eight big power resistors), and interpose a 5.1 kilohm resistor - you'll need four of them. Mouser sells a 500 volt rated resistor - 71-CCF60-5.11K-E3.

    Second, check and see if the bias supply has a 5 megohm resistor going to the output plug. The bias supply wire is the other wire going to the output socket. The easy way to figure this out is to look at the normal bias socket - the bias wire is connected to two of the socket terminals, including the center terminal, whereas all the other wires are only connected to one. On the pro bias socket, the bias wire will be connected to the terminal in the same location as the normal bias, but there is no center terminal. Trace the wire back to the circuit board and look for a 5 megohm resistor after the last 0.1 uf capacitor. If not, you can desolder the bias supply wire at the circuit board, and insert one between the board and the wire. Mouser sells a 1.6 kV rated one: 594-5043DM5M100J

    Finally, for "extra credit", you can modify the T1 to significantly improve its drive capability by substituting four cascode MOSFET constant current loads for the eight output resistors. This will improve detail, tighten up the bass and allow the T1 to drive even the SR007 - no, it won't turn it into a BHSE, but it will bring it considerably closer to a KGST-level amp. This last change is the modification I published in AudioXpress, July 2017.
     
  10. sorrodje

    sorrodje Carla Bruni's other lover - Friend

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    @JimL : In your opinion , is the SRX+ still better than the modified SRM-T1?
     
  11. JimL

    JimL Tongues KG's hairy starfish for fun

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    Yes, I think so. It's more fluid and refined, and the regulated power supply is an advantage over the SRM-T1's passive PS. The SRX-Plus is basically an all-tube circuit, but with some resistors replaced by constant current sources, which are solid state. The constant current sources optimize circuit operation but shouldn't have much sonic signature because their very high active impedance means that very little of the signal current passes into or out of them, so it still has tube sonics. The T1 is hybrid where the signal passes through solid state input and intermediate stages. But the modified T1 is obviously much easier to do than the SRX-Plus, which is a scratch build.
     
    Last edited: Aug 29, 2017
  12. JimL

    JimL Tongues KG's hairy starfish for fun

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    BTW, @JK47, I wouldn't necessarily discard the 6CG7/6FQ7 tubes that came with the amp. They were run very conservatively and may still be good, plus they may sound better than the Electro Harmonix. How to tell? Well, if you plug them back into the amp and you can zero the outputs, they are still good.
     
  13. JK47

    JK47 Guest

    I actually bought the AudioXpress, July 2017 issue for your article on the SRM-T1 mods ;)

    The tubes that came in my T1S were made in the USA GE's, and sounded considerably worse than the new Electro Harmonix I installed. Not to mention they tested horribly on my tube tester, severely mismatched triode sections, microphonic, and noisy.

    I'm going to enjoy my T1S as is for now before any further mods. It truly is a nice combo, much better than the SR-207/SRM-252S I had last year, for practically the same money.
     
  14. RiddleyWalker

    RiddleyWalker Friend

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    Since we are on the topic of tubes on these older Stax amps, thought now might be a good time to ask my fairly obscure question:

    Does anybody know how to bias tubes on the old SRA-3S? I've biased tubes on my SRM-006T before but not sure how it's done on this ancient unit. I can post some photos later if it would be helpful.
     
  15. JimL

    JimL Tongues KG's hairy starfish for fun

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    Fair enough, they probably were at the end of the life span. I had GEs in mine which were fine on my tube tester, so it's hit and miss. Looking at some old posts on HF, both spritzer and Hirsch reported that the best sounding tubes for the Ti/006/007 were Japanese Toshiba or Hitachi tubes, which still go for pretty low prices on eBay.

    The SRA-3S is capacitor coupled at the output, so you'll have to measure the output voltages at the output plate resistors, which are mounted on the bottom circuit board close to the output tubes and the power transformer. Notice that the four output resistors meet in the center of the board - this is the B+ connection point. You want to measure the voltage at the other end of the resistors, which are at the right or left edges of the bottom circuit board. BTW, I assume you have replaced all the electrolytic caps as they are well past their prime.

    If you look on the vertical circuit board closest to the output tubes, you will see two trimmers at the top, each close to two 100 uf caps, which I believe adjust the balance between the tube sections. You want to adjust the balance so that the voltage across the 50k output resistors is the same for each channel. The easiest way to do this is to clip the voltage meter probes between the two resistor leads at either the right or left edges of the circuit board, then adjust the balance to zero volts. A voltage differential of less than 20 volts is acceptable.

    Also, on the same vertical circuit board are two trimmers on the left and right side near the top. I believe these are used to set the plate voltage of the output tubes - the nominal value according to the schematic is 320 volts from ground. Anything within 10-20 volts of nominal should be acceptable.

    Note that the four trimmers are pretty cheap looking, and probably will not tolerate a lot of tweaking, which is why I wouldn't obsess over getting the exact voltage values. In any case, there will be some drifting as the tubes warm up and/or age, and also as the AC power voltage changes, so close is good enough.
     
  16. RiddleyWalker

    RiddleyWalker Friend

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    Thank you @JimL ! You are a gentleman and a scholar.
     
  17. JimL

    JimL Tongues KG's hairy starfish for fun

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    The consensus from people like Muppetface and Ali-Pacha seems to be that the T1 does fine for the Lambas even without my mods. Enjoy!
     
  18. alucart

    alucart Facebook Friend

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    I was just browsing the Stax website using Google Translate (http://www.stax.co.jp/index-J.html) and found this potentially troubling information as the first paragraph:

     > 【Attention!
       The STAX ear speaker is designed to be used in combination with a genuine driver unit (dedicated amplifier).
       If it is damaged (damaged) by connecting to a driver amplifier or adapter other than STAX, please be careful as it will be out of warranty.
       When repairing an ear speaker, be sure to present the product name and serial of the driver unit you are using in combination.
      (Please be aware that damage and troubles using other manufacturer's amplifiers and adapters are increasing!)

    I don't know whether this is a new development or not? I own a SR-007 run with an KG amp, currently under warranty, but haven't yet asked the Australian distributor whether they would be doing the same for fear of provoking the issue, but given that they send them back to Stax for repairs, I imagine that distributors will follow suit?
     
  19. JimL

    JimL Tongues KG's hairy starfish for fun

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    I suppose Stax could make an issue of if if they wanted, but in fact, the amplifier which has the highest voltage and current capability is the original Stax SRM-T2, which has +/-500 volt power supplies. AFAIK, no other amplifier, including the Gilmore amps, has higher voltage power supplies, and most have less voltage output.

    All of the GIlrmore amps have 5 megohm protection resistors in the bias supplies following the last capacitor, and all of them from the KGSSHV onwards have 5.1 kilohm protection resistors at the outputs, same as the modern Stax amps. The same goes for the SRX-Plus. So if you have one of those amps, they should be every bit as safe as any modern Stax amp.

    Some of the older Stax amps, such as the SRM-1 and SRM-T1, do not have those bias or output protection resistors, and some of the older KG amps such as the original all triode, KGSS, and original KGBH don't have the 5.1 kilohm output resistors, but that's an easy DIY fix.

    Based on the reverse engineered schematics that Kevin Gilmore has published, the Cavilli LL has the 5 megohm bias resistor, but not the 5.1 kilohm output resistors, the Kingsound M10 and M20 also lack the 5.1 kilohm output resistors.
     
  20. AllanMarcus

    AllanMarcus Friend

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    Buy a cheap stax amp and keep it in the closet. If your expensive headphones need warranty work, say it was connected the stax amp.
     

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