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The Stax Thread III

Discussion in 'High-end Audio Forum' started by currawong, Aug 20, 2013.
  1. HiP1
    I have a SRM-006tA for sale, if you want :)
  2. hypersonic
    Sorry, not a fan of used gear:beerchug:
  3. HiP1
    no worries :) if you change your mind, you can make an offer, I dont really know what it is worth :D
  4. Tugbars
    driving 009 with an amp below kgsshv would be waste of potential for 009.

    About comparison of 009 vs 009S: 009S has way better tonality than 009. 009 bass has... problems... serious problems in terms of tonality. 009 sounds too bright and that is giving a pseudo detail sensation. What really happening is that the listener gets super exposed to the trebles/mids and thinking the presentation is full of detail. 009S has all the detail which 009 has too.

    A well driven 007 is way superior to underdriven 009 in many areas: 007s have significantly better bass and way better tonality overall. There is no frequency range where 007 fails to provide proper tonal balance and bloom to enjoy music. Rather than getting underdriven 009, i'd get 007 with KGSSHV. There are many people who prefer well driven 007 over well driven 009 too.

    If you like bright sound signature, good soundstage and extremely detailed presentation, Raal Sr1a, is simply what the 009 should have been. They do everything what 009 does way better and effortlessly.

    Everything written here are my personal subjective opinions. I own SR007 and i'm driving them with my KGSSHV Carbon. I had 009 and 007 for one week with me to decide which one i liked most. I am aiming to get SR1A as soon as possible.(I'm waiting for direct drive amp of Schiit)

    Good luck!
    Last edited: Sep 14, 2019
    DelsFan and nanosword like this.
  5. hypersonic
    I really appreciate the advice. However in my experience I regretted almost every time I buy something at the middle ground. I wish I have the thick wallet to afford the best but I don't right now, so I'd choose the cheap but okay option. I've been reading a lot of posts and it seems 353X is not really that bad.
    I'm so intrigued by the Raal I actually read every pages on the SR1a thread!
    Base on the impression they're pretty much perfect, but there are drawbacks I personally could not accept.
    I can't have a bulky power amp. People are saying to reach full potential you'll need more than150W per channel into 8 ohm and that's pretty much exclusive to gigantic "on the floor" amp.
    I really doubt schiit can do it in small chassis with a small price tag. Heck there are members saying even the "reference" Benchmark AHB2 is lacking.
    Of course using a smaller amp is "alright", I can find very decent, reasonably priced 50Wpc amps that will work, but that's a similar situation as cheaper amp driving 009/S!

    Also there are issues with the build. Some owners are getting funny smell from their headphones. And the mounting/wear system could certainly use some more refinement.
    Maybe the next iteration!
  6. Tugbars
    Schiit Vidar + Raal SR1A is enough. Benchmark AHB2 or NAD amps are just overkill.

    KGSSHV design is based on 353X, it's just a stronger version of it. 353X is quite good but as you turn the volume knob, the amp will get compressed and will start sound bad.
    Last edited: Sep 15, 2019
  7. hypersonic
    Many members over at the SR1a thread seem to disagree. Well everyone has different standard on "enough".
    I don't quite understand how an amp will get "compressed", is this a flaw with the volume control? Or it is worse at certainly volume level?
    Last edited: Sep 14, 2019
  8. catscratch Contributor
    Wasn't the original KGSS published on headwize around 2000 or so? KGSSHV appeared around 2010. The 353X appeared in 2015.
    Last edited: Sep 14, 2019
    Jones Bob likes this.
  9. tabness
    I tried to calculate electrostatic driver unit requirements a while back (posts by jcx were super helpful in getting started and I am fortunate enough to work with some audio engineers who were very helpful in filling in the gaps) so this may help:

    First you need to know your listening level. Honestly you shouldn't be listening at or beyond 85 dB for extended periods (the OSHA requirements are a really minimum guideline here) and relaxed and safe listening levels are between 75 to 80 dB.

    The peak/RMS ratio of audio depends on exactly what you listen to. Classical music has the most demanding peaks (18 to 22 dB crests) whereas modern compressed hip hop/pop/rock can have peaks as low as 3 to 5 dB and pre loudness war music is somewhere in between around 10 to 14 dB peaks.

    SR 009 specs:
    Electrostatic capacitance: 110 pF including cable
    Impedance: 145 kΩ including cable at 10 kHz (the impedance would be at tens of megaohms at low frequencies and tens of kiloohms at higher frequencies)
    Sound pressure sensitivity: 101 dB / input 100 Vrms / 1 kHz (I would assume the sensitivity would vary across the frequency response)
    Maximum sound pressure level: 118 dB / 400 Hz

    The 353X has a max output voltage of 400 Vrms (roughly 1130 Vpp). I believe Stax actually measures these whereas I think the Vpp given for the third party amps is generally derived and not measured.

    How much voltage needed for something higher or lower than the stated sensitivity spec can be calculated by: 20 Log 10 (V / Vref)

    The 353X would probably be in the range of the 313/323S/717/727II in terms of how much current it outputs (5.5 to 6.6 mA).

    More current is needed to swing voltage at higher frequencies. Electrostatic transducers are pretty close (though cannot be exactly) pure capacitors so you can get pretty close to how much current is needed.

    2 * pi * frequency * Vpp) / 1000000 = slew rate (in volts per microsecond)
    slew rate * capacitance (F) = current needed (A)

    You can do the calculations with your listening level and extra headroom required for peaks but given the 009 can do 101 dB at 1 kHz with 100 Vrms and has a pretty flat response (measurements) and almost anything anyone listens to audio wise would require only a full power bandwidth of 3 to 5 kHz the 353X really seems to have enough to drive the 009 unless you start listening to really loud levels.

    Now you could say it isn't enough to reach "real life" levels (I have read that classical music can have peaks that hit 120 dB live) but in that case the 009 transducer itself falls short of being able to replicate real life volumes. Plus the musicians in orchestras generally wear ear protection themselves anyway so just turn it down lol

    The 353X was going to be my amp of choice and I still might grab one in the future. I ended up going with a T1S first because I wanted a nineties Stax amp and I had hopes/plans (now thankfully materializing) of grabbing an Omega. Though now I realize I need the darker bronze faceplate version to match the Omega...

    Even if you want to get a different amp later it wont be much of a resale hit on the 353X you'll lose like $300 (as compared to the hits of selling one of the multithousand dollar amps)

    I remember reading somewhere (here or on the other place) that the 353X is basically a lower powered 717 with some transistors removed and that apparently according to Stax the KGSS is a copy of the 717 (I have read here that the 717 is a licensed version of the KGSS with a different output stage as well though).
    Last edited: Sep 14, 2019
    hypersonic likes this.
  10. Amish
    Of those two amps I would grab the 353x.
  11. statfi
    The amp "gets compressed" when you ask it to put out more that it can. It is not a characteristic of the volume control per se. On the same recording, with a fixed volume setting, compression may happen on loud sections and not on soft ones. Also the recording level matters and the output level of your source component. The "amp will get compressed" is roughly the same as saying that the "amp runs out of power". Ultimately, all amps will compress. So the presumed qualifier of the statement is "at reasonable listening levels".
  12. hypersonic
    Thank you for the informative post! Now I'm more confident with the purchase.
    I don't listen at loud volume, perhaps even quieter than average, it seems the 353X will suffice. I don't pursue "real life" experience from headphones because it's impossible. In a concert hall, loud passages can shake the floor and the audience will feel the vibration with their bodies.
    That's part of the sensation which cannot be reproduced by headphones.
    Thanks for the clarification. I know this effect, although rarely find it on enthusiast grade gears. (If there is, it's subtle) I misunderstood Tugbars' post because he said whenever the volume knob is turned.
  13. nemomec
    Not in my experience the SR-009 has for me a very deep going bass with a perfect structure without any distortion. SR-009 vs SR-009S, the SR-009 is more transparent (transparent means not brighter) as the newer version, the SR-009S is also good but has a modern more dynamic sound signature with a little bit hoter upper mids for me. I prefer for serious classic and singer/songwriter music the SR-009/BK, for electronic and pop music the SR-009S. Very important is that you have high quality devices (amp + source) for the SR-009! Unfortunatelly you can´t reach the top level with the Stax amps but a Stax SRM-T8000 with SR-009/S/BK is a good start.

    Yes, i also prefer a SR-007 or a Advanced Lambda SR-L700 against a underdrivern SR-009, but if you have a serious SR-009 setup i think there is no reason to take a SR-007. I had this combo with many different SR-007 versions serveral times but in the end i was using the SR-007 maybe only in 1 of 10 sessions.
    Last edited: Sep 16, 2019
    purk likes this.
  14. Tugbars

    yes, i should have said, as you turn the volume knob after a certain level. You'll get slightly lesser bass extention, lesser soundstage and trebles might sound a bit rolled off compared to using a powerful amp. Dynamic amplifiers the same voltage swing at 1khz and 20khz is easy. Same voltage swing for electrostatic amps is harder, you need certain amount of current output for that.
    I'll quote KG here:

    I have used Carbon to test both. 009 and 009S have better layering and wider soundstage but 007's tonality was better overall. It's a matter of taste i think.
    Last edited: Sep 15, 2019
    hypersonic likes this.
  15. tabness
    Those values seem to be calculated for both full voltage swing available by the amp and the full 20 kHz sine wave.

    In real world usage the required output stage current would be far lower because most music power bandwidth would be in the range of 3 to 5 kHz (there was a study cited earlier in this thread that found one example of music requiring 15 kHz) and there shouldn't really be a need to swing that much voltage on the amp anyway (not to mention I have read that slew rate limitation distortion isn't the easiest to hear anyway).

    Using 95 dB to 101 dB as the sensitivity of the 009 at 100 Vrms (as Stax measured at 1 kHz where there is a peak) the 353X at lower than the max output voltage (200 Vrms) would still give an extra 6 dB of headroom basically allowing for for 101 to 107 dB peaks which if you're listening close to the upper limits of reasonable average levels (75 dB to 80 dB) gives you 20 to 25 dB of headroom for peaks which covers the tough requirements of classical nevermind other stuff.
    Last edited: Sep 15, 2019
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