The Stax I thread

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

  1. Rthomas

    Rthomas Friend

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    4000 Euros :D

    Stax land is not cheap.
     
  2. ogodei

    ogodei MOT: Austin AudioWorks

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    Never heard of this at all. The combo estat/dynamic amp seems a bit gimmicky but the rest of the line seems interesting. Looks like its mostly sold in Austria and Germany, could be difficult to hear in the US
     
  3. Degru

    Degru Facebook Friend

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    Looks like a similar type of thing to Audiovalve Solaris. Personally I think that money is better spent on building a Lundahl box and getting a good speaker amp to push it. Will get you a lot further and much more flexibility with amp selection.
     
  4. Ranjan

    Ranjan New

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    Hi, I wanted to provide the background of how I went about choosing the driver unit/amp for L700.

    P.s.I don’t have my ears measured or trained etc. I am just a music lover.

    I had several sessions spanning 1-2 hour each at the store carrying almost all the Stax drivers. I had my music from LG V50 going in to stax drivers via RCA cable (so the internal DAC of LG V50 was engaged). My music preferences are Bollywood / Indian songs (spans from jazz to classical to rock etc and Indian music is mostly available in CD quality or lower) and I prefer to hear at medium volumes.

    Here is a brief summary from my impressions while trying out various Stax driver units:
    • started with 353x: It sounded quite clean and I could hear the proverbial ‘details I had never heard before’. The soundstage was wider (as compared to my other can, HD6xx) which gave a feeling of much bigger scale as well. Bass was also present (definitely more vs HD6xx) but it was not very punchy / had no slam as I have heard from ZMF cans.
    • Then switched to 727: did not seem much of a change from 353x
    • Next 006ts: level of details were still the same but I noticed a little change: decay on some of the instruments was slightly longer, which to my ears started mingling with the next notes. It seemed a little bit lower in details as well vs 353x. Based on this, I preferred 353x over 006ts
    • The story continued in the same direction when I switched to 007tII and then to T8000. They had more of the decay element which melded with the next note(s)
    • If you can (or can’t) guess what came next in this direction, it was actually 252s. It sounded the most melded of all the above driver units.
    • SRM-D50, the Dac/driver combo was unlistenable to the extent that I would not even get it for free. It sounded close to or worse than 252s. So, in a way it combined the overlapping notes with, I guess, the underperforming DAC implementation (muddy / mixed). In a busy song with many instruments, I can discern between them while listening from LG V50 out to 353x. But it was very difficult (and in some busy passages, even impossible) to hear different instruments.
    So I ended up choosing the 353x. There was only one issue: I found the vocals to sound a bit on the leaner side vs listening directly from LGv50 via earphones Sony MDR-7550 or HD6xx. I did not have budget to spend big on a Dac at the same time while purchasing L700 and the driver unit. So I tried IfI Zen Dac (shop was advertising the new budget King on the block) which added the meat to the vocals, especially male vocals. This is exactly what i was missing.

    So now my current setup is Laptop to Ifi Zen DAC to 353x Ltd and L700.

    Looking for a DAC now which could have nice matching with this combo of 353x Ltd plus L700. Suggestions would be helpful (I will probably put a query on the advice thread)
     
  5. Cspirou

    Cspirou They call me Sparky

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  6. Philimon

    Philimon Friend

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    I bought a SR-30pro that comes with an SRD-4. Is the SRD-7 a sonic upgrade? And is the SB version best? I cant afford much.

    I am going to combo with a cheap tripath amp with tone controls. Would upgrading amp for a SR-30pro+srd make sense, like the eBay JL Hood @purr1n reviewed? I would get the new Schiit Loki as well for bass boost unless eq is not recommended. If I upgrade chain + pro bias I’d like to try some stats as well. I have owned a vintage Lambda+SRD7SB and 95X in past but would like to try again plus some new (to me) stuff.

    Anyone tried SR-30pro? Ive read comment that SR-30 may have been Stax bassiest electret, but also seen many comments that the SRX is completely superior. SR-30pro is much cheaper though. Ive seen Tyll’s measures of SR-Xmkiiipro go down flat to 20Hz. Pro versions are supposed to have more low end.

    I also got trigger happy on vintage stuff recently and bought a Pioneer SE-500 piezoelectric. @takato14 had a strange fascination for them (modded). Ill post about this further in a general vintage thread.

    [​IMG]

    [​IMG]

    (not my photos)

    https://www.stereophile.com/images/ifmeasure/StaxSRXMk3Pro.pdf

    edit: oops. Ive learned SR-X is not an electret. I thought it was since it looked so similar to SR-30 and SR-40. Thats explains why SR-X is in another league in comparisons. Such newb.
     
    Last edited: Mar 13, 2021
  7. Philimon

    Philimon Friend

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    Probably a terrible job here. Supra-aural difficult with EARS. Low bass subjectively.

    SR-30 pro.jpg

    [​IMG]

    [​IMG]

    [​IMG]

    SR-34 professional

    Just received. Burned-in for about 5min before measurements. Letting play in background and will try measurements again in some hours.

    I bought these out of curiosity and because I was thinking of using the enclosure for ortho driver transplant mod. But I no longer need the enclosure.

    First impression is hell no. Where’s the bass?

    Need to check for channel imbalance. I didnt hear one but Ive read its not uncommon so will look into that before listing.
     
    Last edited: Mar 18, 2021
  8. Tachikoma

    Tachikoma Almost "Made"

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    Electret films degrade over time, I think. Not much you can do unless you can replace the electret membrane.

    I have a question for the amp gurus around here: As far as I can tell, the main reason output transformers are necessary in tube amps is to block DC and transform the plate resistance of the output tubes to something low enough for speakers. With electrostatic headphones/speakers, why are either of these things necessary? Could you not utilize this DC as a part of the bias for the membrane?
     
  9. peef

    peef Friend

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    I think the devil is in the details on this one. Here's what the proposed scheme would look like if I'm reading this correctly, assuming a tube output stage running in fixed bias (negative bias applied to the grids). The cathode sits at ground, the stator sits at ground, and the plates idle at the bias voltage of 580V so that the grounded membrane sees -580V relative to the stator. It does work, and I've heard of ESL folks using negative bias voltage.

    [​IMG]

    By contrast, here's the more common bipolar power supply setup with anodes sitting at ground potential, and a separate fixed bias supply.

    [​IMG]

    The first big consideration is safety. In the setup with DC on the output, there would be a pin on the front of your chassis sitting at 580V capable of sourcing several milliamps. The bias supply has a large value ballast resistor that limits the output current, so while it's not great either, it is safer.

    The second is actually building the high voltage power supply. With a resistor or CCS load, the plates can't swing above the power supply's voltage, so a 1kV power supply would not be unreasonable to deliver 400V swings. The options for power supply parts aren't terribly compelling-- large value 1000V capacitors are rare and tend to be expensive, or not particularly good (e.g. two electrolytics in series). Two 350-450V supplies and a separate bias supply can often be cheaper and better.

    Tube availability isn't great either. EL34s still work, but I don't think you could wire them as a triode (as in the BH) without violating the g2 voltage rating.

    If the amp is to use negative feedback, that gets tricky, too, since the input and output do not sit at the same DC voltage. And you probably do want some sort of DC feedback there, or there is nothing to keep the output voltage from drifting up or down. (not to mention-- what if the +out goes up and the -out goes down?)

    And the last one I can think of is dust, but maybe this is a moot point with dust covers.

    It's not too uncommon to cap couple the output from the anodes. Since the driver itself is a very small cap, Stax released some designs with output caps as small as 10nF. They can sound quite good-- much better than OTLs for dynamics might, with the large electrolytic coupling caps.
     
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  10. Tachikoma

    Tachikoma Almost "Made"

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    Thanks for the detailed reply :D The scheme I had in my head would see the tube sitting at whatever bias is comfortable for said tube, and then adjusting the low-current bias supply to make up for the difference*, as the motivation I had was to ascertain whether an ordinary tube amplifier could be converted into a 'stat amp simply by bypassing the output transformer.

    *Obviously, I have no idea whether the separate HV supply will interact with the tube circuit...

    This alone is probably enough of a reason to not pursue this line of thought, though. Then again, maybe it would be less than 100V with most tubes - assuming it doesn't interact with the separate HV for the membrane and blow itself up.
     
    Last edited: Mar 19, 2021
  11. peef

    peef Friend

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    It's going to depend a lot on the specific output stage that you are trying to convert. Some use the output transformer as the plate load, or as part of a feedback loop. So the transformer would likely need to stay, and may need to be loaded with a resistor on the secondary. This would only really work in a push pull amp, as Stax are designed to be driven with both stators out of phase.

    If the amp is push pull, the best way to do this is likely to cap couple the output to the stators and build a separate +580V supply, and throw a dummy load on the OPT's secondary (i.e. a lot of work :)). This would be similar to a parafeed output stage. Make sure to use caps with a sufficiently high AC voltage rating. If the tube sits at 400V, and swings 300vpp, you are probably looking at a 700V+ part with a 300VAC rating. I would take a look at the Wima FKP4 or some of the newer Kemet parts. The transformer might not present a sufficiently high impedance to the tubes when you throw the stators in parallel, so there might be some higher distortion or roll off in the highs.

    I've tried doing the opposite-- running a Stax amp with a parafeed step down transformer to drive speakers. It's a lot more straightforward and works quite well.
     
  12. Tachikoma

    Tachikoma Almost "Made"

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    Isn't the reactive impedance of an electrostatic headphone still in the tens of thousands even at high frequencies (approximately 40k ohms at 20 kHz for 200 pF)?

    Anyway, one last dumb question, lets say I have a no-negative-feedback 45 push-pull biased at -50V or so, and a bias supply running at -530V. What is going to happen when I connect the stators directly to the tubes, and the bias supply to the membrane?
     
  13. peef

    peef Friend

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    It is. The problem is that the OPT primary's shunt capacitance is likely a few nanofarads, so its reactive impedance is much lower. The primary is effectively in parallel with the stators as it spans from one 45's plate to the other, so most of the current will go to driving that primary rather than into the drivers at the frequency extreme where they need it the most. It may not be a problem in practice-- just a watch-out.


    The -50V you are talking about is between the 45's grid and cathode, right? The voltage you need is the tube's anode relative to ground (likely several 100s of volts) so that you can construct a negative bias supply that generates 580V relative to the anode. Maybe post a schematic? If the anodes are indeed at -50V, you'd be applying a 480V bias (-50V - (-530V) = 480V). I don't think you need to be bang on 580V but it might sound a bit soft if the bias is too low.

    Especially if you're considering DC coupling, make sure you add a ~5K series resistor with the anodes. This is a ballast to protect the drivers and should be rated for the full voltage swing (you can put a few 300V rated ones in series). And if you use really low wattage ones, they can double as a fuse!
     
  14. Tachikoma

    Tachikoma Almost "Made"

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    Ah, thought I might have read that wrong, I just looked up the typical operating points of a 45.

    This was mostly a weakly intellectual exercise on my part, but I'll keep that in mind if I can summon the chutzpah to try it.

    I was mainly inspired by Broskie's account on how he directly connected his (electret) headphones to the plates of the EL34s on a Dynaco ST70 https://www.tubecad.com/2017/06/blog0382.htm

    Late edit: Even with a 5k resistor, having 200+ volts on the stator is probably a bad idea if the membrane has any chance whatsoever of touching a stator.
     
    Last edited: Mar 21, 2021
  15. Philimon

    Philimon Friend

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    Getting consistent supra-aural headphone measurements is difficult. Getting seal with hard silicone ears and flat leather pads is unlikely. Subjectively sounds like more bass than measured. However, still sounds overall light-weight and bright. See modded 6XX for reference. I was expecting less attack from these but they are not bad from mid-bass up. Harder and sharper from what I remember of 95X. I'm going to try eq on treble using amplifier tone control.

    My EARS have an inherent left/right imbalance - sound balanced to my ears. Refer to left-side please.

    Wife has always liked Stax. She wants to hear these before sell / return even though I explained they are technically electrets (as I watch life drain from her eyes :D).

    I got a decent deal at $80 if anyone's interested (no original packaging).

    Would I recommend these? Not unless you're a collector or curious.

    Stax SR-30pro.jpg
    Stax SR-30 pro LEFT.jpg
    Stax SR-30 pro RIGHT.jpg
    SR-30pro vs 6XXmod.jpg

    Edit: The Pioneer SE-500 and Yamaha YHD-1 have just arrived, so done messing with SR-30pro.
     
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    Last edited: Mar 19, 2021
  16. florilège

    florilège New

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    hello
    could you please tell me how good are the sigmas normal bias with srd7?
    thanks
     
  17. padam

    padam New

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    Hi, Welcome.

    They are definitely a good entry to the world of Stax.
    They have a "wow" factor to them. not just because of how they look, but also because of the musicality, airiness and soundstaging. Drive them with a decent speaker amp and you are good to go. I brought these to a local headphone meeting many years ago and everybody was floored by them, I'm guessing because they were so used to "narrow-sounding" headphones and they expected a more analytical sound.

    Personally, the normal bias Lambdas (using the same transducers) are just a brighter, much more refined version of that same musical sound: you get even less distortion, better extension in the highs and lows, still plenty of air (definitely sounds like an "earspeaker", unlike let's say the SR-X Mk3 that can be described more as an "electrostatic headphone") they are cheaper while also being easier to drive, so I've felt that giving up some of that big staging is worth it for that.

    For me, there is a certain "Je ne sais quoi" to normal bias Staxes that seem to be missing from most of their later Pro bias counterparts.
     
  18. Ant Page

    Ant Page New

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    I have the opportunity to buy a SRM-T1 tube energizer. I just bought the L300 LTD. I've heard these headphones have a lot of treble and not that much bass. Would this be a good amp for them?
     
  19. Marvey

    Marvey Super Friend

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    Yes. The SRM-T1 would be a great amp for the L300. It's not like you have much choice. The latest SRM-353 isn't as good as the T1 IMO. Among the available for new STAX amps, I like the SRM-007T too for the Lambdas, but that's in another price bracket.
     
  20. MuppetFace

    MuppetFace Sultana of Seafoam Green - Moderator

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    Depends on the price honestly. Don’t pay $1k or something like that. Sometimes the more well known amps get flipped for a lot higher.

    A used SRM 323 or even a little 252 would drive the Lambdas well.
    You can’t really go wrong with the 300 LTD.
    It’s one of the less fatiguing modern Lambdas IMO.
     

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