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The Stax Thread III

Discussion in 'High-end Audio Forum' started by currawong, Aug 20, 2013.
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  1. Joong
    The phones are capacitive loads so that the low frequency power are limited and hence the low frequency tones are weak.
    This fact leads to the limitation of Electrostatic phone's weakness as opposed to dynamic phone including planar which are driven by inductive load that transmit full power at the lower frequency as opposed to capacitive load of the ES phone.
    It is correct statement?
  2. Ampeezy
    Thanks for the info, yeah that is a fear of mine. The sr-007 out of the carbon, has a decent helping of treble. Any more might border on excessive for me, which leaves me a bit stumped with the L700, and especially the sr-009. 
  3. mulveling Contributor
    Another variable -- my 007 is a Mk I, which is said to be notably darker than more recent models. I haven't heard any newer 007, unfortunately. The 007 Mk I is definitely on the dark side for my tastes, and it probably gets as close as it's gonna get to my preferred sound when driven by the Carbon (or perhaps from the BHSE with brighter tubes). 
  4. Ojisan
    Thanks for the info! Should be a fun journey. 
  5. JimL11

    Not really.  As I mentioned, electrostatic headphones resemble capacitors so the capacitative impedance at low frequencies is very high, up around 7-9 megohms.  However, capacitors don't (or shouldn't) make any sound, and ideal capacitors don't burn up any power, because with any AC frequency, the voltage and current are precisely 90 degrees out of phase.  In fact, the fact that headphones DO make sound means they aren't precisely the same impedance as capacitors - by the physical law of conservation of energy they must burn up energy to turn it into sound, which means there is a component of the signal current that is IN PHASE with the signal voltage.
    The impedance of a headphone gives the relationship between voltage and current that is needed to drive it.  For electrostatic headphones, the voltage requirement is high but the current requirement is low, so stat amps need high voltage but only a few mA of current.  For dynamic headphones the voltage requirement is low but the current requirement is high.  So dynamic headphones only need a few volts or less, but may need a 100 mA of current.  
    Electrostatic headphones can produce deep bass - in fact the Stax Lambda Pro was originally developed at the request of Mercedes Benz because they needed a transducer that could accurately reproduce the lowest frequencies at loud levels for analysis and design of their automobiles.
    joseph69 likes this.
  6. Ampeezy
    What kind of analysis requires an electrostat of all drivers to produce deep bass lol?
  7. Whitigir
    My 009 has the best bass that I have ever came across, period. Not even Utopia can compare
    joseph69 likes this.
  8. astrostar59

    Do you use EQ?
  9. Ampeezy
    On a slightly different note, my carbon has the TKD 4CP-601 volume pot. Any thoughts on the quality of this particular pot, and which pot out there could be a good upgrade? like the Khozmo?
  10. Whitigir

    Nope, just pure transmission :)

    I used gold point in mine :D


  11. kevin gilmore

    ​and that is the problem with transformers used to drive electrostatic elements with such a wide impedance range. You can optimize for low frequency or high frequency, but not both.
    transformers for speakers (martin logan, quad etc) are very carefully designed, and typically bigger than most of those power amps.
    the demograf probably throws around enough power into big enough transformers that it might perform well. If it does not kill you first.
    the amp schematic shown on the previous page has all sorts of issues, but mainly controlling the dc voltage of the output stage. So by the time you dc couple everything and add a offset servo
    it looks a lot like a carbon.
  12. Pokemonn

    regarding EQ, i found good old article about 009 with harman target response curve.

    this is 009 FR curve graph compensated by harman target response curve. i EQ it to flat with few db boost 200hz center like HD600/800 graph.
    if you dont like harman target curve, please ignore or modifi it. lol
  13. hpeter

    If such amps have negative reviews, then i´d like to see schematics and circuit working points, to understand why :D

    I see several choke benefits.
    1) DCR is low (DC voltage lost on it is low - low heat. Can´t say that about resistors of mosfets).

    2) For example 400H choke has only ~2k DCR; at 1kHz has reactance 2,5 Megohms. Resistor represents same value at any freq, DC.
    3) MOSFET gyrators can replace choke, but you need to use 2x anode voltage. Amp consumption.. (choke has EMF, gyrator does not)
    4) DHT or any good triode, working into ultra high impedance, will have low THD and maximum gain (very close to µ)
    (choke or gyrator are excellent)
    5) Transistors like to explode - release smoke when near limits (high power peaks). Choke survives.

    Example with ideal triode stage: with choke 400H 2kDCR 15mA, you will need just 300Vsupply.
    Output swing would be almost 0..600V peak (minus a little voltage lost on DCR)

    To match that with MOSFET gyrator, you´ll need 600V supply, and heat lost on mosfet will be 10x of choke (~4,5W)
    Supply power consumption will be 2x.
    With high current-voltage stages, consumption and heat lost, will make mosfet unattractive
    Choke/transformer has 2 problems, $$ and size. :devil_face:
    Makes more sense to me, spend 250€ on chokes, than $$$ for gold usb cable :wink:
  14. Thaudiophile
    Any impressions on Stax Sr omega please?
  15. Ampeezy
    Does the carbon currently max out at a 450V supply? and what differences are there if any between that and one with a 400V supply?
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