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  1. K

    TOPPING EHA5

    same problem i have with toroidy transformers. shipping exceeds the part cost.
  2. K

    TOPPING EHA5

    at no audio frequency can the eha5 generate 700vrms without the amp going into shutdown mode. bob katz and others have tested this. the nfca modules are limited to about 4 watts of power output, and that is nowhere near enough to drive those transformers. a pair of edcor transformers and a bias...
  3. K

    TOPPING EHA5

    1600 volts peak to peak measured stator to stator is 571 volts rms measured stator to stator. electrostatic headphones are a balanced load and need to be measured as a balanced load. 400 volts rms measured stator to stator is 1120 volts peak to peak measured stator to stator. typical of...
  4. K

    Stax Tube Amplifier Distortion vs Solid State

    better sinad? not really. a few db due to fully regulated power supplies. the noise of a 60db gain amplifier is due to thermal noise. unless you happen to have an infinite supply of liquid nitrogen.
  5. K

    Topping A90 Discrete (A90D) - Teardown and personal thoughts

    this was the schematic of the nfca module as used in the eha5. so the 90d may be slightly different as it probably does not have the 18khz filter. and the volume pot is replaced by a discrete relay attenuator. high res pictures posted elsewhere. too big to fit here.
  6. K

    Topping A90 Discrete (A90D) - Teardown and personal thoughts

    schematic of the nfca module for anyone that is interested.
  7. K

    Tice TPT Enhanced Line Conditioner Review

    you take say 3 meters of this stuff and coil it up in a box. what you have is an unterminated transmission line. not an antenna. being an open transmission line it acts as a notch filter whose frequency depends on the inductance and capacitance of the cable etc. picking reasonable numbers for...
  8. K

    TOPPING EHA5

    Its all about size (as in core cross sectional area) and maximum flux before saturation. its obvious from the graphs above that the core saturation of the eha5 transformer is about 1.4 tesla indicating the cheapest of core materials. better and much bigger transformers are available from lundahl...
  9. K

    Electrostatic Headphone Amplifier Review & Comparison

    biggest problem with the attenuator above is that the resistance is too low and will effect the gain and frequency response of the amplifier. the appropriate pair of high voltage 909k resistors is a far more reasonable dc load. the lower power stax made tube amps will measure orders of...
  10. K

    TOPPING EHA5

    so after working on a very old stax amp, turns out that plugging a pro bias headphone into the normal bias jack results in at least 8db less volume and significant balance issues. tried with a number of different headphones. that means you have to turn up the volume a bunch which might cause...
  11. K

    TOPPING EHA5

    2 x lundahl transformers plus la90 + bias circuit is about $1100.
  12. K

    Topping estats amp EHA5 (details updated)

    100 volts peak to peak 10khz square wave
  13. K

    Topping estats amp EHA5 (details updated)

    very nicely done for $400. led's under the sails to make it look like there are tubes inside.
  14. K

    Topping estats amp EHA5 (details updated)

    class D making 2000 vppss. not any time soon. or ever. full frequency range electrostatic output transformers are VERY hard. and quite large and stupidly expensive. the lundhall's are $5k each. you need 2. when square wave pictures of the topping are published we will know whether they know...
  15. K

    Topping estats amp EHA5 (details updated)

    posted elsewhere direct from the manufacturer. a90d circuit driving transformers.
  16. K

    What is so tricky with SMPS in audio?

    especially as amplifiers get bigger and bigger, the sweet spot is a switcher, followed by a lc filter and then a really good linear regulator. noise ends up in the sub microvolt range. when you need 10+ amps to drive your planar headphones, you save at least 40 lbs in mains transformer and large...
  17. K

    Electrostatic Headphone Amplifier Review & Comparison

    simmconn built and tested his carbon with an audio precision with an attenuator first picture is with 450v power supplies second picture is 400v power supplies third picture is the hand built attenuator for the audio precision comments from simmconn about how to trim the attenuator Here is...
  18. K

    HeadAmp Gilmore Lite Mk2 Review (headphone amp)

    the led's are used as adjustable voltage references. i could easily crank the front end gain by 10db (change 4 resistors) and then the thd would be .0004% but it sounds better the way it has been designed
  19. K

    HeadAmp Gilmore Lite Mk2 Review (headphone amp)

    this amplifier was one of the very first amps that have a dc servo that is outside the audio feedback loop. the opamp controls the front end current sources.
  20. K

    Electrostatic Headphone Amplifier Review & Comparison

    unlike dynamic headphones, electrostatic headphones are balanced only. So measuring either of the amp outputs to ground is meaningless.
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