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High Rollers
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About JimL

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  1. Apparently the Shangri-La Jr. is no longer on the HFM website. V2, here we come?
  2. Goodbye Tyll. Happy Travels

    Good for you Tyll! Enjoy your richly deserved retirement! Will miss your reviews and commentary, but that's selfish on my part.
  3. New cans for a very *bad* Head-Caser.

    So if it sounds like sh*t, the wearer can't complain.
  4. Pass Labs discussion

    So, this appears to be a variation on his "Zen" amp that was first published in AudioXpress a number of years ago, basically a single MOSFET amplifying device into a current source, so single-ended class A, phase inverting, around 20% efficient, 14 dB gain (5x) and 2 watts our at 1% distortion, so either efficient speakers or headphones, although maybe not enough voltage output for something like a Susvara or HE6.
  5. i'm on a roll... the kgsshv

    The original Stax SRX schematic that the ESX was based on actually showed two heater supplies, but Singlepower's Mikhail Rothenberg was too ignorant to realize the reason for that (the input tube cathodes and heaters need to sit at zero or positive voltage whereas the output tube cathodes and heaters need to sit near B-), so he tied them together at ground. The excessive voltage between heater at ground and cathode at roughly -400 volts broke through the insulation layer between heater and cathode damaging the tube resulting in the problems described.
  6. Why am I getting the feeling that the Koss ESP950 is a better built headphone for a less than a tenth of the cost?
  7. Sennheiser HE-1

    This has always confused me because in KG's original KGSS Headwize article he said that he wanted the best amplification for the then new SR-007 but didn't want to pay the money for an SRM-717 - which implies that the 717 preceded the KGSS.
  8. Headamp has them listed at $4999 but Woo Audio has them listed at $3999. Don't know why the difference in price.
  9. Well, they only cost $3,999, not $6000, so "obviously" there had to be some cost-cutting somewhere. Obscene profit is an integral part of the business plan, you know. Hey, at least Sennheiser used honest plastic - remember those bright yellow foam ear pads and black headband on the HD-414s?
  10. The Headcase Stax thread

    Wasn't he raving about these just a month or two ago?
  11. The Headcase Stax thread

    Remember that increasing the output standing current means the output stage has to dissipate more power, which means more heat output. So you need to have enough heatsink in order to keep the output transistors and heatsink MOSFETs cool enough with the increased current. IIRC the onboard heatsink version KGSSHV is not designed for higher current but the off-board heatsink version can tolerate more current if the heatsinks are big enough.
  12. The Headcase Stax thread

    So, there are a couple possibilities. The first is that you have reached the limits of the amp, and the second is that you've reached the limits of the headphones. If it is the second, then there is no solution to the problem other than changing to different headphones. If it is the first, it depends on whether you are hearing distortion due to the amp running out of voltage, or current. The KGSSHV uses +/-450 volt or +/-500 volt power supplies, so its voltage limits are higher than the BHSE (which uses +/-400 volt PS), and close to or the same as the DIY T2 - in fact, there is less than 1 dB difference between the max voltage output of the KGSSHV with 450 volt PS and the DIY T2. The alternative is that you are hearing distortion due to current limiting, which could be alleviated by increasing the standing current in the KGSSHV. However, a more important point is, that if you are listening regularly at "deafening volumes", you are likely irreparably damaging your hearing. One sign of this is that if you hear ringing in your ears after a listening session, that is, as someone colorfully put it, "the scream of a dying acoustic nerve." You can replace headphones and amplifiers. You cannot replace your ears. Once your hearing is gone, it is gone.
  13. i'm on a roll... the kgsshv

    The 580V voltage is for the headphones - this is sometimes called biasing the headphones. When you change the resistors on the output stage you have to adjust the currents in the output stage so that the output sits at zero volts with respect to ground - this is referred to as biasing the output stage. These are two separate things that are not related to each other except that they are sometimes referred to with the same term - "bias."
  14. Hmm. I think you need to do a bit more math and some simple measurements. 1) The advantage of a cascode circuit is it has a high gain. The disadvantage is it has a high output impedance - roughly, the plate resistance. With a plate resistance of 140 kilohms into a MOSFET buffer with 100 pf input capacitance, that produces a -3 dB roll-off point of approximately 11-12 kHz, as Kung points out. Since there is no feedback to extend the frequency response, the amplifier will roll-off above that point at 6 dB/octave. You should be able to easily measure this using a sine wave generator, a good DMM, and a 100 pf cap as a dummy load. 2) Your notion that a 5.1k output resistor degrades the performance of the amp in controlling the diaphragm is questionable. Most electrostatic headphones approximate a 100 pf capacitor. The impedance of the headphone is therefore approximately 80 kilohms at 20 kHz. The traditional way of calculating the ability of an amp to control the transducer is the damping factor, which it the ratio of the impedance of the transducer divided by the output impedance of the amplifier. In this case, 80 kilohms divided by 5 kilohms is 16, which is perfectly adequate. Another way to look at it is to ask what the roll-off frequency of a 100 pf headphone is when driven by a amp with 5 kilohms output impedance - the answer is over 300 kHz, which is definitely sufficient.
  15. Blue Hawaii BJT Build thread

    Wow, way cool!