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  1. JimL11

    The Entry Level Stax Thread

    Don't know about current Woo Wee but in the past, apparently Woo had some issues about not having the appropriate safety resistors in the circuit, so I would go with the Stax.
  2. JimL11

    KOSS ESP-950 Thread

    Actually, the T1 is a hybrid, with solid state in all stages except the output. And the high levels of distortion in "tube amps" is as much myth as reality. In fact, the T1 is specified to have 0.02% distortion at 100V RMS which is a very loud level, and well below the consensus level of audible...
  3. JimL11

    KOSS ESP-950 Thread

    "Rather then buy a modded Stax amp the Phantom seems to deliver more power then any Stax amp ever made." Well, it's not quite clear. The iCan website says the Phantom can deliver 640V, however it doesn't say whether that is RMS or peak voltage. The Stax SRM727 is speced at 450V RMS at 1 kHz...
  4. JimL11

    Kingsound M03 - Can it drive Stax?

    That really is NOT a good idea. The Topping LA90 is a power amplifier, which can put out up to about 30V RMS. The Kingsound M-03 is a portable stat amp (conceptually similar to a Stax SRM252), which is rated at an input level of 0.3V RMS. That is 100-fold lower voltage than what the LA90 can...
  5. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    That should be adequate heat sinking. I am assuming you are using ceramic high voltage insulators and heat sink grease to attach the 10M90S. No other obvious thoughts.
  6. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    Mouser is a reliable supplier - that's where I get my FETs. So there are a couple possibilities. The DN2540 regulates the current, so if the current is much higher than set, it likely means the DN2540 is blown. In theory the TO92 version should be enough, since it is the bottom FET, so it...
  7. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    That is a subjective question so it depends a bit on what your sonic preferences are. I had a 727 with global feedback mod, and I preferred my modded T1, which sounded a bit smoother. I sold the 727, still have the T1. A couple friends who heard both also preferred the T1. The modded 727 does...
  8. JimL11

    The Entry Level Stax Thread

    Looks like the JJs are equivalent to 6SN7GTA/GTB, which have higher voltage and power ratings than standard 6SN7 tubes. So they can be used in place of 6CG7 tubes as long as you have the correct adapters - depending on how tall they are with the adapter you may or may not be able to replace the...
  9. JimL11

    The Entry Level Stax Thread

    Dominic Stritt is "firschi" on Head-Fi. The CCS mod is what I published in AudioXpress, July 2017. This substitutes a cascode MOSFET constant current source (AC impedance > 170 megohm) for the plate resistors that are used in all the Stax tube output amps (SRM-T1/T1S, T1w, 006 and can be...
  10. JimL11

    KOSS ESP-950 Thread

    Well, the Koss energizer has a bit higher bias voltage and power supply voltage, but it has pretty low current capability (according to Kevin Gilmore it only has 2 mA standing current per channel, while the portable Stax SRM-252 has about 4 mA/channel), not surprising as plastic doesn't make...
  11. JimL11

    The Stax Thread III

    Perhaps that is because the SRM-1 never had XLR inputs to begin with. Prior to the SRM-T1S, all of the Stax amps had single ended RCA inputs only. Based on the schematic, the SRM-1 MkII has a diff amp topology input section (but used single-ended) so in theory it could be modified to take XLR...
  12. JimL11

    The Stax Thread III

    I don't know if putting a 10 ohm resistor in parallel with the SRD-7 will fix your distortion problem or not, but it probably won't hurt. There are a few amps that need an output load to be stable, and their manufacturers often recommend that they not be powered up without a speaker load...
  13. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    Well, it's not that complicated a circuit - 2 MOSFET's and 3 resistors plus a trim pot per current load - you need 4 current loads, which replace the plate resistors. I hard wired everything and attached it to a large single heatsink, but if that's too complicated, Kevin Gilmore has free...
  14. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    Are you looking to do it yourself or are you looking for someone to do it for you? Where are you located?
  15. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    Not specifically, but the idea is the same. Are you referring to the 007Tii (uses 4 6FQ7 tubes) or the 700T (uses 2 6SN7 tubes)? Both have essentially the same circuit as the T1 except for the output tubes, with the same input and intermediate stages. The amount of standing current in the...
  16. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    No idea, if we are talking 2V for the LED and 100V zener, that's 50 LEDs give or take, which is a pretty long chain. That will generate 50 times the noise of a single LED, or sqrt 50 = a bit more than 7 times the noise voltage assuming they are uncorrelated. You would probably have to measure to...
  17. JimL11

    Stax SRM-T1 Repair, Re-Cap, Mod

    Don't forget that even if an individual LED is quiet, lots of LEDs in series will have their noise add up.
  18. JimL11

    HiFiMan Shangri-La Jr (New $8000 Electrostat)

    As far as I know there is not an authorized "727" mod for the KGSS, nor is there a Stax SRM-007t that uses the 6S4A. Spritzer did mod an SRM-007T to use the 6S4A tube, however, but of course that voids any warranty. It requires cutting all the circuit board traces to the tubes except for the...
  19. JimL11

    The Entry Level Stax Thread

    The T1/006 amps use the 6CG7/6FQ7 output tube, which is a 9 pin miniature tube that is similar to the older 6SN7(GTB?) octal output tube that is used in the T700T. Reportedly the input and intermediate stages of the two amps are very similar, if not identical. The output specs for the new model...
  20. JimL11

    The Stax Thread III

    It does have the adjustable bias. Electrically, the CCS mod could be done but physically, you would have to find a way to mount the heatsinks for the CCS. In the T1 and T1S the heatsinks can be mounted to the side of the chassis near where the output plate resistors were on the circuit board...
  21. JimL11

    The Stax Thread III

    Here is a website that lists when Stax products were introduced. https://en.wikipedia.org/wiki/List_of_Stax_products According to this, the SRM-727A was introduced in 2006, the SRM-727 II in 2007.
  22. JimL11

    The Stax Thread III

    I would add that a used SRM-T1 series is around $600 compared to a used SRM-727II which is generally north of $1000. Parts cost for the CCS mod including replacement electrolytic caps and heatsinks is around $100 (a bit more if you use a Gilmore circuit board), and can be built in less than a day.
  23. JimL11

    The Stax Thread III

    According to Kevin Gilmore, the D50 circuit is the same as the 353 but run at lower current and lower voltage power supplies. He says the circuit of both is similar to the 717 but simplified, with resistors in place of current sources. Due to biasing issues, spritzer feels the 717 sounds too...
  24. JimL11

    The Stax Thread III

    So, options within your budget. The standard SRD-7 is standard bias only. The SRD-7 Mk II or Pro has pro bias. A standard SRD-7 can be converted to have pro bias if you are willing to do a little DIY or have someone do it for you. Of the standard Stax amps, the SRM-323 is the least expensive...
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