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JimL

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About JimL

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  1. The Headcase Stax thread

    Fixed it for them.
  2. The Headcase Stax thread

    Not a member of the Stax mafia, but...it's a glorified SRD-7 in a fancy case.
  3. SRX-Plus Build Thread

    I agree with Jose. The output voltage can jump around when the amp first starts up, BUT, the output voltages track - in other words, if the R+ output is +50 volts, the R- output is also close to 50 volts, and the same with the L+ and L- outputs.. This is because the output stage is differential. Since it is the difference in voltage that produces sound, ss a result, the headphones see very little difference between the two stator plates, so there is no appreciable turn-on thump.
  4. The Headcase Stax thread

    Yes, I think they are doing a baseline EQ for 8 dB down, then varying the compensation with volume to match the Fletcher-Munson, Robinson-Dadson or some other equal loudness curves, plus adding in some expansion, but the variation occurring separately in three frequency bands, possibly depending on the loudness within each band. At least, that's what they seem to be saying - or I could be completely off base. Hard to know from the vague description, and I have no idea what sort of psychoacoustic research they have to back it up, if any.
  5. SRX-Plus Build Thread

    Could be a couple of things going on. First of all, what are your input stage plate resistors? That plus the input tail current source sets the plate voltages. If your B+ is around +370 volts, and you have 250k plate resistors, you need the tail current source to be running at 2 x 185/250k = 1.48 mA. If you are running 300k plate resistors, then the tail current source should be 2 x 185/300k = 1.23 mA. If B+ is at +340 volts, you want the upper plate voltage to be at 170 volts, which means the tail current source should be 2 x 170/250k = 1.36 mA for 250k resistors, and so on. Once you have set the tail current source to the proper value, you should have the plate voltages close to the desired value. If you are not able to balance the tubes, you need to either swap tubes around until you can achieve balance, or replace the tubes. Not sure about the source of the hum, but if the tubes are bad that is a possibility so I would try replacing them. Otherwise, there could be a ground loop, and those can be a b***h to track down. You should begin by checking your grounds - the amp board should go to a star ground, as should the PS board. Sometimes hum can come from the power cord ground, in which case lifting it from ground with a 10-100 ohm resistor can help. I seem to recall someone posting a diagram for the KGSSHV showing how to connect all the grounds, inputs and outputs, but I can't find it at the moment. I am working on an update to the shunt regulator so I wouldn't recommend building it at this point. The KGBH PS board is well sorted out and works fine.
  6. I got a notice that it is up on Massdrop. The Massdrop pictures seem to show it with a wall wart type supply. I've already got a Mk I so I didn't pay a lot of attention to it.
  7. Cleaning out dust

    If you're serious and not tongue-in-cheek, the specs on the RKV Mk III through the "impedance" (transformer) give just over 1 watt into 8 ohms. It's not specified for 4 ohms, but that is a tougher load. You should be able to figure it out from there.
  8. Modifying Stax's SRM-T1

    Speaking of old circuit boards, I remember doing mods on Dynaco phenolic PAS-3 boards.
  9. Modifying Stax's SRM-T1

    Well, you can do the same mods on the newer SRM-006, and similar mods on an SRM-007 using 7.5 mA constant current loads.
  10. The Headcase Stax thread

    Actually, he says the transformers are from the Stax F81X electrostatic loudspeakers. As to why a transformer designed to sit between a power amp with a couple ohms or less impedance and a large capacitative load (the F81) would be a good choice for a 6336A tube output with a couple hundred ohms plate impedance driving a small capacitative load of around 100 pf...?.
  11. The Headcase Stax thread

    Don't know about the pictures. Copied directly from p12 of the HF thread "Stat SR009 and T2 successors confirmed for spring 2017"
  12. The Headcase Stax thread

    You missed the best one, the Guerra (Italian for "war"), which has...wait for it....output inductors. Oh, wait, sorry, here's what the manufacturer says, "Although it may seem like our truncated circuit, it has been designed with great care and the output inductance has been realized as a high level transformer, on two holes, with different splits, just like a secondary output transformer!" Outside: Inside: Looks like passive power supply.
  13. Just up on InnerFidelity - Katz's Corner has a review of the KGSS Carbon and Dynalo Mk II built by Mjolnir Audio - well done, kevin and spritzer! He used an SR-007 Mk II with port mod and LCD-4 for the reviews.
  14. kgst

    Shouldn't be a problem.
  15. Trilogy H1 electrostatic amp

    Of course, Trilogy is not clever enough to use MOSFET current sources.
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