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mwl168

High Rollers
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Everything posted by mwl168

  1. I reserve my left hand for some very special purposes, hehe! Table updated!
  2. I am moving Kerry's mini GRHV\GRLV GB discussion to its dedicated thread here. I also included JoaMat's mini T2 here to see if we have enough interest for a GB. The table will be updated periodically as more people participate. Apologize if I missed someone or something - just let me know so I can correct the data. I put down one set for those that have not decided on the number of sets they want. The plan is to have assembled GRHVxxx boards, rest of boards will be PCB only. See discussions on the PS in this thread.
  3. Thanks guys for your kind words. I hope to have better news soon!
  4. I owe everyone a long past-due update. Long story short, I injured my right hand in early April right around the time we set out to test the final boards before sending the Gerber files for estimates. Actually got parts ordered and delivered but I was way too optimistic with the recovery schedule of my hand and I am finally to the point I think I can handle a soldering iron. I am back in touch with Kerry to sort out a few things needed for testing. Apologize for the lack of communication for weeks. Hopefully we will be back on track with the GB soon!
  5. mwl168

    KG Balanced Dynahi build discussion thread

    For this compensation cap in the feedback circuit, does it pay to use Mica caps instead of ceramic caps?
  6. mwl168

    Speaker Porn

    Love those vintage Sansui gears. Brings back some golden memories!
  7. As proposed, I started this thread for all to share your KGSSHV Carbon build experience and to exchange Q&A. This is a natural follow up thread to the Carbon Group Buy thread. Here are the version of Gerber files used for the boards in the group buy: kgsshvcarbonv5.zip (amp board) kgsshvpssicfetdual2new.zip (GoldenReference HV power supply, all-in-one version) kgsshvpssicfetsinglenewrightfat.zip (GoldenReference HV power supply, B+ and bias) kgsshvpssicfetsinglenewleftfat.zip ( GoldenReference HV power supply, B- and 7815/7915 based +/-15V regulator) goldenreference4.zip (GoldenReference LV bipolar power supply) goldenreference4plus.zip (GoldenReference LV V+ power supply goldenreference4minus.zip (GoldenReference LV V- power supply) bias.zip (stand alone regulated Pro and Normal bias supply) I (or others) will follow up with BOM. EDIT 10/8: Updated the BOM and Mouser project for the Carbon V5 to use Vishay RN60D 174K resistors for the two 175K positions. The correct part to use is Mouser part # 71-RN60D1743F. It's a mil-spec resistor that is actually 1/2W even though it's listed as 1/4W. The previously listed Xicon is 1/4W rated and not sufficient for these positions. EDIT 10/13: Updated the BOM and Mouser project for Carbon V5 to use 3M 961102-6404-AR for the servo jumpers. Note that the BOM does not match the shared Mouser project due to parts availability at Mouser. I apologize for the errors in project/BOM. EDIT 9/10: link to shared Mouser project for the GR HV Dual. Need to add 2 LT1021-10 and missing parts not available at Mouser. Please help check for errors. http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=54687aa8fa EDIT 9/12: link to shared Mouser project for the GR LV Dual. Need to add 2 LT1021-10 and your choice of insulation kits to mount uninsulated sands. Please help check for errors http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=b6d687c7f7 EDIT 9/20: link to shared Mouser project for the Carbon V5 (1 channel only). Please help check for errors. http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=7F837B24AA EDIT 10/19: GR HV Dual BOM in spreadsheet. More complete than the shared Mouser project above. GR HV BOM_Oct19.xls EDIT10/11: GR LV Dual BOM in spreadsheet. More complete than the shared Mouser project above. GR LV BOM_Oct 11.xls EDIT 12/11: Carbon V5 BOM (1 channel) in spreadsheet, uses KOA Speer resistors. HV Carbon V5 BOM_Dec11.xls
  8. mwl168

    KGSSHV Carbon Build Thread

    I took the AC filament directly off the windings of the Antek transformers for the BH and GG. And yes, B+, B-, bias and +/- 15V for the JFET front end (I use +/- 18V) are all you need for Carbon. Add filament supply for GG and BH. Plus supply for the HV delay if you decide to implement it (I recommend you do).
  9. mwl168

    KGSSHV Carbon Build Thread

    I need to correct myself. The above statement should be "Both boards have the built-in HV soft-start circuit...". The soft-start circuit is intended for HV delay but the "delay" part needs to be implemented separately off board. There are many such delay modules available on eBay or you can simply wire a manual switch like I did.
  10. mwl168

    KGSSHV Carbon Build Thread

    The first and third boards in your pics are what commonly referred to as the GRHV dual boards. First board contains B- and 7815/7915 LV regulation. Third board contains B+ and bias (+580VDC) supply. Both boards have the built-in HV delay circuit. For Carbon, GG and BH they are all you need but you can replace the onboard LV regulator with the GRLV. Most builders seem to be using ac filament supplies (myself included). The second board looks to me like what Kevin has laid out for a different purpose. IIRC, it contains a B+ supply and regulated filament supplies. It’s what I plan to use for JoaMat’s mini T2 build for front end tubes plate B+. You can use it for the same purpose on the Megatron but many simply use a drop resistor from the B+. The other GRHV boards are basically different dimension boards Kevin laid out to accommodate different chassis layout options. Other than that some earlier version boards do not have the built-in HV delay circuit, they are all the same identical circuit.
  11. mwl168

    current feedback electrostatic amp

    Enjoy your beer 😉
  12. mwl168

    current feedback electrostatic amp

    My experience and logic with the CFA amp echo what Jose said. Both the BH and Megatron cost lots more and are much more complicated to build than the CFA and I do prefer my BH and Megatron to the CFA on an absolute scale. Yet the CFA is a very nice sounding amp in its own right. To my ears it has a very organic and musical sound signature. If I state my personal preference between the three KG-designed all solid state amps I have built (CFA, Carbon and KGSSHV), some people will probably be choking their beer through their noses. Kevin can correct me if I am wrong but I think the electrostatic CFA amp is meant to be an easy and low-cost to build amp and it just ends up punching well above its class. The dynamic CFA on the other hand is a different story! Just my own 2 cents worth.
  13. mwl168

    current feedback electrostatic amp

    22.5mA current is a lot for a push-pull amp so you can reduce it quite a bit to manage the heat. Changing either the 2K or 500K accomplish the same thing - IIRC, they form a voltage divider. Curious to hear what you think of its sound compared to your other amps.
  14. Hi All: Ignorant people like myself and newbies often need various technical advices and assistance when dabble in this wonderful hobby. Many of these are general topics that do not specifically apply to one specific device. These valuable advices and suggestions are scattered in various threads over time and difficult to find. I thought it may be a good idea to have a dedicated thread where these discussions and information reside. So I thought I'll start this thread and see if it gets traction. So here goes my first question - inrush current limiter and fuse. My thinking has always been that the main fuse need to meet two main requirements; 1. provide protection to both the device and user when the device malfunctions and 2. able to survive the inrush current when the device is first powered on. To me, these two requirements are somewhat contradictory. A high current rating fuse that can survive the power-on inrush current, with the help of inrush current limiter(s), may not provide proper protection against device malfunction and vise versa. For my PSU for Kevin's ES amps, is it better to use one single inrush current limiter and a higher current fuse or to use a lower current fuse and use two inrush current limiter in series? Also, do I need to worry about the voltage rating of the inrush current limiter (in my case a NTC thermistor)? What's the actual voltage drop on the inrush current limiter during power-on? I would really appreciate your experience, thoughts and advices. Thanks!
  15. mwl168

    KG Balanced Dynahi build discussion thread

    Base on the Toshiba 2SK170 and 2SJ74 datasheet, with the marking side of the JFET facing you, the left-most pin is the drain and the right-most pin is the source.
  16. mwl168

    KG Balanced Dynahi build discussion thread

    Thanks Jose. It still looks to me that the drain pins are inserted into the emitter slots?
  17. mwl168

    KG Balanced Dynahi build discussion thread

    Thanks Jose. I think you meant P channel (J74) on top and N channel (K170) on bottom? Also, looking at the photo, it looks like the D pin of the JFET is inserted into the E slot of the socket?
  18. mwl168

    KG Balanced Dynahi build discussion thread

    So I am confused now with the JFET - BJT pin mapping looking at the photos and posts in this thread. It's clear that BJT Base -> JFET Gate. Knowing that the Toshiba JFET Drain and Source are interchangeable, which one is theoretically correct? BJT Collector -> JFET Source, BJT Emitter -> JFET Drain OR BJT Collector ->JFET Drain, BJT Emitter -> JFET Source
  19. mwl168

    matching resistors

    IIRC, years ago I used the IRC 0.1% resistors to build my first Dynalo. I measured each of the resistors when I received them and I was not impressed with the accuracy and the tolerance of those I received. I have since adopted the practice of spending the same (or less) money and buy large quantity of good quality 1% resistors and hand pick and match them. Personally I think I have better outcome with the latter practice.
  20. mwl168

    matching resistors

    It may help to know if the purpose of the exercise is to only match same spec'ed resistors to each other or if the absolute accuracy of the resistor value is also critical.
  21. mwl168

    KG Balanced Dynahi build discussion thread

    So I rigged together the test circuit both Jose and Chris suggested that used a 12VDC supply and measured the whole batch of 2SK170BL and 2SJ74BL (12 each). The 2SK170BL IDSS measured between 7.7 - 11.2 mA, the 2SJ74BL measured between 7.0 - 11.0 mA but mostly between 8.0 - 11mA. Toshiba datasheet states 6 - 12mA for BL grade. The good news is that the relative measurements between samples are consistent with those from the ATMega 328 tester. I am pleasantly surprised that I should be able to find 4 pairs of K170 within 3% and 2 pairs of SJ74 within 1% and another 2 pairs within 5% of these random samples. Not great but OK. Unfortunately the match between P and N channel pairs are not nearly as good. Forgot to mention; if you are going to do this, make sure you do it in a constant ambient temperature environment and you sit a good 2 + feet from the sands being measured. For a while the measurements were jumping all over the place only to find out it was caused by my radiant body heat. Christ!
  22. mwl168

    KG Balanced Dynahi build discussion thread

    Hmm, relatively consistent with my measurements but way off from what the datasheet states. Wonder if I am not reading the datasheet correctly or something else is amiss?
  23. mwl168

    KG Balanced Dynahi build discussion thread

    Thanks all. That’s very good to know. Also happy to know the 2SJ74’s appear to be authentic and the tester is not defective. It’s almost funny - the cost of 3 of those SJ74 exceeds what I paid for the tester. Jose, do your testers show similar SJ74 results as what I posted (value wise)?
  24. mwl168

    KG Balanced Dynahi build discussion thread

    I received a batch of 2SJ74 and 2SK170 from BDent today. I proceeded to test them using one of those ATMG328 testers I got. Interestingly, the tester shows the 2SJ74 pinout to be 1=S, 2=G, 3=D, the S and D pinout are reversed from the datasheet. What gives?
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