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mwl168

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Everything posted by mwl168

  1. mwl168

    The ultimate DIY? A Stax SRM-T2!

    Is that a custom chassis of your own crafting?
  2. mwl168

    DIY mini T2 Build Thread

    I am starting this thread for all that are or will be building JoaMat's mini T2 to share information, ideas, thoughts and experiences. The attached schematic is an updated one .The resistors in the BOM are thick film ones and can be replaced with thin film ones for likely better outcome. The power supply requirements for this amp are +400VDC, -460VDC (EL34 output stage), +220VDC (6922/6DJ8 front end), +15VDC, -15VDC (servo, cathode current source) and 6.3V filament supplies for the 6922/6DJ8 and EL34 tubes that can either be AC or DC. I also plan to use the +15VDC for the CPC1117N high tension delay. Schematic mini T2.PDF BOM mini T2.xlsx
  3. The previous PCB order has been officially declared missing. The Fab house was kind enough to provide a refund coupon for me to reorder the PCB which I did. I used a different, higher-cost shipping option this time. With better luck this time I should receive the PCB in about 2 - 3 weeks.
  4. 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.
  5. mwl168

    Speaker Porn

    Love the Harbeths and love the stools they sit on.
  6. We have another hitch and delay. I ordered the updated GRLV boards in September and they were sent out to me around Sep 18. The tracking info shows that the package cleared US customs on Sep. 30 and was en route to me via US post network. I have not received it yet and local post office confirmed that they do not have it either. I got in contact with the manufacture and they asked me to wait for a few more days before they can open an investigation. I am going to give it another week and if the package is till absent the manufacture will provide a coupon at that time for me to reorder the boards. Apologize for the further delay. Will provide another update in a week or so. Table updated.
  7. Not too late. I will add you to the GB.
  8. Quantity of 1 for the mini T2 represents a pair of left and right channel boards.
  9. mwl168

    Speaker Porn

    Need a bigger TV.
  10. 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!
  11. 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
  12. mwl168

    Voluntary amp builders?

    At the risk of stating the obvious regarding measurements; there is a key factor of “correlation”. I remember more than 20 years ago I read an article to the effect of the three legs of measurements- “What do you measure? How you measure it? How do you interpret the measurements?”. As an example, it’s obvious that measurements of an amp’s physical dimensions have no direct correlation to how it sounds. I always wonder, much like many research in medicine, if some day someone(s) will eventually figure out a comprehensive set of measurements that truly have a direct correlation to how a device sounds to human ears (if that’s even possible).
  13. mwl168

    Happy Birthday johnwmclean

    Happy Birthday John!
  14. mwl168

    current feedback electrostatic amp

    1. I use the digital volume on my DAC but you can easily add a volume control to the amp. 2. This chassis I use is quite small - dimension is 160mm x 70mm x 311mm. It's only for the amp circuits and you cannot fit the entire amp in it. There is a PSU in a separate chassis. As an example, you should be able to fit the entire amp including the PSU in a chassis like this. 3. My rough estimate for parts alone would be about $700 US that also covers chassis, transformer, connectors, wires and a reasonable 4-gang volume pot. Like most things these days, labor is the biggest investment. Cost can escalate quickly if you start getting into fancy chassis, volume pot and boutique parts (resistors, capacitors, wires, etc.).
  15. mwl168

    The Headcase Stax thread

    Depending on how small is small. You can consider Kevin's current feedback design which is the smallest desktop electrostatic amp I have built to date. All parts are current, simplistic power supply and very good sounding to my ears. Even though money saving isn't the main reason for me to go the DIY route, this current feedback amp is also the cheapest to build. The amp board (per channel) measured 184mm x 64mm. There is a thread in the DIY forum dedicated to this amp.
  16. mwl168

    The Headcase Stax thread

    The good news here is that for the KG electrostatic amps that are often mentioned here (such as Blue Hawaii, KGSSHV, Carbon, Grounded Grid, etc.), there are proven PCB's for both the amps and the PSU's that many have built working and reliable amps with, myself included and I do not have a science degree and never forged a knife in my life! Extra safety precaution does need to be followed strictly given the high voltage involved! With that said, if you source correct parts from reliable vendors (Mouser, Digikey, etc., not eBay, not Taobao...), stuff the right parts in the right spots on the PCBs, exercise good soldering practice (many good tutorials on Youtube) and pay attention to layout of components (circuit boards, transformers, connectors, etc.) and wiring, your success rate is very high. On top of that, many knowledgeable people here will come to rescue should some things do go wrong provided that you have done your homework! It's lots of fun and a very rewarding experience!
  17. mwl168

    The Headcase Stax thread

    It's never too late to pick up the soldering iron. If you invest the effort to learn, with diligence and good common sense those DIY amps you mentioned in your posts are really not that difficult to build.
  18. mwl168

    The Official Head-Case Photography Thread.

    Found this photo from quite a few years back. Canon 5D II with 135mm/F2 lens.
  19. mwl168

    Head Case Motorsports

    To me, in actual driving the car actually feels much torquier than the number suggests. You may be pleasantly surprised. The chassis is very well balanced. Too bad the car is heavier and way too complicated than I would prefer. Wish I also had the carbon roof!
  20. mwl168

    current feedback electrostatic amp

    Where I live, the ambient temperature at this time (end of August) is around 70 F, about 22 Celsius. The heatsink temperature of the amp gets to about 45C fully warmed-up. When I first cased the amp, the ambient temperature was around 27 Celsius and the heatsink was ~ 48C not quite 50. I can see the heatsink hit high 50's C in Taiwan where the ambient temperature can easily hit low to mid 30's C this time of the year.
  21. mwl168

    current feedback electrostatic amp

    Finally cased my ES CFA amp. Returned the bias resistors to 1M with the larger heatsinks. Running 20mA bias for the output sections.
  22. mwl168

    Technical Assistance/Advice Thread

    Good point. I should have mentioned that I mount the aluminum angle to the heat sink using M5 screws, which, in my experience, on top of having fewer holes to work with, is much easier to tap and far less likely to break the tapper. I drill the mounting halls on the angle slightly larger than the M5 screw diameter to provide some margin of error so I don't need to be as precise when I drill and tap the heat sink..
  23. mwl168

    Technical Assistance/Advice Thread

    You really have two options when it comes to mounting resistors to heat sinks: 1. mount the transistors directly to the heat sink which requires you to drill and tap the heatsink 2. mount the transistors to an aluminum angle then mount the angle to the heatsink Of the two options, I would opt for option 2 when possible. Drilling and tapping the heat sink is tricky and unforgiving. If you make a mistake like broken the tapper while tapping the heat sink, you may be forced to abandon that heat sink altogether. Drilling and tapping (optional) 3mm- thick aluminum angle (which I typically use) is much simpler and forgiving. Aluminum angle is also easier and cheaper to replace. I speak from personal experience.
  24. mwl168

    KG Balanced Dynahi build discussion thread

    Almost done casing the Dynahi. The input XLR sockets are temporary, waiting for the Neutrik ones to arrive. Also, cased the dual GRLV PSU which I will be using for both the SUSY Dynahi and balanced CFA. Two Antek 100VA transformers and the GRLVs are set for 30VDC rails.
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