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  1. I was going to name it 'Double the Carbon, double the voltage, double the fun', but I'm afraid that would be too wordy. Ever since I measured the output swing capability of the Carbon, I wanted to see if it can drive my ESL speakers. To do that, I'd need a beefed-up version that can output at least 1kVrms before clipping. That's 1414V peak, out of a ±750V to ±800V PSU. To simply scale up the Carbon amp and the GRHV PSU without major changes to the PCBs, a few hurdles would have to be overcome. First is the 900-V rated 10M90s in the cascode CCS that bottom out with ±450V PSU. When I was browsing the high voltage FETs at Mouser, I found the UnitedSiC UF3N170400B. It's a 1700V 6.8A SiC JFET, naturally in depletion mode, perfect for the upper device in the cascode CCS. The threshold is about 9V, which helps the DN2540 to get further into the constant current region yet keeps the power dissipation still in check (no heat sink needed even with the TO-92 package). The drawback is the package. The TO268-7 isn't too friendly for a DIY thermal solution. I had a few carrier boards made with aluminum-based PCB. According to simulation, the little board would give me 9 degree temperature difference from the package case to bottom of the board when the FET is dissipating 9W. I chose black solder mask, hoping to get a bit better heat radiation capability. 10 boards cost me about $3 at JLC. They also have copper-based PCB with a special process to have the base copper flush with the top surface for a much, much higher K. Too bad the NRE is about $150, so I chose the cheaper route with aluminum. The insulation is good to 3kV so this board can be bolted directly on the main heat sink without additional insulation. Isn't that great? The next bottleneck is the 600-V rated STN9360 when the PSU voltage reaches ±600V. I replaced them with the 900-V rated 2SA1968s. Thanks to the cautionary words from spritzer, I started cleaning up traces with high voltage differential that are getting too close to each other. I removed the middle pad 'A' in the 10M90s footprint, and re-wired a couple of traces on the back. With the bias changed from 24V to 13V above B-, the JFET can be used as the output device as well. At almost $10 a pop, they are considerably more expensive than the SiC MOSFET they are replacing. So the full-JFET configuration shown below is more of a proof-of-concept than anything else. The feedback dividers are changed from 200k:200 ohm to 440K:470 Ohm to maintain the gain and allow the output swing to double, without having the feedback current overtaking the idle current through the input JFET. Two 10pf 1KV caps are in series as a 5pf cap, since I don't have the proper 2kV rated caps. Not a great idea. I was lucky it didn't blow up. Technically the board is now ready for up to ±850V. I tested the SiC-JFET 'doubled carbon' config with ±400V PSU. The performance is slightly worse than the original Carbon. Is it worth the effort? We'll see. (To be continued...)
  2. As several people have asked for the PSU boards, and some whether caps are available lets probe the interest. Group Buy moving ahead - collecting payments, and then ordering. Please bear in mind that lead time is 12 weeks ... edit: added: "Group Buy moving ahead - collecting payments, and then ordering.", and price confirmation.
  3. EDIT 8/4: attach updated GB details and remov outdated chart EDIT 7/31: attach updated GB details and remov outdated chart EDIT 7/27: attach GB details and remov outdated chart EDIT 7/23: attach PCB cost quotes and limit first time poster to 4 set of amp boards max. EDIT 7/19: proposing use of HV Carbon V5 board to replace both V2 and V3 boards. See posting # 190. EDIT 7/13: attach snapshot of final order entries and board count. EDIT 7/12: This GB is officially closed as of 7/12/2015. Due to the changes Kevin made to the PS boards, it'll take a few more days for these boards to be checked before I officially request quotes from the fab houses. I hope to have information on the cost of the various boards to share in a week or so. I will post an image of the spreadsheet here for all to review. EDIT 7/9: Please double check and confirm or make any final updates to your record on the spreadsheet by end of day Saturday, July 11. On Sunday, July 12, I will officially close the GB, lock down the counts of the various boards, post a snap shot of the spreadsheet on this thread for your review and proceed to request final quotes from the fab houses. As promised, I am planning a KGSSHV Carbon GB which includes both the amp boards and the PS boards. First I like to gauge the interest for the GB which will also help me estimate the cost of the PCB boards. My plan is to make 2mm thick PCB with 2oz copper. (EDIT 0731: HV PS boards are upgraded to 3oz copper) For the amp board, we'll most likely use the latest board, kgsshvcarbonv2.zip and kgsshvcarbonv3.zip that Kevin posted on June 30 which has the cascode CCS and uses mostly current parts including the PZTA SMD parts. This board measures 5.45 x 4.05 inches according to Kevin. THIS BOARD HAS NOT BEEN CHECKED NOR TESTED AT TIME OF WRITING. For the HV PS board, we have the following options (these HV boards contain built-in LV supply): 1. the GoldenReference dual HV (kgsshvpssicfetdual2new.zip that Kevin posted on June 27, 6 x 6.48 inches). I have checked this board by tracing the PCB visually and Kevin has corrected the issues I spotted and updated the schematic accordingly (see Kevin's post #4802 on the KGSSHV thread for the schematic). I cannot guarantee I did not miss something. THIS BOARD HAS NOT BEEN TESTED. 2. the split/single, "skinny" PS boards (one board for each rail), they are kgsshvpssicfetsinglenewleft.zip and kgsshvpssicfetsinglenewright.zip which were also posted on June 28 (3 x 6.48 inches). THESE SINGLE PS BOARDS HAVE NOT BEEN CHECKED NOR TESTED. 3. the split/single, "fat" PS boards (one board for each rail), they are kgsshvpssicfetsinglenewleftfat.zip and kgsshvpssicfetsinglenewrightfat.zip which were posted on June 28 (4.05 x 5.45 inches). THESE SINGLE PS BOARDS HAVE NOT BEEN CHECKED NOR TESTED. For stand alone Golden Reference LV PS, two options (THESE PS BOARDS HAVE NOT BEEN CHECKED NOR TESTED): 1. the dual LV (goldenreferce3.zip) 2. the single LV (goldenrefernceplus4.zip and goldenreferenceminus4.zip) We'll need to at least check these boards before proceeding to have them fabricated for the GB. I will try to find time to trace them but can really use others' help for double-checking. To gauge the interest and to help get an idea of the volume in order to determine the cost, please respond with the following information (be specific) if you are interested in participating in this GB: 1. How many amp boards do you want. (one channel on each board, you need two amp boards for one complete amp.) 2. Which HV PS (dual, single skinny or single fat) and how many of them do you want. (you need at least one dual board or two single boards for one complete amp.) The HV PS has built in LV and bias sections. The separate LV PS and Bias boards are optional. 3. Please use this link to register your request: https://docs.google.com/spreadsheets/d/1GWDWwLfsIDtwn1HB-x76lS6WyWwLd5lwsORFKiUuuEQ/edit?usp=sharing The chart below is for reference only and not up to date. The spreadsheet contains the up to date information. Please let me know if I missed anything. It's advisable to read the the following posts at the minimal for relevant information to this GB: 16, 34, 42, 51, 68, 80, 89, 92, 113. More to come. Thanks! EDIT 6/28: updated information due to the newly released "fat" single PSU and updated gerber files for PCBs EDIT 7/3: added Golden Reference LV and Bias board options and start using sorenb's shared spreadsheet EDIT 7/6: remove early spreadsheet image Note: For the single PS boards, quantity of 2 indicates the participant will receive 1 left and 1 right boards (or 1 plus and 1 minus for the LV).
  4. Another round of Carbon etc. state your interest here When ever there are enough boards for ordering participants will be asked to pay estimated price. Shipping will be added whenever the cost is known. Boards from PCBNet. Distribution via @mwl168 in US/Canada, and from Denmark, Europe for the remainder. /S
  5. "Description (Gerbers) copper/pcb thicknes": Everything is one channel, and two will be needed for stereo. As for the KGSShv PSU, only the Single Right Skinny is offered: containing one High Voltage rail and a BIAS supply. Those who needs a full supply will need two of those + the Golden Reference Low Voltage. Überamp (Uber1 + Uber2) 4oz/2mm Unbal2bal (Uber3) 3oz/1.6mm Golden Reference Low Voltage (GoldenReference6) 3oz/1.6mm Transconductance Amp (CurrentSourceAmp2) 1.6mm/3oz KGSShv PSU (kgsshvpssicfetsinglenewright), 1.6mm/3oz KGSShv Carbon Amp (Carbonv6), 1.6mm/3oz Grounded Grid (.........) , 1.6mm/3oz (as requested by JoeHpj A spreadsheet here to keep track of everyones orders. Quotes are from PCBNet, and not yet confirmed but probably close. The spreadsheet will automatically update the final price based on the total amount. Shipping is done from MD, US to US/Canada, and Denmark for non-US/Canada.
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