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  1. A few of us over at another thread started by Blueman2 are contemplating getting SRX Plus PCBs fabricated. See this thread: http://www.head-case.org/forums/topic/12445-plan-to-build-srx-where-to-find-bom-boards/ Discussion of the SRX Plus design can be found here: http://www.head-case.org/forums/topic/11996-srx-revisited/ I've checked with PCBNET and we can get the cost the amp board to $25 if we order at least 15 boards. The board will be 2mm thick with 3 oz copper, the board size is 9.35" x 6.85" ( 2 channels on one board ). Kevin has recently updated the board with teardrops enabled. We have not decided on the PS to use yet. The SRX Plus needs a +/- 340VDC and -20VDC supply in addition to filament supplies for the 12AT7 (x 4) and 6SN7GTB (x 2). JimL is working on a PCB of the shunt regulator he used and published on Audio Xpress. I think a GR HV configured for those voltages will also work. No promise, but if we have enough interest to start a GB, I will run it following similar process and logistics as we did on the Carbon GB earlier this year. Please state the number of boards you like if you are interested as well as your thoughts/preference of the PS. If we cannot reach consensus on the PS to use I am inclined to confine this GB just to the amp board. Thanks and Happy Holidays! EDIT 1/9/2015: Kevin has laid out a PCB for the shunt regulator JimL designed for the SRX Plus and added the 580VDC bias. The PSU board measures 8.9" x 5.05" and requires off-board heatsink. I have also upgraded the boards to 2mm thick and 4 oz copper. The amp board will be $25 each and the PSU board $20 each PSU if we can reach the quantity of 20 boards each. Here are the board counts: MLA: 2 AMP 2 PSU UFN: 1 AMP 1 PSU blueman2: 2 AMP 2 PSU gepardcv: 1 AMP 1 PSU jose: 1 AMP 1 PSU palchiu: 1 AMP 1 PSU charlo89: 2 AMP 2 PSU DefQon: 1 AMP 1 PSU (please let me know if your friend is interested and how many) JimL: 2 AMP 2 PSU sorenb: 2 AMP 2 PSU mwl168: 2 AMP 2 PSU eggill: 1 AMP 1 PSU Samsie: 1 AMP 1 PSU b0bb: 1 AMP 1 PSU GeorgeP: 1 AMP 2 PSU Rodeodave: 1 AMP 1 PSU Bdrew: 1 AMP 1 PSU
  2. This thread is a follow on to the original SRX Revisited thread and the SRX-Plus Group Buy thread. As of 2024, I count at least 12 members with working SRX-Plus Amplifiers: JimL congo5 MLA Sorrodje mwl168 luca jose blueman2 Juggernaut1101 tomislavkufrin simmconn oldie ============================================================= Here is an initial Bill of Materials for the Amp. Please provide input on errors and omissions and I will update. This is my first ever electronics build, so bear with me as I learn the ropes. I am initially building a KGBH psu, so do not have the BOM for the JimL shunt psu. I have linked to a post for the PSU BOM below. SRX-Plus Amp by JimL (SRX6 board by KG) Caps 7 0.1 µf/450 V 2 100 µf/6 V, NON-POLAR!! 4 .22uf / 1000v Resistors 18 100 O, 0.25 W gate stoppers for DN2540, and sense resistors 2 102 O, 0.25 W (source resistor for output cathode sink) ***Congo5 advises using 75 O instead 4 250 O, 0.25 W (source resistor for output current load) ***Congo5 advises using 200 O instead 4 500 O. 0.5 W 6 1.0 kO, 0.25 W gate stopper for 10M90S 2 1.43 kO, 0.25 W (source resistor for input current sink) ***Congo5 advises using 1.2 kO instead 4 2.0 kO, 0.5 W 4 5.1 kO, 1 W/500 V 8 124 kO, 0.5 W, 350 V rated 8 220 kO, 2 W, 500 V rated 4 300 kO, 0.5 W, 350 V rated 4 500 kO, 0.5 W, 350 V rated Silicon 10 Supertex DN2540 N-Channel depletion mode MOSFET (TO220) 6 IXYS IXCP10M90S current source (TO220) Trim Pots 2 20 O multiturn trimmer for output current sink—set current to 17 mA 4 100 O multiturn trimmer for output current load—set current to 7 mA 2 500 O multiturn trimmer for input stage current sink—set current to 1.33 mA 2 5 kO, 0.75 W multi-turn trimmer for input stage balance Tubes 4 12AT7, may also use 12AX7 or 5751 for top tube only 2 6SN7GTA or 6SN7GTB Connectors 3 3 pin 3 2 pin 1 4 pin Heatsinks 2 25 x 16.5 x 16.1mm Aluminum Heat Sink 4 42 x 35 x 25mm Aluminum Heat Sink This list is based on the BOM from the December AudioXpress article by JimL. I have adjusted it for the SRX6 board designed by Kevin Gilmore. Changes I noticed were: Use of a bipolar 100uf capacitor across the 5K input pot, which removed the need for 2 100uf caps and 1 100K resistor per channel. Change from 510K to 500K resistors going into the output tubes (6SN7's) Change from 250K to 300K resistors at upper input stage As noted above, changed values of the resistors in series with the trim pot of all the cascoded CCS as advised by Congo5 and MLA (Output current source: 200R in place of 250R, Output current sink: 75R in place of 102R, Input current sink: 1.2K in place of 1.43K) I recommend against trying to build the Shunt PSU as I am not sure JimL ever got this working to his satisfaction. I recommend you try another PSU. For the Shunt PSU BOM, refer to this post by jose. Note that the original board showed use of a TIL731 which is incorrect. It should use SPX431.
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