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  1. 2018 PCB Group Buy with TKD pots

    I have updated the GRLV and the CFP2 BOM, based on the layout, if you guys have any interest to that. I can not upload it, I can not attach here either, out of quota :-( https://mega.nz/#!8kYl3YoQ!3t851N3SOzj_pxxcOZtUznVPTXJw4jBhG7tySlaWgUI https://mega.nz/#!B4YhmBRD!Zk4EP4vQCHMur2VUzOVsliOkhzwgmH7TpERhRc5fDB4 It is important to mention that I did not built yet these, I have used the assumptions as I described before at the amp, at the psu it was pretty straight forward, there are only an an antiparallel diodes on the opamp input and some small caps on the output and some at the opamp power rails what was missing from the schematics.
  2. 2018 PCB Group Buy with TKD pots

    Hi All, I'm sorry for the long text, but it might be interesting for you. I have reconciled the schematics <> BOM <> layout and found the following differences: Q27, Q28 are BC556, BC546 at schematic, but PZTA56, PZTA06 on layout and BOM. I guess just for the SM packaging. Q22, Q23 are BC556B ? and Q24, Q25 are BC546B ? These are missing from the BOM. Since layout says PNP=BC556B, NPN=BC546B, I guess yes, it is the same type. Trimmer is RV1 on the schematics, TR1 in the BOM. It is just a minor designator change I guess. C2 is 100uF on the schematics, 47u in the BOM. I guess value is changed. C5 is 4uF on the schematics, 100uF in the BOM. As I see C5 designator is changed, I see 4u7 in the DC servo loop and C5, C6 just added to the power rails. R23 is missing from the BOM and layout. I guess it is cancelled. 2 x 100nF (on +- power of the opamp to ground), 1x 100nF parallel (?), 1x 22pF missing from the schematics, no designator in the BOM. I guess those are added later, but the two 100nF close and parallel is interesting. U4 on schematics is IC1 in the BOM. No other IC so it is surely just a designator change. R10 is 50k on schematics, 10 ohm in the BOM. R9 is 10 ohm on schematics, does not exist in the BOM. R9 vs. I guess R10 is a mistake in the BOM. Should be R9. R12 is 200ohm on the schematics, but 2 x 110 ohm on the layout and in the BOM. I guess it is just rearranged. R17 10k on schematics and BOM (but a 20k is inserted also with no designator), 20k on the layout. I guess that is changed to 20k. There is a 1k on the layout, series with the input, missing from both schematics and layout. I guess it is added later. Is it added always or only in case of oscillation problems? R14 and R32 are both 34k on schematics, instead R14 built as 68k on layout and in the BOM. R8 is missing from the BOM. R16, R29 is missing from the BOM. The diodes are missing from the BOM. I guess all 1N4148 now. Are you guys sure there is not a more recent schematics than the cfa2cmirror.pdf? I have updated the BOM, but would need confirmations on the above before this update can be valid. Thanks a lot!
  3. What Are You Building Today

    A DAC, including an RPI as player. Input is ethernet. DAC chip is my favorite, AD1865. From the RPI it fed through an I2S buffer and reclock, than an I2S to PCM converter. That is not my design. The DAC board is my design, at the end, there is no low pass filter, the interstage transformer acts like that. Than, the triode amp and buffer circuit is designed by a friend, I built it on cnc milled plate and point to point wiring. Several modifications made, first I did not like it. It was too dry and sterile. That time the end stage was based on ECC83s. It is redesigned and made with 5687s. Now, it is pretty good. Once I "finish", I will design and get cut and bent a copper case. But now, I'm in a stage that I need a decent headphone amp, tho be able to listen to music when the kids are sleeping in the other room.
  4. 2018 PCB Group Buy with TKD pots

    Thank You! So, for layout drawing, I can create from the gerbers. As I see the GRLV is the goldenreference6d.zip, the CFA2 is the cfp2hmt.zip linked earlier here. I did read through the "And now for something completely different" thread, but the base doc links are pointing to http://gilmore.chem.northwestern.edu/*** I thought the cfa2cmirror.pdf is used for simulation of the CFA 2. Is that accurate to create the BOM based on that? Is that the schematic used to create the layout? On the schematic of the GRLV, I assume it is the latest : goldenreferenceboard.pdf, can I use that to create the BOM and start ordering components? Thanks a lot!
  5. 2018 PCB Group Buy with TKD pots

    Thank You for the group buy! I'm excited to try the GRLV + CFA 2. May I ask someone links the GRLV and the CFA 2 build docs, like schematics and layout, which transistors should be matched etc? I did found some jpg schematic, but not 100% sure it is the version on the GB. The links from Kevin does not work for me for a few days now. Also, how do you guys match transistors? With a simple low current beta meter or you make a simple circuit and simulate the current in the application? Thanks a lot!
  6. and now for something completely different part 3

    Noise is just one parameter. Internal resistance, reaction time etc. is another - which is less important with class A amp, but still, I do not think that only noise counts. ... and, it is not straight forward that a better measured would sound better. I'm almost sure I will stay with the GRLV, but I'm still curious. Long time ago, with preamps I did like the battery supply. That was NiCd.
  7. and now for something completely different part 3

    Hi All, What do you think on running this amp on 4 SLA battery? I know, not very practical, need decent batteries for hours of listening. I'm really excited to build CFA 2 and supplied from GRLV, but I'm just thinking about battery also. Probably I would not stay with batteries, but I'm curious if you have tested. ? Before, I had more effect from one PSU to another sometime than one amp to another. I have used to start the amps and do initial tests with a HP6624 PSU and strange, but I was never able to build one as good as this monster rack PSU. .... but, not listened to the GRLV .... yet. Thanks!