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Posts posted by Helium

  1. 10 hours ago, johnwmclean said:

    One channel of my latest build has little to no drift at all (no servos installed), which is odd behaviour from my experience.
    After 45 minutes warmup offset and balance can be trimmed to under 1VDC.
    From a cold start everything is now under 1 volt and stays that way. I’m curious as to the reason, do I need fix or leave as is? 

    Wait a minute, are you telling that no drift is something wrong?

    From my experience there is some drift (0.5~1VDC without servo, and ~200mVDC with optoservo installed, both balance and offset), and I wish it wasn't there.

  2. Did anyone experience how vulnerable DN2540N5 are?

    They are damaged so easily that I had to scratch my head.

    E.g. desolder it from a donor known good GRHV, actually new (don't ask why, I had to get spares) and it's detected OK in circuit as N-Ch depletion mosfet.

    I desolder it, test it and BAM it's no longer depletion mosfet, it turns into kind of Voltage regulator. And doesn't work of course. I spoiled 4 pcs already, despite the fact that I know how to desolder and handle components. And only one out of 5 was OK after desoldering.

    • Sad 2
  3. 17 minutes ago, Beefy said:

    Would the phase of the transformer secondary windings be an issue here? There doesn't seem to be anything indicating the start of a winding, both wires of each winding are the same color.

    I know that getting the phase wrong can cause issues when tying windings together to create your own centre tap.

    I checked phase of all windings prior to connecting. Yes, they are not marked, I marked them by myself. And connected both HVs in phase.

    4 minutes ago, jamesmking said:

    can I ask a possibly dumb question, I see the grlv with fully populated + and - sections,

    the board attached to the side wall seems to be a grhv but it only looks like a single rail grhv which would mean its either +400V or -400V i does not look like a dual output board to me..... ???


    Yes, it's single -400 board. The other one (+400) is dismounted ATM and waiting for a part for replacement.

  4. 9 minutes ago, jamesmking said:

    since the grlv and grhv have separate transformer windings they are floating with respect to each other.

    with only one amp being grounded through the grhv that amp board is tied to that psu but would have no idea what the LV voltage is since the LV floating with respect to the hv psu and nto referenced to it. The other amp board being grounded through the LV only would have no idea what the hv voltage is in relation to the lv voltage....

    you would see this by measuring the voltages on one amp board with the multimeter neg on that amps ground and then measure the voltages on the that amp board with the multimeter neg on that amp boards ground.

    Another way to think of it is electricity flows in a circle, for the amp connected to the hv board the electricity comes out of the hv board goes into the amp board and returns to the hv board through the ground wire, The Lv electricity enters the amp board BUT has no return path direct or indirect to the LV board... and visa versa for the amp board connected to the lv ground only....

    This is why I check the psu voltages of a fully built amp at the amp board using the amp boards ground and not at the psu using the psu ground....





    Wait a minute please. I see what you mean.

    Is the transfotmer up to the task? That's most unfortunate if it's not. Is Star ground of everything a cure?

  5. Thank you folks.

    4 hours ago, jamesmking said:

    0. make sure there is continuity between the grounds on the amp boards, hv psu and low voltage psu. HV psu ground -> amp ground       LV psu ground to -> another amp board with no ground connection between the LV and HV boards is not going to work. All 4 pcbs needs to share a common ground.


    2 hours ago, audiostar said:

    This is no good!
    Connect all grounds (LV, HV+, HV-, all amp boards) together to a single (star) point.

    Yes, currently GRLV has no ground connection with HV ground.

    Didn't know that non-tying LV and HV grounds is so critical. Usually it ends up with hum/noise, such sort of things.

    I will fix that and see.

    I the mean time I adjusted CSS with GRLV 15VDC to 18mA, so AMP boards are presumably good. Currently amp is almost done, need to replace DN2540N5 on +400 PS.




  6. I've ran into an issue building Carbon.

    I'm using split PS boards + separate GRLV.

    When I connect PS boards to transformer (without AMP boards) everything is fine, and voltage is +405/-406VDC (bias is a bit low at 563 but that's non-relevant issue and a matter of zener tolerances).

    But as soon as I connect AMP boards, transformer starts to heat up a lot (I didn't risk to leave it connected for more that 15 sec). Maybe it will start melting.

    Here is my connection:

    +400 goes to each AMP's B+ terminal, -400 goes to each AMP's B- terminal (obviously). However GND from each PS from goes to nearest AMP board only and are not tied together or by a sort of star terminal, therefore GNDs are not shorted.

    Am I missing a point here? Should connecting GNDs of each split boards remedy the transformer heating problem?

    Easy to check by yourself, one must say, but one of my DN2540N5 went bad and I cannot check it right now.

    This is my transformer spec (must be plenty of power, so insufficient VA rating must not be a reason?):

    PRI:230V SEC:
    > 2x 330V under load (350mA) (separate windings)
    > 2x 18V under load (500mA) (separate windings)
    - VA rating around 300VA


    • Sad 2
  7. Wow Soviet) A good old wine)

    Correct me if I'm wrong, but like AMP series, thread all the way down to gasket (rarely beautifully looking) implies that the gasket is left outside the panel. I usually like to put connector inside the case (this is low voltage Neutrik Speakon, but same idea).



    • Like 1
  8. On 6/21/2021 at 3:43 PM, starcat said:

    Yeah, they take a long time but are fun to make 🙂 I just completed the umbilical for the BHSE I am building (with original HeadAmp boards) and it took long as well despite using an AMP connector with crimp type pins. To be honest, I liked that connector much more than the Amphenol we use for the T2. It is like cutting wires, crimp pins on both sides and insert into the connector housing and voila. The pins are automatically isolated within the connector housing as well, so no fiddling with shrink tubing or soldering into the connector and the pins are available for different AWG sizes as well. A very nice system. 

    Craig, do you have any part number for that special glass fiber insulation and how long are your umbilicals? I am planning for 90cm, 3ft. 




    Hi starcat. What are P/N of the connectors and housings and pins you are using?

    I'm tempted to try these. As far as my quick search revealed, pins and wire entry seals don't come in bundle and are sold separately, aren't they?

    My concerns is that CPC series seems to be rated for 250VDC/VAC only, and that there is no space between the thread and the gasket, which means that the gasket itself will be outside the panel/case. Any considerations?

  9. Thanks, I've already start thinking angle grinder FTW to butcher my nice completed T2 PCB.




    Just kidding, I would do it on CNC if that happened. Kevin, so how do I wire, simply each PS board to each channel (=half T2 board)? I'm afraid I will encounter heavy ground loops.

  10. Just wanted to share one of my most favorite acquisitions among hundreds of manual and electric tools.

    Heinrich deep throat is capable to punch holes in the center of 400mm panel (hello large enclosures like Modushop Slimline).

    No burrs, very clean holes, any hole is perfectly perpendicular to surface, and waaayy more accurately positioned than made by drill bit as you can never avoid drill bit wandering. Precision is close to CNC milling.

    I also use smaller punch Roper Whitney XX with smaller throat.


    • Like 2
  11. 1 hour ago, AngelWing said:

    2. 2 Golden reference HV and LV Boards

    You will need 1 x HV board with bias section and 1 x HV with +/- 15VDC  low voltage section. If you populate +/- 15VDC low voltage section on one of HV boards, you don't need separate GRLV board. If you go with separate GRLV board (more luxury solution), you can use either single GRLV board producing both positive and negative 15VDC, or split boards, each producing +15VDC and -15VDC.

    Also, if you go with separate GRLV board, you can do with 2 x HV boards with bias section (saves money if you order boards at PCB house). You need to populate bias section on one them only.

    1 hour ago, AngelWing said:

    3. 2 KGSSHV Carbon boards.


    1 hour ago, AngelWing said:

    1. It looks like KGSSHV is a balanced input amp. What will it require so that I can run it unbalanced?

    Nothing required. It will accept unbalanced input as well, sound volume will be less.

    1 hour ago, AngelWing said:

    2. This image here: https://www.head-case.org/forums/uploads/monthly_2015_12/IMG_1617.JPG.8b2de600707a2057508ca7688eae8dd6.JPG has what it seems like 7815 linear regulator and no GRLV so is GRLV really required? Ignore the shoddy wiring(will not follow it).

    7815 is noisier than GRLV. GRLV presumably produces cleaner +/-15VDC. Piece of advise: go with amb's Sigma22 for low voltage. Much cheaper than GRLV to buid.

    1 hour ago, AngelWing said:

    That is single +/- GRLV. You can go with split positive and negative GRLVs, as mentioned above.

    1 hour ago, AngelWing said:

    4. Can I keep my ODAC amp in same enclosure maybe shielded ? Is ODAC good pairing?

    Not recommended IMHO. What if you need to upgrade your DAC in the future?

    1 hour ago, AngelWing said:

    5. What are Opto servos?

    Not needed for Carbon (=no tubes). Leave unpopulated.

    1 hour ago, AngelWing said:

    6. Lastly a loaded question. What will be the best way to make GRLV and GRHV so as to use least amount of components and not sacrifice lots of quality? It seems there are various designs of the PSU and I would like to save some money if possible.

    Use GRHV onboard low voltage section, if you want to cut costs. Or use Sigma22 instead of GRLV, and order 2 x HV bias boards instead of 1 x HVbias + 1 x HV w/low voltage.

    Really not many options to save money. Most expensive parts are main filter caps (40 USD/ea, and you need 4 of them), balanced potentiometer of your choice, transformer(s) and casework. None can be dropped out.

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