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  1. #31

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    Quote Originally Posted by zingo View Post
    This is one reason I prefer to buy Chinese equipment with the Grant Fidelity name on it, even used like this buffer. Ian and Rachel ensure not only that the product does what is advertised and that the circuit is accurate, but also that it is not dangerous or troublesome.
    Grant Fidelity makes good stuff; I've had a DAC from them before, the Yaqin buffer now, and I've been eyeing something like this for a while.

    I'm not immediately wary of most Asian manufacturers (I have a Little Dot amp I'm using while the Darkvoice is being modded - both are being fed by a Stello DAC), but they do make some questionable calls sometimes. Luckily, I like modifying things, so it's easy enough to address whatever minor oversights there are.

  2. #32
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  3. #33

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    Quote Originally Posted by zingo View Post
    That is indeed very worrisome if it's true.

    I just came across the schematic for the CD3 in one of the threads on DIYaudio (link here). Some of the people in that thread also mention the lack of a ground leak resistor for the capacitors.

    I'm still not entirely positive from looking at it that such a high voltage rating should be necessary. I'd appreciate your opinion.
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  4. #34

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    During normal operation, the 0.47uF caps seem to be subjected to 65-70VDC, the 0.22uF caps about 35VDC. The highest AC voltage I can find inside the amp is the transformer line at 145V. Highest DC voltage is 190V at the first filter cap. Highest AC voltage I could measure across any of the Sonicaps was ~40V

    Maybe the 250V/275V spec is to account for the fact that the amp comes in 220V variants? That seems kinda silly, but it's the only thing I can think of.
    USB Interface: Stello U2, Nuforce uDAC2 ║ DAC: Stello DA100 Signature, Keces DA-151 MK2
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  5. #35
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    I was thinking about the resistors as well, and I can't see where it would hurt to solder in a 1M resistor to ground before C1/C3 and after C2/C4.

  6. #36
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    I grabbed some 1/2w 470k resistors today and will be installing them as bleeders from the input and output to ground.

  7. #37
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    Last night I powered off the buffer, then unplugged it a few hours later. It was left that way over night, to be worked on tonight. After opening the unit to install the resistors, I first checked the voltage at the inputs and outputs; 20mV which does show some retention. I then tested the filter caps which were both at 20V! After draining the caps, I installed the resistors from all four RCA jacks to a local ground, and rechecked the circuit.

    This will provide a little extra insurance for future operation, and I'll install bleeder resistors on the filter caps when I install the ANSAR caps.

  8. #38

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    Quote Originally Posted by zingo View Post
    Last night I powered off the buffer, then unplugged it a few hours later. It was left that way over night, to be worked on tonight. After opening the unit to install the resistors, I first checked the voltage at the inputs and outputs; 20mV which does show some retention. I then tested the filter caps which were both at 20V! After draining the caps, I installed the resistors from all four RCA jacks to a local ground, and rechecked the circuit.

    This will provide a little extra insurance for future operation, and I'll install bleeder resistors on the filter caps when I install the ANSAR caps.
    I think I have lots of 1/2W resistors on hand. I'll have to put a few in place - luckily I'm not using the buffer in the meantime.

    Do you have any pictures of what you did? I'd be interested to see where you soldered them.

  9. #39
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    I can probably snap some tonight, but I soldered one end of the resistor to the rear of each RCA jack, and then solder the other end of all the resistors to a chassis ground that was near-by. The layout was easier than I was expecting, and I didn't have to do any modifications.

  10. #40
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    I marked in green where I installed the resistors, and it's the easiest mod I've done in a while. I'll be looking through my stash tonight to find two more resistors and two film bypass caps for the PS caps; why not!

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  11. #41
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    The last set of caps arrived, so the buffer's getting the full install tonight!

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  12. #42
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    Pulled buffer apart tonight and it's prepped to install caps tomorrow. Installed bleeder resistors as PS caps were at 25V after being off for a few hours, so now I can't anywhere that the circuit holds a charge. The bleeders are easy to do, and make it much safer to work on!

  13. #43

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    It really makes you wonder why they would do something like neglect having bleeder resistors on capacitors. It certainly wouldn't have added much cost on their part.

    I didn't get a chance to do the mods to my CD3 today, but I plan on doing it tomorrow. Do you mean to say that even the PS caps didn't have a bleeder resistor in place? That's an absurd level of oversight.
    USB Interface: Stello U2, Nuforce uDAC2 ║ DAC: Stello DA100 Signature, Keces DA-151 MK2
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  14. #44

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    Hey... ya know...

    Sometimes you just forget things... like the bleeder resistors...

    It happens! :-P
    www.Vr3Mods.com ///// www.Version3Audio.com

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro

  15. #45
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    Most people don't open up their electronics, and I bet the outputs discharging was a rare fluke, so the circuit not having bleeder resistors would not effect 99% of users.

  16. #46
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    Quote Originally Posted by zingo View Post
    Most people don't open up their electronics, and I bet the outputs discharging was a rare fluke, so the circuit not having bleeder resistors would not effect 99% of users.
    I just have to keep reminding myself that I am the 1%...

  17. #47

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    Quote Originally Posted by zingo View Post
    Most people don't open up their electronics, and I bet the outputs discharging was a rare fluke, so the circuit not having bleeder resistors would not effect 99% of users.
    If that story up higher about the chip-amp is to be believed, then this would also seem to put people at risk whose amp/preamp/etc doesn't have DC blocking at the input. But that in itself is pretty bad practice.
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  18. #48
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    True, but he also claimed it was in combination with a bad RCA connector, so it seems it was a poor combination of things; or maybe a bad unit. That doesn't mean the unit wouldn't benefit from bleeder resistors, but the overall design seems to be decent, and certainly sounds decent out of the box.

  19. #49
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    Quote Originally Posted by blairfrischx View Post
    During normal operation, the 0.47uF caps seem to be subjected to 65-70VDC, the 0.22uF caps about 35VDC. The highest AC voltage I can find inside the amp is the transformer line at 145V. Highest DC voltage is 190V at the first filter cap. Highest AC voltage I could measure across any of the Sonicaps was ~40V

    Maybe the 250V/275V spec is to account for the fact that the amp comes in 220V variants? That seems kinda silly, but it's the only thing I can think of.
    I noticed that the power supply caps in my Grant Fidelity are 220uF, where the schematic is 180uF, and many pictures of the Yaqin CD-3 show 200uF. I don't know if this is one of the alternations that GF made (along with a little different wiring), but I'll take it!

  20. #50
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    Finished installing the input and coupling caps, and I have film bypass caps on order for the PS that will go in next week. The sound already has more texture and body, and that was just while watching TV. I'll put some hours on them tomorrow and do a little critical listening with some of my favorite music to get a better idea of what aural gains were made.

    The install was actually very easy after I figured out the that bottom side of the circuit board (the side you don't see), does not have any pads on it. All the soldering is done on the top side, so just trim the cap leads to fit, make sure they don't do too far through the holes, and solder in place. The four ANSAR 0.47uF caps barely fit together in the provided space, and the thick lead (same as ClarityCaps in my experience) BARELY fit through the holes in the board. It was a tight fit, but everything was installed cleanly, and looks great!

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  21. #51

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    Those do look good! Definitely a lot more substantial-looking than the Sonicaps.

    All the soldering being on the one side of the board makes it a lot easier to do this mod. It's easy to remove the old caps without having to remove the actual board, which would be a pain.
    USB Interface: Stello U2, Nuforce uDAC2 ║ DAC: Stello DA100 Signature, Keces DA-151 MK2
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  22. #52
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    Thanks. The ANSAR PPA and SPA caps are very solid and do look good. This is my second project using them and I'll be using them from here on our if I can find them.

  23. #53

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    The final shipment of parts (Nichicon electrolytics, new toggle switch, and more Mundorf E-Caps) for the Darkvoice showed up today. I did some work with the ground wiring throughout (bare copper wire bent to shape) but haven't finished reattaching everything to the face of the amp yet.

    The new toggle switch doesn't stick quite as far away from the case, so it should theoretically be less likely to find itself snapped in half. Additionally, I've been grinding down the diameter of one of the holes on the faceplate to accommodate the larger Neutrik jack I've ordered. I don't own a Dremel, so it's a bit of a pain to work.

    I'm glad to have some sort of update, at least. Maybe I will actually have it back up and running before the end of April!
    USB Interface: Stello U2, Nuforce uDAC2 ║ DAC: Stello DA100 Signature, Keces DA-151 MK2
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  24. #54

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    It really is very pretty inside with new parts. Just look at this:



    I think I'll leave cathode bypass resistors out for now. They're really simple to fit in later, and it'll help me hear what effect they actually have. For now, just resistors and wires.
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  25. #55

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    Another progress pic, just because I like actually being productive:

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  26. #56
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    Very nice looking!

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    I have to say, I'm a big fan of the look of the PRP and Kiwame resistors next to one another.

    I'm having a bit of trouble soldering the Cardas Crosslink 1i cable I'm planning on using for input -> potentiometer wiring onto the RCA jacks. They conduct heat too fast for solder use, and it's a bit difficult to get a good joint.
    USB Interface: Stello U2, Nuforce uDAC2 ║ DAC: Stello DA100 Signature, Keces DA-151 MK2
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  28. #58

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    Quote Originally Posted by blairfrischx View Post
    I think I'll leave cathode bypass resistors out for now. They're really simple to fit in later, and it'll help me hear what effect they actually have.
    Wow, what was I thinking? Cathode bypass capacitor*** I have a couple different ones to try in that application from Panasonic, Nichicon, and Elna.

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    Quote Originally Posted by blairfrischx View Post

    I'm having a bit of trouble soldering the Cardas Crosslink 1i cable I'm planning on using for input -> potentiometer wiring onto the RCA jacks. They conduct heat too fast for solder use, and it's a bit difficult to get a good joint.
    Think Litz! Cardas has an enamel coating applied after the wire strands are drawn to gauge. You have to dip the stripped end in a solder pot to melt it off. Or the method DK uses, a wire brush in a Dremel tool to buff the coating off the wire strands.

    EDIT: Link to diyaudio page.....

    http://www.diycable.com/main/product...roducts_id=680

    DK's thread...

    http://www.polkaudio.com/forums/show...SDA-SRS-1.2TL&

    I learned this when I upgraded internal speaker wiring in a pair of Carver speakers years back.
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  30. #60
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    Some enamels you can also burn off with a torch from experience.

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