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The Zishan dsd's corner

Discussion in 'Portable Source Gear' started by neog007, Nov 17, 2016.
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  1. Ivan TT
    Re: opamps as buffers, insure that those you use are unity gain stable and have ability to drive capacitive loads without output resistors.
    This pretty much excludes about 99% of opamps out there unfortunately. Having said that, I’m not saying there will be problems or that opamps would not work, just advising cautious approach.
    OPA1688 works well as a buffer and has slightly brighter signature compared to 1622 btw, and it’s cheap!
     
    Merlin-PT, DBaldock9 and ThanosD like this.
  2. ThanosD
    These ones
     
    DBaldock9 likes this.
  3. DBaldock9
    Have you tried BUF634U?
     
  4. Ivan TT
    No, not in DSD, but tried it in Z3.
    I was a wee while ago, but the impression was warm and clean sound.
    From what I understand BUF634 works best in a composite arrangement (inside of opamp's feedback loop), this gives low output impedance and lower distortion/noise. I don't believe it's achievable with AK4497 Zishan (unless another separate opamp is used in addition to BUF63)
     
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  5. Merlin-PT
    It's my personal taste that I'm trying to tune, so what I'm describing about the opamps is the deviation from what I want, my taste.

    @Ivan TT
    Thanks!
    I have some opa1688 and I like them, it's like you say, slightly brighter than 1622, I was already using them in the socket, it's a good combination with the 8066 I have in LPF.
    I didn't liked 1688 in LPF much, but in the socket I prefer them to 8066 again or others.
    I didn't tried any buffers yet.

    @ThanosD
    I have those panasonic FM and don't find them too warm.
    I'm using nichicon Fine Gold, I like these FG a lot, but maybe they don't fit. These are are not too warm for me and the panasonic sound brighter (in a good way) compared to FG.
     
    Last edited: Mar 8, 2019
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  6. Ivan TT
    I notice that I don't tinker with my DSD as much as I used to, but listen to it a lot.
    I don't have an answer to this question, but I do believe there's few extra things that could be done to AK4497 DSD (some of which I've done, some just musing over):
    1. Replace capacitors around opamps with PPS (around dip socket) and COG (LPF). This cleans sound up even more.
    2. Remove LPF altogether
    3. Remove input output caps (DC coupled design)
    4. Separate DAC's 5V VREF similar to 3.3V x2 LDOs
    5. Remove connection to the ground from delay relay when closed
    6. And the mother of them all: Hook up INA1620 directly to differential outs (using internal resistors + PPS caps) and straight to 3.5mm out (I'm keen to try it but need to buy another DSD for this)
     
    Last edited: Mar 8, 2019
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  7. ThanosD
    That sounds promising. I will probably know for sure if I like them next weekend. Regarding the OPA1622, Arrow has the small (SOIC?) chips, but unfortunately I don't know if I can solder something that small on an adapter.
     
    DBaldock9 likes this.
  8. Ivan TT
    I would not even try (actually had to ask more experienced friend to solder INA1620 to an adapter), but there's plenty of them on DIP8 PCB on ebay, at a reasonable price too.
     
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  9. Merlin-PT
    @Ivan TT
    That's a lot of food for thought.

    I would like to keep LPF for balanced output, but at the same time maybe use the socket opamp without LPF.
    Do you know if there's a problem to have both LPF inputs and socket inputs connected at the same time to the DAC caps?

    I also thought of connecting different external batteries to DAC and/or opamps, only to see if there was much to gain with better power, but I don't think removing the DC-DC converters is enough to try this, so it's risky to do this.

    @ThanosD
    You mean opa1688? 1622 looks very difficult and needs hot air.
     
    Last edited: Mar 8, 2019
  10. Ivan TT
    Yup, I had this configuration for some time, although I took the output directly from DAC (bypassing input caps).
    The only POTENTIAL problem is that DAC sees much lower input impedance compared to datasheet configuration (and I assume it is configured for high impedance LPF via software), but I did not notice any changes in sound.
    I used MELF resistors instead of those that should be removed, they are easier to arrange/hook up compared to SMD ones.
     
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  11. Merlin-PT
    Thanks, I'll try that, I had it planned. :)
     
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  12. DBaldock9
    Which brand(s) of Polyphenylene Sulfide (PPS) Film Capacitors, and C0G (NP0) 0805 Multilayer Ceramic Capacitors (MLCC), do you think would sound best in the DSD circuits?
     
  13. DBaldock9
    The OPA1622 is a Dual Op-Amp in a VSON-10 package (which doesn't have protruding leads, like a DIP or SOIC).

    Last year, I bought a pair of OPA1622 from this eBay vendor - https://www.ebay.com/itm/HIFI-OPA1622-DIP8-high-current-output-dual-op-amp/272852157906
    But - They've changed the pins on their currently available board - mine do not have any plastic on the pins below the circuit board, so they plug all the way down onto the DIP8 socket (for a lower profile fit).
     
    HeyManslowdown97 likes this.
  14. Ivan TT
    Does not really matter, I source Panasonic PPS and whatever cog are reasonably priced from arrow.
    COG supply appears to be unstable and ever changing, but it seems only reputable manufacturers continue supplying them.
     
    Last edited: Mar 8, 2019
    HeyManslowdown97 and DBaldock9 like this.
  15. HeyManslowdown97
    Was looking at them today à la Browndog Adapters cuts down on size. Also no protruding pins on top make for better enclosure!

    Speaking of which soldered some opa amps to the Browndog adapter. What a breeze (no pun intended as I used solder iron) to solder on a good board instead of directly to Zishan plastic! (Gotta say a couple Hail Marys before operating directly on the Zishan)

    The 3.7 3000mah has got to go. Wanna drop a 35000mah or 4000mah same size or smaller :D
     
    Last edited: Mar 9, 2019
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