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The Zishan dsd's corner
Oct 9, 2018 at 2:14 AM Post #1,036 of 3,711
Ivan TT said:
Mind if I chime it re: AK4497 mod?

1. AD8620 is an improvement compared to OP275, especially OP275 that finds its way into DSD. Not the best sounding opamp for LPF IMO, but a very good one nevertheless. I sourced some from taobao - B-brade, which is a better grade and I have doubts about them, it's likely they are not genuine. Are those used in the mod genuine is anyone's guess, but cheapest genuine part I could find retails for $13 per opamp.

2. AD797 rocks, and it is either NOS or second hand, based on the colour scheme (recent iterations look differently, I have genuine A and B grades). I note that it is soldered in, so no opamp rolling in this version. Also, AD797 is the only opamp that was picking up EMI/RFI in my DSD (out of 20+ opamps I tried), not sure if that would be the case with modded DSD though.

3. Tantalum capacitors are generally considered inferior to electrolytics for audio (DC-decoupling in this case), higher THD etc. They are sometimes used in space-restricted designs (F.Audio FA1), but I'm not entirely sure how it is an upgrade.

4. Zishan DSD benefits immensely from improved power supplies (3.3, 5 and 9V) and changed/improved bypass capacitors (All opamps have 12uF bypass caps, but do not have 0.1uF that every datasheet recommends). Missed opportunity IMO.

5. 22Ohm output resistors is such a last century. Forget about BAs, hybrids and dynamic driver earphones don't seem to be affected too much though. No easy solution here I'm afraid, but a missed opportunity IMO. The good news is that AD8620 has higher output current compared to OP275 and is capable of handling high capacitive loads (cable and headphones form a capacitive load), so one can bridge 4 output resistors on the balanced out, this should improve things with BA's.

6. 12V improves driveability of Hi-Z earphones, but of no benefit for Lo-Z (i.e. 16-32 Ohm) ones. Opamps are claimed to sound better on higher voltage rails, so may improve things a bit.

Since my statements above appear inconclusive even to me, I believe this modded version would be an improvement, but not a drastic one and would still not realise full potential this player has.
Click to expand...

I'm trying to mod this monster on my very own, and I'm no electronic guy. I'm just stealing ideas everywhere and do the trial. Here are some of my thoughts:
- AD8620 is good, but it's expensive, esp. the BRZ version. Why not follow AK's "recommendation", OPA1612? I do see OPA1612 is a better option in some ways.
- AD797 is a monster - it can be both a good servant and a bad master. It all depends upon how you can tame it. Are there something else easier?
- Tan caps are debatable, I believe, given the original caps were audio-grade. To my ears, the tan caps are cleaner. However, I sometimes have the thought of these caps being too clean, and I should say, less musical.
- Higher voltage magnifies everything. This is a 2-edge sword. Still, I guess it'll do more good than bad, but I'd still choose to skip. Instead, why not conduct more stability mod to the circult?
- Oh, I didn't know those aren't 0.1 caps. I always struggle with output resistors and coupling caps. I don't know when I can just let go of them. I really don't want to fry anything because of this. On the other hand, I always have this question in my head, "will my stuff really fry if I short these resistors and caps?"

Sorry for my murmuring.
 
Oct 9, 2018 at 4:10 AM Post #1,037 of 3,711
dumbears said:
I always struggle with output resistors and coupling caps. I don't know when I can just let go of them. I really don't want to fry anything because of this. On the other hand, I always have this question in my head, "will my stuff really fry if I short these resistors and caps?"
Click to expand...
The main issue is DC voltage that may not only reduce dynamic range, but will fry headphones if something went wrong (i.e. one of the rails becomes disconnected), supplying headphones with 6V RMS signal that would fry them for sure. So output caps are a fool-proof device for mass-market device where it is quite possible that the end user will do something silly (at least I did, on more than one occasion). It's safe to remove output caps ONLY if you follow specific protocol religiously after each and every mod or opamp swap: measure DC component after EACH opening of the case and opamp swap BEFORE plugging headphones in.
I have output caps removed and depending on opamp usually have under 1mV DC component (on some opamps 0.1mV), there's no consensus but up to 20-30mV are considered acceptable.
So I would NOT recommend removing output (de)coupling caps UNLESS you accept full responsibility for possible damage.
Input caps (x4) should not be removed.
dumbears said:
- AD797 is a monster - it can be both a good servant and a bad master. It all depends upon how you can tame it. Are there something else easier?
Click to expand...
Plenty of choices, mainly from AD stables (at least that's my preference): AD823, AD825, AD826, AD8065/6, AD8599, OPA627, LM6172, OPA1642, Muses2, Muses8920 etc.
 
Oct 19, 2018 at 12:55 PM Post #1,041 of 3,711
guys, i've got zishan dsd ak4497eq, just want to ask, there's a plug hole in bottom right.... i think its 3.5mm.... what is it for?
IMG-2106.jpg


also under dac, theres option "cut-off fre of dsd filter"..... should i leave it default? thanks
 
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Oct 19, 2018 at 1:22 PM Post #1,042 of 3,711
BillyX said:
guys, i've got zishan dsd ak4497eq, just want to ask, there's a plug hole in bottom right.... i think its 3.5mm.... what is it for?
IMG-2106.jpg


also under dac, theres option "cut-off fre of dsd filter"..... should i leave it default? thanks
Click to expand...

The 3.5mm jack is a Digital SPDIF output.
 
Oct 19, 2018 at 11:46 PM Post #1,044 of 3,711
I’ve read this thread and have been interested in this since the newest iteration came out. So I bought one.
What are the flaws that this player does possess? Does it have any song cutoff or loud clicks? I guess I should have asked before pulling the trigger, but hey, you know how that goes. Itchy trigger finger. :)
 
Oct 20, 2018 at 12:08 AM Post #1,045 of 3,711
abartels said:
I was hoping it was an spdif input instead of output
Click to expand...

The DAC circuit on the DSD is based pretty closely on the AK4497 spec sheet - so you could probably refer to that, and modify the board, changing the output to an input (with a switch to select internal or external digital data).
 
Oct 20, 2018 at 3:09 AM Post #1,046 of 3,711
DBaldock9 said:
The DAC circuit on the DSD is based pretty closely on the AK4497 spec sheet - so you could probably refer to that, and modify the board, changing the output to an input (with a switch to select internal or external digital data).
Click to expand...

It depends if there's a transciever chip used like 4118.....
 
Oct 22, 2018 at 2:23 AM Post #1,047 of 3,711
Does anyone here know the max SD card size this will read? Want to get something bigger, like 128 gig but not sure if it will read
 
Oct 22, 2018 at 6:25 AM Post #1,049 of 3,711
As my boss was off to China for a week, I asked him to bring me back a Zishan DSD (4497EQ version) . Have been using my rooted Galaxy S5 with Viper4Audio so far, but also have a Zishan Z1 (I prefer the S5, even though I think for the 23$ I paid the Z1 sounds crazy good - a world of diff with my previous Xduoo X2 that was double that price). In the end the Zishan set me back 90E, as a Chinese business relation bought it off Taobao and I managed to avoid more shipping and import taxes - lucky! Can't wait to get home and load up my SD card to try this thing out with my K's 500 earbuds. I paid 75$ for those when they were released, so I can still call this a budget combo :darthsmile: !
 
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