[DBaldock9]

That's a really nice soldering kit. I dabbled in surface mount soldering years ago modding video equipment. I wouldn't know where to start with audio. I've sold all of my tools over the years. A good fluorescent lighted magnifier is worth it's weight in gold I can tell you that. As well as a good solder sucker.

I've got one of these magnifiers, with LED lights. I bought it, to help my Mom see better to read, back in 2016. After she passed away, my Dad told me to take it, to help with my hobbies.
https://smile.amazon.com/gp/product/B019R1A8HW/

I also have a magnifying visor, like this one -
https://www.vellemanusa.com/products/view/?country=us&lang=enu&id=351145

Now that my new soldering equipment is arriving, I'm going to be doing some more mods on my DSD.

 

[shutterbox]

I really wanted to get the zishan 4497 as a portable source to drive iem/ciems but for its 22ohm impdendance, many of iems would not be performing their best and I have no need for it to drive high impedance headphones since my desktop amp could do that

 

[max232]

I really wanted to get the zishan 4497 as a portable source to drive iem/ciems but for its 22ohm impdendance, many of iems would not be performing their best and I have no need for it to drive high impedance headphones since my desktop amp could do that

I have two low impedance phones that I use with mine and they sound great.

 

[max232]

I've got one of these magnifiers, with LED lights. I bought it, to help my Mom see better to read, back in 2016. After she passed away, my Dad told me to take it, to help with my hobbies.
https://smile.amazon.com/gp/product/B019R1A8HW/

I also have a magnifying visor, like this one -
https://www.vellemanusa.com/products/view/?country=us&lang=enu&id=351145

Now that my new soldering equipment is arriving, I'm going to be doing some more mods on my DSD.

If you figure how to add a bluetooth chip to it hit me up. That's the only thing I miss. Some will diss the sound quality and rightly so, but for the convenience.

 

[DBaldock9]

If you figure how to add a bluetooth chip to it hit me up. That's the only thing I miss. Some will diss the sound quality and rightly so, but for the convenience.

Do you want your DSD to receive, or transmit, audio via Bluetooth aptX?
There are DIY circuits for either, but there's no one-chip solution for both.

 

[max232]

Do you want your DSD to receive, or transmit, audio via Bluetooth aptX?
There are DIY circuits for either, but there's no one-chip solution for both.

Transmit. I have a JBL noise canceling headset that I'm fond of. It works with a wire as well but that option has proven to be very fragile. I think I'll try one of the Chinese bluetooth adapters on eBay and maybe a small USB power pack to run it?

 

[DBaldock9]

Transmit. I have a JBL noise canceling headset that I'm fond of. It works with a wire as well but that option has proven to be very fragile. I think I'll try one of the Chinese bluetooth adapters on eBay and maybe a small USB power pack to run it?

Here's a Bluetooth 5.0 aptX HD Transmitter / Receiver, which has SPDIF Input & Output, and an internal 600mAH battery.
https://www.aliexpress.com/item/Bli...eiver-Transmitter-Audio-2-in/32893538587.html
I don't know what it would take to get an SPDIF signal from the ARM or ASIC in the DSD, but if it's available, then the digital audio signal could be transmitted directly, rather than decoding to analog, and then re-encoding in the Bluetooth circuit.

 

[max232]

Here's a Bluetooth 5.0 aptX HD Transmitter / Receiver, which has SPDIF Input & Output, and an internal 600mAH battery.
https://www.aliexpress.com/item/Bli...eiver-Transmitter-Audio-2-in/32893538587.html
I don't know what it would take to get an SPDIF signal from the ARM or ASIC in the DSD, but if it's available, then the digital audio signal could be transmitted directly, rather than decoding to analog, and then re-encoding in the Bluetooth circuit.

I dug through my spare parts, low and behold, I actually have one. It's a "No Name" brand and I'm sure it doesn't have nearly the specs as the one that you were so kind to research for me. It does have some sort of built in battery but I'm not sure of the capacity as of yet. I've connected it to a JBL bluetooth speaker and it sounds pretty decent. Plenty of volume. I haven't had a chance to try the headphone as I has to RMA them the other day.

 

[DBaldock9]

Few Zishan DSD AK4497EQ mods:

1. Removed output capacitors and added them to 9V pool, added 0.1uF bypass caps on top of 10uF stock ones.
2. Replaced filter opamps for AD8599ARZ, AD8620ARZ in substractor.
3. Replaced 3.3V and 5V LDOs for low-noise ones (also around CPLD), caps replaced for 10uF XR7
4. Replaced oscillators for 25PPM MEMS.
5. Replaced input caps for Nichicon BP Muse 10uF

Improvements are incremental yet substantial, of a special note reduction in upper mids and highs harshness (my main issue with stock AK4497 DSD) and slightly better defined lows after LDO replacement and less grainy highs after oscillators upgrade, switching filters produces more noticeable effect too.

@Ivan TT - Thanks for the notes on your upgrades!

Since my DSD isn't opened / disassembled right now, I had a couple of questions about your mods -
For #1 - Is there any issue with DC offset / output going to your earphones, with the output caps removed?
For #2 - I've replaced the OP275 op-amps in the LPF, with AD8620ARZ. Where did you install the AD8599ARZ op-amp(s)?
For #3 - Did you happen to count the total number of 3.3V and 5V LDO Voltage Regulators, that can be replaced on the two circuit boards?
For #4 - How many, and what frequency, of oscillators did you replace?

Thanks!

 

[Ivan TT]

@Ivan TT - Thanks for the notes on your upgrades!

Thank you, but most of the credit goes to the player.ru forum community, learned heaps there!

For #1 - Is there any issue with DC offset / output going to your earphones, with the output caps removed?

In stock - no, 5-9mV
The main issue is DC protection when swapping opamps, if not seated well there is chance to get rails on the output, ouch!

For #2 - I've replaced the OP275 op-amps in the LPF, with AD8620ARZ. Where did you install the AD8599ARZ op-amp(s)?

LPF. I personally don't like AD8620 in filter, but do like AD797 while dual version does not exist, AD8599ARZ is the closest one can get.

For #3 - Did you happen to count the total number of 3.3V and 5V LDO Voltage Regulators, that can be replaced on the two circuit boards?

Can count now
5V - 1,
3.3V - 6 (1+5)
I'm not 100% if caps need replacement as stock measure 12uF (10uF in 3.3V LDO datasheet), even if they are Y5V and are subject to capacitance fluctuation with temperature.

For #4 - How many, and what frequency, of oscillators did you replace?

Both, as per links:
https://www.arrow.com/en/products/dsc1001di2-049.1520/microchip-technology
https://www.arrow.com/en/products/dsc1001di2-045.1584/microchip-technology
I recommend touching pads up with solder before using air soldering as they are a bit smaller than stock.

 

[DBaldock9]

Thank you, but most of the credit goes to the player.ru forum community, learned heaps there!

In stock - no, 5-9mV
The main issue is DC protection when swapping opamps, if not seated well there is chance to get rails on the output, ouch!

LPF. I personally don't like AD8620 in filter, but do like AD797 while dual version does not exist, AD8599ARZ is the closest one can get.

Can count now
5V - 1,
3.3V - 6 (1+5)
I'm not 100% if caps need replacement as stock measure 12uF (10uF in 3.3V LDO datasheet), even if they are Y5V and are subject to capacitance fluctuation with temperature.

Both, as per links:
https://www.arrow.com/en/products/dsc1001di2-049.1520/microchip-technology
https://www.arrow.com/en/products/dsc1001di2-045.1584/microchip-technology
I recommend touching pads up with solder before using air soldering as they are a bit smaller than stock.

I suspect that changing the capacitors probably would be a good idea - after reading the first line after the Table in this article - https://www.maximintegrated.com/en/app-notes/index.mvp/id/5527

With a bit of creative dead-bug installation & wiring, you should be able to stack and use a pair of AD797 op-amps in the OP275 location.
1 - Solder lengths of jumper wire (with high temperature insulation) to the pads for pins 1-3 & 5-8.
2 - Lay some Kapton tape over those pads/wires.
3 - Bend / straighten pins 1-3 & 5-8 on the bottom AD797.
4 - Put a layer of silicone glue on the board, to hold the chip level when pin 4 is soldered to pad 4 (-Vs).
5 - Solder and glue the bottom AD797 to the board - and wait for the glue to set.
6 - Flip the top AD797 upside down, so it's input pins are over pads 6 & 7, and glue it to the bottom chip.
7 - Add a jumper wire from pad 4 (-Vs) to the top AD797 pin 4.
8 - Route and solder the other jumper wires to the appropriate pins.

Then, do it all again, for the second LPF...

Mouser has a 49.1520-MHz oscillators, which has higher precision, but a lower maximum operating temperature:
https://www.mouser.com/ProductDetai...GAEpiMZZMve4/bfQkoj%2bJQ7KfD/rQaL5YkJCKgcvFY=
I can't find any higher precision 45.1584MHz oscillators in-stock (except the large through-hole style).

 

[Ivan TT]

Then, do it all again, for the second LPF...

LOL, sounds easy enough

Another way is to get 1.27mm spaced pins (I have some) and after some bending and twisting solder on single-to-dual PCB, but I am OK with AD8599ARZ for now and also have some PPS capacitors in the filter that do not leave much space for experiments.

I hear you re: caps, as you can see SOME have been upgraded on my digital board already (different colour), and by the way there's no need to do anything about those 0603 caps as LP5907 does not even have that pin connected.

But my main effort is with OPA1622 set to unity as low-Z output drivers, most likely will have 3 of them sitting on a cut strip of breadboard + 0.1+10uF bypass caps, true ground and enable pin sourced from the relay transistor. Which may or may not work

 

[DBaldock9]

LOL, sounds easy enough

Another way is to get 1.27mm spaced pins (I have some) and after some bending and twisting solder on single-to-dual PCB, but I am OK with AD8599ARZ for now and also have some PPS capacitors in the filter that do not leave much space for experiments.

I hear you re: caps, as you can see SOME have been upgraded on my digital board already (different colour), but my main effort is with OPA1622 set to unity as low-Z output drivers, most likely will have 3 of them sitting on a cut strip of breadboard + 1+10uF bypass caps, true ground and enable pin sourced from the relay transistor. Which may or may not work

One thing I'm seriously considering for my DSD, is fabricating an intermediate board, that will allow the analog circuit board to be flipped over - placing the battery between the boards, and allowing easier access to the socket - in a deeper or wider case, so that larger op-amps can be installed.

 

[dumbears]

I know this will sound both rude and stupid. However, I still have to ask due to m curiosity. Nevertheless, pls pardon me. Aren't those removed caps coupling caps of L+, L-, R+, R- signals? This is based on the datasheet of AK4497.

 

[DBaldock9]

I know this will sound both rude and stupid. However, I still have to ask due to m curiosity. Nevertheless, pls pardon me. Aren't those removed caps coupling caps of L+, L-, R+, R- signals. This is based on the datasheet f AK4497.

I had asked @Ivan TT about that photo, and he said it's a sample photo, with the large capacitors removed, so the circuitry underneath is visible.
His amp has the capacitors installed, per the design.