This is the following post regarding building the miniaturized DAC that should sound good, just like full-size desktop DAC. But the difference is in the small chassis. The reason for this is because in my opinion, a DAC unit is not to be shown as the main show unit in the audio system. So let it be hidden somewhere else at the back of the system and let the tube amplifier, speaker and source player as the part of the main show in the audio system.
In this post, I will make another DAC using the components that what I have left in my bin. I think in this post, the description will be more in technical. I will try to explain the building concept for the good sounding DAC based on my experienced. This build will be more complex, harder to follow for beginner, but for some reason, I just want to do it.
So, let's begin for this AD1865 miniaturized DAC build.
The chassis I choose for this DAC build is pretty small, almost the same like my previous miniaturized PCM56 DAC build here just slightly longer. This chassis is an universal aluminum enclosure, commonly use for simple switching power supply or relays for industrial.
For the DAC itself, I will be using YM3623 as digital receiver. This is old receiver that use in 80's, up to early 90's before the more advanced CS8412 coming into the market as the better replacement. YM3623 digital receiver is become not popular because it only transfers single format, which is right-justify 16-bit data output. Other than that, some believe that the jitter (digital noise) is larger than 200 ppm, while I cannot measure it and I didn't find someone publish this jitter result.
In my opinion, YM3623 is not bad at all. When the coming of CS8412 as digital receiver, I saw many high reputable audio brands still using this YM3623 in their top of the line DAC product. Maybe they just like me, use all remains in stock for their latest product design. But I always believe as long as we use this YM3623 as the digital receiver to feed into the good oversampling IC, it will be working remarkably.
This is the PCB for this DAC project, I made it from ground up. it contain the DC-DC converter as the virtual ground/ voltage splitter, same as my previous post for miniaturized PCM56 DAC. You can check the schematic for this DC-DC converter on the post before.
The sampling frequency in YM3623 is 384fs. Luckily the most advanced oversampling processor for DAC at that time that accept this 384fs was created by Sony. It is CXD1144, known as the most complex oversampling processor that contain 2 working oversampling in parallel in a die.
So connecting the YM3623 to CXD1144 is just a pin connection together based what the designated pins required. I post already the schematic for this connection, together with the AD1865 DAC after it on this post here here
For the sound quality comparison that I've made in my spare time between YM3623 - CXD1144 compare with CS8412 - SM5813, all with the same DAC and same analog filter, the result is might surprise anyone. The YM3623 - CXD1144 sound rounded, clean but not too sterile and silent but CS8412 - SM5813 sound sterile and somehow missing the center point of imaging.
At these stages, building small complex DAC like this is not about fun anymore. This is become so much technical advanced, skill and patient.
So, I continue.
AD1865 DAC is 18-bit right justify input format. CXD1144 can set the output to 18-bit that matching with the AD1865 DAC. I set the CXD1144 oversampling mode to 8X. Some might prefer to having smaller oversampling like 4X, but for me, I want to push the limit for this CXD1144 to perform. Other than that, I didn't notice a different in the sound quality between 4X to 8X oversampling. At least this is for my ears.
Back to the digital receiver, the YM3623 can use the data input directly from the optical receiver, without any buffer circuit compare if configure to received in the SPDIF input. So in this DAC project, I am prefer to using TORX-176 as the optical digital receiver.
Using this optical digital receiver will isolating the noise from the source to this DAC receiver as they are not electrical connected.
This DAC build is now complete; all connection is tested and connected to each designated pin. The DC-DC converter without any load attached also working well.
But the plans sometimes not working as we calculated.
The DC-DC converter current output is not sufficient for the 5V+ DAC current requirement. The V+ voltage drops to 2-volt once the CXD1144 IC is put in place. The CXD1144 current requirements is 500 mA alone (based on the datasheet) and the total current requirement for YM3623, CXD1144 and AD1865 V+ is probably 600 - 800 mA. This current requirement cannot be fulfill from this DC-DC virtual ground design.
As you may know about this miniaturized DAC project is basically to keep all simple, including using an universal SMPS 12-volt DC adaptor for the simplicity. With the DC-DC converter virtual ground inside this circuit is not working with the high load from CXD1144, the overall simplicity DAC plan can be ruin because we need another power supply that grounding isolated to the virtual ground to supply for this current requirements. This can be solve by using another SMPS DC adaptor which I don't want to do it because it is ugly and complicated outside.
So, I need to stop this DAC project for a while and thinking another way.
So, I was thinking to add another DC-DC module inside the chassis that not interfere with the virtual ground from the initial DC-DC converter.
Luckily, I still have the 5-volt module that isolated grounding from the input to output. This module is imported product, the brand is CALEX 12S5.1000 series. I read the datasheet, especially about the ripple rejection is good enough for this digital section in this DAC project. The current output for 5-volt output is 1000 mA, more than enough to supply YM3623, CXD1144 and on the digital side of AD1865.
For the initial DC-DC converter with the virtual ground will only supply for analog side of AD1865 and the op-amp.
Problem solved!
With this DC-DC 5-volt module on-board and CXD1144 installed, I measure the 5-volt output from this module is keep stable without any voltage drop. The module is slightly warm and no need extra heatsink for this application.
So, with this success, I put all IC's and ready to test in my audio system.
This miniaturized DAC components are tightly fit inside this small chassis. It is working great and flawless.
How about the sound quality?
I can say so much better than my previous built: the miniaturized PCM56 DAC. This AD1865 with YM3623 and CXD1144 creating wider soundstage and rounded sound with smooth transients and details. What I can say, technically AD1865 DAC is more advanced than the PCM56 DAC, and CXD1144 is still the most complex and one of the best oversampling processors until now.
I guess this DAC will adding to my DAC collection, not because it is better in sound quality, but it is better in specification and more complex to build.
Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.
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