DIY AD1865 Non-oversampling DAC

I have built several top tier vintage multibit DAC with a great result and now I become addicted to experimenting the sound characteristic on other DAC IC. I will comparing them with what I have right now.

The fun fact about this vintage DAC are:

1. They are all great sounding and musical DAC compares to today delta sigma DAC.

2. The power supply need to have more attention and this direct result to the sound quality.

3. Who said that DAC IC will not give any difference?

Especially on point 3, that statement for sure comes from either a sales man of delta sigma DAC or un-experienced DAC builder, period.

I found that different type DAC IC have their own sound signature, even with exactly same analog stages and power supply. This fact makes me so curious and keep moving to another multibit DAC journey.

Today DAC project is using AD1865N which is very popular because Audio Note manufacture using the same DAC IC on their top tier DAC products. So let's build it!

I got this 2 pieces AD1865N dismantled from used Tascam CD Player. In this stereo DAC build, I only using a piece. I am using the exact schematic from this website which using 74HC04 as glue logic to separate between left and right channel. This schematic also same as the Audio Note use on their DAC product.

The difference with my build right now is at the analog stage. I will using internal AD1865 V out then connecting to the popular Bessel LPF design that I have describe here. The reason I am using this design because this LPF can be operate as small as +/- 5 volt power supply. The power supply for the op-amp can be share with analog voltage input at AD1865N as well.

I try to make this DAC small, same as the casing I have. This casing size using 10 cm x 7 cm PCB board which will include SPDIF receiver, DAC IC, op-amp for LPF and the power supply section.

This project will not become my superior built like the Ultimate TDA1541A DAC here. I will trying to optimized the design to fit all into this small casing.

As usual, I always populated all the components into the PCB board to make sure they are all fit. Then I starting to solder them one by one in the point to point connection.

The power consumption of this AD1865 DAC is very small. In total it only draw less than 250 mW. If  compare to the TDA1541A is about 800 mW and this is almost double the power requirement. So in this case the heatsink for the voltage regulators are not necessary.

Building AD1865N DAC is not as simple as building TDA1541A DAC, but not as complicated as PCM56P or AD1862N DAC.

From the first test, this AD1865N DAC sound thin and less engaging. Something wrong in the design.

Then I make few changes, like in the photo bellow.

I am now adding capacitors on every AD1865N voltage input. The analog voltage is added 1,000uF capacitors and on digital voltage input I adding 220uF capacitor. All capacitor are Nichicon Audio UKA. I also using full rectifier diode design on the single AC input.

Then I also redial the voltage regulator IC to get exact voltage output on each voltage rail. With this adjustment, almost zero differences between all voltage. This is also resulting a very low DC offset on the analog output stages.

Once all above steps are done, then I put back the op-amp into the PCB.

Right now I am using the NE5532 from Signetics. This discontinued op-amps sound so much better compares to JRC or TI 5532. This become a very cheap upgrade to get the better analog sound which is more airy and smoother on high frequency.

With this simple upgrade, what have changes in sound quality?

I could say a lot!

Now the sound quality is superior. AD1865N sound presentation is rich in detail. Lots of micro detail that you could hear some particular sound that you never heard before on the same recording with others DAC.

I also notice the music is more fuller, especially on the micro details like the sound from electric guitar, the string sounds are effortless until the end of the note. This details presenting nice and without artificial effect. It is presenting the detail in natural way.

Sound stage with this AD1865N is wide and have good imaging position. Similar to AD1862 DAC I've built here before, but I can say that that mid range and vocal presentation in AD1865 little bit cleaner compares to the warm sounding AD1862.

This AD1865 is become one of top tiers DAC and my recommendation to everyone who want to build the DAC. This AD1865 IC is still more easy to obtain compares to TDA1541A or even the rare AD1862. So this is a chance to build one just like mine here.

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