Author Topic: My first DAC  (Read 929 times)

Offline naboo

My first DAC
« on: July 18, 2021, 12:54:44 PM »
During lockdown last year I built my first phono pre with @fredeb . It was my first foray into  electronics and I cringe thinking how badly I built it. Nevertheless, it worked, and still does. Shortly after, Ari advertised a mini DAC for sale. I figured I don't have one and I could use some practice at soldering. It went much better than the phono!

Once done, I need 2xpower supplies and decided that it can go to the cupboard for a bit of rest. Recently, I decided to connect my Yamaha Bd player to  the amp and  listen to  a couple of CDs. Then I remembered about the DAC and decided to finish the project. I got the power supplies, hooked them up and the smoke stayed inside :)

So, it ain't pretty by a  long shot - but  it  works and  it sounds good. I'll spend most of today in this chair, letting it burn in.

There are a ton of mods at DIY Audio - I will checkin here with the experts to get some advice on the which options would be the best. But first, I'll let it burn in properly. Then I'll figure  out how to do the comparisons - I'm  in no real hurry.

Offline AudioEars

Re: My first DAC
« Reply #1 on: July 18, 2021, 02:41:36 PM »
Looks like a lot of fun
If I can offer any advice , keep the mains 220vac line away from the input and outputs of the DAC
Nice project

Offline naboo

Re: My first DAC
« Reply #2 on: July 18, 2021, 04:08:36 PM »
Looks like a lot of fun
If I can offer any advice , keep the mains 220vac line away from the input and outputs of the DAC
Nice project
Thanks. Of course, any advice always welcome. That to reduce mains noise?

Offline fredeb

Re: My first DAC
« Reply #3 on: July 18, 2021, 10:17:19 PM »
Well done ! Nice transformers . Looks like a jol .  ;D

Thanks. Of course, any advice always welcome. That to reduce mains noise?

Ja ... good advice there from Audio ears , always keep the mains away from signal cables . Same goes for wires off of transformers to boards ( in this DAC's case rectification and and PSU circuit is integrated on the same board ) . You can also twist any AC power wires and keep them short .

Enjoy ! A nice kit to fiddle with . Install those resistors to correct DAC analogue out filter before opamp . Try different opamps , OPA2134 could be good there instead of NE5532 .

Here's a link to the onboard DAC chip datasheet : https://www.sowter.co.uk/dacinfo/AK4396.pdf


« Last Edit: July 18, 2021, 10:22:32 PM by fredeb »
...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts

Offline fredeb

Re: My first DAC
« Reply #4 on: July 18, 2021, 11:22:27 PM »
LJM developed these boards and sold them as AK4393 , but this board has AK4396 which requires a different Low Pass Filter RC Network .

On page 34 of the datasheet an example of the correct filter configuration is shown for one opamp on the output with table showing roll-off of Low Pass Filter at 20 , 50 and 80 khz .

The subsequently show a 2 opamp option for 3dB gain  and a 3rd order LPF as recommended by SACD format book .

Speaking of opamps I also remembered how good LME49720/LM4562 (same thing) can be .
Get one of those !

How does it sound compared to your cd players integrated DAC at this point ?



...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts

Offline naboo

Re: My first DAC
« Reply #5 on: July 19, 2021, 04:51:32 PM »
You're right, @fredeb - this uses AK4396.

I decided to let it burn in before changing the LPF. Changing the LPF results in better tonal balance - apparently. There is also a fairly strong recommendation from some of the DIYAudio members to change the caps on analogue power rails to a higher value (10 000uF - 22 000uF). I'll probably do the LPF, not sure about the caps. The mod thread has more than three-thousand entries, I'll probably get through two books by the time I'm done with the thread.

For me (bear in mind it is still my first external DAC ), it sounds very good - equal to or better than the Yamaha BD-677 that I have and is used as the transport. I can hear more detail in the upper end than on the Yamaha - but I don't necessarily think that is a bad thing. I also think that this is less forgiving of poor recordings than the Yamaha - but I still need to swop around and listen a bit more.

I thought about recording the analogue output for you guys to have a listen - but I have no idea how to do that properly. Also - it seems kind of senseless because that would then go through your own DACs when you listen to it, kind of negating the point in the first place.

I will play around with changing opamps - I have one extra one. Some of the guys on the modding thread bypadd the opamp altogether. Where do you generally buy from - import?

Once everything is burned in, I'll do some careful listening, and then change the LPF and do any other mods tht sound good. Then I'll start worrying about an enclosure. I think I will live with this for a bit so it needs to be nice.

Offline fredeb

Re: My first DAC
« Reply #6 on: July 19, 2021, 09:35:58 PM »
I can only imagine it will be much better with correct LPF , and then better yet with a better opamp . Leave PSU for now .





...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts

Offline GECO

Re: My first DAC
« Reply #7 on: July 20, 2021, 09:35:05 AM »
Some quick improvements
Add a power filter. Terrible on most audio equipment works great with dacs. Add more capacitance. Again same as above.
Twist your power cables
Add 100nf wima bypass caps on the caps close to opamps. Possible improvement. Subjective
« Last Edit: July 20, 2021, 09:38:03 AM by GECO »

Offline fredeb

Re: My first DAC
« Reply #8 on: July 20, 2021, 10:55:18 AM »
Post the schematic , so that Rudi and others can see .
...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts

Offline pwatts

Re: My first DAC
« Reply #9 on: July 20, 2021, 11:19:36 AM »
My first comment would be, that circuit just from inspection is a pity for a $$$ chip like the AK4396. I have two that are meant for a very special project.
Agree on Rudi's comments. In addition to twisting power cables also try to separate the layout so that there isn't so much crossing of transformer output, input and signal wires.

Changing the regulator feeding the DAC's 5V rails is one of the most profound improvements one can make. Bypassing the local ones and using external dedicated clean ones are worth a lot. Also adding bulk capacitance to the VREF pins.

Using the output direct without an opamp is dangerous. One mistake and poof. Either change the LPF circuit by changing values, topology and opamps or use a separate (even discrete) buffer altogether. Even better will be using a transformer and no buffer, and the AK439x series seem to work exceptionally well with transformers. The good ones are $ though and must be imported.





Offline naboo

Re: My first DAC
« Reply #10 on: July 20, 2021, 06:15:23 PM »
Some quick improvements
Add a power filter. Terrible on most audio equipment works great with dacs. Add more capacitance. Again same as above.
Twist your power cables
Add 100nf wima bypass caps on the caps close to opamps. Possible improvement. Subjective

Thanks @GECO - will try all of the above in time. Could have sworn I heard a hum every time the dishwasher got going this evening (the electrical one - not my wife humming)

Offline naboo

Re: My first DAC
« Reply #11 on: July 20, 2021, 06:24:22 PM »
My first comment would be, that circuit just from inspection is a pity for a $$$ chip like the AK4396. I have two that are meant for a very special project.
Agree on Rudi's comments. In addition to twisting power cables also try to separate the layout so that there isn't so much crossing of transformer output, input and signal wires.
Hmmm... the kit sells/sold for dirt cheap though
Quote
Changing the regulator feeding the DAC's 5V rails is one of the most profound improvements one can make. Bypassing the local ones and using external dedicated clean ones are worth a lot. Also adding bulk capacitance to the VREF pins.
Ok, I think this is one of the suggested changes on the thread, also. I am still learning, will figure out how to change. Would you like to suggest values? I'll post the schematic in a bit.
Quote
Using the output direct without an opamp is dangerous. One mistake and poof. Either change the LPF circuit by changing values, topology and opamps or use a separate (even discrete) buffer altogether. Even better will be using a transformer and no buffer, and the AK439x series seem to work exceptionally well with transformers. The good ones are $ though and must be imported.
I wouldn't consider not using the opamp, but was not aware that it was dangerous. The LPF change is by far the simplest to understand, so definitely starting with that.

Thanks for all the help @pwatts  :thumbs:


Offline naboo

Re: My first DAC
« Reply #12 on: July 20, 2021, 06:33:10 PM »
Post the schematic , so that Rudi and others can see .
Yes, thanks for supplying @fredeb

Attached is the schematic and the LPF changes.

Also a pic that Ari helped with.

Offline fredeb

Re: My first DAC
« Reply #13 on: July 20, 2021, 08:58:10 PM »
Better schematic :

right-click to enlarge



...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts

Offline pwatts

Re: My first DAC
« Reply #14 on: July 20, 2021, 09:30:02 PM »
Thought I was going mad for a while - I was thinking of AK449x, not the preceding AK439x range. It's still no slouch though but the same argument as before will apply except perhaps the bulk capacitance on VREF. For external regulators, the world is your oyster. You can run choose to either just replace the 1117 regulator with something better, or do a whole extra power supply just tapping from the same AC outputs from the transformer, or use a dedicated transformer. There are plenty of LM781x replacement regulators available on e.g. eBay that uses much better regulators that will be a cost-effective first step by just removing the SMT 1117's and jerry-rig the three appropriate pins. Perhaps better to read the book of mods on diyaudio but TBH that is why I've avoided that site for the last few years - there's some REAL talent lurking there but some threads have hundreds of posts and the worthwhile ones are but a tiny fraction of it. Ain't nobody got time to filter through all that.

Note that due to the double whammy of global semiconductor shortages and most of AKM's audio production facilities having been burnt to the ground last October, it will be a while before any new AKM products hit the shelves for anyone, and DIY'ers last in line. I've noted that the AKM-based products on eBay and Aliexpress are now sold without the AKM parts mounted, that's how desperate they are to sell existing stock. Dunno how many hobbyists will be able to solder those packages especially with all the big surrounding caps already mounted, but it shows how dire the situation is.