Dual Mono DAC AK4490/AK4497

[cal1sto]

Originally Posted by UMarcus

Nice, I'm also very interested in this project (especially AKA4497).

Would be I2S Input -> MonoMode Balanced Output possible ?

I'm general interested in minimized designs, especially in analog section, I just take a short look into the Datasheet.

Do you think the output couple 100µC are needed for Balanced Mono Out as used in the example ? I asking because i have alread a DC Couple C in my system.

About modular concept, maybe it would be also nice to have the possibility to use external power supplies / regulators.

Thanks,
regards
Marcus

One final target of this thread is to have one dual AK4497 DAC board (mono mode) to get the S/N of arround 130db, with balanced/unbalanced output to cover all our need.

The 100uF specified into my last post for the AK4490 is to custom the diyinhk board to split all power supply on left and right side of the chip (digital and analog side), this is specialy for the analog 5V where the FB1 and a trace will be cut (to split fully both analog supply).
For the AK4497 example see the attached AKM AK4497 shemas like on the AK4490 there is not output capacitor of 100uF, please share with us what you see or mean, thanks, the dac board as one or 3 LPF per Channels see the mono shemas from AKM for the AK4497 (AK4490 is more or less same).
I think one LPF is more than enought for the line out.

All the power supply will be provided as module with isolated short wire (interference protected).

But near the modular board i want to propose also one single board with all functionality into one litle compact board for the Dual AK4497 / XMOS and the Ultra low noise LDO.

Regards

[cal1sto]

Originally Posted by manudrz

Perhaps a little "cap/shield" on the output to do BAL/SE? Suitable for everyone and flexible, yes like many others designers do...



I think onboards regulators is better, wiring regarding. Mirand audio design is wonderful, but I only need half of his boards...

Could we imagine 3 little PCB:
One below with regs/PSU (too hot?)
One in the middle with AKM
One above with the output ?

I'm still dreaming of a tiny i2s mono board to SE, running the AK at 7V with good regs and AOP.
Just a few ideas, not my design

By the amplifier i build, i take as priority to split and protect the Power supply component from the operational board part , to protect any impact generated by the PSU itself (HF, Temp., magnet...) with a dedicated shielded place into the case, then all power wire enought dimensioned (short as possible, equal in length for same operation type, section size, material) and shielded.

Regards

[UMarcus]

Originally Posted by cal1sto

One final target of this thread is to have one dual AK4497 DAC board (mono mode) to get the S/N of arround 130db, with balanced/unbalanced output to cover all our need.

..
All the power supply will be provided as module with isolated short wire (interference protected).
..

That's great !

Originally Posted by cal1sto

...
For the AK4497 example see the attached AKM AK4497 shemas like on the AK4490 there is not output capacitor of 100uF, please share with us what you see or mean, thanks, the dac board as one or 3 LPF per Channels see the mono shemas from AKM for the AK4497 (AK4490 is more or less same).

Please find the attached shema with marked capacitors.

[cal1sto]

Originally Posted by sangram

The power supply routing on the DIYIHK AK4490 board leaves very,very much to be desired. That's what happens when you route a DAC using 2 layers and don't give priority to the power traces.

No idea about the 4497 boards, but I don't expect better.

There is not even space to fit your own LDOs.

Digital power needs to have extremely low impedance supplies very close to the chip, with HF bypassing at the pins. He's done the latter and not the former.

In addition when we asked for the schematic of the I/V stage he said it was same as datasheet but it's not. The value of whatever components we could make out was totally different, so he obviously has no idea about the board itself.

I would suggest a base board from someone who actually knows what he's selling, like sonnya on these forums. The price is much higher but at least you know that it will be properly designed.

The only remedy for the other board is to use a piggy-back style layout with a power supply placed just below/above the DAC board, feeding power straight to the required pads with very short (<10mm) traces. If you examine the chip layout, it was made to have separate regulators for each side of the chip with very short distance to chip. All 4 sides have power pins and respective grounds.

I agree with you on some point like the low impedance need on the digital side (but with the two 3.3v for each side of the board with a short wire of 50mm i don't measure any impact during operation) , this board is a diy board and we are lucky to have it 2 Layer with enought reported pin to custom it and to be able to cut trace . Target is to use them as study base to build a dual mono board where we could have the power line part already splitted and well placed on board (without need to desolder part and cutting trace to have what should be delivered at the begin, i agree fully with you)
I will take a look on Sonnya board to understand what you mean, thanks.

Regards

[sangram]

Good Luck with your project I had recommended the DIYINHK board to a friend who purchased it as the price is fantastic, but after working with it once I figured it has some issues in terms of execution.

And money would not have solved that, just proper board design technique. That is what you pay the extra money for and is a gap that HK/China manufacturers yet need to cover. They will catch up, but they're not there today.

[marce]

To get the best signal and power integrity a minimum of a 4 layer board would be required..... How much difference this would make is impossible to tell without careful measurements..... But for anything digital these days (and for many many years) I would never go below 4 layers, cost is not that much more than 2, benefits are many, if for no other reason than you can control the digital signals return paths...

[cal1sto]

Originally Posted by UMarcus

That's great !



Please find the attached shema with marked capacitors.

Ok, you mean the high pass filter and DC decoupling from the analog output of the DAC before the LPF part. When you already have a high pass filter in your next board connected to the lpf out (and the opamp is matching this way of operation ) you could modify the shemas on your need, but anyway filtering before getting signal amplifyed (gain) by the LPF is better, so this doesn't (with low esr) affect a lot the analog signal.

Regards,

[cal1sto]

Originally Posted by sangram

Good Luck with your project I had recommended the DIYINHK board to a friend who purchased it as the price is fantastic, but after working with it once I figured it has some issues in terms of execution.

And money would not have solved that, just proper board design technique. That is what you pay the extra money for and is a gap that HK/China manufacturers yet need to cover. They will catch up, but they're not there today.

That is why the first part i did with this board is to split the power supply 2 X 3.3v and 2 X 5V (or 7V) , this split is done by providing and by moding the board , desoldering component , soldering one and cutting trace to physically split correctly the board power. Without this i could imagine bad supply with merged power on this board could have some operational issue

Regards,
Marc

[cal1sto]

Originally Posted by marce

To get the best signal and power integrity a minimum of a 4 layer board would be required..... How much difference this would make is impossible to tell without careful measurements..... But for anything digital these days (and for many many years) I would never go below 4 layers, cost is not that much more than 2, benefits are many, if for no other reason than you can control the digital signals return paths...

I agree fully the minimum of 4 Layer give the best of layering the trace for best signal and power integrity , thanks for your precision We will go this way ^^^^

Thanks

[manudrz]

An other base to mod with ? AK4490 - I2S over USB Audio