CS4397 dac

[Puffin]

After successfully building one of these DACs -- thanks Leo, et al -- I ended up at diyaudio to learn about bypassing the opamp with transformers. The diyAudio thread is very long but full of info on implementing transformers. I ended up installing Jensen JT-11p-1 transformers but there are lots of options. IMO, a worthwhile upgrade.

Do you have any pics of these mods? Welcome by the way.

Rob.

[fandersen]

Do you have any pics of these mods?

I used an old CD player to house the DAC as I wasn't concerned about cramming everything into a small box. The CD player also had a decent power transformer that had an 8v output that I ran through a TREAD power regulator to give me a nice clean 5v for the DAC. Since I was bypassing the output stage I didn't have to worry about the 12v.

Initially I ran the DAC with an opamp, hence the mods that are still on the board for the output. The transforms are connected to the C27, C28, C30, and C31 connections. The input and output filters are based on Jensen recommendations for these transformers.

[fandersen]

Hmm.... the images didn't make it on the last post

[Puffin]

Hmm.... the images didn't make it on the last post

Thanks for the pics. Might try it meself.

Rob.

[janos_904]

hi janos can you explain a bit clearer what you did with the silver mica on c9????I think I would like to give it a go but cannot understand what you have done...alan

Hi, Sorry for my post to be unclear. So, I made an a new spdif input for the DAC. The signal path is the following: BNC (RCA) inlet, Silver Mica in series, and the output leg of the capacitor soldered by a fine silver wire (or by copper) directly to the CS8416 Receiver chip signal input leg. I will make a photo, how it is looks like. After a test period and some advices, I decided to use 10 nF Silver Mica capacitor insteed. (0.01uF 350V 0.3% tol. Russian millitary SILVER-MICA capacitor). It makes a great job, the signal shape is not affected, I recommend it highly. Cheers, János

[janos_904]

Dear Leo, I recommend to re-play with this small board. First of all, please design separated (dedicated) 5V, and 3,3 V power supplies, using low noise power regulators. At the receiver chip in the 3,3 V line advicable to use Os-Con very low ESR polimer capacitors (SEP, SEPC). And the DAC rocks :-). May be you are the only one, who could compare this one to Buffalo. But just after the modds listed above. Cheers, János

[leo]

Hi János ,
I have another one of these dac boards so will start modding it soon. I may even try the Paul Hynes regs with it

[janos_904]

Hi, here goes a photo to help to isolate power lines. It was taken from a polish diy forum. My polish is poor, but the label is may be not correct :-)! On the picture the labeled line goes directly to the Vref leg of the DAC chip. I disconnected it by a sharp blade, and soldered a new 5 V power inlet, according to the green arrow. Be careful, not to cut deep and wide, because of the ground is close. The +5 V analog of the DAC goes at the under-side of the board. It is good to separate too. Now, we can install and connect separated 5 V supply for DAC chip. Don't forget: the receiver still needs 5 V (3.3 V fits too, or not enough?), because to choose one of the spdif input (optical or coax).

[janos_904]

Hi, I have to correct my last post. So, both the DAC's analog power (number 28) and voltage reference (number 22) pins are connected by the very same via. That is the worst case for an a voltage out DAC. I guess, the only way to provide a nice VOLTAGE REFERENCE to the DAC is: simply lift up the reference pin, and connect it to our voltage reference source directly. The song of Cs4397 benefits a lot by dedicated (separated) voltage reference.

[kput]

I have given every major power point to each chip its own, LT317 regulated power supply...thats 6 independent battery powered feeds. I have used silver mica on c9....the sound was at first harsh...I walked away for a few hours , started to sound shockingly good.....eventually I had to recharge my tripath amp batteries, I did not touch the dac board, but when I turned back on...NOTHING.....

1)all the pins on the chips that need voltage are getting what they require
2)have continuity from the digital input and analogue out puts
3)have signal entering the reciever chip
4)have 2.5v dc on the analogue outputs but no AC
5)cannot understand the transistor near c21. I suspect this as it has something to do with the mute function...On the circuit diagram it shows one pin of the transistor connected to pin15(dac), one pion connected to pin 14 of the reciever chip and one pin connected to ground...I cannot find any of my pins on that transistor connected to ground

can any one help...as it was initially working it must be just some stupid mistake I have made