My (friend's) TDA1541A Non-OS DAC

[Andypairo]

After a long wait caused by Schuro's delay I've been able to complete my friend's Alex nuptial gift: a NON OS Dac with the TDA1541A.
He's been trying my battery powered 1543 DAC and liked it so much that I decided to build a version with the 1541A (S1) for his wedding. Unfortunately he already got married 20 days ago... so I'm a bit late but I think he will appreciate...

Now off to the technical details: PCBs were provided from Pedja (that I thank very much), I use 5 different transformers to power everything... capacitors are Panasonic FC after the regulators, Wima MKP 0.1uF (for space constraints I didn't try in this one the 0.22uF styroflex or polypropylene I have (very big) for TDA1541 bit decoupling (2u2 MKS on the high bits), the asynchronous reclocker uses a canned oscillator (but I might switch to Elso's overtone clock the PCB is made for if I find the way to make the inductors needed)

I/V conversion is made with Thorsten's OPA660 circuit, output caps are 4u7 polycarbonate.

Cheers

Andrea

[Andypairo]

the front led is red when the power is on and gets yellow when the receiver locks the signal....

[Andypairo]

Closeup of the completed boards

[Andypairo]

at the moment I fitted a "regular" 1541A for the tests, but the S1 is waiting...
Can't comment on the sound yet, will report in few days.

Cheers

Andrea

[sparkle]

Well that is one very nice piece of the equipment. I hope that Your friend will like the sound/look. Nice work....
regards
daniel

[Andypairo]

Hello,
the first tests revealed some noise problems, surely they are caused by the asynchronous reclocker (since bypassing it the DAC is dead silent), but probably the grounding arrangement doesn't help much

Looking at the photos posted the shielded cables that bring the Iout to the I/V converter have the gnd connected only on the DAC board side, whose Gnd is brought to the I/V board at its input power connector (orange wire).

A strange thing is that if I leave the I/V board placed horizontally (as in the photo) I also get a hum, that disappears placing it vertically...

Any suggestion?

Cheers

Andrea

[Bricolo]

if it's dependent on the position/angle, maybe it is some "magnetic noise" coming from the transformers.

Try to place a thick bar of metal (preferably steel, iron is certainly ok too. Copper is less good and aluminium lesser. The best being mu metal but it's expensive)

[Andypairo]

Hello,
the trafos are not so close.... the metal shield should be inserted between DAC and I/V or between trafos and pcbs?

Cheers

Andrea

[Bricolo]

between the trafos and the pcb

[carlosfm]

Andrea,

You should have ONE ground connection.
Join the grounds of the two signal cales and connect to one point of the dac board and one point of the I/V board.
It's also very important where you connect the gound, so my advice would be to disconnect the ground on the two boards and try with a single cable with aligators.
I think the two boards should be very close one from the other.
The ground cable should be as short as possible.