Pushing the limits of TDA1543 NOS DAC

[rickmcinnis]

Peter,

I hope this is not to far afield from the topic here but I suspect others might be interested, too.

What wire do you /would you use for digital signals - internally from a dac board to a buffer? Not speaking of transport to DAC ...

Have you found wire to make much a difference here? And if so, what do you like?

THANKS,

[KlipschKid]

Hi Peter and Bobken, and all you other Nossers :-),

I've very much enjoyed reading about your development of this humble little chip. I am about to try it out for myself...

I have a question of course ;-) I assume someone must have tried a potential divider instead of a single I/V resistor to ground ? If so, why was it rejected ?

I was thinking a 4.7R series resistor, with the resistor to ground unchanged.

It would increase output impedance, and lower output voltage a fraction, but not significantly and would isolate the dac from cable capacitance ?

In my application, the DAC will feed 1m upocc cables with no DC coupling cap at the DAC. I have 3.3uf Mundorf silver/oil input caps with 100K input impedance at the amp input.

My apologies if this has been covered somewhere, but in my defence, in all the posts and reading I've done on the TDA1543, I can only find one reference to a potential divider here :

http://myweb.tiscali.co.uk/g8hqp/audio/TDA1543IV.html

I hope Dave Kimber will not mind me quoting him. He says, "If people really must have passive I/V then the best option is to use a potential divider which will set a standing DC bias at the output, but very few designs do this."

Thanks for any comments.

Tom

[Peter Daniel]

I never tried potential divider, so can't really comment on that.

Originally Posted by rickmcinnis

Peter,

I hope this is not to far afield from the topic here but I suspect others might be interested, too.

What wire do you /would you use for digital signals - internally from a dac board to a buffer? Not speaking of transport to DAC ...

Have you found wire to make much a difference here? And if so, what do you like?

What I found so far about digital signal path, is that it behaves exactly the same way as analog signal path, every single component influences the sound. I usually try to install all input sockets directly on a board so all connections are done through pcb traces. If I need to use wire, I usually go with DH Labs solid silver hook up wire or this one: Commercial Gainclone kit- building instructions

[samoloko]

Peter

looks like your curent dac schematic differ from Non OS TDA1543 PCB Layout

would you tell us why omit 3300 pF from filt pin - as I read It filtrate noise

what type resistor and cap recommend to use for PLL - Is ordinary Vishay Dale RN good for resistor and how about Vishay Rodersatin MKT for cap

[Peter Daniel]

This capacitor is not specified in CS8412 datasheet and was popularly known as "wildmonkeysect tweak": Cs8412

In our listening tests the modded DAC sounded better without 3n3 cap.

For PLL I'm using nude Vishay and BG NX

[samoloko]

thank you for reply

for PLL I guess that you were not used smd caps - from what I read It Is Important to have very small but quality dieleкtrik

[Peter Daniel]

0.1uF BG NX is actually pretty small; size certainly matters, but quality of dielectric even more.

[juanitox]

hi all , finding this page yesterday http://myweb.tiscali.co.uk/g8hqp/audio/TDA1543IV.html

i wonder why many people use 8V with 1.5K and 2.2K to 2.7K output resistors and not the values seen in this page?

is it just about 2nd order distortions or something else?

[BachAudioDK]

Hi,

I have the "Muse Mini 4xTDA1543" and have succesfully used these resistors:

680 ohm Dac resistor replaced with 212 ohm (270//1k SMD)
390 ohm Bias resistor replaced with 243 ohm (1k//1k//1k//1k//10k SMD)

Vout = 0.675 Vrms
THD+N = 0.029 % (2. harmonic dominant) Measured with Asus STX, 96kHz

I used a 1K+100 ohm multi trimpot to find the optimum Rbias value. It is important to do this to find the sweet-spot, and then later replace with resistors.

While messing around, I tried to tie a capacitor (47uF) across the bias resistor. Some how this raises the hole noise floor about 12 dB, and adding some nice analog "noise" to the music. Using a smaller Cap value of 1uF gives rise to the noise above 10kHz.
Have anyone else tried this ? (the 2. and 3. harmonic stayed at the same amplitude while this cap was on)

Regards
Flemming Bach
Denmark

[Hierfi]

Hi, I also have the Muse Mini 4xTDA1543 and after several mods I successfully terminated the input DIR9001 receiver. Anyway, the problem with connecting a capacitor across the bias resistor is that the resistor is fed by a DC reference voltage. This reference voltage has an output impedance considerably lower than series Bias resistor. If you short the bias resistor out with a capacitor the gain goes up for AC noise. It is like having a capacitor across the resistor in the cathode of a tube circuit. This is done to intentionally increase the audio AC gain of the tube circuit. However you are trying to maintain a constant DC current in the reference circuit. This brings to mind putting in a small inductor in series with resistor to decrease more AC gain and noise, particularly at higher frequencies. regards, Gerrit Aartsen