Changing 1543 DAC from 8V to 5V. Help needed

[Nielsio]

I have essentially this DAC:
http://www.fedde.nu/audio/images/nonoz3.gif

I'm building it into a new/proper case. However,

I have a digital equalizer (Behringer 8024) which outputs AES/EBU through XLR, so I'm changing it so it can accept that. The CS8412 datasheet specifies how to do this.

I also have a JLTi tube-buffered amplifier.
( http://www.customanalogue.com/jlti_m...tic%20Diagram:
http://www.customanalogue.com/diytub..._T-Net-use.gif )

The TDA1543 datasheet specifies that it has lower distortion at 5V, and I think my system (because of the tube buffer stage) works fine without overdriving the DAC chip.

My question:
What are all the things I need to change to run the DAC on 5V?

Thanks in advance.

[jitter]

Just for trying if it works, you could remove the LM7808 and put a jumper wire between pin 3 of the LM7805 and the pad where pin 3 of the LM7808 used to be.
If everything should turn out to be fine, then remove the jumper wire and solder a LM7805 in the place where the LM7808 was. That's it.

The only thing that bothers me is: why use 8 V in the first place?

[Nielsio]

I believe it's what quite some people do (or at least it was a few years ago), together with a non-buffered 3875 amplifier.

http://www.diyaudio.com/forums/showt...483#post173483


No other things need to be changed besides the 7808? Well, that would make my life easier.

[jitter]

Originally posted by Nielsio
I believe it's what quite some people do (or at least it was a few years ago), together with a non-buffered 3875 amplifier.

http://www.diyaudio.com/forums/showt...483#post173483


No other things need to be changed besides the 7808? Well, that would make my life easier.

Happy Newyear!

As I said, try it out first. Some designs with the TDA1543 need more than 5 V for a reason (e.g. in this one). Your's might be fine, though.
Make it work on 5 V and play a CD with good quality recordings (preferably right up to 0 dB level for the peaks) and listen if it still sounds undistorted. A test CD with some 0 dB sinus signals and a scope would be even better...
If it works, yes, 7805 is all that's needed.

[dddac]

no magic here

8-9 volt (almost the max the chip will endure) is used so you can reach 1,6V RMS output voltage, so you need less gain in the rest of the chain. Further, by heating up the chip it sounds better, so 5 volt will sound less. I tried all voltages between 5 and 9 Volt and 8 to 8,5 sounds best

of course you cannot just change the voltage as suggested, you need proper biasing of the output or things will distort your ears off... best done with a fft analyser

For 5 volt you need to change the resitors at pin 6,7,8 to reach maximum output voltage with minimum distortion
My rule ot thumb, after several measering sessions, is that at the minus phase you need 1,5 Volt headroom. At the top 2 Volt

with this you can calculate max outputvoltage round the bias pointRload (pin 6,8) and concesquently Rref (pin7)

you can read about this on my website here

good luck and let us hear your results?

doede


happy new year everybody !!!

[jitter]

Thanx for correcting. Adjusting the resistors and bias was a thing I wasn't sure of if it would be needed (no experience DIYing DACs...yet), hence my advice to try first. Worst case I was expecting a clipping signal at max. signal level (0 dB).

Off topic: I always wondered why a CD-player and other digital stuff has a 2V output @ 0 dB while analogue stuff (like tuners and casette decks) were a lot lower. Are there technical reasons to do so or was it a marketing trick (many people think: louder=better )?
For critical listening I always use headphones (acoustics in my living room are no good) and often find that I need to turn the volume way down to be comfortable. Usually the attennuation of L and R channels is not 1:1 in the first few degrees of turn of the potmeter, leading to clearly perceptible shift to L or R. I want to DIY a DAC and will probably choose a more sensible output level for that one.