TDA1543 DAC issues and observations.

Overall very happy with the results.

The NonozIII schematics is great, I experimented with quite a few things to test the changes and in most of the returned to the original specs.

The voltage regulators were LM78xx and i replaced them with Panasonic AN8008/AN8005M series. I noticed a big improvement in battery life using those regulators. The sound became better, more refined using AN80xx regulators. The DAC is now powered from the battery supply(12AAA 700mAh cells) since the regulators are getting very hot when running from 24V regulated power supply. This is a supply used for my PPA and both PPA and DAC will eventually be powered from it or the battery. The DAC will be using 2 or 4 2N5486 jfets to clean some ripple and provide rail isolation from the PPA ground.

Question:
What would be the best solution to adapt the DAC for 12-24V supplies and avoid AN80xx heat issue? They don't have the heatsink like the LM78xx ones and may be destroyed over time, I think. I was thinking about aditional regulator to bring the output voltage to 12V first but that would affect battery runtime. Transformers are not practical, since I targeted for a portable solution.

For the passive I/V stage I tried using a trebble correction circiut

but didn't like it compared with non-polar BG passive circiut by Fedde. The 3k resistors sound a bit too loud, i replaced them with Riken 1.8k. Riken does make a big difference, more pleasant sound, especially voices are rendered better, bigger soundstage.

One more question:
For phase inverting problem, I'm looking into transformers now. Does anyone have experience which type i can use here? Jensen make some pretty good ones, but they are not easy to find. Also, how much would it affect the sound if I put a lineout transformer on each channel to invert the phase?

And the last question:
Does using SN75179B really imrove the CS8414 jitter handling and the sound? I haven't tried this driver/receiver chip yet, but very tempted to order it from Newark after reading Peter Daniel posts. Peter uses SN75179B in combination with CS8412 chip which is not exactly the same as CS8414, the latter has better error handler as far as I know.

Powering DAC and PPA from the same supply/battery board.

Using 2N5486 to isolate the power from the DAC ground doesn't work. I burned a few 2N5486 transistors last night trying to connect V- V+ from the PPA to the DAC power thru them. My PPA power rail cascodes could've been destroyed this way, but survived I noticed that AOS Electronics using the same approach on his Ally DAC which works in combination with PPA. No idea why mine doesn't work when it should (

Maybe the only way to isolate the DAC ground from the PPA is using the 1:1 transformer?

Anyone can suggest isolation 1:1 transformers in the region of 15-30V suitable for this task? I would need to use a small one to reduce the weight of DAC and save batteries as much as possible.

setmenu said:

Hi IpsilonSound
Are you enjoying the sound of the dac?
I like mine ,especially since implementing Peters[cheers] recommendations
regarding caps and Rikens.
It is sensitive to recordings though, whether the top end sounds
'all there' seems on a bit of a knife edge at times...

I have also noticed when doing a 20-22k frequency sweep , [nothing sophisticated, just a test CD] that as the higher frequencies pass by there are some 'birdies' to be heard
phasing in an out as the frequency changes .
Spot frequency checks reveal all kinds of differences
compared to My Arcam CD23..

Are these intermodulation products ?

Though I can still enjoy the sound of this unit, as long as I don't
think about it too hard.

Here,s a pic of my little dac in bed with its partnering amp for the
portable headphone setup.

Cheers

Setmenu

Click to expand...

Setmenu, yes, the sound is great, I really enjoy it, since tube and analog was the kind of equipment I grew up with, I guess, it's in my subconscience for ever I'm still deciding whether Super-E or single non-polar 4.7uF sound better, what do you think?

Rikens are the best here since the voltage conversion is taking effect. i put 1.8k instead of NONOZ-recommended 3K. This way it sounds better, I think, less aggressive and more open, but more quiet, need to turn up volume a bit more. And I still use a trimpot to adjust the sound, maybe 1.5 or 1.6 Rikens will be in place for the final setup.

For the power caps, I use BG 220uF and bypass also BG.

I don't think the roll-off is a big deal, i couldn't hear any difference when comparing the initial NONOZIII i/V circiut with my prototyped treble-correction circuit. The NONOZ one with Black Gates gives richer and more pleasant sound.

Question: how did you connect your DAC to the amp using a single supply? Since the DAC power ground is connected to lineout ground, there's a conflict at my setup. Since the line-in ground for the amp is an amplified channel and driven separately, it cannot be shorted with a DC ground. I guess, your amp is designed differently, right?

Oh, ok... you've answered already while I was typing this post... thanks! I'll try it out this way soon

Setmenu, you're also using optical toslink, as can be seen on the photo. Did you put the 75 resistor in parallel before the 100nF film caps?

Hi Fedde!

It's cool to hear that you continue tweaking and improving your NonozIII design.
I used your DAC as a basic at first and did some mods to it since then. I could share my experiences. The DAC is still in prototype state until the active opamp i/v stage is over, then, I'll move to schematic-->pcb autorouting-->pcb board using Protel DXP software.
The LMxxxx voltage regulators are all replaced with AN5008 and 2 AN5005 ones. I did lots of listening between LM and AN regulators and AN are much better, as already noted by Peter. The sound is much richer and more cleaner with them. Too bad those Panasonic regulators are not easy to find, even in the N. America.
I used 2 separate AN5005 regulators for the CS8414 receiver. The separate grounds for digital and analog parts of the chip would be ideal, but it's not easy to implement when using a single battery board. With several batteries, i would strongly recommend the total separation for this chip. The sound becomes more relaxed and precise with the separate supplies. The TDA1543 can share the ground with CS8414, many even recommended that.

Also, the optical receiver, I used TORX141 by Toshiba needs about ~3.6v volts of supply, better a separate one. I got a few ADP3301-3.3 voltage regulators in stock, which I plan to use for it. aoselectronics.com uses those regulators for his DAC, I cannot comment yet if they would make any sonic differences if used for CS8414 as well. There are no 8V ones from this line, so I'll stay with Panasonic ones.

The i/v 3k resistors are replaced with 1.8k Riken ones and a pot(~1.6k). You did the right thing to remove the pot and put the Riken resistor there, but it's very hard to find the exact value which gives the lowest distortion, unlike the pot which adjusts easy. I observed the THD changing from .09-.016% when adjusting the pot, though sonically you cannot hear the difference. Also 1.8k gives the ouput of 1v instead of the standard 2v CD lineout, but that's still ok.

I also omitted the Schottky diode,since only DC power is used here.

Have you tried using 2 2N5486 jfets on V- and V+ just like the PPA uses before the virtual ground devided for powering each opamp? It does some good thing to reduce the noise and ripple from the power supply, especially with adapter supplies.

Have you thought about using opamp for active i/v stage for DAC? I like passive one myself, but have no choice, since it will be powered from the same source as PPA amp and the lineout ground must be isolated from the battery V-. The THS4082 for left and right channels, THS4081 for ground will be used. They are 175Mhz voltage-feedback opamps and are perfect for highest quality audio solution, given proper implementation, of course(ground plane, compensation, layout consideration, etc.). It will take me some time to tweak this part for sure.