[wwenze]

I just realized it is possible to reduce output voltage swing without affecting V_bias by changing the value of the 47kohm resistor. This makes experimenting much easier.
 
So V_bias is kept at 3.85V in my case / R17 still 390R
 
Trying a few values of R10 / R11, looks like 0.02% THD is indeed around what this thing is capable of, before the disadvantages of low voltage swing become apparent. A good range for the I/V is around 50 to 200 ohms. I would keep to the higher half of the range; 170R would give 0.5Vrms output voltage.
 

 
Ignore the crosstalk, an unfortunate side effect from the test set-up. Soldered replacement for R10/R11 would avoid that.
 
Of course, best way to minimize voltage swing seen by the DAC IC while having higher voltage swing at the RCA is still to use active I/V.
 
 
 
Also I just realized, the answer for the best value for V_bias has always been there: 2.063V, because that is the value on the V_ref pin and hence would also be the value on the output pin when active I/V is used. Since I_bias gain is calculated to be roughly ~1x, means the best value of R17 should be equal to R10/R11. So, 150ohm or 175ohm for everything is about as good as it gets.

 

[rtaylor76]

Interesting to see this thread still alive, with more modding / testing / measurement

But since this isn't a real TDA1543, unless somebody knows what chip is being used, finding the best values is pure guesswork.

Could they be TDA1545's?

All Multibit DAC's are going to have higher THD and noise specs than 1-bit DAC's. The issue is getting this under control. An active I/V can help, but so does more chips. It also sounds like this box is up to its eyeballs in current draw. I wonder how this box measures up against the Project DAC Box S FL. It is also a quad TDA1543 desktop DAC in a small form factor.

Has anyone

 

[rtaylor76]

Ok, so I removed those 0.1uF caps near the output. it had more top end, but still harsh and fatiguing.

Then removed C6 and C7 and replaced them MKS WIMA's, 10uF, 5%. No more harshness at all. Those stock electrolytics are absolute garbage for audio. Holy cow such better sound. Now this thing rules!

 

[rtaylor76]

Sorry...one more mod I forgot that can improve any DAC I just found about.

I built an -18db pad coax attenuator box using a T-pad passive attenuator:

http://www.electronics-tutorials.ws/attenuators/t-pad-attenuator.html

This really helped out smooth things out for real.

 

[thuNDa]

Yes, those electrolyte outputcaps are no good, i replaced them aswell.
 
This is my state of play:
-some regrounding(CBA to disconnect the groundplane of the TDA's, so i just clipped the legs

)
-Vishay MKT 1820 as outputcaps(2x 10uF in parallel per channel)
-disconnected pin 7 (Vref) of the TDA's and bias with battery instead(this time didn't cut legs, only traces

)
 


 
 
- new case for it, maybe some time...

 

[rtaylor76]

So this week, curiosity got the best of me and I decided to see how well this DAC would sound in my car. I got to thinking that although it is far from perfect, it might fair better than an iPod or a 1-bit DAP.

I use an inverter and the wall wart it came with, but I plan on getting just a straight cig lighter adapter to simply things.

It's plugged into the coax out of my FiiO X3 II. The actual hardest part was getting the RCA output to 1/8" female. I have a cig lighter adapter in my armrest center console, so the whole thing (inverter, adapter, and DAC) all fit nicely packed away.

As far as the sound...my car stereo is at a new level. I was somewhat unimpressed for this next to my Denon DA-500, but those TDA chips has something intrinsic about it. Warm, layered, bottom end for days, and I only have a Pioneer head unit and stock speakers (albeit my fronts are separates).

Compared to the direct out my FiiO - the FiiO is more detailed, but way flatter soundstage and sounds grainy and the lows are not quite as detailed or thick.

One side note - it takes about 10 to 15 minutes for that DAC to warm up. At first it sounds harsh and worse than the FiiO, but even after 5 minutes things start to really smooth out and the bottom end gets much huger. I never noticed this when using it on my desk as it was alway plugged in and on. It gets a frowny face for shot trips.

But overall...unreal....just unreal. My car sounds like I have a reel to reel player in the back. I know there are better Multibit DAC's, but I am just beside myself.

 

[DjBobby]

Got one, out of curiosity. Either it has strong treble rolloff, or my ears are to much used to delta-sigma that it sounds to me kind of damped, muted. Wondering is that the problem of the chips, or rather the mediocre audio output?

 

[rtaylor76]

Got one, out of curiosity. Either it has strong treble rolloff, or my ears are to much used to delta-sigma that it sounds to me kind of damped, muted. Wondering is that the problem of the chips, or rather the mediocre audio output?

Let it warm up for by running audio through it for about half an hour before evaluating.

It still has a slightly muted top end. Removing the two small caps near the output helps lift the high end some, but this also can cause some harshness in the high mids.

The depth really opens up and is noticeable after about 10-15 minutes for me.

Oh, and I also replaced the 25uf high pass filter caps with 10uf Wima's MKP's.

 

[DjBobby]

Let it warm up for by running audio through it for about half an hour before evaluating.

It still has a slightly muted top end. Removing the two small caps near the output helps lift the high end some, but this also can cause some harshness in the high mids.

The depth really opens up and is noticeable after about 10-15 minutes for me.

Oh, and I also replaced the 25uf high pass filter caps with 10uf Wima's MKP's.

Thanks, will try.
Does adding the LPS makes some noticeable difference, or would it be rather an overkill? I mean, LPS would probably cost more than the dac itself.

 

[rtaylor76]

Thanks, will try.
Does adding the LPS makes some noticeable difference, or would it be rather an overkill? I mean, LPS would probably cost more than the dac itself.

You will have to look back at this long thread. Some had good luck, some did not see much change. There is already a voltage regulator that regulates to output 9V to the power rails. An LPS might make a slight improvement, but just remember there are no op amps on this circuit, so it only feeds the DAC and input chip.

Mine came with 12V 1A supply and I tried a 2A supply and I thought it made it sound worse - albeit it might have been a worse power supply.

Those 25uf filter caps are quite garbage, so I think the biggest gains in SQ that is the cheapest, is replacing them. Although desoldering is no easy task - well, at last to leave a whole to put the new leads/legs in.

I also went 10uf due to size constraints, but this does lower the rolloff frequency just a bit.

Also, I didn't even desolder those two tiny caps by the output (the small rectangular ones). I just bent them until they broke off - and there was much more high end fore sure. It was much closer to a standard sounding output to me.

 

[wwenze]

 
Got one, out of curiosity. Either it has strong treble rolloff, or my ears are to much used to delta-sigma that it sounds to me kind of damped, muted. Wondering is that the problem of the chips, or rather the mediocre audio output?

 
It does sound different when stock. However if you do the resistor mods to reduce the distortion, the difference goes away. The treble rolloff will remain tho, thanks to high output impedance, so get good cables.

 

[DjBobby]

I was using it only on coax until now, and wasn't quite impressed with the sq.
Just received the optical toslink to 3.5mm mini toslink cable, which made me possible to connect it to usb to spdif converter SMSL M2, and it sounds a way better. Much livelier sound than through coax. Now it really shines, and will stay permanent in this configuration.
I was wondering, did anybody try to compare the sound switching inputs?

 

[rtaylor76]

I was using it only on coax until now, and wasn't quite impressed with the sq.
Just received the optical toslink to 3.5mm mini toslink cable, which made me possible to connect it to usb to spdif converter SMSL M2, and it sounds a way better. Much livelier sound than through coax. Now it really shines, and will stay permanent in this configuration.
I was wondering, did anybody try to compare the sound switching inputs?

I think I have tried with another DAC, but I don't think on this one. My experience with Toslink is that it has more jitter. However, I think it is better de-coupled from the circuit. Most coax are transformer coupled, which helps reduce HF noise. Toslink just sounded a bit more "flat" to me and not quite as "layered" sounding than the coax. So make sure you are just not hearing more of a "direct" sound and a slightly more spacious sound.

 

[DjBobby]

On the Russian forum found out that the phase of the MUSE dac is inverted: http://reference-audio-analyzer.pro/en/report/dac/muse-audio-4x-tda1543-nos-dsc.php#rw1
Does this affect the sound?
 
Btw. many interesting measurements on the site.
 
 

 

[romanrex]

Phase is not inverted in MUSE AUDIO 4 x TDA1543 NOS DAC. Phase inverted by the ADC E-MU1616m.
Later, all the impulse characteristics will be drawn positively  Рolarity is not tested. Testing only the wave form of the impulse.
Thank you for your interest in the site