TDA1541A 100nF decoupling caps?
- Thread starter Dowser
- Start date
martin clark
pinko bodger
Don't use electrolytic caps - I'd include tants there - because avoiding leakage currents, really, really matters/will corrupt the bit current definition. And these are current-output dacs.
Also note that these are ripple filters for the internal (bit) current sources running at your OS rate, so need to work at min. 176Khz (and above) in a 4xOS unit like Naim's (and other implementations with the SAA7220B) - therefore much larger C values won't help, neither does large physical size (more ESL). Naim's tight-layout use of stacked-film over a fat ground-plane is spot-on when you think about it in those terms.
Increase the value on the MSB on each channel - all the others are of course divided-down from this, so you only have to change two, to affect the lot. Up to 1uF film providing in a very compact package is, iirc, what I went for. Something like that anyway, I suggest.
PS for all that, in my Naim CD2, I would not call the alteration remotely audible AFAICR. IN something with less-well resolved layout and parts choice -who knows. Given a free hand, I'd be looking at SMT parts on a layout like Naim's for the ground plane for sure, for best HF performance.
Also note that these are ripple filters for the internal (bit) current sources running at your OS rate, so need to work at min. 176Khz (and above) in a 4xOS unit like Naim's (and other implementations with the SAA7220B) - therefore much larger C values won't help, neither does large physical size (more ESL). Naim's tight-layout use of stacked-film over a fat ground-plane is spot-on when you think about it in those terms.
Increase the value on the MSB on each channel - all the others are of course divided-down from this, so you only have to change two, to affect the lot. Up to 1uF film providing in a very compact package is, iirc, what I went for. Something like that anyway, I suggest.
PS for all that, in my Naim CD2, I would not call the alteration remotely audible AFAICR. IN something with less-well resolved layout and parts choice -who knows. Given a free hand, I'd be looking at SMT parts on a layout like Naim's for the ground plane for sure, for best HF performance.
Dowser
Learning to bodge again..
Thanks Martin - I'm still going to try, but in my old Marantz CD60 as a first step - stock Philips use SMT caps wihich I always thought was OK...but, didn't matter how far I modded the CD60 it was never anywhere near a CDI, Woodside or even a Micromega Stage 3 with a clock. Want to try and find out why.
a.palfreyman
pfm Member
Think the Arcams used .47 solid tants on the msb and next position, but Mike P advised against this for the very reason Martin gives above IIRC as it alters the sound. Interestingly, the 1540 uses a combo of .1, .22 and .47. As Martin sez, use tight packages. Should be able to get smt films. (Although I struggle to hear any difference between my modded and unmodded cd160s where amongst other things I replaced the 0.1 cerams with 0.22 petp)
I hate Tant especially in audio kit they sound dreadful.
You need, Low Leakage, Low ESR and ESL high speed current in bursts will need this.
In the pass I have used this company and the caps are great check them out.
:-https://paktron.com/
I just love there slogan.
You need, Low Leakage, Low ESR and ESL high speed current in bursts will need this.
In the pass I have used this company and the caps are great check them out.
:-https://paktron.com/
I just love there slogan.
Mike P
Trade: Pickwell Audio
I'm in complete agreement with Martin on this.
Arcam used 470nF on the four MSB pins and I found that swapping these out for films cleans up the sound no end. The first time I did this it was such a big change that it rattled me and I have to admit that didn't like it at first. But after a couple of days listening I realised just how much better it was.
Tantalums, Black Gates and Os-cons are all unsuitable (too high leakage) as are big axial film caps (too high inductance). Yet, you'll see all of these poor choices being recommended if you read around on the www.
In their flagship TDA1541 machines (DAS-R1 DAC and CDP-555esd) Sony used 100nF small dipped radial polyester capacitors.
In the 'statement' machines from Marantz (DA12, CD7 and Project D1) the bit decoupling caps are distinctive blue coloured 100nF dipped radial film caps of some sort. The internet folklore is that these were specially developed for Marantz/Philips and are a key part to the fabulous sound quality that these machines are famous for. I've been unable to find out exactly what they are but my best guess would be metalized polypropylene although I have read at least one (unsubstantiated) claim that they're PPS/foil.
P1110814 by Michael Pickwell, on Flickr
In the Philips CD960 and Marantz CD94 mk1 they are larger than usual 220nF films:
20210508_124811 by Michael Pickwell, on Flickr
Some of the best I have used were 100nF Panasonic surface mount PPS, soldered to the pads on the underside of the board.
20170612_153134 by Michael Pickwell, on Flickr
In the Sony CDP-333esd, M75 and CDP-750 they are axial ceramics and I have found that swapping them to polyester films is a big improvement
M75 ceramic by Michael Pickwell, on Flickr
M75 film by Michael Pickwell, on Flickr
In my first Philips CD960 I tried 220nF Wima polycarbonates and I thought they sounded very 'clean'.
P1110260 by Michael Pickwell, on Flickr
My second Philips CD960 is still running the original dark green poly caps and I have no desire to change them.
Arcam used 470nF on the four MSB pins and I found that swapping these out for films cleans up the sound no end. The first time I did this it was such a big change that it rattled me and I have to admit that didn't like it at first. But after a couple of days listening I realised just how much better it was.
Tantalums, Black Gates and Os-cons are all unsuitable (too high leakage) as are big axial film caps (too high inductance). Yet, you'll see all of these poor choices being recommended if you read around on the www.
In their flagship TDA1541 machines (DAS-R1 DAC and CDP-555esd) Sony used 100nF small dipped radial polyester capacitors.
In the 'statement' machines from Marantz (DA12, CD7 and Project D1) the bit decoupling caps are distinctive blue coloured 100nF dipped radial film caps of some sort. The internet folklore is that these were specially developed for Marantz/Philips and are a key part to the fabulous sound quality that these machines are famous for. I've been unable to find out exactly what they are but my best guess would be metalized polypropylene although I have read at least one (unsubstantiated) claim that they're PPS/foil.
P1110814 by Michael Pickwell, on FlickrIn the Philips CD960 and Marantz CD94 mk1 they are larger than usual 220nF films:
20210508_124811 by Michael Pickwell, on FlickrSome of the best I have used were 100nF Panasonic surface mount PPS, soldered to the pads on the underside of the board.
20170612_153134 by Michael Pickwell, on FlickrIn the Sony CDP-333esd, M75 and CDP-750 they are axial ceramics and I have found that swapping them to polyester films is a big improvement
M75 ceramic by Michael Pickwell, on FlickrM75 film by Michael Pickwell, on FlickrIn my first Philips CD960 I tried 220nF Wima polycarbonates and I thought they sounded very 'clean'.
P1110260 by Michael Pickwell, on FlickrMy second Philips CD960 is still running the original dark green poly caps and I have no desire to change them.
a.palfreyman
pfm Member
Been doing some reading and there seems to be some difference in the audio stages. Most that I have looked at seem to use a transimpedance first stage (i.e. DAC's output current sourced from a virtual earth) whereas the early Arcam Delta 70 uses a voltage divider and discrete transistor stage (followed by an opamp stage with DC servo) whilst the Alpha 5 uses a voltage divider into an opamp stage with final opamp stage and coupling caps. Both of these therefore create a voltage at the DACs audio outputs, dependent on the current being sunk, whereas of course the transimpedance set up doesn't. I do wonder how much of an effect these different arrangements have on the final 'sound'.