Hi,
A few years ago I was building a music streamer based on a pc and TDA1541 board.
Changing the original switching power supply to linear one made a great improvement.
Splitting to two power supply - one for the DAC and one for the computer helped a lot!
Upgrading the OPAMP of the DAC to a higher quality ones mad a great improvement.
The sound is great, but a little "too compressed" as opposed to my DIY turntable. And here goes my question: do you think that building a tube-output stage instead of the om-amps can help? I rely love the sound of the TDA1541, and, yes, I know it is a very old cheep. 🙂 I'm building a new streamer, based on a Raspberry Pi, and there will be much less wires in the new version... Is it time for tube output stage?
Any advice or direction to a proper kit / schematics will be highly appreciated.
A few years ago I was building a music streamer based on a pc and TDA1541 board.
Changing the original switching power supply to linear one made a great improvement.
Splitting to two power supply - one for the DAC and one for the computer helped a lot!
Upgrading the OPAMP of the DAC to a higher quality ones mad a great improvement.
The sound is great, but a little "too compressed" as opposed to my DIY turntable. And here goes my question: do you think that building a tube-output stage instead of the om-amps can help? I rely love the sound of the TDA1541, and, yes, I know it is a very old cheep. 🙂 I'm building a new streamer, based on a Raspberry Pi, and there will be much less wires in the new version... Is it time for tube output stage?
Any advice or direction to a proper kit / schematics will be highly appreciated.
Two comments, possibly relevant, probably not believed: First is that comparisons between (uncompressed) old vinyl and current (compressed, because we're assumed to be stupid) CDs isn't an apples-to-apples comparison. Vinyl has no magic ingredient except that it didn't lend itself to modern "mastering", so couldn't be damaged as casually.
Second is that the D/A conversion needs to work into a very low impedance summing junction, and this is hard to do with vacuum valves. The brute force approach, a very small resistor, less than 10R, is the usual choice, but is its own compromise. Vacuum valves also have no magic ingredient to "add" - all changes to signal are bad. There are no "good distortions". Let others drink that KoolAid; they're mistaken. Told you you wouldn't believe me.
All good fortune,
Chris
Second is that the D/A conversion needs to work into a very low impedance summing junction, and this is hard to do with vacuum valves. The brute force approach, a very small resistor, less than 10R, is the usual choice, but is its own compromise. Vacuum valves also have no magic ingredient to "add" - all changes to signal are bad. There are no "good distortions". Let others drink that KoolAid; they're mistaken. Told you you wouldn't believe me.
All good fortune,
Chris
If I can add a pebble to the pile of gravel, I will first ask myself questions about signal processing before wanting to add a floor to an already complex whole.
Moreover, we cannot say that the 1541 is the master of transparency, it excels rather in the natural, in the bass and the low mid/mid, is never brilliant, it is rather a chip which knows how to to forget .
And I quite agree with Chris, if I had to make a hardware choice rather than software, I would go for a low value I/V resistor between 10 and 80 ohm.
Once again, try the soft side first before tackling the hard side.
Moreover, we cannot say that the 1541 is the master of transparency, it excels rather in the natural, in the bass and the low mid/mid, is never brilliant, it is rather a chip which knows how to to forget .
And I quite agree with Chris, if I had to make a hardware choice rather than software, I would go for a low value I/V resistor between 10 and 80 ohm.
Once again, try the soft side first before tackling the hard side.
It's hard to comment on this branch of topics without stepping on someone's religion, so we're all tip-toeing around. The very low input Z at the summing junction is a Given, for best monotonicity (here, low distortion at low signal levels), and it's made either by brute-force (resistor 10R or less) or shunt applied negative feedback. But it has to be done some way.
If <10R shunt resistor, signal is small and amplification has noise issues to overcome. If summed into a feedback amplifier, the amplifier needs to work really well way up several decades above the audible range, which is also tricky. So the problem shouldn't really be defined as one of vacuum valves vs. (presumably monolythic semi-con) opamps, but rather as the best solution to a surprisingly difficult, and often overlooked (in DIY), problem.
Some interesting approaches come from folk making phono stages for low output MC cartridges: similar challenges.
All good fortune,
Chris
If <10R shunt resistor, signal is small and amplification has noise issues to overcome. If summed into a feedback amplifier, the amplifier needs to work really well way up several decades above the audible range, which is also tricky. So the problem shouldn't really be defined as one of vacuum valves vs. (presumably monolythic semi-con) opamps, but rather as the best solution to a surprisingly difficult, and often overlooked (in DIY), problem.
Some interesting approaches come from folk making phono stages for low output MC cartridges: similar challenges.
All good fortune,
Chris
If you really want to use valves in a DAC: https://www.diyaudio.com/community/threads/valve-dac-from-linear-audio-volume-13.308860/post-5104207
But actually, I think the comment of Chris in post #2 is spot on: it could very well be due to mastering differences.
But actually, I think the comment of Chris in post #2 is spot on: it could very well be due to mastering differences.
I agree with the comments about mastering.
It got much worse when digital radio was introduced.
It looks like you have selected a good motherboard with good onboard sound.
Add a good amount of storage and copy from vinyl to your own digital server.
One of the best CDs I ever bought was a pirate copy made from vinyl scratches and all. It was in a reduced to clear basket at a supermarket.
It got much worse when digital radio was introduced.
It looks like you have selected a good motherboard with good onboard sound.
Add a good amount of storage and copy from vinyl to your own digital server.
One of the best CDs I ever bought was a pirate copy made from vinyl scratches and all. It was in a reduced to clear basket at a supermarket.
A particularly bitter example of mastering butchery is the Van Morrison catalog. The original Warners vinyl sounded perfectly fine, and their 1980s era CDs, despite the technical limitations of the time, sounded just as good and without the zillion plays' wear of everybody's (well, geezers') vinyl. The 1997 re-masterings sounded very wrong, and the 2008 re-re-masterings are almost not recognizable. Other Warners/Reprise artists seem to have kept more control over their catalog, zb Joni Mitchell, but apparently, nobody is really safe.
I'm sorry, but anybody who would do that to Van Morrison will have to answer to a higher power, and the sooner the better.
Harrumpf!
Chris
I'm sorry, but anybody who would do that to Van Morrison will have to answer to a higher power, and the sooner the better.
Harrumpf!
Chris
Thank you for the feedback!
Yes, I do aware for the fact that tubes don't "add magic", and everything will sound live and vivid 🙂 However, running a tube amplifier (EL34) with vintage speakers (KEF Concerta) I simply like this kind of sound, I guess.
I will look into the links you kindly gave me, thanks!
And Chris, what is the compromise in the 10R resistor? That is, what might be the impact over the sound?
Thanks,
Jacob
Yes, I do aware for the fact that tubes don't "add magic", and everything will sound live and vivid 🙂 However, running a tube amplifier (EL34) with vintage speakers (KEF Concerta) I simply like this kind of sound, I guess.
I will look into the links you kindly gave me, thanks!
And Chris, what is the compromise in the 10R resistor? That is, what might be the impact over the sound?
Thanks,
Jacob
See post #5, "If <10R shunt resistor, signal is small and amplification has noise issues to overcome." Although it says < 10 ohm, the same holds with any small resistor.
If I were to interpret your question as "Why can't I just make the resistor bigger?" it would go like this: D/A converters like the TDA1541 reconstruct samples by summing currents from a bank of current sources, some turned on and some turned off, differently for each sample. The current sources are not ideal; rather, they are a ladder of matching resistors fed from a small DC voltage source. Any additional resistance contributes its share to the summed voltage, so you can see how small current sums could be unduly influenced by an extra, unwanted, resistor in series.
The sonic impact of this imperfection in monotonicity is in the same category as other (very) early CD issues, or amplifier crossover distortion - it's a defect that increases as signal level decreases, so is unnatural.
All good fortune,
Chris
The sonic impact of this imperfection in monotonicity is in the same category as other (very) early CD issues, or amplifier crossover distortion - it's a defect that increases as signal level decreases, so is unnatural.
All good fortune,
Chris
An alternative of a small I/V resistor could be a step-up transformer. It can be combined with a tube voltage amplifier stage, or can be used in itself.
I wonder what effect spreading inductance has on DAC settling. Do you put some low-impedance RC circuit on the primary side?
My latest project is a three balanced input, X10 tube buffer with transformer balanced to SE outout.
This will enable me to switch using relays, between my balanced 1541 dac (75r I/V resistor), Chiurutu's balanced R2R no DPS dac and modified Kenwood DP7060 (TDA1547 (Dac 7) with balanced outputs on pins 14,15 and 21,22).
This will enable me to switch using relays, between my balanced 1541 dac (75r I/V resistor), Chiurutu's balanced R2R no DPS dac and modified Kenwood DP7060 (TDA1547 (Dac 7) with balanced outputs on pins 14,15 and 21,22).
Based on this article, I "lampized" my Sony 227ESD CD player with very good results. The CD player has two TDA1541 DACs. I used two 6N2P-EV tubes in SRPP configuration. Maybe you can use it as a source of inspiration.
http://lampizator.eu/LAMPIZATOR/REFERENCES/sony 227esd/sony227.html#NOS_for_the_SONY_CDX1088_digital_filter
http://lampizator.eu/LAMPIZATOR/REFERENCES/sony 227esd/sony227.html#NOS_for_the_SONY_CDX1088_digital_filter
Yes, there is much of interest on the lampizator.eu website.
https://www.lampizatorpoland.com/lampizator-blog
https://www.lampizatorpoland.com/lampizator-blog
You have to calculate with the T = L / R formula. T = 1 / ω, ω = 2 * π * f
The R can be on the primary or on the secondary (reflected to the primary), or both.
I would prefer the primary, as otherwise you have the spreading inductance in series with the transformed impedance.
DACs are fundamentally single ended, so also have a big DC component to be dealt with.
All good fortune,
Chris
All good fortune,
Chris
After working extensively with the TDA1541 I eventually abandoned it and went with the more modern PCM1794. The PCM1794 series allows you to do a dual mono configuration with differential outputs for balanced output. I fed these differential outputs into differential tube stages, with output transformers to sum the signal. Low resistance I/V resistance is mandatory- 10-47 ohms requires high gain and can result in high noise if trying to amplify the resultant signal enough to use. A differential dual mono topology allows you to reject much of the noise.
Still, even after all that I still found better sound, lower THD, and better performance using vintage Signetics NE553x op-amps, and gave up on tube I/V stages.
Still, even after all that I still found better sound, lower THD, and better performance using vintage Signetics NE553x op-amps, and gave up on tube I/V stages.