Time for some measurements!
Of course, taking to account that my simple homemade system: I use a PC with a Asus Xonar with some ampop mods for measurements, directly on it, without preamp or suchlike.
The measurement suite is the ARTA, running in W10.
First, the limits of my test system:
With own Xonar loopback:
Now, some Valve DAC results:
PWM9, loud mode:
Soft mode:
PWM4, loud mode:
Chaos:
Harmonic distortion vs frequency (PWM9, loud mode, -1dB signal):
J-Test (24bits, 96kHz):
Output without any filter or load (raw):
Valve DAC own noise:
Most of this noise is "airborne" due to a lot of bench PSU I'm using for powering it.
All in all, great results for such a simple output using ancient devices!
Very happy with the results.
Of course, taking to account that my simple homemade system: I use a PC with a Asus Xonar with some ampop mods for measurements, directly on it, without preamp or suchlike.
The measurement suite is the ARTA, running in W10.
First, the limits of my test system:
With own Xonar loopback:
Now, some Valve DAC results:
PWM9, loud mode:
Soft mode:
PWM4, loud mode:
Chaos:
Harmonic distortion vs frequency (PWM9, loud mode, -1dB signal):
J-Test (24bits, 96kHz):
Output without any filter or load (raw):
Valve DAC own noise:
Most of this noise is "airborne" due to a lot of bench PSU I'm using for powering it.
All in all, great results for such a simple output using ancient devices!
Very happy with the results.
Yes, I'm very eager to properly listen to it! 🙂
Since it not have a own PSU (the trafo for it is on the way), I not listened in the main system, in the phones system, or even in stereo.
It not have a enclosure, yet.
Tomorrow I will take my bench PSU's that I used for checking/testing/measuring, for a brief listening in the main system. Is impossible to wait hehe
Since it not have a own PSU (the trafo for it is on the way), I not listened in the main system, in the phones system, or even in stereo.
It not have a enclosure, yet.
Tomorrow I will take my bench PSU's that I used for checking/testing/measuring, for a brief listening in the main system. Is impossible to wait hehe
Thank you for all the measurements! I added a link to them to the opening post.
I knew from my own measurements that the chaotic mode distorts substantially more than the PWM modes, but I could not see the high-order distortion well due to the large resolution bandwidth of my set-up. Interesting...
The only real advantage of the chaotic mode is the reduced out-of-band noise. That is, it has more effective noise shaping, reducing the quantization noise in the first few octaves above the audio band that the output filter cannot suppress much.
I knew from my own measurements that the chaotic mode distorts substantially more than the PWM modes, but I could not see the high-order distortion well due to the large resolution bandwidth of my set-up. Interesting...
The only real advantage of the chaotic mode is the reduced out-of-band noise. That is, it has more effective noise shaping, reducing the quantization noise in the first few octaves above the audio band that the output filter cannot suppress much.
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Good thing I did is to move it to my living room, where my main system sits.
Rewarded with a gorgeous sound! And deserves a detailed "review".
But, not so fast... coincidentally or not, the first 2 recordings I listened are some very muffled DSD versions. I not listened to it from years and had forget about... Then, I remembered that one friend of mine, Maurício Timi from Timi Audio, said to me years ago: the first common sound appliances using sigma-delta DAC's have problems with transients. Oh well. But I also remembered about the different topology here, the high-quality signal processing here, and first rate digital filterings. Not the simplistic ones form the era that my friend specified. So, proceed to listen to a lot of different recordings and sources, including Hi-Res PCM, another DSD ones, Tidal and even mp3. From the first really high-quality recording/version, one thing becomes clear: these famous etched/grainy/edgy sound of digital are absent. And, for the first time in my living room, I felt this being the first DAC to surpass my prefered PCM1704+E88CC Aikido one... the instruments assumed a more realistic sounding, with a excellent reproduction of strings, only for example. Reminded me some very high end good great sounding systems I had listened from time to time. Old great sounding recording, and some famous ones, like the João GIlberto and Stan Getz, and the We Get Requests from Oscar Peterson, sounds awesome here.
And, is fun to FEEL the differences about the recordings for the overall sound, and not focusing in the "space monkeys" (artifacts from audio CODECS and so on). The music simply flows!
True, for muffled recordings, the "etching" from common digital systems makes these recordings brighter and more interesting (less boring), but all the sufficient good ones becomes uninteresting due to the "edgy" sound. And is easy to be used to this sounding, if one not have a better quality equipment (like me before the PCM1704 DAC).
The naturalness and ease of the sound here granted a lot of hours of digital sound listening this weekend. To be frank, last years I not have so much time for a lot of listening, then I end to listen only to my vinil records, and when I try to put digital ones, I ends bored. Not so with the Valve DAC... even those suspect Tidal tracks are more palatable (but at same time it make evident the lesser ones).
Like, the sound of the Valve DAC focuses on the music, instead on the effects; something like that describes it well.
My wife are present in last listenings; she not make any objecton of it. Classified it first-rate. She can be being educated/polite, but I can see that it are very pleasant to her, also because we ended to listen it for almost 2 hours, even with she being tired from last busy days.
The Valve DAC survived even some ultra-torture tests: putting som Bass Mekanik to see if the high bass amplitude not generates some noises within the audio: it pass flawlessy. Also, some so-so recording with super high and compressed treble levels, like the Ramones Loco Live; also passed with flying colors (and is more easy to listen and less congested here). Even the most hardest one: to put a treble EQ for the aforementioned muffled recordings. For some tracks, in general it results not so pretty, but here, it survives well this treatment.
Then, the last listening yesterday was watching the TV, using it. Normally I use a flea valve amp for it, with the PCM1704 DAC. Since Valve DAC have only 500mV for a unbalanced direct out one, I need to use my main amplifier for it (the flea amp not have sufficient gain), so is not a scientific comparision. But, my wife and I both liked that we are listening. Also it is very dynamic with the explosions ;-) and impact sounds.
I started the listening using my 2+2:1 audio trafo for summing the balanced out to a unbal. Yes, it results in only 200mV and is not sufficient to maximum volume of my amplifier, and I don't use pre (I hate preamps). Then, for the rest of listenings, I used one side (unbal) mode, and not felt too much issues; the sounds remained with it's characteristics.
But, for main system, I need to return to the PCM1704 for the common use. Since my target use for the Valve DAC, like I said, will be with a inherent balanced system; the one with Stax 'phone. I use for listening music when my wife are studying, and I even use it for gaming also, since it is connected to my hobby room gaming PC (the same one that I made my measurements); is cool to play games with such a high resolution system... In living room, I use mainly for vinyl, or casual digital listening when working in home (or the TV). And, the PCM1704 is not a bad contender, either...
After this listening, I want to add a unbal out (RCA) to the Valve DAC for using it in the main system when I want to.
I believe the Valve DAC sounding will be perfect with such "revealing" system like these Stax one; it calls for a most natural or less aggressive possible sounding DAC.
So, I'm eager to listen to it with this system.
LAST NOTE: I need to refine the adjustment for the noise trimming trimmers. I only make a fast adjustment for one channel for the measurements***, and for another channel I even not touched it (I prefer to make this when I put in my 'phones amp). Even so, the noise is far from being bothersome; is audible only when at idle, near the speakers.
***perhaps I gain some dB of noise floor if I carefully re-adjust the measured channel.
I'm happy to have contributed something! 🙂
Interesting about the details about the modes.
I can add that even if sounds "the same", I will be happy even so, since is amusing to see this rare appliance with valves working (clock oscillator, demodulator). But is cool to hear it sounding first rate...
And not all equipment are satisfying to me; for example, I tried some time ago (2 times) upgrade a DAC using the PMD-100 and PCM63, only to feels losing time, since it sounded completely without any life in the music, erasing all details of the music. This one belongs to my spare parts now.
Oops. In ther first sentence in the last post, as usual, I misspelled some word: Where reads: I can add that even if sounds "the same", the correct is: I can add that even if sounded "the same".
Soon will arrive here the transformer for making a valve rectified PSU for it, and I can try to find some cabinet.
Even if I not finished it yet (but is working perfectly), I would like to leave my thanks here:
Marcel, many thanks for the generous sharing of this very curious, cool and great project, and thanks for all helping!
Even if I not finished it yet (but is working perfectly), I would like to leave my thanks here:
Marcel, many thanks for the generous sharing of this very curious, cool and great project, and thanks for all helping!
This weekend a visitor listened some 3 of my DAC's: the one from Asus Xonar, the TDA1541 one, and the Valve DAC, using my recently-finished system with plasma tweeter... no magic here, the maximum SPL is indeed limited, but the omnidirectional high treble dispersion is to die for.
Is based on the Linkwitz Pluto system, but with ASP made with tubes/valves... and the amplifiers (well, the bass channel is hybrid).
Photos from testing phase. Exception for the interference response from the plasma cabinet, the response is omnidirectional to deep ultrasonic (good for dogs, mice, cat, bats, etc...).
Results? the TDA1541 blows out the Xonar from mere 5 seconds of track listening, with evident more open and even cleaner sound, and the Valve DAC was the preferred in the end. The TDA1541 is step forward from the Xonar, the Valve DAC are another step, to something great. Then, we listened until the end of listening with the Valve DAC, since the visitor says "NOOO" when I said that I will return to other DAC, hehe 🙂
The Xonar I use for testing, and was included for the sake of perhaps... some "reality check" 😎
This time I don't tried the PCM1704, since it are in another room, and I listened to it comparing between the two, like described in the earlier posting.
With such great result, I'm more curious yet to hear it in my 'phones system. Happy that the power trafo arrived yesterday, and some cabinet are in order.
Is based on the Linkwitz Pluto system, but with ASP made with tubes/valves... and the amplifiers (well, the bass channel is hybrid).
Photos from testing phase. Exception for the interference response from the plasma cabinet, the response is omnidirectional to deep ultrasonic (good for dogs, mice, cat, bats, etc...).
Results? the TDA1541 blows out the Xonar from mere 5 seconds of track listening, with evident more open and even cleaner sound, and the Valve DAC was the preferred in the end. The TDA1541 is step forward from the Xonar, the Valve DAC are another step, to something great. Then, we listened until the end of listening with the Valve DAC, since the visitor says "NOOO" when I said that I will return to other DAC, hehe 🙂
The Xonar I use for testing, and was included for the sake of perhaps... some "reality check" 😎
This time I don't tried the PCM1704, since it are in another room, and I listened to it comparing between the two, like described in the earlier posting.
With such great result, I'm more curious yet to hear it in my 'phones system. Happy that the power trafo arrived yesterday, and some cabinet are in order.
Progress in the main cabinet!
Too bad I make myself manually the holes for the keys, and these become misaligned. Since I forget to draw it when I ordered the cabinet.
I need to retighen the switches for finishing.
Tested and working!
Next week I can start the PSU section.
Too bad I make myself manually the holes for the keys, and these become misaligned. Since I forget to draw it when I ordered the cabinet.
I need to retighen the switches for finishing.
Tested and working!
Next week I can start the PSU section.
I guess I haven't followed enough to understand what you actually built. What's the small PCB connected by ribbon cable? Where's the filter PCB?
The small PCB is a last minute change of filter size I made when I making my BOM list for MOUSER; I decided to try one of smaller cores disponibles (the second in size). For that, I created a new board, since the cores are so smaler than the originals (then I ended not using the original board). But I made a gross mistake: I ordered 10 cores instead of 12. So, for now, for one channel, I used different inductors for last section, but with very close value. Next time when I order something from MOUSER I include the missing cores.
Due to space constraints, I put the board in the cover with these cables, since are flexible for it.
Is a PITA to wind it, especially using very fine wire that I used (something perhaps less than #40AWG). But resulted good; noise is at least equal, near or slight better to original specs (my scope are not so good; is a estimative).
I use only 2 inputs, so a simple switch for it suffices. And for the 3 levels of modulation, I use a commom 2 pole switch with center stop (3 positions) with a "glue logic" to translate 2 contacts to 3 outputs. So I need to use only 2 4-pole switches.
The inputs are a optical S-PDIF and a coaxial S-PDIF.
The outputs are a RCA from one phase, for using it with unbalanced equipment (no trafo for this moment), and mini-XLR for using it with my Stax DIY amplifier (fully balanced).
The function lights remained internal (LED's); only the Ne light for the clipping indicator are on front. Since is easy to open the cabinet.
I also need to organize the PSU cables and put a connector for the umbilical cable, when I work in the PSU.
This are a cabinet from a craftsmanship shop, and not had any finishing, so my wife applied some finishing varnish on it.
Due to space constraints, I put the board in the cover with these cables, since are flexible for it.
Is a PITA to wind it, especially using very fine wire that I used (something perhaps less than #40AWG). But resulted good; noise is at least equal, near or slight better to original specs (my scope are not so good; is a estimative).
I use only 2 inputs, so a simple switch for it suffices. And for the 3 levels of modulation, I use a commom 2 pole switch with center stop (3 positions) with a "glue logic" to translate 2 contacts to 3 outputs. So I need to use only 2 4-pole switches.
The inputs are a optical S-PDIF and a coaxial S-PDIF.
The outputs are a RCA from one phase, for using it with unbalanced equipment (no trafo for this moment), and mini-XLR for using it with my Stax DIY amplifier (fully balanced).
The function lights remained internal (LED's); only the Ne light for the clipping indicator are on front. Since is easy to open the cabinet.
I also need to organize the PSU cables and put a connector for the umbilical cable, when I work in the PSU.
This are a cabinet from a craftsmanship shop, and not had any finishing, so my wife applied some finishing varnish on it.
My PSU are completed! And I have the DAC installed!
Not for conquering any beauty contests, and need to tidy some wires yet, but is working and I'm eager to liten with my Stax phones...
Measurements show that the PSU suffices and not contaminates the noise floor with mains garbage.
The PSU is valve rectified, and heaters are rectified by 8A germanium diodes.
I had a hour for listening to it. Including with games (I also uses the phones and this PC for gaming).
But I had a scary fisrt moment: the sounds are weird and strange... I suspected that one of phones being phase reversed. Especially when I test some game; sounds are diffuse. Then I opened my Stax DIY amplifier and corrected the inverted channel.
Sounded like a boost in the sound!
I prefer it than the ES DAC it replaced. This sounds really special. Even with games is interesting to listen to it, sounding natural and well resolving at same time.
But, a thing to mention:
With phones I noticed something:
When I pause a music, it seems to "memorize" the noise about the last level; I believe due to the PC players leaving DC at pause (not zeroing the data). So I 'reset" the DAC using something in the Windows (eg. opening some folder). When this sound stops, the DAC is silent. Ie., The Windows operate correctly, but the players, not.
For other DAC's this are equal to some POP sound. The Valve DAC DAC not make the POP sound, but leaves some noise.
Other equipment can have this behviour, like CD players.
So, is important to remember this phenomenon when trying to zeroing the noise floor: make sure the DAC is at real zero output.
Not for conquering any beauty contests, and need to tidy some wires yet, but is working and I'm eager to liten with my Stax phones...
Measurements show that the PSU suffices and not contaminates the noise floor with mains garbage.
The PSU is valve rectified, and heaters are rectified by 8A germanium diodes.
I had a hour for listening to it. Including with games (I also uses the phones and this PC for gaming).
But I had a scary fisrt moment: the sounds are weird and strange... I suspected that one of phones being phase reversed. Especially when I test some game; sounds are diffuse. Then I opened my Stax DIY amplifier and corrected the inverted channel.
Sounded like a boost in the sound!
I prefer it than the ES DAC it replaced. This sounds really special. Even with games is interesting to listen to it, sounding natural and well resolving at same time.
But, a thing to mention:
With phones I noticed something:
When I pause a music, it seems to "memorize" the noise about the last level; I believe due to the PC players leaving DC at pause (not zeroing the data). So I 'reset" the DAC using something in the Windows (eg. opening some folder). When this sound stops, the DAC is silent. Ie., The Windows operate correctly, but the players, not.
For other DAC's this are equal to some POP sound. The Valve DAC DAC not make the POP sound, but leaves some noise.
Other equipment can have this behviour, like CD players.
So, is important to remember this phenomenon when trying to zeroing the noise floor: make sure the DAC is at real zero output.
Some frightening moment this weekend: the C48 almost shorted out, putting almost 0V in the CCS grid, and "pulling" more than -100V (referred to -300V) to the reference line. Almost toasted the CCS resistors (they changed the color). It seems I take wrong note about the capacitors I choose to this (are some old tubular ceramic caps, and I tested for voltgae breakdown, but only cold). So, to be sure, I subbed all these related caps (C48/C55 in one channel, and others from other channel), to new ones. I have some spare 100pF/500V SMD ceramic and used it.
The CCS resistors continue measuring the same, so I can use the CAD until I make the next purchase and include it.
EDIT: my mistake, using a not sure value of a component this time. But all others are fully specified.
The CCS resistors continue measuring the same, so I can use the CAD until I make the next purchase and include it.
EDIT: my mistake, using a not sure value of a component this time. But all others are fully specified.
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Just for fun, I switched to the apodizing filter when gaming. Since I think the game creators don't bother about it, so the chain certainly not have an apodizing filter in this case. Even if we consider this being recorded with lossy codecs in general, why mess more with it using subpar systems? Well, but then one thing ocurred to me: we don't know about the original sample rate and I bet the Windows resample it (probably varies between 32kHz and 48kHz). With prior resampling, the apodizing filter is valid? Or makes the things worse due to non-original sample rate?
Even if I not noticed differences yet, at least for using the disponible resource...
Or, in doubt, maintain the steep filter?
Even if I not noticed differences yet, at least for using the disponible resource...
Or, in doubt, maintain the steep filter?
Windows does resample by default. They called it "shared mode," which has the effect of resampling all audio the "default" sample rate and bit-depth setting for the particular sound device.
When a signal gets sample-rate-converted in the signal chain from the ADC to the DAC, the apodizing filter should be inserted where the sample rate is at its lowest, otherwise it can't apodize the signal chain. When the sample rate at that point is too low, you may get noticable treble loss when you switch on the apodizing filter.
Understood. Different from eg.Foobar, where the music dictate the samplerate and we can "directly" send to output (maintaning sample rate), games don't have this mode.
So, the best choice is indeed the steep filter (not using apodizing for that).
Thanks to all for the infos.
So, the best choice is indeed the steep filter (not using apodizing for that).
Thanks to all for the infos.