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Integral nonlinearity (INL), THD, etc., in multi-bit DACs
Integral nonlinearity (INL), THD, etc., in multi-bit DACs
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Old 10th April 2018, 06:34 AM   #11
xx3stksm is offline xx3stksm  Japan
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Pcm1704 is already obsolete and now almost gone from the market. I was trying to make generic pcm1704 (not original but same function) for several years. My first choice was LTC2642, which has better glitch performance(0.5nVs) than AD5547(3.5nVs). This is tolerable in an audio application without using deglicher by S/H. My current audio system has both pcm1704 and LTC2642. I compared them carefully and concluded my preference is pcm1704 because it has soft sound like a film camera. The difference exists between them. LTC2642 has clearness like a video camera. Some people may prefer the clarity. I don't know glitch can make the difference. It was a little bit surprising to me they had the difference. Anyway, my first attempt to make generic pcm1704 was not successful.

The second approach was from last year. I needed to find glitch free DAC except for pcm1704. High-speed DAC for RF application is basically glitch-free in the audio band because their clock is very high. DAC2904(14bit 125MSPS) has 0.002nVs glitch. The best solution for audio application is AD9117(14bit 125MSPS) as long as I have tested. AD9117 has at least 15bit equivalent accuracy after internal calibration. Parallelling by two channels of AD9117 has better THD+N performance than pcm1704 by slight DSM to extend bit resolution up to analog noise floor. Up to 15-bit resolution, it operates in multi-bit. From 16bit to 20bit(analog noise floor) is done by DSM.

The second attempt has almost finished. I'm now trying to design PCB. High-speed DAC has another advantage of coexistence with DSM. AD9117 has two possibilities, multi-bit and DSM because of its high sampling rate. DSM(5-bit quantizer) has better THD than multi-bit because it can have digital calibration which multi-bit can't do. My prototype board has large-scale FPGA(xc7a100). It takes some time to shape up the size to small-size one(probably xc6slx25). Unfortunately, I was forced to give up QFP package which is DIY friendly because I wanted to implement both multi-bit and DSM. But now I'm sure the goal is around the corner.
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Old 10th April 2018, 07:12 AM   #12
abraxalito is offline abraxalito  United Kingdom
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Very interesting indeed to hear of your results with non-audio DACs, xx3stksm. I've for some time thought that comms DACs would be an interesting avenue to explore for audio.

What are your thoughts on output stages - the AD9117 is a current-out device, 2-20mA full scale?
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Old 10th April 2018, 07:19 AM   #13
Alexandre is offline Alexandre
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Looking forward to learn from you guys and the development of this discussion.

I wish there was a measurement that correlates with listening satisfaction. I for one am still listening to the TDA1543 and it is an absolute winner for me. John (ECDesigns) says the jitter signature of this particular chip makes it a winner. He also said it resembles an analog tape machine (I agree with his impressions). Itīs somewhere on that giant thread of his.

BTW, I and Richard (Abraxalito) had been discussing small differences between the TDA1543A and the TDA1543. I just wanted to say for the record that the non-A chip is the magic one for me. I havenīt been as happy with the TDA1543A, and believe me when I say I wanted to be happier. Because it fixes some issues with the internal logic of the chip. But it just didnīt give me the emotional response I was used to.
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Old 10th April 2018, 08:50 AM   #14
Alexandre is offline Alexandre
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I have a hunch... The missing measurement is the "time aberration" (my idea of a name ). The Dutch know all about it

See for example:
5534 audio amp

And:
https://www.by-rutgers.nl/ME6211-PRO37R.html

Quote:
I stick to Burr Browns OPA(2)134 because it sounds so good in high impedance applications! Is there no better sounding one? Hardly. Henk ten Pierick developed a measuring program with which he is able to rank the sound of all kind of amplifiers (with tubes, discrete transistors or IC's). He inputs two signals to the DUT: a rather large signal at a low frequency (say 100 Hz) and a smaller high frequency signal (at about 5 kHz) and measures the 'jitter' on the high frequncy signal at the output of the DUT. I do not go into details of his method because:
1. For his method a >$50,000 WaveCrest DTS-2075 time measurement instrument is needed so it has less sense to publish the method.
2. The human sense of hearing seems to be very susceptible to the 'jitter' low frequency signals bring about high frequency signals. You should believe this because no medical reason can be found and the IPO did not investigate it!
3. Henk does not want publishing.

Henk measured a great number of op amps...... Anyhow, an OPA134 follower scores high.
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Old 10th April 2018, 08:55 AM   #15
Alexandre is offline Alexandre
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To finish my "case"
Example of a successful / well-regarded product using both TDA1543 and OPA134:
The Altmann Attraction DAC
Quote:
The performance standard of your ALTMANN ATTRACTION DAC is A Performance Standard.

Last edited by Alexandre; 10th April 2018 at 09:00 AM.
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Old 10th April 2018, 09:11 AM   #16
Alexandre is offline Alexandre
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More from user PA0SU (Rutgers)... https://www.by-rutgers.nl/ME6211-PRO37R.html

Quote:
In the last fifteen years I have built many amplifiers for the ME62 and the PRO 37R (also see the Dutch article [PAoSU]). Electret Microfoons', on my website). The one sounded a little bit better than the other until the OPA134 with the bootstrap came in sight, together with the rutgerS'Clock in the ADC!
The progress is remarkable: strings are 'soft as butter', harps become transparent, pianos sound like live pianos, recorded concerts come into the room as re-living them, switching-off pains.

With the microphones showed above, my recordings undercut many commercial classic concert recordings.
A low jitter clock (<1 ps) is a precondition to discover the differences in full proportions.

Without the help of Henk ten Pierick I never could have made this progress!!
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Old 10th April 2018, 10:29 AM   #17
xx3stksm is offline xx3stksm  Japan
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Quote:
Originally Posted by abraxalito View Post
Very interesting indeed to hear of your results with non-audio DACs, xx3stksm. I've for some time thought that comms DACs would be an interesting avenue to explore for audio.

What are your thoughts on output stages - the AD9117 is a current-out device, 2-20mA full scale?
It's easier to design I/V stage of high-speed DACs rather than audio DACs like pcm1792 because bandwidth is beyond the capability of an OP amp. Analog Device recommends transformer conversion since they are RF and easy to have high-performance SMD transformer. But my target is the audio band and not allowed to use a transformer. Audio band transformer is like OPT for a tube amp. The only solution is a passive one. One register is the best selection which has excellent performance up to 100MHz irrelevant to a current value. Fortunately, DACs for RF have relatively wide compliance voltage. From +0.5V to -0.5V has no performance degradation. You can achieve -120dB THD by DSM. But you need five-minute warming up after power on. Even a monolithic ICs, -120dB requires such stabilizing time. I think a passive I/V is superior to active one If you want to use 11.2MHz DSD in pcm1792.

As to current value, I have tested eight or nine RF DACs(14bit and 16bit with 2mA to 30mA). AD9747 is 16bit with 30mA and has the best SNR in RF as long as I have tested. But it has almost the worst SNR in the audio band. I'm sure it has high performance in RF but not in the audio band. AD9117 is low power version of AD9767 which is a junior version of AD9747. So, AD9117 is far junior to AD9747 but is the best in the audio band. RF DACs have strange inherent performance in the audio band. The more current doesn't mean good performance, usually have an inverse effect. Unexpectedly, low current AD9117(I use it with 6mA) has the best noise power in the audio band. Paralleling two channels achieves 108dB(without A filter). Pcm1792, which is the champion for me, is 112dB in the same circumstance. If you parallel four channels(two AD9117), you can achieve 111dB.
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Old 10th April 2018, 01:20 PM   #18
xx3stksm is offline xx3stksm  Japan
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Sorry, I mistook the part number.
AD9117 is wrong. AD9717 is correct. There are many similar part numbers.
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Old 10th April 2018, 02:46 PM   #19
hollowman is offline hollowman  United States
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Default Yggy metrics

Quote:
Originally Posted by abraxalito View Post
Amir made some measurements (on ASR : Measurement and Review of Schiit BiFrost Multibit DAC | Audio Science Review (ASR) Forum) of one of Schitt's DACs that uses the AD5547. The result of interest to me was the linearity, which looks quite appalling. Mike Moffat said that the result shows a broken DAC but another guy on a different forum found pretty much the same issue with his measurements.
Stereophile's measurements of Schiits Yggy - -which uses the high $$ AD DAC -- are summarized here :
Quote:
It's difficult to sum up the Schiit Yggdrasil's measured behavior. While the processor's analog circuitry is superbly well designed, its digital circuitry appears to have problems with high-level, high-frequency tones, and with the LSBs of 24-bit data. It's possible, of course, that the former will be rare with music, and that the latter will be obscured by the noise floors of recordings. But it does look as if the digital circuitry is not fully optimized. Hopefully, this could be addressed with a firmware upgrade.
—John Atkinson
Dunno ... maybe their DACs were designed by ear?? Still, with Mike Moffat (co-founder of Theta), and with old Theta's measuring much better, the poor lab performance is confusing. That said, non-oversampling DACs (Zanden, etc.) also have tend to produce poor lab metrics.
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Old 11th April 2018, 07:27 PM   #20
miro1360 is offline miro1360  Europe
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AD1862 is superior DAC (still be in fair price on ebay, DIP packages are dismounted from older electronic, this can be guarantee of genuine) ...

PCM1704 (also superior DAC but overpriced) ... from ebay si problem because they are dismounted using hot-air and this process often degrade parameters or destroy smd chip ...
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