Would you be able to tell how much skew between BCK and LRCK was acceptable for the ES9039Q2M at 768k?
So for 192k it should be even better? Or is the state machine dependant on absolute skew regardless of SR?
This an "angst question"
we will soon find out on our own. But we have a signal distribution block ahead of the I2S receivers that introduce about 0.5nS delays because of different trace lengths on the distribution board. It is a up to 14 channel multichannel DAC...
From the I2S timing diagram I figured we should be good at 192k. But who knows as long as you have not tried Will keep you updated!
Thanks for your timely answers!
This an "angst question"
we will soon find out on our own. But we have a signal distribution block ahead of the I2S receivers that introduce about 0.5nS delays because of different trace lengths on the distribution board. It is a up to 14 channel multichannel DAC...From the I2S timing diagram I figured we should be good at 192k. But who knows as long as you have not tried
Will keep you updated!Thanks for your timely answers!
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D
Deleted member 148505
Victor's osc arrived. I just powered it with SMPS for a quick measurement. 2.2Vrms out
With coherent averaging, the harmonics jump all around so I have to choose a good capture.
So far, the Cosmos APU's H3 can resolve -140dB so the unit that I have looks operating normally.
Here's with Motu Ultralite MK5 DAC and ADC (with APU in the middle)
With coherent averaging, the harmonics jump all around so I have to choose a good capture.
So far, the Cosmos APU's H3 can resolve -140dB so the unit that I have looks operating normally.
Here's with Motu Ultralite MK5 DAC and ADC (with APU in the middle)
You must use „Show phase of harmonics“ option, with coherent averaging. Otherwise, distortion numbers are from 6 to 20 dB better than in reality. Or just install latest REW 5.30.
https://www.avnirvana.com/threads/“show-phase-of-harmonics”-changes-calculated-distortion-in-case-of-coherent-averaging.12631/
https://www.diyaudio.com/community/...ion-measurements-with-rew.338511/post-7475209
https://www.avnirvana.com/threads/v5-30-beta-release.12707/
D
Deleted member 148505
@tombo56 thanks for the headsup, I've installed the latest version.
@IVX APU is set to 0dB. Maybe some problem with Victor's power supply as it is directly connected to LRS-350-36, cabling is also shoddy.
Victor's osc
Victors osc with coherent avg
Here's with Motu UL MK5 DAC + ADC with 1.8Vrms output.
Without coherent avg
@IVX APU is set to 0dB. Maybe some problem with Victor's power supply as it is directly connected to LRS-350-36, cabling is also shoddy.
Victor's osc
Victors osc with coherent avg
Here's with Motu UL MK5 DAC + ADC with 1.8Vrms output.
Without coherent avg
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Something does seem amiss with your Victor oscillator set-up.
This is what I get. This is a much older - maybe 10 years old - oscillator from Victor into a Cosmos Scaler set for 0 dB of gain to a Cosmos APU to a Cosmos ADC. Battery power for the oscillator. The oscillator was set for -0.5 dB from 2Vrms output. 384 KHz sample rate. No coherent averaging. This was made with the previous version of REW, but since coherent averaging is turned off, I'm not sure that matters for this.
I see that newer oscillators from Victor have a much better "base spread" from oscillator phase noise than my earlier version does. Progress!
A couple other observations...
You can save a screen shot of the RTA window by clicking on the camera button in the upper left. No need to use Windows screen capture.
Since you're using the high pass filter at 20 Hz, there's no real need to start the spectrum display at 2 Hz. 20 Hz is fine.
This is what I get. This is a much older - maybe 10 years old - oscillator from Victor into a Cosmos Scaler set for 0 dB of gain to a Cosmos APU to a Cosmos ADC. Battery power for the oscillator. The oscillator was set for -0.5 dB from 2Vrms output. 384 KHz sample rate. No coherent averaging. This was made with the previous version of REW, but since coherent averaging is turned off, I'm not sure that matters for this.
I see that newer oscillators from Victor have a much better "base spread" from oscillator phase noise than my earlier version does. Progress!
A couple other observations...
You can save a screen shot of the RTA window by clicking on the camera button in the upper left. No need to use Windows screen capture.
Since you're using the high pass filter at 20 Hz, there's no real need to start the spectrum display at 2 Hz. 20 Hz is fine.
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Actually, the 3rd harmonic gets almost 20 dB worse when working into the 10K load of the APU instead of the 100K of the Scaler. I just checked that now.
But, as I said, my oscillator is probably 10 years old. Victor has made a lot of improvements since then.
This is what I just measured.
Victor oscillator > Scaler > APU > ADCiso. Same levels as before, within a tenth of a dB.
This is the latest version of REW, with coherent averaging turned on.
But, as I said, my oscillator is probably 10 years old. Victor has made a lot of improvements since then.
This is what I just measured.
Victor oscillator > Scaler > APU > ADCiso. Same levels as before, within a tenth of a dB.
This is the latest version of REW, with coherent averaging turned on.
As Cosmos devices become more widespread, more and more questions arise regarding LPF for measuring class D amps. In addition, measurements of some DACs are also complicated by unfiltered RF content.
As I see, users have already rushed to copy the AP AUX0025 filter, which is not optimal or is simply unsuitable for measuring DR of DACs, due to the high impedance = noise, and it may limit class D as well, at least best of Class D amps. In connection with the above, I want to develop the concept of a simple, affordable, and versatile LPF, suitable for both class D and DACs.
Required:
1) low impedance, for the least noise, and minimal distortion.
2) built-in R/R divider with several stages, approximately from 0 to 15 dB.
3) The 4th order of AUX0025 is generally useless, especially if you need a measurement bandwidth of up to 20 kHz, the 2nd order is enough, i.e. LCR about -30db at 400kHz.
4) LPF, of course, is differential(balanced) and capable of operating at different input impedances from 400 ohm Cosmos ADC to 100k Cosmos Scaler.
If there is a divider, then it is advantageous for us to add an LPF after it, so that only the input resistor operates at max voltage, unlike the AUX0025, where all its parts have to be taken for a high voltage. In order not to wind the air coils, you can take a standard SMD part TDK for 1-2A, with a closed core, which will provide immunity from external EMI and distortion below -130dB, which is quite ok for class D and for measuring DAC's DR. You can have two series inductors, for less distortion, and for switching the LPF frequency, if necessary. It turns out that the input resistor will have to be combined from a few MELF0207, about 1000 ohms at maximum, so, to collect a power of 50V^2/1000ohm=2.5W from them in series, and a gold-plated DIP-Switch on them to configure the divider coefficient. Good one 1206 100V 100n C0G/NP0 will give H3 <-140dB at 1kHz and 5V, so not a problem either, especially since <100nF is required. The output resistor of the divider is switchable, in the case of measuring the DAC's DR, i.e. when a divider should be 0 dB, and for class D 200-400 ohm MELF0207 can be used on the same DIP-Switch to give three positions: 200, 400, Off. The output impedance of DACs may be a hundred ohms, but I hope not more nowadays, the switch mentioned above can be useful here, to short one of the composite inductors and adjust the LPF's cutoff. It is clear that due to the very different impedances, such an LPF with the frequency response of a beautiful Butterworth is impossible, I think we can ignore that and prepare several calibrating files for REW, that's a great simplification of HW LPF.
The demand is low, I think 300-500 pieces/year, so for $20 it can be done in the form of RSVA, it could be cheaper, but delivery is at least $5, and Aliexpress also will take 8%.
As I see, users have already rushed to copy the AP AUX0025 filter, which is not optimal or is simply unsuitable for measuring DR of DACs, due to the high impedance = noise, and it may limit class D as well, at least best of Class D amps. In connection with the above, I want to develop the concept of a simple, affordable, and versatile LPF, suitable for both class D and DACs.
Required:
1) low impedance, for the least noise, and minimal distortion.
2) built-in R/R divider with several stages, approximately from 0 to 15 dB.
3) The 4th order of AUX0025 is generally useless, especially if you need a measurement bandwidth of up to 20 kHz, the 2nd order is enough, i.e. LCR about -30db at 400kHz.
4) LPF, of course, is differential(balanced) and capable of operating at different input impedances from 400 ohm Cosmos ADC to 100k Cosmos Scaler.
If there is a divider, then it is advantageous for us to add an LPF after it, so that only the input resistor operates at max voltage, unlike the AUX0025, where all its parts have to be taken for a high voltage. In order not to wind the air coils, you can take a standard SMD part TDK for 1-2A, with a closed core, which will provide immunity from external EMI and distortion below -130dB, which is quite ok for class D and for measuring DAC's DR. You can have two series inductors, for less distortion, and for switching the LPF frequency, if necessary. It turns out that the input resistor will have to be combined from a few MELF0207, about 1000 ohms at maximum, so, to collect a power of 50V^2/1000ohm=2.5W from them in series, and a gold-plated DIP-Switch on them to configure the divider coefficient. Good one 1206 100V 100n C0G/NP0 will give H3 <-140dB at 1kHz and 5V, so not a problem either, especially since <100nF is required. The output resistor of the divider is switchable, in the case of measuring the DAC's DR, i.e. when a divider should be 0 dB, and for class D 200-400 ohm MELF0207 can be used on the same DIP-Switch to give three positions: 200, 400, Off. The output impedance of DACs may be a hundred ohms, but I hope not more nowadays, the switch mentioned above can be useful here, to short one of the composite inductors and adjust the LPF's cutoff. It is clear that due to the very different impedances, such an LPF with the frequency response of a beautiful Butterworth is impossible, I think we can ignore that and prepare several calibrating files for REW, that's a great simplification of HW LPF.
The demand is low, I think 300-500 pieces/year, so for $20 it can be done in the form of RSVA, it could be cheaper, but delivery is at least $5, and Aliexpress also will take 8%.
The AUX0025 was designed whe switching amps were switching as low as 80 KHz. And the 80 KHz would really mess up the internals of the analog inputs on an AP system 1. Things are better today but the switching residue is still a problem. In the older analog systems they can't easily (if at all) differentiate between switching residue and noise and distortion. Today it would be more of an issue with the switching beating with the sample rate and causing sidebands/aliases. Ferrite cup cores can work great as long as the current is low enough to not get to nonlinearities.