SMSL DO400 DAC & HP Amp Review (NTTY)

[torgeirs]

The little hump does not look to come from the ADC

Should the ADC be DAC here?
The auto gain try to output 4 volts.
So gain is 26 dB at -50 to -26.
Interesting numbers coincidence though. The autogain is perfect for the ADCiso
Thanks for showing that autogain can be used with REW

 

[IVX]

BTW, REW has the settling time adjustment in case the autorange is too slow.

 

[torgeirs]

Look:

https://www.audiosciencereview.com/forum/index.php?attachments/loxjed40pro-imdsmpte_educ-jpg.543852/

The lower level (purple) trace is very similar to what I reported for the DO400. The little hump does not look to come from the ADC.

If the dB scales on (guess it must be ) generator level and IMD level has same spacing the square of the autogain betterment is easyer to see. Near 26 dB better IMD measurements max.
Guess ‘input level of ADC’ graph will look weird with autogain as the input level of the ADC will be about the same for 26 dBs of generator level.

 

[NTTY]

Should the ADC be DAC here?

No, I really meant the ADC as that was the initial question

The auto gain try to output 4 volts.
So gain is 26 dB at -50 to -26.

Yep and note the ADC is set at 10Volts max input, because that’s my preferred setup.

Interesting numbers coincidence though. The autogain is perfect for the ADCiso
Thanks for showing that autogain can be used with REW

BTW, REW has the settling time adjustment in case the autorange is too slow.

Indeed, and from memory I went 100ms.

 

[torgeirs]

No, I really meant the ADC as that was the initial question

To me the hump looks to orginate from the ADC. Don’t understand how fixed gain can introduce a hump in the DAC?
Guess it will be settled with a check of generator level or Measurement level

 

[torgeirs]

Or maybe @IVX can settle it by stating. ‘The ADCiso don’t have a hump!’
I will continue to use the combo anyway. If it has a hump or not

 

[NTTY]

To me the hump looks to orginate from the ADC. Don’t understand how fixed gain can introduce a hump in the DAC?
Guess it will be settled with a check of generator level or Measurement level

There’s no introduction of hump in the DAC.

The difference between the two measurements is because of the (up to) 20dB difference in gain (from the scaler to the ADC) between the two measurements, making noise to dominate the IMD results in one case (blue trace at low lower levels in the previous page graph).

 

[torgeirs]

I have no problem measuring distortion down at the -160 dB level if FFT is long enough, so still dont understand.
At -140 the noise has to be in the -100 dB FS range to camuflate distortion at -140 dBFS

Think this is a very useful feature if the scaler-ADCiso so thats why i’m pondering this.
To set the ADCiso to 5volts and scaler to autorange with a REW pause between measurement seems like a golden ticket to clean measurements. So thank you again
Did not bring my combo on holyday so can’t verify myself at the moment.

 

[torgeirs]

Here is 3 measurements, all with x9039 DAC. D200 from SMSL

• DAC into 1kHz LPF (Low pass filter). Removes some distortion from DAC. 6dB Gain at 1k
• DAC into Scaler. 7 dB Gain
• DAC into Scaler 26dB Gain

THD vs generator level, dBFS and dBr

So can see the DAC has a large distortion hump starting at -44dB and rises 15 dBs in only 3 dBs generator level difference.

But are the ADCiso free of charge?

 

[torgeirs]

Nope
On the ADCiso the distortion starts to rise at lower dB generator level. The ADCiso distortion at -44dB meet the DAC distortion at about the same level.
+ 6dB distortion from DAC and ADC versus ADC alone

 

[torgeirs]

DAC-LPF-ADCiso at 1.7V and 10V sensitivity


DAC-Scaler 7dB gain-ADCiso at 1.7V and 10V sensitivity


DAC-Scaler 26dB gain-ADCiso at 1.7V sensitivity

 

[torgeirs]

Over is 1k sine but all frequencies hits the THD wall of the DAC, 26dB gain on scaler

 

[torgeirs]

Just a few overlays to show that autogain and gain 26 is same under -4V out
0dB gain of scaler and 26dB or autogain
Genarator level and input level. Both dBr

Notice funny effect of autogain and input level near 0dB on X axis

This is autogain 0.1 dB step measurement. 1k. 2nd and 3rd forms a perfect THD storm in DAC at -44dBFS


Same with dBFS.
Gets that sawtooth feeling in the last 26dBs

 

[NTTY]

I’ll grab my D200 too and run the same, when time allows.

 

[torgeirs]

Guess the aurogain gives most improvement for the worst grades of the ADCiso, but that will be interesting to see. Maybe not.
5 to 8 dB improvement in THD measuements between -40 and -15 generator dBFS is quite a feat for the scaler on my B grade ADCiso