[gaboo]

1212m/1820m have this ultrasonic rolloff issue.

From the 48Khz RMAA numbers, it seems that 0404 does not start to roll off as much, i.e. 0.5dB on 1212m at 20Khz. But I cannot find any 192Khz (which require the brand new drivers), or even 96Khz RMAA results.

Would anyone here be so kind to test 0404 at 192Khz?

 

[lan]

I thought the new drivers aren't out till December?

 

[S_Dedalus]

My 0404 is +.2dB at 20Khz and around -4 at 40Khz

 

[gaboo]

You probably measured in loopback, which may be one reason. I think 0404 has worse AD than 1212m. If it is anything like 1212m, then the AD filter is digital, so it should move with Nyquist. But it might have even a worse analog DA filter...

1820m only goes down -1.75dB at 40Khz (on 192Khz clock).

 

[Glassman]

stop that panic gaboo, 1212m has 0.2dB @ 20kHz on it's outputs, 0404 has different filter and actually amplify HF content a bit before it acts as a low pass filter, that is a common behavior of certain types of analog filters..

 

[gaboo]

Quote:

Originally Posted by Glassman stop that panic gaboo, 1212m has 0.2dB @ 20kHz on it's outputs, 0404 has different filter and actually amplify HF content a bit before it acts as a low pass filter, that is a common behavior of certain types of analog filters..

By panic you mean false hope that 0404 may be better in this respect? I'm almost sure it isn't, but it never hurts to ask...

 

[Wodgy]

Gaboo, are you saying that the analog filter on these cards does not change to correspond with the Nyquist frequency? Can you post measurements to confirm this?

It's not uncommon for a DAC to use the same analog filter for both 96kHz and 192kHz conversion. (As long as you do digital oversampling, you can also use the same filter for 48kHz conversion.) The highly-regarded Benchmark DAC2 actually uses a filter appropriate for 96kHz signals even when handling 192kHz signals. Yes, you're throwing away valid ultrasonic information with 192kHz sampling, but the argument some people make is that there is very little musical content above 48kHz (microphones simply don't go beyond this).

 

[gaboo]

Quote:

Originally Posted by Wodgy Gaboo, are you saying that the analog filter on these cards does not change to correspond with the Nyquist frequency? Can you post measurements to confirm this?

ICHi said "fixed analog filter" on the E-MU forum. The 0.5 dB rolloff at 20KHz shows up at all frequencies. There are tons of 44.1 & 48Khz measurements, so there's no point in repeating those. I've found only one 192Khz result (it's the one I linked on the E-MU forum). I could try to reproduce it if there's doubt about it...

Quote:

It's not uncommon for a DAC to use the same analog filter for both 96kHz and 192kHz conversion. (As long as you do digital oversampling, you can also use the same filter for 48kHz conversion.) The highly-regarded Benchmark DAC2 actually uses a filter appropriate for 96kHz signals even when handling 192kHz signals. Yes, you're throwing away valid ultrasonic information with 192kHz sampling, but the argument some people make is that there is very little musical content above 48kHz (microphones simply don't go beyond this).

That's probably what E-MU designers thought about reproduction. My A900 cans only go up to 40Khz (on paper), so I'm not worried about the loss.
The 1212m AD filter is supposed to move with Nyquist, but we won't know how good it is unless someone uses a better ultrasonic source that has flat freq output to 96Khz.

 

[Wodgy]

Quote:

Originally Posted by gaboo ICHi said "fixed analog filter" on the E-MU forum. The 0.5 dB rolloff at 20KHz shows up at all frequencies. There are tons of 44.1 & 48Khz measurements, so there's no point in repeating those. I've found only one 192Khz result (it's the one I linked on the E-MU forum). I could try to reproduce it if there's doubt about it...

Thanks for the link. It looks like a fixed filter with a corner frequency at 48kHz, which is reasonable for pro gear. The filter is not as steep as one would like, but this is likely an engineering decision, not a design flaw.

 

[Glassman]

it is two pole filter and judging by the slow rolloff I guess it's Bessel, which means the best filter you can get in terms of sonic quality.. 0404 might use a lot steeper Butterworth filter, but it doesn't mean it's better sonicaly..