Metrum Octave Dac - What are the Chips used

[Telstar]

Fck iPhone I lost my message. Will try to rewrite later on computer

[jitter]

Originally Posted by SoNic_real_one

Do you think it does even hold a candle to DAC1?

Sonically, yes, the Octave sounds better than the DAC1.

To me, the 5kHz @ 44.1kHz one looks like is a 4 bit sinusoide... Those distortions are not outside the audio band, I bet that using some headphones you could hear the difference.

Don't bet too much money, though. I listened to a 5 kHz sine on my Sennheiser HD600, but no difference with the DAC1. Things get really different, though, in the treble and with the volume turned up quite a bit. Then all sorts of strange sounds depending on the frequency of the sine can be heard. To answer 5th elements, yes there are things happening in the audio band. The reason they're not audible is because they're low level, constantly changing with the music and masked by it.
It's this dynamic behaviour of the hearing threshold that really gets in the way of the interpretation of these measurements. "What you see is what you get" really doesn't work in this case.

I am very interested in a mix of 19+20kHz 1:1 - for both of them.

Here they are, this time limited to the audio band:
Octave; 44.1 kHz; 19 kHz + 20 kHz sinewaves, 1:1;
Octave; 96 kHz; 19 kHz + 20 kHz sinewaves, 1:1;
DAC1; 44.1 kHz; 19 kHz + 20 kHz sinewaves, 1:1.

[ThorstenL]

Hi,

Originally Posted by jitter

Sonically, yes, the Octave sounds better than the DAC1.

This is where trouble starts.

Without having heard the Octave I'd still agree.

The real question is, how do we reconcile this?

The Non-OS Stuff I design does usually measure a little less extreme (in detail, not on THD+N) but it is still far from DAC1 levels or even the new Weiss.

Do we really "like distortion that much", or do the common measurements simply fail to correlate with "good sound"?

Ciao T

[Telstar]

Originally Posted by Telstar

Fck iPhone I lost my message. Will try to rewrite later on computer

OK, so what I wrote is pay attention to the first two sinewaves, the second one 1khz at 96k sampling rate is very good. Now imagine the 20khz sinewave if the sampling rate was 352/384khz.
To basically eliminate the need for an aliasing filter, we need DXD resolution, native or oversampled... and a R2R DAC

A good paper:
http://www.digitalaudio.dk/media/dxd...ution_v3.5.pdf

[Telstar]

Originally Posted by ThorstenL

Hi,
Do we really "like distortion that much", or do the common measurements simply fail to correlate with "good sound"?

I have >19khz hearing and my ears still prefer a filterless DAC.

I think the answer is this:

Originally Posted by jitter

As I wrote before: the perfect low pass filter is already in us!

...But something that gets intermodulated from a NOS filterless DAC must still affect the signal in the audible band and creates the "lively" sound mostly associated with NOS dac probably. To move much higher in the frequency spectrum this spuriae is the better solution.

Also, the time distortion of sigma-delta dacs is NOT measured by conventional means.

[SoNic_real_one]

Originally Posted by jitter

Here they are, this time limited to the audio band:
Octave; 44.1 kHz; 19 kHz + 20 kHz sinewaves, 1:1;
Octave; 96 kHz; 19 kHz + 20 kHz sinewaves, 1:1;
DAC1; 44.1 kHz; 19 kHz + 20 kHz sinewaves, 1:1.

Thanks! The first two are what I was expecting from my tests, the DAC1 looks like you have only one frequency there...

[jitter]

Please view the pictures in my previous post again. I discovered that, like Sonic remarked, not all of them were two sine waves. This has been corrected.

[SoNic_real_one]

The DAC1 is freakishly good. Seems that they are right about the 110kHz samplerate chosen for up-conversion. And their reason behind the chosen ASRC (AD1896) seems to be right. I won't touch an ASRC that is not DSP generated, but their implementation seems to work.
Hey, now that you like that much the Metrum, don't you wanna sell that garbage of DAC1? I can help you to take care of that poor old DAC

[jitter]

Hahaha, who knows? Actually, I already have another purpose for it...

[abraxalito]

Originally Posted by ThorstenL

I also noticed a few things, but being in the industry and all I think I should avoid comments in public...

One thing that sticks out as a discrepancy is the difference between the freq response as plotted on the AP and as tabulated in the results. The AP response measurement is done at 48kHz - I'm inclined to ask 'why?' as hardly anyone uses that SR these days.

If you look closely at the AP plot - the red line gets thicker above 18kHz and doesn't follow the slope downwards. This almost looks as though it was touched up by hand. But it shows a mere 0.7dB droop at 20kHz which does not accord with either the theory or the tabulated measurements.

Secondly the THD in the table looks uncharacteristically poor, even for a NOS DAC. I wonder if the imaging products got into the measurement? Just estimating by eye from the FFT I'd guess some 10dB lower than what's presented (-60.5dB). The wideband FFT for -10dB stimulus actually shows a test tone around -4dB and harmonics all below -83dB so its surprising that tabulated figure is so poor (-62.3dB).