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pschelbert:
--- Quote from: blgentry on July 20, 2016, 07:48:21 pm ---I think you're probably misinformed about how modern DACs work. Do you use a very old DAC? Or one of the 2 or 3 or 4 modern DACs that use multi-bit DAC chips? If you're using a modern DAC that is not multi-bit, you can't "circumvent the filter", because there isn't one! Modern DACs are Delta Sigma, so the steep filter you are describing is not required.
Brian.
--- End quote ---
I use a sigma-Delta DAC, RME Fireface UFX.
It does upsampling additionally internally. There are steep digital filters used. Its an urgent need in any DAC to avoid aliasing (see details of the chip).
The trick shifts this filter to a higher frequency. The edge-effects are then much lower. The introduced filter with a lower edge frequency does dominate, hence the design of how it's done is then up to you. May be its not better then the built in ...
Peter
pschelbert:
--- Quote from: kstuart on July 20, 2016, 09:58:30 pm ---With an external filter you cannot "do everything a Schiit does and with even more precision".
The whole point of the Schiit filter is that it is the only filter that has perfect precision. It is not an approximation. Read the description above.
--- End quote ---
Hi
there is nothing like a perfect filter. Its all a compromise. Steepness versus ringing versus lin-phase or mixed- or minimumphase.
Also there is no perfect precision. A real implementation has always some precision restriction. However it does not hurt, as the DAC-chip is the limiting factor anyway in all these implementations. On the digital side the precision is way higher than what is possible in the analog domain.
Peter
blgentry:
--- Quote from: pschelbert on July 21, 2016, 01:47:18 pm ---I use a sigma-Delta DAC, RME Fireface UFX.
It does upsampling additionally internally. There are steep digital filters used. Its an urgent need in any DAC to avoid aliasing (see details of the chip).
--- End quote ---
I think you're misinformed. A Delta Sigma DAC changes multi-bit input into an internal Delta Sigma format, which is usually 1 bit or as many as 4 or 5 bits. This is at a very very high frequency. So any filter used at the output will be at a super duper high frequency.
Maybe I'm wrong. I'm open to seeing evidence that a modern DAC uses a steep filter in the audible band (around 20kHz). I'm pretty sure that none do, but show me one and I'll gladly tell you that I was wrong.
Brian.
pschelbert:
Hi
yes thats right, but for the conversion to this superhigh frequency, antialiasing must happen, with a sharp steep filter.
pschelbert:
--- Quote from: blgentry on July 21, 2016, 04:21:30 pm ---I think you're misinformed. A Delta Sigma DAC changes multi-bit input into an internal Delta Sigma format, which is usually 1 bit or as many as 4 or 5 bits. This is at a very very high frequency. So any filter used at the output will be at a super duper high frequency.
Maybe I'm wrong. I'm open to seeing evidence that a modern DAC uses a steep filter in the audible band (around 20kHz). I'm pretty sure that none do, but show me one and I'll gladly tell you that I was wrong.
Brian.
--- End quote ---
Hi Brian
thats the DA of RME UFX. ex BurrBrown, now TI
here you go:
http://www.ti.com/lit/ds/symlink/pcm4104.pdf
***************************************
Datasheet excerpt:
The PCM4104 features delta-sigma architecture,
employing a high-performance multi-level modulator
combined with a switched capacitor output filter.
Linear Phase, 8x Oversampling Digital
Interpolation Filter
*********************
See page 11 and page 13 for filter and blockdiagram
Peter
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