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In Reply to: RE: REVIEW: Metrum Acoustics Octave DAC Processors posted by sbrians on March 22, 2014 at 08:33:25
It's good to read that you are finally enjoying your CDs. Many of us had feared that the CD era would leave decades of forever lost musical performances behind it. Relatively recent DAC products are starting to erase those fears, even for audiophiles shopping at sane price points.Regarding sigma-delta versus fully multi-bit conversion technology, I suggest not being too quick in assigning the sound of your Metrum DAC to that difference. There are many factors which determine the sound of a DAC. There are any number of musically well regarded DACs utilizing sigma-delta conversion, such as from dCs, not to mention DSD is a sigma-delta based technology.
FYI - The DIY DAC design community strongly suspects that the DAC chip which Metrum probably utilizes in the Octave is the DAC8581 from T.I. This chip is a generally available DAC chip that's targeted at waveform synthesis applications, but not specifically at consumer digital audio. The DAC8581 features a voltage output, so, doesn't require an external I/V converter circuit.
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Ken Newton
Edits: 03/23/14 03/23/14Follow Ups:
I think that cannot be it, if the TAS review measures more resolution than 16 bit? But I don't care what it looks like or words or numbers that describe it. I only care about the sound, which works great for me.
TAS doesn't normally perform lab tests, so, that would be interesting to read. Is this report available online somewhere?
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Ken Newton
I linked it below, and again here. I thought about it - I still have not read it, but the effective resolution could go up with the number of paralled chips, for all I know, so that may not be much of an indicator? But I doubt that paralleling can get you more than the inherent # of bits in a DAC.I just corrected my link here. Also it is not TAS, it's this other one:
Edits: 03/23/14
That TAS review is for the Hex, not the Octave. In addition, it's a subjective report without any lab testing. Your suspicion that paralleling DAC chips does not increase net bit resolution (lower the quantization noise) is correct. It lowers the thermal noise floor, which is a different thing. What also produces confusion is that many vendors say their DACs accept 24-bit audio data, but what they don't often say is that their DACs may actually convert only 16 of those bits.
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Ken Newton
Edits: 03/23/14
..."many vendors say their DACs accept 24-bit audio data, but what they don't often say is that their DACs may actually convert only 16 of those bits."
I remember being furious as Stello Audio for this very thing. I had the Stello DAC 100 Signature that their website went out of its way to highlight that fact that its USB input accepted up to 24/96. They made it a selling feature. What they didn't tell you is that the signal was then downgraded to 16/48. Deceptive dogs! I will never buy any product from them again.
...have changed things they are correct only in that it'll "accept" 24/96 but then downgrades it. I first found out about it on a forum somewhere I then had them admit to it in an email where he then tried to sell me their USB convertor thingy.
Some, like the MHDT Stockholm do say that they accept the high res. signals, but use a 16 bit DAC chip.
Stello DA100 page says:
"True 24Bit Delta-Sigma DAC" at the link below:
nt
I corrected/edited my post prior to your reply. I have the correct link now.
Okay, thanks, I've now read the review by Martin Colloms. While the review states that there's approximately 18-bits of resolution, I don't see that figure basked up by the printed lab data. At best, the data appears to indicate approximately 16-bits of resolution. Perhaps, there's a misprint somewhere. At any rate, it wasn't my wish to argue over which mystery DAC chip Metrum might or might not be employing. I'm glad that you are enjoying CD format music like you never have before.
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Ken Newton
Edits: 03/23/14
Your past posts summarizing what you found to be strengths and weaknesses of different DAC design aspects helped me very much in finding what was critical to me which helped to lead me to this DAC.
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