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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: Re: Drive by Viola recital for the Audio Alternativist posted by Randy Bey on September 20, 2000 at 05:05:29:
Hi there,> The Audio Note Japan being the DAC with a separate DAC for every bit?
> The circuitry alone in such a unit must be prodigious.Not one DAC for each Bit, 16 DAC Chips per channel in parallel.
Each doubling up the number f DAC's will reduce Noise AND distortion by 3db. So 2 DAC chips give 3db lower Noise+THD, 4 DAC's 6db lower N+THD, 8 DAC's 9db lower N+THD and 16 DAC's 12db lower N+THD.
The single PCM56 in the non selected grade offers -80db guaranteed N+THD for Full Scale, the K-Grade -92db. This is measured at 4 times oversampling (the Datasheet is ambigous, but the shown circuit for measurements is clearly 4 times oversampling).
If we want to be simplistic we can view the Oversampling as eqivalent to paralleling 4 DAC's (for the engineers, I know it is not like that at all, but the Impact on N+THD is similar in magnitude), so by removing oversampling we make the (measured) distortion and noise 6db worse. Audio-Note parallels these many DAC's to ensure that under all conditions the resulting converter is as close to the technical capabilities of 16-Bit Digitalk Audio, WITHOUT resorting to any "tricks" that improve the measured performance.
In my latest DAC (diy) I have used the Philips TDA1541 DAC hip, which due to it's "dynamic element matching" offers a performance close to the 16-Bit theoretical Limit using only ONE Converter Chip and NO oversampling.
I follow this with a 20 Ohm HANDWOUND (Bifilar, thus non-inductive and I used OFC Copper wire, not constantan), a 1:10 Microphon Stepup Transformer (Amplimo TM-3) which is followed by a passive LCR Filter, using OFC wound chokes, silver Mica Capacitors and non-inductive wirewound resistors. Then a E182CC in SRPP. Powersupply Valve rectified and with polypropylen capacitors, choke filtered. To avoid the compatibility problems that used to show up with the Audio Note UK Dac's using this circuit, I used a very large output Capacitor (22uF - which allows loads down to 2kOhm theoretically) with multiple bypasses. I also used a linearising additional Anode Resistor for the upper Triode Section (see Tubecad Journal).
I'm not sure this sounds as good as the Audio Note Japan DAC (or the AN UK DAC 5), but it sure sounds a hell of a lot better than pretty much anything else I have ever had a chance to hear....
Later T
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Follow Ups
- Re: Drive by Viola recital for the Audio Alternativist - Thorsten 09/21/0014:08:52 09/21/00 (0)
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