[Elecraft] Quantization noise and DSPs

[James R. Duffey]

Bill - I have one of the original W9GR DSPs. In my experience, it is not
possible to hear the quantization noise of the analog to digital (A/D)
converter. There are other digital artifacts though, some clock feed throug=
h
is noticeble on very quiet bands and the artifacts from the noise reduction
and voice enhancement are also evident in an A/B comaprison.

The noise introduced by quantization in a perfect analog to digital
converter is the least siginificant bit (lsb) divided by the square root
of=A012. In practical use without AGC, one tends to put the noise level at
several bits, which is far above the quantization noise introduced by the
A/D converter.=20

8 bits are enough dynamic range for CW signals, but without AGC, it does
require some riding of the volume control. I also have DSPs with 12, 16, an=
d
24 bit A/Ds as well, some with AGC, but only the 24 bit DSP can ignore the
volume control.=20

All in all I have more audio filters than I can recall; collecting them is =
a
bad habit of mine. My favorite CW filter is an analog one, the DaTong FL-3.
My favorite DSP for CW is made by Zim, VK3GJZ, with 24 bit CODEC it sounds
like an analog  filter with no detectable digital artifacts. See:

<<http://www.users.bigpond.com/gzimmer/Alesis.html>

for more information on Zim's filter.  My favorite overall DSP is the
Timewave 59+, but the DaTong is a close second. In my experience, DSP is no=
t
of as great a utility in CW as it is for voice or data. I have not noticed
the delay mentioned by Andrew on the 59+ or Zim's filter, but I do not
operate high speed CW except on contests. I have noticed it on the NIR-12
though, which was unexpected.

I have not seen or heard the K-2 DSP, so I cannot comment on it. I expect
that its greatest utility will probably be to eliminate heterodynes on SSB
and as a  filter for data signals. I have heard and used the K2 with the
KAF2, which is a good sounding combination on CW, even at the narrow
setting. I suspect that most K-2 CW only ops will think the DSP overkill.
Now, if you operate SSB on 40 M after dark, the DSP will be a godsend. - Dr=
.
Megacycle KK6MC/5
______________________
James R. Duffey KK6MC/5
Cedar Crest NM 87009 DM65

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