[rollei_list] Re: OT Ancient Computers (was Re: Re: Rollei -Singapore) now analogue versus digital
- From: Frank Dernie <Frank.Dernie@xxxxxxxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Tue, 13 Jan 2009 08:59:16 +0000
Quite so.
IMO most shortcoming of digital are to do with anti-aliasing filters.
Higher sample frequencies help, whether going for more bits helps is
unlikely, I think, technically but appropriate for marketing.
I also had the experience of digital recordings sounding harsher than
the analogue but more like the feed......
I am the owner of several master tapes, analogue and digital, but they
are only of academic interest, if they were of musical interest they
would never have been given to me!
The high frequencies on LP is poor for the tracing reasons you note.
The plethora of mechanical resonances in the turntable also bring the
shortcomings down in frequency. I designed turntables and evaluated
the "opposition", all of the ones I know of made quite significant
additions to the signal from the disc due to arm and other structural
resonances and air and structure borne time delayed vibrations. I am
quite sure that the extra ambience attributed by many to analogue is
not on the recording but added by the turntable. The turntables people
like add the resonance and feedback at levels and frequencies they
find pleasant.
Frank
On 12 Jan, 2009, at 22:26, Richard Knoppow wrote:
In the long ago I did a lot of custom recording. At the time we
used mostly 15 IPS tape, mostly on Studer machines with Dolby A. As
a back-up we began to use a Sony digital adaptor running on a VTR.
This was an early device and had problems but worked pretty well.
The general opinion was that the digital recordings sounded "harsh"
compared to the tape. However, what I found was that digital sounded
more like what I heard in the monitors during recording, the
harshness came from the microphones being used and their positions.
Both mics and techniques had evolved to overcome the mushiness of
tape.
Disc recoding has a set of vices all its own. Among them are some
inherent distortions which are very hard to reduce plus the fact
that the "scanning" errors become worse toward the inside grooves
due to the reduced goove velocity. Oval rather than round needles
help reduce scanning errors at all speeds but still can not
completely overcome the odd order harmonic distortion of the system.
Typical disc systems have harmonic distortion on the order of a few
percent and can have lots of intermodulation distortion. Analogue
tape recording using biased direct recording has other types of
distortion plus the lateral print effect that causes loss of high
frequencies over time, especially the first few hours after a
recording has been made.
Digital has none of these plus it has absolute timing, meaning no
flutter or wow. The greatest problem with digital as it is practiced
is that the sampling frequency was chosen to accomodate the
bandwidth limits of what is now very old analogue recording
technology. The problem comes not from the sampling frequency itself
but rather the anti-aliasing filters. Because the sampling rate is
close to the Nyquist minimum the filters must of necessity be very
sharp which can cause all sorts of problems with phase shifts and
ringing. Raising the sampling frequency would probably eliminate
this completely.
---
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