Re: [ARSCLIST] 78rpm EQ and postprocessing

[Eric Jacobs <ericj@xxxxxxxxxxxxxxxxxxx>]

My views on this have evolved over time as I've experimented with
different processes.  I know others will disagree, but I've come to
my beliefs through a fair amount of empirical testing, careful
instrumentation, and listening tests to validate my results.  Just
to be clear, I'm talking exclusively about mechanical/grooved 
media below.


Summary for preservation work:

1.  FLAT EQ always - I don't care if the original recording was
    done with a well known EQ (ie. RIAA, NAB).  The phono 
    equalizer always has a sonic signature which is impossible
    to remove.  You can reverse the gain aspects of phono EQ
    easily, but you can't undo harmonic "effects".  If you want 
    the most flexibility for downstream preservation/restoration
    work and the best results, FLAT EQ is a must.

    NOTE: for listening, not digitizing, a phono preamp like 
    the Elberg MD-12 and other preamps with historical curves
    is essential.

2.  High bandwidth electronics throughout the playback and
    digitization chain.  I try to keep the minimum analog 
    bandwidth to 50 kHz.  High bandwidth is not about accurate
    signal capture, it's about accurate noise capture (and 
    impulse noise has very high frequencies in its spectra).
    The better you capture the noise, the easier it is to
    identify and then surgically remove it without affecting 
    the signal.

3.  24-bit / 96 kHz minimum sample rate.  Again, this is for
    better noise capture for easier noise removal later.  Even 
    spoken word recordings will audibly benefit from this 
    approach.

4.  Moving coil transducers/cartridges.  The waveform that a 
    MC cartridge produces when it hits an impulse (ie. groove
    contamination) is quite different from a moving magnet 
    because of its very fast transient response.  This impulse 
    waveform allows better differentiation between "noise" and 
    "signal".


CAVEAT: A high-bandwidth approach is costly.  Low output
moving coil cartridges require more expensive low-noise 
phono preamps with higher gain.  Moving coils can be sensitive 
to phono loading, so properly setting up a moving coil for a 
flat response is more time consuming.

On the subject of EQ for restoration/re-issue, this posting 
could easily triple in length.  Analog versus digital EQ?  
Solid state versus tube EQ?  32-bit versus 64-bit?  Digital EQ
in software versus hardware?  I'll save that for another day ;-)

Eric Jacobs

The Audio Archive
tel: 408.221.2128
fax: 408.549.9867
mailto:EricJ@xxxxxxxxxxxxxxxxxxx


-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx]On Behalf Of Jos Van Dyck
Sent: Saturday, November 19, 2005 10:45 AM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] 78rpm EQ and postprocessing


Eric Jacobs wrote:
>
>There are tricks to making the break inaudible on a stylus transfer.  
>Choice of cartridge and EQ are critical, giving you options in post-
>processing that might not otherwise exist.

Could you elaborate on postprocessing and the impact of cartridges 
and EQ settings for best 78rpm transfer?
Some recommend RIAA EQ (others say flat) and do correct EQ in software.
Other sources recommend a special EQ amp such as Elberg MD12:
<http://www.vadlyd.dk/English/RIAA_and_78_RPM_preamp.html>

Thanks,
Jos