On Tuesday, March 09, 2010 4:57 PM, Corey Bailey wrote:
> My plan is to transfer through an RIAA preamp, flat using 
> outboard analog EQ and flat using post EQ via software then 
> comparing the files.

Interesting question.  What follows is a somewhat heretical
response, given that common practice in preservation is to
transfer FLAT.

Transfering FLAT will cost you about 6-7 bits of dynamic 
range - an audible loss.  EQ in the digital domain will not 
recover that lost dynamic range.  If the material you are 
dealing with has some good dynamics, transfering FLAT could 
be "lossy" (for lack of a better description).  Good quality
shellacs, for example, will suffer noticeable dynamic loss
if tranferred FLAT and EQ'd later.  One could argue that it
might be better to transfer with the wrong EQ and fix it 
later than with no EQ (ie. FLAT).

The FLAT EQ makes sense in the context of knowing neither
speed nor EQ for older disc formats.  It's a conservative
technical approach in terms of EQ.  But does it make sense
in terms of dynamic range?  You can fix EQ, but you cannot
restore lost dynamic range.

An alternative and compromise to FLAT transfers might be
to EQ the bass alone (electric recordings), leaving the
treble EQ FLAT.  This would preserve more of the dynamics,
while leaving lots of transient information for any 
denoising and restoration work.

Corey, you may want to run a test using a modern LP or
even a 1950s 78 shellac:

    (a)  transfer FLAT EQ -> digital RIAA EQ
    (b)  transfer RIAA EQ

and compare (a) and (b).

Has anyone else noticed that FLAT transfers of electric 
disc recordings sound a bit "flat" (pun intended) or 
lifeless when equalized later, as compared to equalized
in the analog domain at transfer time?

Eric Jacobs

The Audio Archive, Inc.
tel: 408.221.2128
fax: 408.549.9867
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Disc and Tape Audio Transfer Services and Preservation Consulting