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The Radiotron Handbook entry shows only one curve "used by R.C.A. Victor for 78 r.p.m. shellac discs, 45 r.p.m.  and 33 1/3 r.p.m. fine groove" discs.  As there was no RCA Victor before 1929, this does not tell the whole Victor story and does not answer the specific question Steve Smolian asks (about electrical Victors made in the short period before November of 1925).

Maxfield and Harrison's 1926 paper describing the Western Electric system clearly indicates a bass turnover of 200 Hz and pre-emphasis ("constant acceleration") above "approximately 4000 Hz". This was before electrical record players were widely available and this curve was developed in consideration of playback by acoustic record players.

As has been mentioned, Victor raised the bass turnover over the years from 200 Hz to 300 Hz and finally to 500 Hz.  Nick Bergh knows the cutting equipment used and speaks with authority on the subject of EQ.  I showed him a Victor ledger sheet from December 1926 which includes a column marked "Eqlzr." and it only shows the words "on" or "off" which doesn't tell us what we'd really like to know!  It's safe to say that at Victor, experiments with various cutting equalizations were being done 
on an ongoing basis.

Doug Pomeroy
Audio Restoration and Mastering Services
193 Baltic St   
Brooklyn, NY  11201-6173
(718) 855-2650
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> Date:    Thu, 19 Dec 2013 18:36:58 +0000
> From:    "Gray, Mike" <[log in to unmask]>
> Subject: Re: Record equalization
> 
> From Radiotron Designer's Handbook, 4th Ed. 1953, p. 728, item 17.5: 
> 
> 
> "There is no 'optimum' cross-over frequency because the choice is necessarily a compromise. Where distortion is the principal criterion, a low cros-over frequency from 250 to 350 c/s will be adopted for standard groove 78 r.p.m. Where needle scratch is troublesome with 78 r.p.m. a high cross-over frequency of say 500 c/s may be adopted." 
> 
> 
> On page 730, under Practical recording characteristics: 
> 
> 
> "There does not appear to be any generally accepted definition of published recording characteristics." 
> 
> 
> In the two figures on this page, European characteristics show several cross-over points, ranging from 300 Hz (Decca ffrr) 
> to 600 Hz for EMI 78 rpm. Note that there is no pre-emphasis at all for the EMI discs, which are 'flat' up to 10 Khz. 
> 
> 
> American 78s, however, show a boost of ca. 12 db at 10 KHz ... 
> 
> 
> FWIW 
> 
> 
> Mike Gray