Re: [ARSCLIST] Equalizers

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

> On 18/07/04, Steven C. Barr wrote:
>
> > Keep in mind that prior to some point in the 1930's, equalization was
> > "made up on the spot" by the recording engineer, and there was no
> > standardization of any type, even within labels.

----- I am not sure I agree with this way of looking at things. The recording
level was made up at the spot, yes, but the EQ was a function of the loading
of the cutterhead on the amplifier and the mechanical damping of the
cutterhead, and so to a large degree was determined quite precisely by
components of high precision (number of turns in a magnetic circuit, precise
airgaps, rubber or oil of a defined quality). Frequently the microphone
characteristic went into this as well.

Temperature would have an influence, though, but it would not vary much in a
studio. On the road that would be different, though. The important EQ, that
of the cross-over between constant-velocity and constant-amplitude, was fixed
this way. Voigt, who wrote a marvellous paper in Wireless World in (I do not
have it to hand, sh---!) ca. 1941 ("Getting the best from records"), tells us
how the mistake of calibrating HMV's microphone in dry hydrogen made them not
discover an involuntary increase in sensitivity about 3 kHz, i.e. a pre-
emphasis centering on that frequency.

The later controls
> > on amplifiers and pre-amps refer to a fairly-standardized intra-label
> > curve (one per label). These controls appear on most "hi-fi" gear of
> > the fifties and early sixties, but apply only to records of their
> > era...equalization of earlier 78's has to be done "by ear" (unless
> > someone can decode the cryptic notes found in surviving recording
> > ledgers if any exist)...
>
> Don Cox commented:
> Also the manufacturing tolerances on resistors and capacitors in those
> days were very wide, so even if somebody designed a circuit to give some
> desired EQ, the results could be somewhat diferent.

----- the few bodies that worked with an in-house system (off-hand I can only
think of the British Broadcast Corporation) also had calibration discs that
enabled them to control the response from input to output. A disc recording
and reproducing chain was just regarded as another black box insert and was
to contribute no change in the transfer. In those days it was long and medium
waves, so an upper frequency limit of 4500 Hz was the norm.


Best wishes,


George