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INSTRUCTIONS FOR OPERATION OF ESOTERIC SOUND RE-EQUALIZER
INTRODUCTION:
Today's modern audiophile equipment can sometimes be frustrating to owners of old records, especially
when their collection includes many old 78's or old mono Lp's. All modern preamps are designed solely
for today's microgroove, RIAA equalized recordings.
In the 1950's, almost all preamplifiers included selector switches having several different RECORD
COMPENSTIONS. Occasionally, on the more expensive units, this function was divided among two
switches labeled TURNOVER and ROLLOFF. These terms should be explained: Turnover refers to the
bass boost that must be applied in the preamp to compensate for the purposeful diminishment of bass
during record cutting to avoid crosscutting of the grooves. Rolloff refers to the treble loss the preamp
must provide to compensate for high frequency boost applied during record cutting. The benefit of the
latter is a reduction of surface noise during play.
Up until 1954, there were a variety of
recording characteristics applied to records
as they were being cut, such as AES, LP,
NAB and FFRR. Actually, most of these
compensations have use only for records of
a relatively brief period, say between 1940
and 1954. Before 1940, most records were
cut flat with only a low frequency turnover of
6 db per octave below frequencies below
from 300 Hz to 800 Hz. This also applied to
broadcast recordings(transcriptions) and
Vitaphone type recordings used before
sound-on-film. Therefore, if you play a
pre-WWII 78 rpm record on a modern
preamp, you are actually effectively playing
it with a scratch filter whose cutoff begins at
2200 Hz. This accounts for the lack of highs
and slightly muffled voices experienced with
these records. Of course, after 1954 all records were cut to the RIAA characteristic.
One way of dealing with the equalization problem is to use a graphic equalizer, but it is very difficult to get
accurate results by this method. Another way of dealing with the record compensation problem is to
modify your modern stereo preamp with an equalization switch for both RIAA and other compensations.
This is probably the best way to handle the problem, but it may spoil the cosmetics of your $1000 preamp.
There is also the problem of what to do with tape recordings made off of modern RIAA compensated
phono amplifiers. They will suffer from the frequency response distortion caused by the RIAA amplifier
and they cannot be played through the phono input of a special or antique record amplifier.
Because of these problems, the RE-EQUALIZER was designed. It is used after the RIAA phono stage,
and connects to the system just like a common graphic equalizer. It will then compensate any signal
source for proper equalization. The RE-EQUALIZER allows the use of any phono amplifier and will not
degrade the performance of any audiophile unit.
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