Proper Playback of 78 rpm Records
There are three factors which must be taken
into consideration when playing 78s:
widths have varied over the years
equalizations varied until they were standardized in
the mid 1950's
- recordings were not made at a
speed of exactly 78 rpm until the mid 1930.
Proper stylus size
There was a gradual decrease in the groove widths of
78s throughout their production history owing to
gradual refinements in the recording process. Proper
contact between stylus and groove walls is essential to
obtain optimum sound quality during reproduction.
Thus it is important that the proper size and shape of
stylus be chosen for optimum-quality playback.
Also, by choosing the appropriate stylus, one can
compensate for different types of wear. For example, a
smaller stylus can be used to track lower into the
groove to compensate for a record with upper groove
damage. In some instances tracking different parts of
the groove will not make much difference, but in other
instances there will be a remarkable improvement.
Some experimentation with different styli, listening for clarity of sound and amount of background
noise, will illustrate the importance of choice
The National Library of Canada has about 24 styli, but
3 or 4 should be adequate for most uses.
Proper playback equalization
Every modern (post-1955) power amplifier has two
components built into the phono input: a preamplifier to boost the low level signal from the cartridge, and
a built-in equalizer set to the Record Industry
Association of America (R1AA) standardized playback
equalization curve. It is the latter of these that can
present some problems to 78 playback.
This equalizer cuts high frequencies and boosts
bass frequencies; the standard determines at which frequency this begins to occur.
At the high end, the process functions to counteract the fact that high frequencies are boosted (i.e.,
exaggerated) during mastering to act as a form of
noise reduction during playback. When a disc is
played back through an RIAA standard phono preamplifier, the high frequencies are cut by the same
amount they were boosted in the mastering process
restoring the high frequencies to their proper levels
and, consequently, proportionally cutting high frequency surface noise.
Likewise, at the low end, low frequencies are
reduced during mastering to reduce groove modulation distance. (Low frequencies
require more power to
propagate which requires larger groove modulations.)
This allows a more dense winding of grooves, thus
allowing for longer playing time and prevents grooves
from running into each other. At playback, through
the equalization, the low frequencies are boosted by
the same amount which they were reduced during the
mastering process, restoring the low frequencies to
their proper levels.
This built-in equalization, with its set playback
filtering curves, must be by-passed to properly play
78s. 78 rpm record playback equalization ranges from
none (acoustic: no cutting or boosting of frequencies)
to RIAA equalization. Playback curves varied from
company to company and varied within companies.
To playback a 78 with proper equalization, an
Owl 1 Restoration Module can be used. The Owl
1 has a phono preamplifier so that the output
cartridge can be plugged directly into the Owl. The
Owl output is then plugged into an auxiliary input of
effectively by-passing the power amplifierís phono input. The Owl consists of a low frequency
"Turnover" knob which boosts bass frequencies below
a certain level and a high frequency "Rolloff" knob
which attenuates high frequencies above a certain
level. Also included is an RIAA setting. The Owl comes
with guidelines giving proper playback equalization
for various record labels throughout time.
Proper playback speed
Though referred to as 78s, the 78-rpm speed did not
become standard until the mid-1930ís. Variations in
speed will change the recordings pitch and will make a
remarkable difference to the timbre
of a recording. A
5% difference is equal to approximately a semitone
(the note A becomes an A flat and so on). A "78"
recorded at 76.6 rpm must be played at 76.6 rpm for
Determining proper playback speed can be difficult. Having a score to determine the correct key is a
good start. Unfortunately singers had no qualms
about transposing a piece to fit their voices, and, of
course, not all recorded music is available on sheet
music. Also, "concert A" pitch, now A=440Hz, has
varied over the years (and is in the process of changing
now throughout the world). Keep in mind, when
pitching 78s, that stringed instruments prefer sharp
keys and brass instruments prefer flat keys. When
pitching a vocal recording listen carefully to the
singerís diction, resonance and vibrato speed.
Using the proper stylus and equalization and accurate
pitch will result in a good quality 78 rpm reproduction. However, if more complex filtering is required, a
Packburn Audio Noise Suppressor can be used to
remove transient noises (i.e., pops and clicks).
Though expensive,it is a useful device. As the
Packburn works best when the signal arrives directly
from the cartridge amplified but unfiltered (flat), a
phono preamplifier made by Stanton (Model 310) can
be used. Once filtered by the Packburn the signal can
then be routed to the auxiliary input of the Owl
1 for proper equalization.
Finally, if you really want to do a "bang-up" job
and happen to have a spare $120,000, you would wish
to consider purchasing a CEDAR (Computer
Enhanced Digital Audio Restoration) system. This
computer system, developed in Cambridge, England,
removes pops, crackles, hiss etc., miraculously well.
You'll be the envy of the neighbourhood!
Gilles is Audio Conservator, Music Division, National
Library of Canada, Ottawa, Ontario, and a member of