The
whole point of a tape recorder is, obviously, it's ability to faithfully
record sound. To demonstrate the recording ability of the Wollensak 5750
that matches historical
usage, a stereo phonograph record was used.
The
music is a selection from Pavane by Gabriel Faure,
Op. 80. It was recorded from the album titled: "The French Touch", performed by the National Philharmonic
Orchestra, conducted by Charles Gerhardt - dated 1978 on RCA Red Seal records.
Number ARL 1-2783 Stereo.
Procedure:
The
line output of a Marantz Stereo system (with a Technics Direct Drive Turntable)
was plugged into the line inputs of the Wollensak 5750 and a recording was
made. For maximum fidelity, the Wollensak 5750 was set to record at 7-1/2
ips on a vintage Scotch® brand - 150 formulation recording tape. This
is the tape most users of the Wollensak 5750 would have had available in
1967, when the machine was in production.
The
recording on the Wollensak 5750 was then digitized into a
raw WAV file sampled at 44Khz on a Pentium-4 computer running Windows XP.
It was then converted to MP3 format using Apple's iTunes.
It
is important to note that MP3 compression actually lowers sound quality by
removing some of the audio information from the original "raw" -
WAV - file. This is unavoidable due to bandwidth needs.
There
is a popular misconception that because MP3 is so widely used, it actually
improves sound, which is not the case. So what you are hearing here is
somewhat less than the actual performance of the
Wollensak 5750 reel to reel tape recorder!
Results:
To
understand the recording results it is important to note the operating specifications
of the Wollensak 5750:
- Frequency
Response: 40 - 17,000 Hz
- Wow
and Flutter - .25% RMS
- THD
(Total Harmonic Distortion) - 5%
Commercial
recordings usually exceed these specifications, and the Marantz Stereo system
(as well as the Technics turntable) have a broader frequency response - 30
- 20,000 Hz and lower THD - 1%. All turntables have some degree of
wow and flutter, but the Techniques turntable has a direct drive motor (no
belts or idler wheels in the transmission), reducing it to below detectable
levels.
The
Wollensak 5750 did a very good job with the recording. The most noticeable
defect is tape hiss (which is natural to all reel to reel tape recorders)
and some "gurgling" - similar to the problem of trying to talk
when you need to "clear your throat."
The
amplifier circuitry can contribute to this type of flutter or "gurgling" as
is heard on the recording. The Wollensak 5750
uses a number of electrolytic capacitors to filter the line (sometimes these
are called "filter caps") and smooth out the electrical signal
being processed in the amplifier. I was able to identify them (all 14) thanks
to a SAMs Photofact book, which I ws able to purchase from Stereo
Manuals.com.
Electrolytic
capacitors have a dielectric and electrolyte which over time can fail due
to dryness or other conditions brought about by age (much as a battery chemical
will become exhausted even if the battery is stored on a shelf and not used).
The only solution is to replace the capacitor, a time consuming and potentially
expensive process. To accomplish this on the Wollensak 5750 requires "major surgery",
as the amplifier board is located deep within the machine, and most of the
frame must be removed to free the board for alterations. The author has chosen
to delay this procedure as long as possible, for obvious reasons.
The
issue does not occur when the machine is in playback mode of a commercially
produced tape, and a careful check using sensitive headphones reveals the
source. There is a hum when the recording function is engaged, but the hum
is different on each channel. That hum (or pair of hums) is a giveaway of
one or more failing electrolytic capacitors in the recording circuit. Since
there are two circuits, one for each channel in the stereo mix, with different
low frequency hums, harmonic distortion is introduced, which accounts for
the "gurgling".
Mechanical
wow
and flutter seem negligible, certainly within the specs of the machine (.25%)
Bass
frequency response in the recording matches the output of the turntable and
stereo system fairly closely.
Stereo
separation is quite good.
Summary:
The
Wollensak 5750 restored/rebuilt tape recorder does an acceptable job of tape
recording from a phonograph record, preserving the quality of the original
while introducing some level of tape hiss.
But
the story doesn't end here. After approximately 40 years of being abandoned
in an attic or basement or who-knows-where, how well does the Wollensak 5750,
even "resurrected" deal with the future that is now? What can it
do when recording from modern digital equipment, especially virtual music
created on a computer, with its wide frequency response and high sampling
rate of 44Khz?
For
a real challenge - an all digital master selection demonstrating the Wollensak
5750's ability to record material from a CD, please
click here.
For a video of
playback performance, please click here.
For a sample of
stereo playback performance of a commercial tape, please
click here.
Please
note that ClydeSight Productions DOES NOT rebuild or sell vintage
reel to reel tape recorders, nor can we help anyone involved in such a project.
The tape recorders shown in these pages are part of a personal collection
and are not for sale. We Do Not recommend
that unqualified or inexperienced persons attempt to restore vintage audio
equipment.
Visit
www.clydesight.com Master Site
Web site copyright ©ClydeSight
Productions - 2007
