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Reel to Reel Tape Recorder Stereo Recording Demo
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This page provides a demo of the Wollensak 5750 reel to reel tape recorder stereo recording from an all digital audio CD. This piece of vintage audio equipment was restored/rebuilt after a purchase on E-Bay and it arrived as a complete "DOA" (Dead On Arrival).
Music Files (1.8 MB) Must Be Started Manually - Keep scrolling down.
For a video of playback performance, please click here.
Note: Sample music files are located further down this page and must be manually started because, there are two of them, and having them both play at the same time would be pointless.
The whole point of a tape recorder is, obviously, it's ability to faithfully record sound. To challenge the recording ability of the Wollensak 5750, a full digital recording on CD was used as a "master". This presents some challenges that the machine was never designed to handle, and was done as an experiment to see how well the machine can handle modern audio demands. Overall, it has done a good job.
The music is the theme - called "Dream Angels" - from the popular divination program "The Dream Angel Oracle", available from ClydeSight Productions as a direct download computer file (a prototype CD cover is shown here.) The theme is available as an MP3 download for free to Web site visitors, and has proven very popular.
The source music is an all digital production, made with the Roland XV-5080 synthesizer and processed through Mark of the Unicorn's Digital Performer software on a Macintosh G4 computer. The resulting sound is called "The XV Orchestra" because it has characteristics that go beyond the limitations of the Roland XV-5080 (thanks to Digital Performer) enhanced through the software's music studio mixing and filter boards.
The original digital recording was saved as a raw AIF file sampled at 44Khz. This was burned to a CD. The CD was then played on a Sony High Density Linear Converter CD Player (model CDP-261) with the line outputs directly patched into the line inputs of the Wollensak 5750. 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.
For this Web page, that recording was played back into the computer and captured as a RAW AIF file, 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.
To understand the recording results it is important to note the Wollensak 5750 operating characteristics:
- Frequency Response: 40 - 17,000 Hz
- Wow and Flutter - .25% RMS
- THD (Total Harmonic Distortion) - 5%
By today's standards these specifications are rather poor, although they were standard for 1967. Typical frequency response of a CD is 20 - 20,000 Hz, and THD is below 1%. Wow and Flutter simply do not exist on a CD, as they are generally faults of mechanical analog recording systems.
However, the amplifier circuitry can contribute to flutter or "gurgling" as is heard on the recording, especially the bell tones. 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".
Nevertheless, the Wollensak 5750 did a fairly good job with the recording. The most noticeable defects are tape hiss (which is natural to all reel to reel tape recorders) and the very noticeable harmonic distortion of the bell tones in the music. The problem is most likely caused by the weakness of the "filter caps" within the recording part of the circuit board.
Wow and flutter seem negligible, certainly within the specs of the machine (.25%)
Bass frequency response in the recording falls short of the original, probably because the amplifier simply is not designed for it.
Stereo separation is quite good, although the original file has a bit more "presence".
Hearing is Believing
Below are two sound samples. One is the actual recording made by the Wollensak 5750, and the other is the actual source material. Both are presented as MP3 files because such compression is required for the Internet. It should be noted that MP3 compression also introduces some levels of distortion. With some quick mouse movements, it is possible to do an A-B comparison. However, if both files are played at the same time-- well, now won't THAT be interesting!
The Wollensak 5750 "Dream Angels" recording. The "Dream Angels" source file.
For what it is, the Wollensak 5750 restored/rebuilt tape recorder does an acceptable job of tape recording.
As a 40 year old machine, with no adjustments made to the electronic circuits it does perform quite well.
It records as well through microphones as it does through direct line input. The purpose of the machine in the author's case is nostalgic and to play back vintage pre-recorded stereo tapes, so the recording function is not that critical. (Why would one record a CD to reel to reel tape, given the rarity of reel to reel machines?) However, if it is needed for a project, it can be depended upon for a relatively faithful reproduction. And of course, if necessary, the filter caps can be replaced.
But the story doesn't end here. This test was a bit unfair, expecting the Wollensak to record a high end digital file from a CD when such equipment wasn't even dreamt of at the time the machine was made.
What if we turn back time and go into history and try the machine in the way it was used in 1967? Easy enough, all we need is a stereo system and phonograph. And of course, ClydeSight Productions has this audio equipment!
For a video of playback performance, please click here.
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