Needed a change of pace so decided to go after a project I planned almost five years ago, namely measuring my Otari MX-5050 BIII-2 Reel to Reel take deck! Otari was the last company in the world making Reel to Reel tape recorders and sadly, ceased production a few years ago. I got my sample from the Reel to Reel master, Ki Choi. I think it cost something like $5,000 to $6,000 new. Used ones go from a range of prices from $2K to $4K from what I see. As always, it is a risky thing to buy one online as conditions of these decks is all over the place and service is not cheap. Mine is extremely clean and as the sub-model indicates, is a more recently sample
Here is a shot of the beast as best as I could fit it in my lightbox:
View attachment 155831
What makes this model unique and valuable among tape heads these days is that it comes with both NAB and IEC equalization. The latter is what is used for a lot of tape production today (what little of it there is). A lot of consumer decks don't support it and require a hack or outboard equalization/amplifier. The fancy red spool is aftermarket which I bought at an audio show. Costs a couple hundred dollars just for that! Blank tapes are $60 from what I recall. And pre-recorded ones like the one on it are $290 but go way up to something like $600. Each! For some 30 minutes of music as these are recorded at 15 inches/second. So not a practical format for most people. But for those of us who wished we had such a nice unit when young and poor, it brings bag fond memories and good listening as you watch the spools turn and meters dance.
Being rather old, there is hardly an measurements of them by today's standards. There is also chicken and egg problem of how to get an accurate test tape. The de-factor ruler in that world is MRL and that is the tape I used for my testing. It has just a set of test tones and it too is very expensive. How good it is, I don't know. The measurements in the box come from a chart recorder! Let's say it is a few generations behind my Audio Precision analyzer.
Otari MX-5050III-2 Measurements
1 kHz tone has been the standard forever in audio and hence it naturally came on the MRL tape so I used it to run our usual dashboard:
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Distortion is at -57 dB or so but add a bunch of them and some noise and we land at SINAD of 46 dB. It is strange to see the elevated low frequency noise. Subtracting FFT measurement gain gives us a noise floor that is in the 40s! I wanted to see how much of it was the tape format and how much was the machine so I stopped the playback and measured the noise out of the unit:
View attachment 155833
Yuck. There is that rising low frequency noise floor but also a bunch of solid tones. What on earth is the 1 kHz and its harmonics coming from? No wonder folks get outboard electronics for these decks (although who knows how good they are).
BTW, the convention for measuring these older electronics is a-weighting so I thought I turn on that filter and see if SINAD gets better:
View attachment 155834
It goes up 3 dB so that low frequency noise is hurting it some. BTW, this is why I don't use a-weighting in my measurements. It really hides a lot of sins in equipment performance at lower frequencies.
There are skirts around the main tone if you look carefully which indicates jitter/speed variations. Watching the dashboard in real time showed a ton of variations. It is a jarring experience coming from today's systems. At 20 kHz, I measured 19.8 kHz frequency so we have about a 1% speed error.
There is not a whole lot more on the tape than a set of fixed frequencies to measure frequency response. My old Audio Precision analyzer could run a sweep against external sources like this by detecting the frequency and then plotting its level. The new APx555 I have now can't do that. It expect you to record its own sequence on the unit and play that to get asynchronous measurements. So I had to resort to the real-time recorder to plot the frequency on the right, and level on the left:
View attachment 155835
The first frequency is 32 Hz and highest is 19.8 kHz. I set reference at 1 kHz to 0 dB. We see a bass boost at 32 Hz by 1.6 dB or so. And a massive droop at 16 and 20 kHz. Not sure if this is a fault of this unit or in general. It might be this unit as the other channel took a nose dive above 1 kHz! I had cleaned the heads and could see nothing obvious that could cause this externally. Worse yet, I don't know if the tape is bad this way (I assume not but it is possible). I loaned out my last blank tape so need to buy another to record and playback and see how that behaves.
Conclusions
I sort of assumed SINAD would land in 40s and it did. I didn't expect the rest of the garbage this deck produces, nor the one bad channel. Need to find the time to tear it open and see what could be done to improve it. I have not listened to it in months. When I did, my favorite second generation master tape from rock music of 1970s is superb. It easily outperforms the digital ones which have been remastered to death. It is eye and ear popping how much nicer they sound than digital. I often play that tape when people come over first and their jaw drops on the floor in how good it sounds. Tape hiss is there during gaps between tracks and the highs sound a bit distorted to me but neither takes away from enjoyment of that tape. It makes me grin thinking about it as I type this!
Tape gives me the experience of the analog recording without loudness wars and remastering without the limitations and aggravation of LP. I also find the format so much more gorgeous to look at as it plays than anything out there, digital or analog. It is a shame that its popularity has pushed the price of used decks so high.
Anyway, we have first super hard set of measurements of any tape deck now. Gives us some anchoring as far as objective results are concerned.
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