Measurements of Nakamichi Dragon Cassette Deck

[restorer-john]

No tweaking at all. Bias was not adjusted, just at +/- 0.

Well, that response is pretty darned good for any deck. The head wear must be minimal and the alignment must be pretty much spot on. Well done.

 

[DSJR]

The Dragon meters weren't that good on peaks to start with, but a second sample I used a few years later did seem better here. I also understand the internals were gently tweaked as production went on but cannot confirm it. It was said that by the end, the Dragon was basically as good as the CR7. I've too much emotional baggage attached to this model, but yeah, it was aspirational for us Brits who couldn't afford a 1000ZEX.

I've an ancient lower grade Denon 24HX mouldering in the loft. No idea if it still runs and these three head Denons had a habit of stretching the head-block springs, causing audible wow.

 

[MakeMineVinyl]

Yes, that is very, very good performance.

 

[guenthi_r]

Had some weird problems with my "better" measurement setup (mainly powersupply)...
Will repeating measurements the 737 with cheaper setup soon.

What a mess, maybe defective powersupply?

 

[guenthi_r]

OK, problem detected!
Using my SMS Sanskrit 10ht Mk2 as signal generator is not a good idea, lots of distortion from 180-500hz (with & without external power supply)!
Anybody knowing an good signal generator with lower distortion?
Or is this "performance" enough for measuring the Pioneer 737...

With external powersupply:

Without Powersupply:

 

[restorer-john]

OK, problem detected!
Using my SMS Sanskrit 10ht Mk2 as signal generator is not a good idea, lots of distortion from 180-500hz (with & without external power supply)!
Anybody knowing an good signal generator with lower distortion?
Or is this "performance" enough for measuring the Pioneer 737...

View attachment 135187

You have nothing to worry about. That loopback is more than good enough for any tape deck. You are 2-3 orders of magnitude better than any cassette deck can manage on a good day.

 

[musicforcities]

Was thinking that you could use a tape adapter, like:
https://www.amazon.com/Reshow-Car-Audio-Cassette-Adapter/dp/B07FKFMRGF

I guess that would have to be measured though somehow.

Good idea but those tend to be rubbish. And won’t let Amir into account wow, flutter are not like a flexible tape moving across a head at a precise speed and tension etc.

Amir: You really need to engineer a cassette deck testing rig that would allow you to input your analyzer’s test signal directly to the record and playback heads. And some stroboscopic optical device thingy to measure wow and flutter. Seems easy and it’s not like you are busy or anything…. ;-)

 

[musicforcities]

It's an apples and oranges comparison and you know it. S/N is a valid, standalone measurement. So is total harmonic distortion.

Amir lumps them together with SINAD.

Of course any tape based analog format is going to have more THD than digital, but S/N is a function of how quiet the electronics and the noise reduction system are.

How will you know how quiet in real terms anything is, if you have harmonics dominating a SINAD number? Remember, S/N is measured in the absence of signal. SINAD notches out the fundamental and measures everything else. It's deceptive.

I see your SINAD and raise you wow and flutter! And tape bleed through. And head vs tape alignment. And wear of tape head and tape. And….come on man, it’s not Amir who is being deceptive or in denial here?

 

[restorer-john]

I see your SINAD and raise you wow and flutter! And tape bleed through. And head vs tape alignment. And wear of tape head and tape. And….come on man, it’s not Amir who is being deceptive or in denial here?

We are talking electrical noise and distortion, not mechanically induced issues, media flaws or wear. All of those things have their own measurement protocols.

 

[musicforcities]

We are talking electrical noise and distortion, not mechanically induced issues, media flaws or wear. All of those things have their own measurement protocols.

I’m just saying that all those things would seem accumulate in, to use your phrasing “real terms”.
And I would have thought wow and flutter is electro mechanical.

Maybe I’m being thick, but it seems Not taking into account distortion due to transport is like measuring a cars performance only by the engine while ignoring the suspension.

 

[Robin L]

I’m just saying that all those things would seem accumulate in, to use your phrasing “real terms”.
And I would have thought wow and flutter is electro mechanical.

Maybe I’m being thick, but it seems Not taking into account distortion due to transport is like measuring a cars performance only by the engine while ignoring the suspension.

The one thing that Digital record/play changed permanently is wow 'n' flutter and pitch. The inability to hold a correct pitch, or produce a vibrato-less pitch: those are musical distortions, serious ones, and are of greater importance to the music itself than distortion or noise.

 

[JJB70]

The cassette tape was a format of its time. It's easy to deride compared to modern digital technology but it was a transformative technology in providing an easy to use and affordable means for people to record their own stuff, make their own compilations and make music mobile. All of those things are taken for granted now and there is several generations who don't realise just what a difference the cassette tape made to so many people who could overnight listen to their own choices of music while out walking or jogging, in the car etc. The quality was generally dismissed by audiophiles even at the time but its audio performance was good enough whilst unlocking possibilities we had never had before. I had a Nakamichi deck back in the day and a nice Sony ES and although I am under no illusions about how they would measure I thoroughly enjoyed the audio performance that they provided. Measuring such devices is like measuring the performance of an E Type Jaguar and concluding it's a rubbish performance car, well yes it is compared to a modern Ferrari, Porsche, McLaren etc but there would be something seriously wrong if that wasn't the case. The cassette tape gave us a capability nothing else offered for many years and despite poor measurement it actually worked very well if judged according to what it offered at the time. And the Nakamichi Dragon was a work of art, the build shames modern audio gear.

 

[musicforcities]

Don’t me wrong. I was a total cassette nerd back in the day. I had silly serious debates about TDK type II vs Maxell type II! Or even tdk sa vs sa-x. I had a few of those tdk metal tapes with cases made out of metal. I once had a second hand Nak deck that physically flipped the tape over for you. It was their first answer to auto reverse. I lusted for a dragon I still have a Nak cr deck in the closet and a couple bankers boxes of tapes. The Nak motors are works of art. My first Nakamichi experience was my fathers 700…a vertical oriented three head deck with touch controls etched into a 19”x10” slab of brushed stainless steel. It was a work of art visually. The 700 never actually sounded that great however. Alignment was a bear. Any tape recorded on a different machine or commercial tapes were muddy even with alignment. It may have needed some work. But whew it was fun.

 

[USER]

I should be getting my Nakamichi RX-505 from the shop this coming week. If anyone can walk me through the measurement process, I'd love to post some for you all.

I have a bunch of blank tapes, some ABEX test tapes, and a miniDSP SHD that can be used as an interface with my laptop. Would I be able to use REW? Are the programs used above readily available?

 

[tamagaba]

Complete and professional upgrade is required on each piece. These are 30 year old assets
We know this was a compromise after the open reel but some types had very good audible sounds
I have a baby Naka too

 

[MRC01]

For cassette tape deck comparison, I calibrated and measured a Denon DRM-540 recently. It's no Dragon but was a good deck for its time, and after cleaning, demagnetizing and calibration (fine tuning the azimuth, speed, bias) it met its specs in the user manual. Would be interesting to see how it compares with others.

 

[MRC01]

I should be getting my Nakamichi RX-505 from the shop this coming week. If anyone can walk me through the measurement process, I'd love to post some for you all.

I have a bunch of blank tapes, some ABEX test tapes, and a miniDSP SHD that can be used as an interface with my laptop. Would I be able to use REW? Are the programs used above readily available?

Yep, you can use REW to measure a tape deck. You'll need a calibration tape, which typically has a 3 kHz tone on one side, and a 8-12 kHz tone on the other side. You use this to tune the speed, azimuth and channel balance (these tapes are mono). You can get one on eBay.

Azimuth is the angle of the head, you want it perfectly parallel to the tape. If you don't have a scope, the next-best way to adjust it is to play the high frequency tone (8-12 kHz) with the tape deck output into your sound card, use an app that shows you the input level (Audacity works, especially if you go into settings and narrow the range of the VU meters). While it's playing, slowly turn the azimuth screw back and forth to find the position that maximizes the signal level.

You adjust the channel balance using the internal playback level pots. Once you have this perfect when playing the calibration tape, and the azimuth is also right, then you can make recordings and adjust the internal recording gain pots to perfect the channel balance during recording. Then measure frequency sweeps in REW and adjust the internal fine bias pots so the 2 channels stay perfectly in sync throughout the frequency range.

 

[USER]

Yep, you can use REW to measure a tape deck. You'll need a calibration tape, which typically has a 3 kHz tone on one side, and a 8-12 kHz tone on the other side. You use this to tune the speed, azimuth and channel balance (these tapes are mono). You can get one on eBay.

Azimuth is the angle of the head, you want it perfectly parallel to the tape. If you don't have a scope, the next-best way to adjust it is to play the high frequency tone (8-12 kHz) with the tape deck output into your sound card, use an app that shows you the input level (Audacity works, especially if you go into settings and narrow the range of the VU meters). While it's playing, slowly turn the azimuth screw back and forth to find the position that maximizes the signal level.

You adjust the channel balance using the internal playback level pots. Once you have this perfect when playing the calibration tape, and the azimuth is also right, then you can make recordings and adjust the internal recording gain pots to perfect the channel balance during recording. Then measure frequency sweeps in REW and adjust the internal fine bias pots so the 2 channels stay perfectly in sync throughout the frequency range.

I was able to tune the cassette player using a variety of ABEX tapes I have and I have sent it in to a shop for general service, so that part is taken care of. The confusing part for me has to do with using REW to get frequency responses and measure THD and noise.

Do I simply record a sweep from REW onto a tape and then analyze it with REW after digitizing the results, or perhaps do so through a loopback connection? Is this the basic idea? I have a variety of blank cassettes that I can try out.

 

[rdenney]

I was able to tune the cassette player using a variety of ABEX tapes I have and I have sent it in to a shop for general service, so that part is taken care of. The confusing part for me has to do with using REW to get frequency responses and measure THD and noise.

Do I simply record a sweep from REW onto a tape and then analyze it with REW after digitizing the results, or perhaps do so through a loopback connection? Is this the basic idea? I have a variety of blank cassettes that I can try out.

I looped back through the tape monitor (only possible on 3-head decks) when I tested a Teac open-reel deck after fixing it up.

I used a Presonus Studio 24C as the interface. Computer running REW to USB to 24C line output to deck input through tape record and then playback heads to tape monitor output (with monitor switch on) to 24C line input to USB to REW. It played and recorded a sweep, just as if it was evaluating speakers. Calibration was arbitrary, left over from when I last tested speakers, but that’s not important. Record level was set to “standard” input and output, per service manual, using a SSVM AC microvolt meter.

Rick “would work on any 3-head deck” Denney

 

[MakeMineVinyl]

When doing frequency response sweeps with cassette decks, remember that most will not tolerate the full audio spectrum at 0dB on the meters - they will go into tape saturation at higher frequencies. For this reason, response sweeps are usually done at -20dB or so. Metal tapes were more tolerant in this regard. With open reel decks, 15ips (or 30 ips) is the only speed which can tolerate the full bandwidth at 0 VU and not run into saturation.