Akai GX-620 Reel to Reel Tape Deck Measurements

[Jim Shaw]

The distortion measurement shown below is exactly what I expected:

Notice the predominance of odd harmonic distortion that is typical of analog tape. Odd harmonics are not beloved music artifacts when audible. We fought them throughout the life of analog magnetic tape. These harmonics were a key reason that, even in the good old days, tape was unable to be dubbed (copied) more than one or two generations before the music became annoyingly changed.

Another generic graph here shows one big reason why the analog tape studio industry started but never stuck to using 30 ips. Notice that signals below 50 Hz mostly vanish at 30 ips, but not so badly at 15 ips. Rock music notwithstanding, there's a lot of music below 50 Hz.

 

[PeteL]

Bias is almost always user adjustable. On professional recorders like Revox it was standard operating procedure to set bias.

I think that Revox was the consumer audio branch of Studer, which where making Pro Recorders.

 

[AndreaT]

Nice machine. Problem w RTR was the source tape for recorded bands: ultra-expensive, rare, very sensitive to heat and age, recorded on a different RTR with very variable electromechanical parameters. I believe it was a problem never appropriately solved because of the small market for recorded material compared to LPs and in the 1970’s and 80’s the compact cassette.

 

[Tks]

Even if this thing measured worse it doesn't matter.. This thing just look so damn cool.

 

[dfuller]

I think that Revox was the consumer audio branch of Studer, which where making Pro Recorders.

Yes indeed, Revox was the consumer branch of Studer - Studer machines are considered among the finest pro tape recorders ever made (along with later era Ampexes - I'd be hard pressed to choose between an ATR-102 and a 2-track A820).

 

[gitaarwerk]

I would never use reel to reel tape; but man, they look gorgeous! And it's cheaper than a Van Gogh

 

[Stephen H]

Very interesting results. This almost looks like a target curve for speakers-in-room. Harman Synthesis?

View attachment 239248

The correlation is remarkable.

My dad said something very similar. Some people would like it for room EQ curve..

 

[tomchris]

Ah, the tacile design cues of old audio equipment.

Did they ever make a reel to reel tape machine without solenoids, that is, with a 'silent' mechanism?

 

[tamagaba]

It is a 30-40 years old mechanical unit with electronics
A complete renovation is required (proper competence)
Then let them listen and measure

 

[Biagiod]

from 1983It is a 30-40 years old mechanical unit with electronics
A complete renovation is required (proper competence)
Then let them listen and measure

I totally agree. Frequency response is not adequate nor macthes Akai specifications. I expect a bit more from a reel to reel recorder, even if 40 years old. A Nak cassette recorder performed much better than today results, which can't simply be.

from 1983

Vintage Test Report: Nakamichi Dragon Cassette Deck Page 3

Recording level is shown on a twenty-segment peak-indicating fluorescent display calibrated from -40 to + 10 dB. During tape adjustments the meter 's dynamic range is reduced and its resolution increased. The adjustments themselves utilize built-in 400-Hz and 15-kHz test-tone generators and are...

www.soundandvision.com

I am afraid mechanical vintage hi-fi is just vintage after 4 decades.... hi-fi is gone, which is a real pitty
cheers

 

[JaccoW]

I totally agree. Frequency response is not adequate nor macthes Akai specifications. I expect a bit more from a reel to reel recorder, even if 40 years old. A Nak cassette recorder performed much better than today results, which can't simply be.

from 1983

Vintage Test Report: Nakamichi Dragon Cassette Deck Page 3

Recording level is shown on a twenty-segment peak-indicating fluorescent display calibrated from -40 to + 10 dB. During tape adjustments the meter 's dynamic range is reduced and its resolution increased. The adjustments themselves utilize built-in 400-Hz and 15-kHz test-tone generators and are...

www.soundandvision.com

I am afraid mechanical vintage hi-fi is just vintage after 4 decades.... hi-fi is gone, which is a real pitty
cheers

If you want, I do have some old radio recordings from around 1985 that still sound pretty amazing, even at 3¾ ips. I'll just record them using my ADC.
I believe some of the older recordings can be excellent but getting everything up to spec today is hard work.

 

[Jim Shaw]

Bias is almost always user adjustable. On professional recorders like Revox it was standard operating procedure to set bias.

Indeed. It's why, in the days when analog tape was the best we had, we bought tape stock in large lots from the same manufacturer. For critical live recordings, our techs would reset the bias just before the event, and make certain that all the tape stock came from the same batch. And we'd check head alignment, clean the heads, and demagnetize them, too.

A magnetized head can wipe off some high frequencies and raise the noise level in just one pass of playback. And more with each pass...

 

[mhardy6647]

I think that Revox was the consumer audio branch of Studer, which where making Pro Recorders.

In essence, yes. Both were tied to Willi Studer. ReVox was more like "prosumer" though, not just used by hobbyists.
The Studer studio machines are pretty incredible.

I have a pretty nice ReVox (an A77 rehabbed for me as a half-track, high speed deck by Charles "Stellavox" King) -- A Studer 80-series deck will always be beyond my means, though.

 

[fpitas]

In essence, yes. Both were tied to Willi Studer. ReVox was more like "prosumer" though, not just used by hobbyists.
The Studer studio machines are pretty incredible.

I have a pretty nice ReVox (an A77 rehabbed for me as a half-track, high speed deck by Charles "Stellavox" King) -- A Studer 80-series deck will always be beyond my means, though.

I'm surprised how cheap this one is:

Studer A80 2” 24 Track Analog Tape Machine | Reverb

Vintage Studer A80 2” 24 track tape machine. One of the best sounding tape decks ever made. This guy needs a little TLC. It was last in use around 2000 and it has been in temperature controlled storage ever since. I ran some basic tests on the machine yesterday and here’s what I found. The t...

reverb.com

Maybe has problems?

 

[mhardy6647]

"needs a little TLC"
The one person I know with a (quarter-inch) A80 family member has a whole parts/organ donor deck to help keep it going.
It is a wonderful piece of hardware, though.

 

[fpitas]

"needs a little TLC"
The one person I know with a (quarter-inch) A80 family member has a whole parts/organ donor deck to help keep it going.
It is a wonderful piece of hardware, though.

I don't want to know what 2" reels of tape cost.

 

[mhardy6647]

I don't want to know what 2" reels of tape cost.

Believe it or not, used ones of no particular provenance (i.e., that don't contain, say, lost Prince tracks) might actually not be so bad, since they're of somewhat limited usefulness to most folks.

 

[dfuller]

I don't want to know what 2" reels of tape cost.

new ones from ATR Magnetics (which as I understand it are basically Ampex/Quantegy GP9) are about $365.

 

[fpitas]

new ones from ATR Magnetics (which as I understand it are basically Ampex/Quantegy GP9) are about $365.

Not as bad as I thought.

 

[SMJ]

You could minimise adjustments by using the same tape type for each recording, the sensitivity and record parameters varied significantly and it's best to stick with formulations that were around when the machine was made. Yes, standard operating procedure was to check bias on each recording for important stuff (in the BBC anyway).

A playback calibration tape is essential to set the correct replay frequency response and level. A tape with 1kHz and 10kHz tones can be used with a stereo meter (with an S +20 facility) to check the phase at both frequencies allowing you to align the playback azimuth.

Once that is done, record a 1kHz tone and monitoring off the playback, increase the bias until the output reaches a peak and then starts to fall. When it has fallen by 1dB, that's your optimum.

Then you can check the record level and frequency response and adjust for minimum phase difference by adjusting the azimuth on the record head at 1kHz and 10kHz.

Steve J