Head direct-out and after-market playback electronics

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
It would be really fun if more real audiophiles became interested in tape playback. In the meantime, independent thinkers who seek the truth might want to know what's behind the trend to after-market tape stages.

Below are some of the better questions I've heard. Other questions for inclusion on this list are invited and welcome. If there is reader interest, we can then set out to answer them.

Is it true that the amplitude response of analog audio tape machines was the technology's biggest shortcoming?

Is it true that even the most prestigious and respected professional tape machine makers of the past (firms like AEG-Telefunken, Ampex and Studer) had audibly serious flaws in their tape playback electronics?

How does one verify the amplitude response of an analog tape machine's playback electronics?

Can the above verification be done by listening alone?

What makes the new outboard tape stages better?

Where, why and how did this trend get started?

Is it a scam?

What does a competent designer of any outboard tape stage need to know about the playback head that will be used?
 
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Ron Resnick

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Jan 24, 2015
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This is a great opening post, Fred! :)

Please proceed!
 

topoxforddoc

Well-Known Member
Feb 20, 2015
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Cheltenham, UK
As a strict amateur, I understand that it is the tape transport and tape path, which is critical in the ability of a R2R to provide the best sound. That's why professional studio machines have a rock solid chassis, precision machined guides and ideally precision guidance for the tape path.

The problem with "good" consumer machines e.g. Technics 1500 series is that the tape transport is good by consumer standards, but much less so by studio standards. Also the electronics are limited in performance by cost constraints etc, which studio machines are not. I think that different studio machines have a different sound e.g. my Sony APR 5003 sound better on playback than my Studer A807/II. I was told by the famed UK mastering engineer Simon Heyworth that different manufacturers have a different house sound. but I think that all of the studio machines sound excellent.

Charlie
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
. . . it is the tape transport and tape path, which is critical in the ability of a R2R to provide the best sound.
Charlie

The answer to the first question is, of course, no.

AC bias and successively improving tape formulations made controlling the amplitude response very doable.

The much greater engineering challenge facing the top-tier professional machine makers was perfecting the system's time-base accuracy. In other words, perfecting the tape transport.

Yet implementing servo-constant-tension and servo-capstan on a transport design also exhibiting vanishingly low flutter was (is) hardly trivial. Tape transport manufacturing and development costs for the top-tier machines often consumed 80 percent or more of the budget.
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
12,467
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It would be really fun if more real audiophiles became interested in tape playback. In the meantime, independent thinkers who seek the truth might want to know what's behind the trend to after-market tape stages.

Below are some of the better questions I've heard. Other questions for inclusion on this list are invited and welcome. If there is reader interest, we can then set out to answer them.

Is it true that the amplitude response of analog audio tape machines was the technology's biggest shortcoming?

Is it true that even the most prestigious and respected professional tape machine makers of the past (firms like AEG-Telefunken, Ampex and Studer) had audibly serious flaws in their tape playback electronics?

How does one verify the amplitude response of an analog tape machine's playback electronics?

Can the above verification be done by listening alone?

What makes the new outboard tape stages better?

Where, why and how did this trend get started?

Is it a scam?

What does a competent designer of any outboard tape stage need to know about the playback head that will be used?

Good Morning Fred,

if a person owned an apparently properly functioning master level recorder, and was not completely satisfied with it's sonic performance, what next step would you recommend this person to take?

and understand the perspective (rightly or wrongly) of this person is that he sees that the transport is superlative, yet the playback electronics is 70's and 80's vintage solid state with the compromises involved in being inside that RTR chassis, and he considers that separate optimal discrete circuits likely will have clear sonic advantages (analogous to his discrete phono preamp). and also that the tapes he plans to acquire will all be produced within a small window of EQ and gain and type. so maybe he thinks (again rightly or wrongly) that he won't need to make fine adjustments for very good playback performance.

what should this tape lover do?
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
Good Morning Fred,

if a person owned an apparently properly functioning master level recorder, and was not completely satisfied with it's sonic performance, what next step would you recommend this person to take?

This is a great question Mike, so let's add it to the list of others and then try to work through them one at a time.

The answer to the second question is, of course also no. That assertion was mostly a myth.

Yet it might well be true for some of the consumer tape machines.

The basis for comparing any tape playback amplifier electronics lies within question three.

As some may remember, back in the early 1970's, Richard Burwen, John Curl and Mark Levinson sought to explain that a deviation of amplitude response versus frequency, measuring as little as one-tenth of a dB, can be audible to expert listeners. (Many people did not believe this. Yet it has since been proven true.)

So, it must follow that the amplitude response of an analog tape machine's playback electronics must first be closely calibrated to a common standard before any meaningful comparisons can be made. Just as no one would tolerate having someone secretly changing tone controls while a loudspeaker comparison was taking place, skipping the alignment steps when comparing playback electronics is equally inexcusable.
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
Question three was:

How does one verify the amplitude response of an analog tape machine's playback electronics?

Answer:

For the end user, the simplest (and arguably the best) way is to use a reproduce alignment calibration tape.

An important caveat is that you need to carefully select which cal tape to use.

The most common and popular ones, having maybe only 12 or 13 discreet tones spanning 10 octaves, might never reveal serious response anomalies occurring between the chosen spot frequencies.

The more knowledgeable tape electronics designers of course know this and might demand cal tapes having 120 or more discrete frequencies (affording one-twelfth octave resolution).

Question four was:

Can the above verification be done by listening alone?

Answer:

No. The (usually many) various response errors across the band would quickly become far too confusing for even the most expert listener to keep track of. You will first need to plot the reproduce responses and then set the electronics so that there are essentially no differences between the two (or more) units you are comparing. Only when that is done, can you make meaningful comparisons as to sound quality.
 
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Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
Skipping question five for now, question six was:

Where, why and how did this trend get started?

My answer would be in Campbell, California, in the 1970's. The company was called Inovonics.

The Inovonics after-market solid-state tape electronics were developed as replacements for the vacuum tube record and repro electronics in Ampex 350 and 351 professional tape machines. Designer Jim Wood continued his work on tape electronics for almost two decades, during which time many different product refinements (with all new model designations) were made.

Later, analog circuit designer David Hill (Crane Song) developed the Aria replacement electronics (also solid state) for the Ampex ATR-100. Aria electronics were sold exclusively by ATR Service Company.
 

microstrip

VIP/Donor
May 30, 2010
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(...) The most common and popular ones, having maybe only 12 or 13 discreet tones spanning 10 octaves, might never reveal serious response anomalies occurring between the chosen spot frequencies. (...)

What type of anomalies are you addressing? Just amplitude versus frequency?
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
Question eight was:

What does a competent designer of any outboard tape stage need to know about the playback head that will be used?

Answer:

At minimum, the head's inductance, its gap length, its resonance frequencies (both natively and with specified cabling attached) and its output voltage.

Also of interest will be the intended tape speed (this relates to gap length).
 

microstrip

VIP/Donor
May 30, 2010
20,806
4,698
2,790
Portugal
Question eight was:

What does a competent designer of any outboard tape stage need to know about the playback head that will be used?

Answer:

At minimum, the head's inductance, its gap length, its resonance frequencies (both natively and with specified cabling attached) and its output voltage.

Also of interest will be the intended tape speed (this relates to gap length).

Can you explain us why the gap length and tape speed matter?
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
What type of anomalies are you addressing? Just amplitude versus frequency?

Correct.

I'm purposely leaving phase response errors out of this discussion (for simplicity).
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
Can you explain us why the gap length and tape speed matter?

There's a relationship between reproduce head gap length and recorded wavelength, producing signal loss (called gap loss) when those wavelengths become very short, such as is seen with low tape speeds.

Many designers of tape playback electronics have utilized the resonant frequency of the repro head and its cabling to effect an improved high frequency response under these conditions. This is called gap loss compensation.
 

microstrip

VIP/Donor
May 30, 2010
20,806
4,698
2,790
Portugal
There's a relationship between reproduce head gap length and recorded wavelength, producing signal loss (called gap loss) when those wavelengths become very short, such as is seen with low tape speeds.

Many designers of tape playback electronics have utilized the resonant frequency of the repro head and its cabling to effect an improved high frequency response under these conditions. This is called gap loss compensation.

Thanks.
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
Good Morning Fred,

if a person owned an apparently properly functioning master level recorder, and was not completely satisfied with it's sonic performance, what next step would you recommend this person to take?

Mike, I have shortened your question to make it easier to answer.

But your intuition is correct. With analog tape, the transport (the time base) definitely comes first.

Before you set out on a quest to find the best sounding tape playback electronics, you'll first want to remove all the time base distortion (FM and AM haze) originating from the transport and headblock. It's absolutely audible.

So your first step is easy: ditch the recorder!

What you want for optimum playback is a s.o.t.a. reproducer transport and headblock. (Not a 30-year-old studio recorder/reproducer.)

Have you ever heard of ATAE Model One and Model Two reproducers?

If you're interested, we should talk!
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
12,467
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Mike, I have shortened your question to make it easier to answer.

But your intuition is correct. With analog tape, the transport (the time base) definitely comes first.

Before you set out on a quest to find the best sounding tape playback electronics, you'll first want to remove all the time base distortion (FM and AM haze) originating from the transport and headblock. It's absolutely audible.

So your first step is easy: ditch the recorder!

What you want for optimum playback is a s.o.t.a. reproducer transport and headblock. (Not a 30-year-old studio recorder/reproducer.)

Have you ever heard of ATAE Model One and Model Two reproducers?

If you're interested, we should talk!

Fred,

I have 2 RTR decks.....one 1/4" and one 1/2', so I want both with recording capability. if I could afford another one, maybe it could be playback only. I'd love to get one of your 'super' playback-only decks.
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
The take-away point I'd like to offer to anyone contemplating hacking into the head wiring to connect an outboard tape stage, is that you should first measure the original head and its playback electronics using a calibration tape with many frequencies. (Sweep tapes are available as well.)

Only when you have established the base-line playback amplitude versus frequency response of your tape playback system, can you begin to make an intelligent assessment of whether or not a new outboard tape stage is effecting a real improvement.

Purportedly audiophile quality tape stages that do not even align to the standard playback equalization curves could never be taken seriously by anyone who understands tape playback. Using those products would be akin to playing back tapes with unknown tone control settings inserted.
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
12,467
11,363
4,410
The take-away point I'd like to offer to anyone contemplating hacking into the head wiring to connect an outboard tape stage, is that you should first measure the original head and its playback electronics using a calibration tape with many frequencies. (Sweep tapes are available as well.)

Only when you have established the base-line playback amplitude versus frequency response of your tape playback system, can you begin to make an intelligent assessment of whether or not a new outboard tape stage is effecting a real improvement.

Purportedly audiophile quality tape stages that do not even align to the standard playback equalization curves could never be taken seriously by anyone who understands tape playback. Using those products would be akin to playing back tapes with unknown tone control settings inserted.

Fred, thank you for the excellent feedback on this subject which is beyond the knowledge of most of us tape lovers. it sounds like we need technical assistance to attain proper information for the proper matching of output electronics to the heads. what sort of services along this direction can you provide or suggest to readers?

and I realize we have jumped over the question of whether we need alternate output electronics to begin with; which is, of course, a question.
 

Fred Thal

[Industry Expert]
Jul 15, 2016
161
11
123
Fred, thank you for the excellent feedback on this subject which is beyond the knowledge of most of us tape lovers. it sounds like we need technical assistance to attain proper information for the proper matching of output electronics to the heads. what sort of services along this direction can you provide or suggest to readers?

and I realize we have jumped over the question of whether we need alternate output electronics to begin with; which is, of course, a question.

Mike, I think you're asking exactly the right questions here. Helping critical listeners hear what's actually on the tapes is a worthwhile pursuit and I'm happy that you're interested.

As I see it, the first answer is very simple.

Just ask the purveyors of tape stages to specify the head and cabling to use with their electronics. (They should be delighted to do so.)

And also ask them to publish meaningful performance specifications, showing for example that the connected tape stage accurately aligns to the standard playback equalization curves.

Those simple steps would go a long way towards rescuing high-end audiophile tape playback from the embarrassing quagmire it's stuck in today.
 

Bruce B

WBF Founding Member, Pro Audio Production Member
Apr 25, 2010
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www.pugetsoundstudios.com
Mike, I think you're asking exactly the right questions here. Helping critical listeners hear what's actually on the tapes is a worthwhile pursuit and I'm happy that you're interested.

As I see it, the first answer is very simple.

Just ask the purveyors of tape stages to specify the head and cabling to use with their electronics. (They should be delighted to do so.)

And also ask them to publish meaningful performance specifications, showing for example that the connected tape stage accurately aligns to the standard playback equalization curves.

Those simple steps would go a long way towards rescuing high-end audiophile tape playback from the embarrassing quagmire it's stuck in today.

I did this some time ago.... using freq. sweeps for measuring and testing outboard tape stages vs. stock electronics. Thought I had posted graphs somewhere. I'll have to look.
 

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