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Thread: Head direct-out and after-market playback electronics

  1. #1
    [Industry Expert] Senior Member Fred Thal's Avatar
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    Head direct-out and after-market playback electronics

    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?
    Last edited by Fred Thal; 10-20-2017 at 12:39 PM. Reason: grammar
    Adolph Friederich (Fred) Thal
    Technical Director and Founder, Audio Transfer Laboratory
    Managing Director, ATAE ataudioeng.com

  2. #2
    Site Founder And Administrator Ron Resnick's Avatar
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    This is a great opening post, Fred!

    Please proceed!
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    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

  4. #4
    [Industry Expert] Senior Member Fred Thal's Avatar
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    Quote Originally Posted by topoxforddoc View Post
    . . . 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.
    Adolph Friederich (Fred) Thal
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    Managing Director, ATAE ataudioeng.com

  5. #5
    Member Sponsor [WBF Founding Member] Mike Lavigne's Avatar
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    Quote Originally Posted by Fred Thal View Post
    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?
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  6. #6
    [Industry Expert] Senior Member Fred Thal's Avatar
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    Quote Originally Posted by Mike Lavigne View Post
    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.
    Adolph Friederich (Fred) Thal
    Technical Director and Founder, Audio Transfer Laboratory
    Managing Director, ATAE ataudioeng.com

  7. #7
    [Industry Expert] Senior Member Fred Thal's Avatar
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    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.
    Last edited by Fred Thal; 10-21-2017 at 12:14 PM. Reason: typo
    Adolph Friederich (Fred) Thal
    Technical Director and Founder, Audio Transfer Laboratory
    Managing Director, ATAE ataudioeng.com

  8. #8
    [Industry Expert] Senior Member Fred Thal's Avatar
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    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.
    Adolph Friederich (Fred) Thal
    Technical Director and Founder, Audio Transfer Laboratory
    Managing Director, ATAE ataudioeng.com

  9. #9
    VIP/Donor [VIP/Donor] microstrip's Avatar
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    Quote Originally Posted by Fred Thal View Post
    (...) 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?
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  10. #10
    [Industry Expert] Senior Member Fred Thal's Avatar
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    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).
    Adolph Friederich (Fred) Thal
    Technical Director and Founder, Audio Transfer Laboratory
    Managing Director, ATAE ataudioeng.com

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