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Thread: Cassette and Bias

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    Arrow Cassette and Bias

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    The "classic" low-end and midline home stereo cassette decks would typically have bias control and settings internally & factory set,... but for what tape specifically?

    Could you assume, as we did in the 80's, that any Japanese mf'd cassette deck would be set up for TDK-SA tape as a standard? (I don't know how or why we assumed this in the 80's, but it was an assumption).

    Higher end cassette decks would tend to include bias-fine tuning control on the front, with the majority of them having no other facilities such as internal test tones. Why include this feature as a half-ass component, or rather, how would the layman in practice determine how to set this control without proper test tones?

    The cream of the crop high end cassette decks had bias control and test tones, like Tascam 122 master decks (I-think) and Nakamichi's, which some NAKs were really slick and had auto alignment. Swift! However, I've never owned a 122 or Nak.

    Further, on older Tascam Portastudios I seem to remember they stated in the manuals they were set up for TDK-SA tape. Newer manuals wouldn't specify brand names. That's by memory & isn't iron clad in my mind ATM. Be that as it may,... is all well and fine.

    Here's the gut of my question:
    1) If bias control is so important, why is it inaccessible on most cassette decks as an internal adjustment? Or worse, as an adjustment control that's only half-implemented? Was it assumed that it's factory setting would be good to go forever, or the user incur bench time? Was it really that important?

    2) Are all the (formerly available) cassette Type II tapes "bias compatible" to such a close degree that they're all basically the same? Is there an average or middle-of-the-road setting that's good for all?

    I've read on Tapeheadz reviews of name brand tapes, shootouts, etc., and the users often go on how different tapes need different biases. Of course, this is the NAK-crowd, so some of that is to be expected.

    3) For my Tascam Portastudios, typically I'd never adjust or tinker inside (only by necessity!), but if I did, what tape would be the "best" tape to bias to,... then just use the rest as is? I have a great many varieties of Type II cassettes, including Maxell, TDK, Fuji, JVC,.... Ampex,... probably more that I can't remember. Memorex,... Emtec,...

    4) Would using different brand name Type II cassettes require you to tinker with the unit nearly endlessly? Is there a strategy involved? I don't know if it's bias is an issue specifically, but most laymen would notice very slight differences in fidelity between different brands of cassettes in a shootout.

    I limit the scope of my questions to Type II tapes, as that's more "audiophile" level sound quality & is mostly what I use, myself being a big Portastudio user and casual tapehead for general use. I used to be super-into cassette recording in the 80s & 90s,... less so now with the advent of CDr.

    Could anyone offer any wisdom, tips or advice on the subject. Granted, it's light fodder and not a major concern, as my cassette recordings sound generally good.

    As a parting shot, as bias is taken as a higher concern in reel-reel recording, why aren't the controls on most machines easily accessible? Most home recording decks would have internal adjustments under the bottom panel, while the high end or studio machines have these controls easily accessible. Then, regardless of what I read it's always emphasized that bias is set to the reel tape used. However, where does this leave the person who has a large variety of tape to use? Bench teck or DIY every time you change batches?

    Aaaggghhh. For a non-important issue, this one is really bugging me?

    Forget the quick response: "Go-digital"!!!
    Last edited by A Reel Person; 04-03-2009 at 13:27.
    Quote Originally Posted by Lt. Bob
    ... subtleties of sound make a difference to those who really listen.

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    Forget the quick response: "Go-digital"!!!
    Utter heresy.

    I look forward to other's responses to this because its one of the things that sort of lingers in the back of my mind too. I think with regard to consumer cassette it may be more of a splitting hairs thing to some degree. Dunno...

    I always (right or wrong) sort of equated Type I/II/IV differences as far as bias to +3/+6/+9 etc. In other words you'll find a closer bias compatibility within different +9 open reel tape...yes there are other differences in formulation that make up that ideal bias demand and hence maybe fine-tuning is desirable to some, but we generally say that, for instance, 996/499/GP9/SM900 are "bias-compatible" right? Or am I wrong? I know that to be true with 456/SM911 for instance...

    So that's been my thinking and I've always figured that I was good to go if the manual of a cassette deck recommended a Type II tape then I assumed it was factory set bias compatible with that general formulation and as long as I was using a Type II tape I was good to go, or at least good enough to go.

    My Onkyo TA-2058 has auto bias tuning on it as well as a -2, -1, 0, +1, +2 fine tuning knob...the manual (IIRC) doesn't go into any real technical detail about what is going on nor any instruction on when to use it or why...back when I was using that deck much more and before I really had any technical understanding of what bias is in this regard I used to generally set it to +1 because the recordings sounded a little sparklier to my ears and I liked that...so it was a "crispy" control as far as I was concerned. Now you've got me curious to re-read that part of the manual.

    I'm wondering if cjacek will have some input on this...he has a cool tape deck that takes it to a whole new level...maybe he doesn't want me saying anything...but that's not stopping me from pressing the "Submit Reply" button with verbage intact now is it...?

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    Arrow Thanx Beatz!

    I have a 90s Technics RS-B465 which has a Bias control, but I've always left it in the middle position & haven't experimented with settings at all. Likewise, I think my Technics RS-B555's also have this setting, as yet in middle position and untouched.

    I've always figured the class (TypeII) was specifically compatible enough across the board, but why the user adjusment controls for bias? There's something there I've been overlooking literally for decades!

    When you get down to tinkering with the controls and find it most pleasing on "lightly crispy" setting, isn't that entirely subjective?

    I also seem to remember hearing that the interband static from the analog FM tuners would be a nearly-flat source of pseudo-pink noise,... sometimes useful for adjusting,... but then you're still in the subjective realm to judge sound quality, aren't you? Anyway, who has analog FM anymore???

    I have a BSR-EQ3000 that has a pink noise generator. Would this be useful for setting bias fine-tuning?
    Last edited by A Reel Person; 04-03-2009 at 13:57.
    Quote Originally Posted by Lt. Bob
    ... subtleties of sound make a difference to those who really listen.

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    When you get down to tinkering with the controls and find it most pleasing on "lightly crispy" setting, isn't that entirely subjective?
    Absolutely...that was my point. This silly bias fine tuning knob that to me was a "crispy" control...no clue.

    I have a BSR-EQ3000 that has a pink noise generator. Would this be useful for setting bias fine-tuning?
    I don't think so...all the bias "fine-tuning" on any of my reel machines is done using a 16K tone, and then you can always drive a 30 or 40Hz tone in and listen for "rocks" but I have no clue if that works for cassette machines with the more limited low-end response.

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    Arrow Ageed,...

    and so I've read, needing proper test tones.

    Thank you!
    Quote Originally Posted by Lt. Bob
    ... subtleties of sound make a difference to those who really listen.

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    Red face Bias Revealation

    Hi,
    I have a Tascam 103 with a bias control on the front with a center detent position. I also have a Tascam 122 MKIII with all the bells and whistles. The manual for the 103 says to simply monitor your recording in real time switching between the the input signal and the third head and adjust to get a sound that is close as possible to the input. If you only have 2 heads you can rewind and listen to your adjustments, not as good as 3 heads but still possible. I have learned alot about bias this winter, I have started calibrating all my machines. Basically bias is a very high frequency signal, say 150KHZ, that is mixed with your signal to help excite the magnetic properties of the tape. As biased is increased from the minimum setting the bass and treble rise together, but the treble is always ahead of the bass, so too liittle bias results in too much treble and not enough bass. As you continue to increase the bias the bass continues to rise but at some point the treble levels off and will decrease with more bias. This is called overbias and is what you want. As the treble continues to fall with increased bias the bass is still rising and will at some point meet the falling treble for a flat response. If biased is increased further bass will continue to rise while treble will continue to fall resulting in too much bass and not enough treble. I am glad I finally understand this myself, for 15 years I wondered what was going on.
    Victory Pete

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    Arrow !!!

    Thank you for such an informative and lucid answer!!!

    2-head setup is always way more of a pain than 3-head recorder setup!!!!

    Alas, I have NO 3-head cassette decks, but several 3-head R/R's!!!!

    I think I've heard the basic "get the recording sounding as much like the input signal as possible" technique described, but I don't explicitly recall ever reading the User Manuals for any of my cassette decks!! My-bad!!
    Last edited by A Reel Person; 04-05-2009 at 18:44.
    Quote Originally Posted by Lt. Bob
    ... subtleties of sound make a difference to those who really listen.

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    I think Portastudios would have to have been one of the worst for adjusting bias.

    1. 2 head machines.
    2. 4 to 8 tracks to adjust
    3. On some models the case splits into two halves with not enough extra cable length to adjust the bias (and other trimmers) on the bottom PCB without having the top half in the way, resting on your knuckles.

    It would have been so much better if they'd included a "bias trim" control on the front panel. Assuming the deck was in basic alignment you could easily trim out any high frequency misalignment with just one control -
    instead of having to strip down the machine and adjust 4 to 8 separate trimmers. A no brainer IMO.


    Cheers Tim

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    Arrow Agreed!

    Whether it's older access-thru-bottom or newer split-case models, the adjustment access on Portastudios is very challenging!

    Thank you!.........
    Quote Originally Posted by Lt. Bob
    ... subtleties of sound make a difference to those who really listen.

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