Do all type II cassette tapes share the same bias?

[cjacek]

Perhaps a silly question but, as you may very well know, there are several type II tape formulations, even from the same manufacturer. Maxell, for example, constantly "upgraded" the tape and yet still called it "type II", which to me means the bias from the 70's udxlII, for instance, is no different than the later XLII and XLIIS. Same thing with TDK etc..... Can a tape go through revisions and still be bias correct to the original?

[The Ghost of FM]

I believe that most of the improvements made with popular type II cassette formulation had more to do with slightly raising MOL numbers and improving on reducing the drop out count as well as improvements in the shell designs. All of this while maintaining the same bias and eq requirements from consumer decks which often didn't offer the end user much in the way of tweaking the calibration to suite a particular tape... At least not on the front panel.

The only tapes that stood out in my mind as being significantly better were the latter formulations from TDK called the HS-X series which was marketed as a metal tape that could be erased with decks only designed to erase type II cassettes. They seemed to hold the highs a bit better then the SA and SA-X formulations. Denon also had a similar product called the HD-8 series for a while at the same time that the TDK stuff came out...I wonder if TDK made those for them?

Cheers!

[cjacek]

Thanks so much Jeff. I really appreciate it.

[Beck]

Yeah, I would say they were considered "Close enough" in practice, but could in fact be finely tuned. A deck with fine bias control on the front panel allows you to eak out the best performance from a given tape without too much fuss. Many felt the standard bias designations were too broad. Cassette like open reel can sound a bit different if over or under biased... nothing drastic though, IMO. It's only cassette.

[Tim Gillett]

Originally Posted by cjacek

Perhaps a silly question but, as you may very well know, there are several type II tape formulations, even from the same manufacturer. Maxell, for example, constantly "upgraded" the tape and yet still called it "type II", which to me means the bias from the 70's udxlII, for instance, is no different than the later XLII and XLIIS. Same thing with TDK etc..... Can a tape go through revisions and still be bias correct to the original?

I think it's a good question.

I have a booklet from TDK called simply TDK Audio Cassettes, with all sorts of info about their cassette tape range at that time.
Under the heading "operating bias", each of the three different type II tapes of that time are given a bias requirement compared to a reference tape.

So, SF is quoted as +1.0db, SA also as +1.0db and SA-X +1.5db. I take it they therefore required a bit more bias than the reference type II tape, with SA-X requiring a little more than the other two.

At least I guess that means that was the bias needed for the other quoted specs to hold true. As we know, bias can be altered along with record eq (within limits) to give more or less sensitivity, headroom etc in the higher or lower frequencies. And there is always a manufacturing tolerance within one reel of tape and between batches etc. Nothing's perfect.

So, in answer to your question, I guess, yes and no. I guess the TDK tapes at least were pretty bias compatible but there was also room for fine bias tweaking to achieve the factory test results right down to the letter.

Regards, Tim

[cjacek]

That's very helpful. Thank you very much. The TDK specs, especially, give a bit of credence to what I wondered about. Thus, in the most strict sense, type II tapes are not neccessarily bias equal but they're "close enough". OK.

So, I guess, if one wishes to be anal about it, especially when talking about a portastudio, without a bias fine tune knob and a pain to adjust it otherwise, would perhaps be better served using the exact tape formulation which it was setup for originally? On the other hand, the recorder may have drifted some [electronically] so the extra 0.5 or so bias requirement may be a non issue. I doubt one can hear an extra half db + - of bias anyway. But yeah, it's only cassette indeed!

[Tim Gillett]

Originally Posted by cjacek

That's very helpful. Thank you very much. The TDK specs, especially, give a bit of credence to what I wondered about. Thus, in the most strict sense, type II tapes are not neccessarily bias equal but they're "close enough". OK.

So, I guess, if one wishes to be anal about it, especially when talking about a portastudio, without a bias fine tune knob and a pain to adjust it otherwise, would perhaps be better served using the exact tape formulation which it was setup for originally? On the other hand, the recorder may have drifted some [electronically] so the extra 0.5 or so bias requirement may be a non issue. I doubt one can hear an extra half db + - of bias anyway. But yeah, it's only cassette indeed!

No problem. I dont know just how much say 1.0db of bias change translates into say 10khz level change. I mostly used a cro when looking at, and adjusting bias waveforms and there was no db scale to read, so db's is not a language I'm familiar with in terms of bias levels. But having said that, I think bias level with cassettes, especially slow speed, can be pretty touchy. Even more so using NR.

I think the most common biasing issue with portastudios today would be overbias due to a worn head, ie metal having been removed. I think we discussed this in a recent thread.

The recommended advice often was to try different tapes until you found one which sounded true on your machine and then stick with it. That's fine up to a point but of course machine wear can eventually change the bias requirement and you're no longer calibrated to that tape. The best way is still to regularly maintain and calibrate the machine, to whatever tape is used, whether it's reel to reel or cassette.
As Beck says, the fine bias adjustment on some decks is a great help and I feel it's a pity it wasnt incorporated on some of the top portastudios. OTOH it is only an overall bias adjustment and there's no guarantee all four or eight tracks will have altered by the same amount.

Regards, Tim

[cjacek]

Yeah, fine tune bias adjust would have been cool on the portastudios, especially the top of the line ones. In fact, I wonder how much extra $$ it would have cost to put in a seperate playback head and front panel [full] electronic adjust trims on the 246, kinda like the ones they have on the half track Otari open reel recorders? Those features I'd take over some others. The way I figure it, the 246 cost almost an arm and a leg in its day and thus an extra hundred dollars or so, for the privilage of the extra head and adjustment trims, wouldn't matter to the person who had that type of money. I mean, what's $1800 vs $1950, when you have that kind of money.

Tim (Beck): do you recall what the TASCAM 246 cost retail? When did you buy yours?

Thanks guys,

Daniel