Were some decks adjusted to use one bias more than another?

[TAGO MAGO]

I recently purchased a Technics RS-615 cassette deck which was manufactured around 1977 and whenever I use a high bias tape, such as a TDK SA-X on the proper Cr02 setting the tape is way too bright, although Sony HF, a general purpose tape, produces a spectacular result.

Since back when this deck was made, chrome tapes, while having been around, had yet to gain the popularity they would in the following years, would this deck have been adjusted to produce optimal results on a normal bias cassette or did someone calibrate the deck on their own to get these results?

 

[dshoaf]

Discussions about biasing and tape formulations raged throughout the 70s. Many higher-end tape vendors would make public announcements about what brands and type of tape they used in calibrating their gear at production. Some even offered custom adjustments for tape brands and type that you could send them - Crown, Ampex and others come to mind.

For cassette decks, most consumers found the whole thing way too complicated and would accept what the manufacturer chose. It was the few who did notice that some types of tape seemed to work better than others - the exception to the rule. One of the reasons there are low/high/normal/CRO2 s setting types was to minimize the choices they had to make. Blank cassette pricing generally escalated with the bias settings, too. That is, the higher the bias setting the higher the cost of tape.

As a bench tech, I was paid occasionally to set up a tape deck using specific tape types. Playing with the inner controls, you could get some rather startling changes with types of formulations. IMHO, many of the enthusiasts for this sort of thing lost sight of the reason for all the different tape types: keeping the noise floor as low as possible.

Hope that adds a bit of perspective - all it does is make me feel old.....

Cheers,

David

 

[Deleted member 89059]

Sony, with the WM-D6(C), basically said "Use BHF, HFX, UCX and METALLIC for best results; for other brands of tape, ask yor dealer to re-align the unit". The innards have eight to twelve bridge points, depending on how you count.
Probably why the Sony UX recorded "better" than the TDK SA.
On better home decks there are manual Bias Compensation/Adjustment/Tuning knobs.

 

[jan_stevns]

Sony, with the WM-D6(C), basically said "Use BHF, HFX, UCX and METALLIC for best results; for other brands of tape, ask yor dealer to re-align the unit". The innards have eight to twelve bridge points, depending on how you count.
Probably why the Sony UX recorded "better" than the TDK SA.
On better home decks there are manual Bias Compensation/Adjustment/Tuning knobs.

yep - and even better decks may have automagic systems, that adjusts several items, so the tape in use is matched allmost perfect.

lot's of decks can do that stunt

 

[Jon_Logan]

Does the deck have a "Cr02" marking? If so, set it to that for SA-X. If it has a "FeCr02" marking, that's no good. I don't even think that tape is made. "Sounds bright" sounds like the tape is waaaay underbiased. It will be thin, tinny, and have high distortion.

 

[cgutz]

Interestin discussion.

In 1978 I had a Technics RS631 tape deck. My friend had a Sony TCK5. Both about the same price range. Mine sounded great with normal bias Maxell tape, but the high ends weren't as strong on a CRO2 bias Maxell tape as my friend's Sony.

I took it to my local authorized Technics service center. They said it was in spec on bias. I contacted headquarters, they said send it in. They too indicated on the service form that while it was in spec when received, based on customer request, they tweaked the bias for UDXLII Maxell tapes. It sounded better when I got it back.

I noticed that Technics deck was really sensitive to brand of tape. Maxells were the best, TDK, Sony, BASF, etc weren't as good as sound.

I eventually sold it and bought a Sony TCK5 (still operating, but not in use) because I felt overall it was a better deck.

 

[dshoaf]

yep - and even better decks may have automagic systems, that adjusts several items, so the tape in use is matched allmost perfect.

lot's of decks can do that stunt

Yeah, those came in as I was exiting the repair biz back then (got a real job in computers!). That was a nice little feature but I never had a deck that had it.

Cheers,

David

 

[Jonny Ramone]

Regular SA tape from the same time period would probably work better, but aren't cheap. You can experiment with other chrome tape. Most decks seem to be set up for 1 tape, as there are usually only 1 set of bias pots and sensitivity pots. My 1984 Technics deck worked best on early 80's SA, and late 80's SD tape.

 

[TAGO MAGO]

On better home decks there are manual Bias Compensation/Adjustment/Tuning knobs.

Funny you should mention that since is one of the few decks that I own that does not have an adjustable bias knob and I do have a Denon DR-M44HX that automatically tunes to the tape being used.

I have a Pioneer CT-F8080 that is about this age and works pretty well at any tape I throw at it. Of course that Pioneer is a slightly better deck than the Technics 615 and probably was adjusted at the factory to work on a wider range of tape. The Technics being a cheaper unit, may have been designed to work with cheaper tape (I think that was their entry level "front loader" at the time).

I have enough decks where the Technics can become the "special normal bias" deck. Although once I get relocated and get the Denon out of storage or my Nakamichi BX-300 fixed, the Technics might just become a playback deck in the bedroom. As long as it was a chrome tape recorded on a different deck, it sounds fine.

 

[Geoff777]

I recently purchased a Technics RS-615 cassette deck which was manufactured around 1977 and whenever I use a high bias tape, such as a TDK SA-X on the proper Cr02 setting the tape is way too bright, although Sony HF, a general purpose tape, produces a spectacular result.

Since back when this deck was made, chrome tapes, while having been around, had yet to gain the popularity they would in the following years, would this deck have been adjusted to produce optimal results on a normal bias cassette or did someone calibrate the deck on their own to get these results?

This deck had one selector for Normal (ferric); Ferrichrome; and Chrome
The switch does bias and equalisation
If Sony HF (Normal) sounds OK then it may have been fiddled with internally
Some decks had only one pot inside and the difference ratio between Normal and Chrome was fixed - so if you turned up the Chrome bias it also turned up the normal bias (lets not talk about Ferrichrome for now!).
However - this may not be the case - often there was more than one pot - and sometimes also Left and right seperate bias pots.
If you can find someone to look inside they may be able to shed some light.
If the ratio of ormal to Chrom is fixed then turning up the bias to work with TDK SA-X will dull the sound of the Sony HF
Sony HF was broadly similar in Bias requirement to TDK D
If TDK SA-X is too bright - maybe TDK SA would be better. SA-X required a little more bias.
Hopefully there will be some seperate pots and the situation can be resolved.
(Please bear in mind this is a vintage machine with limited response by todays standards)

 

[TAGO MAGO]

Yeah, I'll take a look at the bias pots. I am going to have to disassemble and clean and re-lube the deck due to years of neglect. The keys want to jam up and the non-counter operated auto stop mechanism either works all the time or not at all. Of course it might get new rubber as well.

Part of me says that is a lot of work to put into a deck that is lower end than my other decks, but the heads are in good shape and the motor is quiet, so I'll just think of it as a tune up.

 

[TAGO MAGO]

Okay, to tell you how far off this machine is, just for kicks I tried recording on an late 70's, early 80's Avanti C-90 I had lying around. Those of you who know, Avanti made horrible cassettes that were sold in the three pack baggies. I initially expected a horrible sounding recording and instead it turned out pretty good sounding apart from some hiss and the occasional dropout.

Basically the TDK SA-X in this deck sounds thin and tinny while the Avanti tape sounds great. I wonder what this guy had this deck adjusted to use? Concertape?