Tape Bias

[Holy Zoo]

Dear Anyone Who Knows,

I have a cassette deck that has a bias trim knob. It also has a built in 400hz and 10khz signal generator.

Can someone teach me what to listen for when twiddling with the knob?

Thanks!

Signed,

Clueless in Capitola

[-=Rudy=-]

What brand of deck?

Keep in mind I have a two-head deck. On my Harman Kardon, the test tones were recorded, then played back. The Dolby calibration levels, IIRC, were calibrated using the lower tones. After those were aligned right at 0dB on the meters, the higher-frequency tone was recorded, and bias adjusted so that the bias level on the right meter matched the Dolby level recorded on the left. It's been so long that I don't really recall it exactly right, but the meters were used in the calibration of the deck.

I made some killer TDK D-90 cassettes that impressed a lot of friends who couldn't believe a cheap cassette blank could sound so good.

[Clay]

My deck is currently set up as:
Bias high and EQ normal
limiter off.
Dolby off
Last tape played was a MFSL.
I always set bias and eq as recommended by the tape for recording and Dolby off.
For playback I adjust for the best sound. I like highs so I set it for the best highs without hiss. I don't usually have hiss so I go with the most highs.
Someone else can explain the technical reasons for adjusting the bias and eq to match the tape type. I also only use Maxell XLII tapes.
If you post the model, I may be able to find a manual for a similar model around the house or on line for a free download.

Maxell XLII specs:
High Bias
IEC type II
EQ 70us

EQ is for the type of tape:
Chr
Fe-Cr
Normal
(Metal for new decks is probably available)

If you never listened to a MFSL cassette, you should try it it sounds better than CD on a good deck. I use a 1975 top of the line Sony. It is so good most people cannot tell if it is the tape or CD/LP if switching the same song around on the pre-amp.

[Casino]

I have a Nakamichi that has a signal generator to set bias automatically, but I find I can do it better by ear. If you have a 3-head deck it's a lot easier, as you can take a musical selection with good bass and highs and compare the original to the recording instantaneously. You can adjust as you listen. Cymbals, bells, etc. obviously will be dulled with too much bias. Too little will exaggerate highs and could increase distortion.

[Holy Zoo]

Originally posted by Rudy@A&MCorner
What brand of deck?

BIC T-04M, 2 speed, 3 head (separate record and playback heads).

On my Harman Kardon, the test tones were recorded, then played back. The Dolby calibration levels, IIRC, were calibrated using the lower tones. After those were aligned right at 0dB on the meters, the higher-frequency tone was recorded, and bias adjusted so that the bias level on the right meter matched the Dolby level recorded on the left. It's been so long that I don't really recall it exactly right, but the meters were used in the calibration of the deck.

Thanks Rudy - I'll play around and see if I can make heads or tails of it with the above in mind.

jeff

[Grant]

HZ,

On a three head deck, there should be some means to calibrate it with the meter.

On my Sony decks, I adjust the bias first, bringing the meters up so they are equal. Then, adjust the sensitivity until the meters are equal with the Dolby calibration mark.

If you don't have a test tone ocillator, use a broadband signal like FM tuner noise and adjust by ear. I used to tweak my settings with actual music.

You have to do this with every tape. Even the same grade of tape from the same manufacturer will be slightly different from batch to batch. I even calibrate each side!

[Tony Plachy]

Originally posted by Holy Zoo
Dear Anyone Who Knows,

I have a cassette deck that has a bias trim knob. It also has a built in 400hz and 10khz signal generator.

Can someone teach me what to listen for when twiddling with the knob?

Thanks!

Signed,

Clueless in Capitola

Do have the manual for the deck? If so there ought to be a calibration procedure in it because you have most of what you need to calibrate. If no manual try the web to download one.

[Beagle]

With my three head Denon deck, I monitor and adjust the bias (while going back between tape and source) until they sound about the same.

[Grant]

Originally posted by Beagle
With my three head Denon deck, I monitor and adjust the bias (while going back between tape and source) until they sound about the same.

To me, this seems like the best way to do it, because even tones aren't like music, and you can't always get all tapes to match up to the source perfectly. I had my best luck with TDK SA-X and Sony High Bias. Sometimes even TDK D came out a winner. And, I used either Dolby B or S. Since I have no reason to use Dolby S anymore, I stick with either B or none at all.