Cassette tape types

[mitajohn]

Originally Posted by knobtwiddler

The very last cassette decks made in the late 90s had Dolby S - taking the humble format's SNR up from around 60dB (on a healthy deck / tape) to 80dB.
NB - the 215 is the best deck I've heard. I got one out of a duping house. It didn't record well, but it played like new.

Sony produced cassette decks equipped with Dolby B,C and S.

I have measured the record-reproduce SNR on a Studer 8 track machine equipped with Dolby SR at nearly 96dB linear, not weighted! It was too close to the noise measuring gear limit!

Yes Revox B215 is a superb cassette deck as it's professional brother Studer A721, equipped with transformer balanced Ins/Outs and parallel RC. But both they have a little flaw: While they are 3 headed decks, the R/P head block is constructed in such a way not permitting azimuth adjustment of the record head! You had to live with the manufacturer's set-up. If you were lucky your head block would be close to "a few" degrees of azimuth error between the record and reproduction heads.

[knobtwiddler]

That is highly interesting, thank you, John. I suppose that could explain the disparity between recording / playing on the 215 that I had? In terms of playback, I felt it sounded better than the machine I made the tapes with. I didn't get a chance to take measurements.

I am seriously thinking about a later Sony machine at this point. The Naks are too much of a headache if they go wrong.

I have to agree with Paul's point re: TDK tape and Japanese machines. I've been digging through cassettes this week. The SA and MA have definitely stood the test of time well and sound as good as I remember them. I have a few of the TDK 'CDing', which definitely do not sound anywhere near as good as the SA. Am wondering if this is due to biasing, or simply that CDing is not as as SA (few tapes are).

[cheerfulcharlie]

Originally Posted by stevehertz

Looking at the age profile of members, most of us will be struggling to hear above 10khz. I tested myself a few weeks ago, 10k ok, 12k nothing.

True and ironically young ladies (who apparently have the best frequency response of all) have never appeared to be remotely interested in all this bells and whistles stuff LOL..and were quite happy to enjoy their tunes on a Dixon's Matsui special..

[TIMTAPE]

Originally Posted by mitajohn

...Yes Revox B215 is a superb cassette deck as it's professional brother Studer A721, equipped with transformer balanced Ins/Outs and parallel RC. But both they have a little flaw: While they are 3 headed decks, the R/P head block is constructed in such a way not permitting azimuth adjustment of the record head! You had to live with the manufacturer's set-up. If you were lucky your head block would be close to "a few" degrees of azimuth error between the record and reproduction heads.

I agree. The only such head I know of which provided independent fine mechanical alignment of the record head to the repro head in the one block was Teac's for their pro Tascam cassette decks such as the 122 Mk III. In the photo I show three separate views of the head. In the right hand headblock the playback head is removed to show the record head's adjustable base normally hidden underneath the playback head. The black Philips head screw to the right of the record head is its azimuth screw and could be adjusted from the front panel while recording a tape and monitoring the playback. So in this sense the Teac headblock's adjustment equalled that of the Nakamichi 3 head decks. The shot of the headbase viewed from underneath shows the black Allen screws for pre adjusting front and rear height of the record head. A beautifully designed and manufactured unit in my opinion.

But an Achilles heel of all non Nakamichi head designs: omitting a pressure pad lifter. A shame perhaps that Nakamichi and the other manufacturers didnt come to some sort of agreement on its use in non Nak decks.

[mitajohn]

The Sony TC-K555ES deck is equipped with a similar head block.

As mentioned in it's Service Manual on page #2:

Three-head system
Separate record and playback heads allow optimum gap settings
and impedance ratings for distortion-free recording and greatly extended
frequency response. For good tape·to-head contact the
heads are mounted in one block and each head is separately adjusted
for precise azimuth alignment. The three-head system also
enables you to monitor the recorded tape while actually recording.

[TIMTAPE]

Thanks John. Any chance of a photo of the Sony head and the adjustment screws?

Tim.

[mitajohn]

There is a pic on page #17 of the SM, but not so good.

NB: The SM can be found easily searching the net...

[TIMTAPE]

Got it, and instructions to adjust record azimuth on page 25. Looks like the screw being on the play head side means the record head has a similar mounting plate as the Teac, running underneath the play head. I guess underneath the play head was the only way it could be squeezed in.
Well done Teac and Sony. Raises the question why the Revox (Sony sourced) head didnt also carry this feature.

[Ted Kendall]

Originally Posted by TIMTAPE

...an Achilles heel of all non Nakamichi head designs: omitting a pressure pad lifter. A shame perhaps that Nakamichi and the other manufacturers didnt come to some sort of agreement on its use in non Nak decks.

Quite so, but without the semi-hyperbolic face grind and guttering of the Nakamichi heads, sufficient tape-to-head contact may not have been maintained.

[TIMTAPE]

Originally Posted by Ted Kendall

Quite so, but without the semi-hyperbolic face grind and guttering of the Nakamichi heads, sufficient tape-to-head contact may not have been maintained.

Sure, without the pressure pad face the usually straight ahead facing head faces have to be angled differently. I've set up a couple of dual capstan decks for playback only, with the one playback head in the normal centralised position and with my own pressure pad lifter added. Record and erase heads removed. Tape path much simpler and head wear reduced. If I had the machining gear I'd add some gutters to the head face.

[mitajohn]

I found two nice photos of the SONY head block and tape path without the pressure pad and I reproduce them here.

[TIMTAPE]

Thanks John. I found in my cassette deck heads box an old Sony TC-K444ES headblock. Photo shows a comparison with a Tascam 122 MkII/III, with play heads removed for clarity.

Definitely not identical. Teac positions the record azimuth screw next to the record head while Sony places it on the other side next to the play head.

But note the similarities even to apparently the same mounting hole dimensions.

[mitajohn]

Thanks, interesting photos.
BTW the B215 headblock is manufactured by Cannon.

[mitajohn]

Originally Posted by mitajohn

Thanks, interesting photos.
BTW the B215 headblock is manufactured by Cannon.

Correction: "manufactured by Canon".

[knobtwiddler]

Not to be confused with ITT Cannon who make the connectors

I made a similar mistake when my email wouldn't work. I wrote 'SMPT' and not SMTP...

[mitajohn]

Without any doubt it's a Canon made head block...