[Coco] Importing CCRs

[Kevin Diggs]

Gene Heskett wrote:

> Yes I am Art.  The first 'tape' recorders used a rouge coating (to get the 
> iron in a fine grain condition for the higher frequencies) on one side of 
> a 1/4" wide kraft paper tape.  Between the surface roughness of the kraft 
> paper (your basic brown paper bag paper) and the lack of an exciting bias 
> field, the recordings were poorer technically than even todays $10 
> machine can do.  Head life was often less than 500 hours due to the 
> highly abrasive nature of the rouge too.  When the advent of an AC 
> magnetic bias was discovered, which linearized the magnetic properties, 
> the distortion dropped from 80% to 5% in one swell foop, with an 
> accompanying improvement in the noise ratio by about 20 db.  Then it was 
> found that any harmomic distortion in this high frequency bias (running 
> at 80 to 120 khz) also had a pronounced effect on the background hiss and 
> by the time they were done finetuning that and the tape coatings, we have 
> bidirectional stereo recordings at 3.75 ips with 15khz top ends and 60 db 
> snr's.  And distortions were gradually lowered, while peak recording 
> volumes which in the 50's were hard clipped at maybe 6 db above the 2% 
> distortion level, to almost 16db above the 2% distortion levels.  2% was 
> generally where the VU meters were calibrated to show 100%.
> 
You are a bottom less fountain of fascinating facts. Make sure you eat 
plenty of broccoli, carrots, peas and corn. Get a Black & Decker Handy 
Steamer if you have to.

What is rouge? Is it like rust water?

What do you think of cassette decks? I have a Realistic SCT-30 3 head 
deck. It is circa 1980 and sounds pretty good. It has a record level 
calibrate (they call it a Dolby calibrate) and a bias fine adjustment 
knob (on the back?). I think it was made by Hitachi. I once found a 
review of it in some magazine. And they said it was an awesome deck. 
Dolby SNR was like 65 and the top end was around 16k. That review raved 
about how hard you had to drive it to saturate it. I have often thought 
of turning off the bias and seeing what the recordings sounded like.

Most cassette decks have little dolby symbols at +3 db. Do you know what 
they mean?

And to get really silly and pointless. What kind of music quality do you 
think you could get if you took Modem modulation techniques and know how 
and tried to do MP3 digital music with a standard analog cassette deck? 
A modern modem connection is about 50 Kbit, right? A cassette deck is 
stereo (ignoring cross talk issues). I suspect that a cassette deck also 
has greater fidelity than a phone line (ignoring wow and flutter). Think 
it could do 128 kbit?

This is kinda what Philips tried to do with DCC (Digital Compact 
Cassette). Only in my opinion they went in the wrong direction. They 
came out with a new digital gadget that could play analog tapes. They 
should have started with a really good analog deck and did the best they 
could squeezing a digital recording ON A STANDARD TAPE. I have had VERY 
limited success in trying to trick an Optimus DC-2000 into thinking an 
SAQ-X tape is a DCC digital tape. It did work better than trying to get 
a DVHS deck to think a modified normal tape is an SVHS tape. Never seen 
more than a few still pictures with that.

What do you know about back tension?

I bought a Sony DTC-790 DAT deck off eBay. I have not quite gotten it to 
work right. Could the head be bad? If you look at the signal off the 
heads with a scope it is clean for the first 40% of the 90 degree arc. 
But the last part is unstable. Either missing or comes and goes. Think 
it is the head? Or a back tension or alignment issue? I've already 
replaced the pinch roller.

Do you know anything about DVHS? I got one of these off of eBay. It is 
pretty cool. Kinda like a cross between a VCR and a computer tape deck. 
I looked at the drum once. Don't want to know what it might cost to 
replace that thing. It has ALOT of heads! Though if you think about it I 
don't think the information density is very high on DVHS. Couldn't you 
get 2 hours of HD content on a DDS4 tape? Isn't the native capacity 20G 
for DDS4? Don't know if the data rate is high enough?

kevin