Can anyone tell me about the AKAI High()Com Noise Reduction
used in AKAI Cassette Decks like the GX-F37?

How did it compare to dolby B, C and DBX?

I heard Nakamichi also used High()Com Noise Reduction.
Is it the same noise reduction?

Did Nakamichi or AKAI make it?

HighCom was designed by Telefunken in the late 1970s as the simplified,
consumer counterpart to their "Telcom c4" professional noise reduction
system. Telefunken and Aiwa sold outboard noise reduction processors
using the HighCom system in its original form, and Telefunken also sold
separate modules and ICs for this system.

Nakamichi derived their own version which used the Telefunken ICs but
divided the audio frequency range into two parts and used separate
HighCom processors in each half. Recordings made with the Nakamichi
version of HighCom are not compatible with the others.

The system is considerably more powerful (reduces noise and
print-through more effectively) than Dolby "B". If I recall correctly
it is also somewhat more powerful than Dolby "C". Like those two
systems it uses a recorded set-up tone which is used to set the gain in
playback for more accurate tracking. While the system is more tolerant
of playback gain errors than Dolby B or C, dbx is more tolerant than
either of them, and numerically it does reduce noise more than the
others--but dbx is highly problematic, or rather it tends to expose
severe problems in the underlying media (tape modulation noise, for
example). One could even say that it reduces noise too much for its own
good. I was never able to use it for classical recording. And I used
HighCom only once, unfortunately under odd conditions which prevented
it from being calibrated properly, so I hesitate to give an opinion
about it.

--best regards

On 23 Jun 2005 20:16:44 -0700, "David Satz" wrote:

HighCom was designed by Telefunken in the late 1970s as the simplified,
consumer counterpart to their "Telcom c4" professional noise reduction
system. Telefunken and Aiwa sold outboard noise reduction processors
using the HighCom system in its original form, and Telefunken also sold
separate modules and ICs for this system.

Nakamichi derived their own version which used the Telefunken ICs but
divided the audio frequency range into two parts and used separate
HighCom processors in each half. Recordings made with the Nakamichi
version of HighCom are not compatible with the others.

The system is considerably more powerful (reduces noise and
print-through more effectively) than Dolby "B". If I recall correctly
it is also somewhat more powerful than Dolby "C". Like those two
systems it uses a recorded set-up tone which is used to set the gain in
playback for more accurate tracking. While the system is more tolerant
of playback gain errors than Dolby B or C, dbx is more tolerant than
either of them, and numerically it does reduce noise more than the
others--but dbx is highly problematic, or rather it tends to expose
severe problems in the underlying media (tape modulation noise, for
example). One could even say that it reduces noise too much for its own
good. I was never able to use it for classical recording. And I used
HighCom only once, unfortunately under odd conditions which prevented
it from being calibrated properly, so I hesitate to give an opinion
about it.

--best regards


-- I still have an Telefunken Studio 1M portable HiFi set (tuner,
cassette recorder and amplifier all-in one with detachable 3-way
speaker boxes, ca. 35 W/channel). It has the HighCom too. But I used
it only once when I dubbed a tape on which I recorded two friend
musicians at a beach restaurant patio to a cassette. It was long ago,
in 1983 and I still have that cassette. I recorded the tape with 2
Uher dynamic microphones connected to an Uher Royal magnetophone {a
better term than a tape recorder}, at 19 cm/s, 7 1/2 inch/s.

The cassette is still very listenable today, although it's HighCom
processed. At the Telefunken set, you have a switch which has, besides
the High Com on, also a position for reproducing Dolby recorded tapes
which uses a part of the HighCom to roughly match the Dolby B so when
I today reproduce that particular cassette, I use Dolby B.

Here I've found a Japanese page about servicing and obviously a total
recapping of an Nakamichi High Com II where it can be seen 4 High Com
ICs. This is what David said, the two frequency bands were processed
separately and there must have been good results of such an approach
but yes, they are incopatible to all but Nakamichi -- a drawback.
This is what I can conclude of the images as ofcourse I can't do much
with Japanese.

http://www.kantama.com/annex/highcomII/highcomII.htm


Edi Zubovic, Crikvenica, Croatia

ACH wrote:
Can anyone tell me about the AKAI High()Com Noise Reduction
used in AKAI Cassette Decks like the GX-F37?

I think it's basically the consumer version of Telcom C4.

How did it compare to dolby B, C and DBX?

I never used it, and I never even used Telcom C4 to be honest.

I heard Nakamichi also used High()Com Noise Reduction.
Is it the same noise reduction?

It should be the same, although given the vagueries of cassette alignment,
it may be just like Dolby where no two machines ever have quite the same
NR.

Did Nakamichi or AKAI make it?

Neither one, it was licensed from Telefunken.
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

David Satz wrote:

Nakamichi derived their own version which used the Telefunken
ICs but divided the audio frequency range into two parts and
used separate HighCom processors in each half. Recordings made
with the Nakamichi version of HighCom are not compatible with
the others.

I thought the Nak version was the standard way to implement the "home
version" of C4, ie. that it was always a two-way compander.

The system is considerably more powerful (reduces noise and
print-through more effectively) than Dolby "B".

Oh yes, it gives ferric casette tape the same dynamic range as 38 cm/s
halftrack stereo. I recorded the LiveAid concert with HC2 and recently
made it into mp3's, quite acceptable. I probably have the service manual
somewhere, got it prior to replacing opamps in one of the two HCII's I
have.

When watching the adjustment tone on the meters it is quite obvious that
casette tape dropouts do get exaggerated, I did make some radio
recordings on 9.5 cm/s reel to reel using HCII, seems to be a better
setup.

Fairly precise tracking is required for a natural sound, and this
includes internal adjustment of the unit, something that is "fairly
easy" to do with a few standard lab instruments and the service manual.


Kind regards

Peter Larsen

--
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