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Conference cookie::notes$archive:cd_v1

Title:Welcome to the CD Notes Conference
Notice:Welcome to COOKIE
Moderator:COOKIE::ROLLOW
Created:Mon Feb 17 1986
Last Modified:Fri Mar 03 1989
Last Successful Update:Fri Jun 06 1997
Number of topics:1517
Total number of notes:13349

56.0. "Nakamich OMS-7/OMS-5" by PYRITE::WEAVER () Sat Dec 08 1984 23:22

The following is a re-type of the brochure on the Nakamichi OMS-7/OMS-5
Compact Disc Players.  I thought it might be of universal interest.

						-Dave


		  Digital Sound From Nakamichi
________________________________________________________________________

If you've always wanted a compact disc player but never felt
comfortable with the harsh and unrealistic music of "digital sound"
that many CD players sound, the Nakamichi OMS-7 and OMS-5 Compact Disc
Players are what you've been waiting for.  Nakamichi...the company
that created the OMS-1000 - the worlds first commercially available
optical memory system, a research tool capable of recording and
reporducing a variety of optical recording media - has designed compact
disc players that met Nakamichi's standards - Nakamichi Sound!

Perfect Filtering

Every CD player uses some form of low-pass filter to recontstruct a
continuous analog signal from the sampled data that emerges from the
D/A (Digital-to-Analog) converter.  There are two possibilities: direct
D/A conversion at the disc data rate (44.1 kHz) followed by an
extremely steep ("brick wall") analog filter (Fig. 1), or,
"oversampling" the data to increase its frequency and permit digital
filtration, and then follow the digital filter with a gently sloping
analog filter (Fig. 2).

When data is converted from digital to analog form at the 44.1-kHz rate,
sidebands surrounding the sampling frequency extend as low as 24.1 kHz
(44.1kHz - 20kHz) as shown in Fig. 1 (c) requiring 9- to 11-pole
filters having an extremely steep slope.  Such "brick-wall" filters
inevitably have severe phase distortion and non-constant group delay at
high frequencies which result in audibly inferior sound.

The approach taken in the OMS-7 and OMS-5 is completely different as
shown in Fig. 2.  After quadruple oversampling digital filtering and
D/A conversion, the signal spectrum soncists only of the desired
baseband information (from 0 to 20kHz), and the sidebands surrounding
176.4kHz (4 times 44.1kHz) and its harmonics.  As a result a gently
sloping [analog] filter is all that's needed as shown in Fig. 2(c)
producing constant group delay and linear phase-filtering and virtually
no phase distortion.

Perfect D/A Conversion

Many CD players share a single D/A converter between both channels,
converting left and right information sequentially - not
simultaneously - so there's a timing error between the two channels
that causes an interchannel phase difference.

Another problem is that left and right signals are separated after
conversion, that is, when they are in analog form.  The switching
circuit used to separate the channels can introduce noise and
distortion.

In the OMS-7 and OMS-5, by using dual D/A converters, left and right
data samples are separated prior to conversion, that is, while they
are still in digital form.  The deinterleaving switch cannot introduce
noise or distortion, and the two channels can be converted
simultaneously by separate D/A converters.

Direct-Coupled Linear-Phase Analog Signal Processor

In designing the OMS-7/OMS-5's analog circuitry, we've gone to
extraordinary lengths to preserve the pristine purity of the original
sound.  To eliminate the possibility of digital noise from every
source, the OMS-7/OMS--5 analog circuitry is separately constructed and
enclosed in a special module called Direct-Coupled Linear-Phase Analog
Signal Processor.

The entire module is housed in a shielded enclosure to ensure
electrostatic and magnetic immunity.  Not only is the analog circutry
powered separately from the digital circuitry, but left and right
channels are separately powered by regulated bipolar supplies.  Even the
grounding systems are independent to ensure total shannel isolation at
all frequencies - not just in the midrange.  The analog circuits are
directly coupled to eliminate distortion - causing capacitors.
High-purity oxygen-free-copper (OFC) wiring and gold-plated output
terminals are used to ensure the purity of the signal.

The results are flat response with minimum ripple right up to 20kHz,
THD that never exceeds 0.005%, and channel separation that approaches
100 dB over most of the band is a remarkable 90 dB at 20kHz!

Precision-Engineered Drive and Servo Systems

The Nakamichi OMS-7/OMS-5 disc-drive mechanism is mounted on an
exclusive zinc-alloy diecasting which is suspended on coil springs so
that it floats free of the disc-loading mechanism and the main chassis.
This makes it vitually impervious to external shock and vibration.  The
disc is driven by a cog - and vibration-free linear torque motor to
ensure smooth rotation.

Focusing errors are detected through a critical-angle prism.  Tracking
error is determined by a heterodyne detector.  These two detectors feed
[the] precision servo mechanism to keep the laser on track and in perfect
focus even when the disc is slightly warped.  The servos have
exceptionally fast response time to allow precise cueing and quick
access to any portion of the disc

OMS-7/OMS-5 Feature Comparison Chart
						      OMS-7   OMS-5

Quadruple Oversampled Digital Filters			X	X
Independent Left & Right D/A Converters			X	X
Direct-Coupled Linear-Phase Analog Signal Processor	X	X
Floating Disc-Drive Mechanism				X	X
Precision Centering Mechanism				X	X
Cog-Free Linear-Torque Drive Motor			X	X
Critical-Angle Focus-Error Detector			X	X
Heterodyne Tracking-Error Detector			X	X
Fast-Responding Precision Servo System			X	X
Direct Load-Play/Load-Pause				X	X
Direct Track Search					X
Direct Index Search					X
24-Program Memory					X
Memory Clear						X
Memory Recall						X
Bidirectional Skip Search				X	X
2-Speed Cueing						X	X
Repeat Play						X	X
Remaining Track and Time Displays			X	X
OFC Wiring and Gold-Plated Output Jacks			X	X
Headphone Output with Volume Control			X
Wireless Remote Control					X

OMS-7/OMS-5 Specifications

System..............................Compact Disc Digital Audio
Signal Detection....................Contactless optical system
				    with solid-state laser element
Error Correction....................CIRC system
Number of Channels..................2 channel stereo
Sampling Frequency..................44.1 kHz
				    [176.4 oversampling]
Quantization........................16 bit linear
Disc Rotational Velocity............Approximately 200 to 500 rpm
				    (Constant Linear Velocity)
Wow and Flutter.....................Unmeasurable
Frequency Response..................5 Hz - 20,000 Hs +/- 0.5 dB
S/N Ratio...........................Better than 92 dB (A-WTD)
Total Harmonic Distortion...........0.003% (1 kHz)
Channel Separation..................Better than 92 dB
Output (Line).......................2 V (1kHz, 0 dB), 100 ohms
 (Headphone)(OMS-7).................20 mW(1 kHz, 0 dB,
				    output control max.) 8 ohms
Power Source........................100, 120, 120/220, 220
				    or 240 V AC; 50/60 Hz
				    (according to country of sale)
Power Consumption...................30 W maximum
Dimensions..........................435(W) X 100(H) X
				    308(D) millimeters  17 1/8(W) X
				    3 15/16(H) X 12 1/8(D) inches
Approximate Weight..................7.5 kg; 16 lb 9 oz.

Remote Control Specifications
(Supplied with OMS-7)

System..............................Infrared pulse transmission
Power Supply........................3 V DC (1.5 V X 2)
Dimensions..........................57(W) X 175(H) X 19(D)
				    millimeters 2 1/4(W)
				    X 6 7/8(H) X 3/4(D) inches
Approximate Weight..................140 g; 5 oz

*Specifications and appearance subject to change for further
improvement without notice.

T.RTitleUserPersonal
Name
DateLines
56.1BAGELS::ROSENBAUMSun Dec 09 1984 01:285
Well that certainly reassures the EE, optics expert, mechanical engineer,
and physicist residing in the left side of my brain.  They don't actually
say it sounds better, do they?  Has anybody heard it?

__Rich  :-)
56.2PICA::HIDERSun Dec 09 1984 02:254
Well, the specs sound impressive..  Well, they did until I compared them
to the Yamaha CD-2, now they don't look so hot..

still, its the sound, features and quality that counts..
56.3SUMMIT::GRIFFINMon Dec 10 1984 01:563
I assume we have to pay for the flowery advertising...  Ballpark $ anyone?

- dave
56.4PYRITE::WEAVERMon Dec 10 1984 13:2313
I think Tweeter was quoting somewhere around $1200 for the OMS-7
and $800 for the OMS-5.  The sound should be the same between the
two players, so if a decision comes down to between the two, it
should just be a question of features.

I have always noticed a little extra player induced hiss with my
Sony CDP-101 player, I may consider switching.  The thing that
impresses me the most with the Nak is that they have taken great
pains to isolate the digital and analog circuitry.  Does anyone
know if any of the other models around go to this degree of
isolation?

					-Dave
56.5CSBCOM::PARKERTue Dec 11 1984 16:359
I heard the /7 last night here in North Carolina.  All the funky high ends
and wierd horn sounds that I had come to associate with CDs in general
are gone!  This is the first player I've heard (and I've heard most of them)
that I want to take home and use for awhile.  I'm borrowing one for the
weekend and will post another note if impressions on living with it are
different from now.  Incidentally, my dealer is discounting th /7 by
about $100.

/dave
56.6ADVAX::J_ROTHWed Dec 12 1984 00:4013
I seriously doubt that there's any sonic difference between the Nakamichi
and other good CD players (unless you're the type that can hear gold plated
connectors and the like).  It is likely that the Nak player has had better
than average attention to details such as layout and shielding; but any
player that's working properly will have a noise and distortion level that's
below the level on your recordings.  (re .4 - your CDP101 may have a problem,
its noise shouldn't be audible).  It would be interesting to see if it has
substantially better than average error correction and tracking capibility.

Of course, its psychologically gratifying to own asymptotic products like
that if you can afford it...

- Jim
56.7XENON::MUNYANWed Dec 12 1984 01:508
Re: .4

You might want to take a look at the Kyosara if price is no object.  I've
heard several people talk about it and it appears to be the top as far as
quality components and isolation goes.  But then again who can put up with
a suggested retail of $1600.00 (although I haven't seen it at this price).

Steve
56.8CSBCOM::PARKERWed Dec 12 1984 15:2024
Before you condemn, try it.  Listen to the Nak vs teh Kyocera or the 
Sony or the NAD or the Yamaha as I have now done.  Admittedly, I have a 
high-end set-up, Audio Research Tube amp and preamp, etc.  But the differences
in CD players are there, real and non-subtle.  They are demonstrable on
any number of good quality systems as well. My stuff just makes it more
quickly apparent.

I must say that my Sota turntable and Koetsu arm with Monster Alpha II
cartridge still handliy trounces ANY CD. Nak got the high end right, I
can now listen without a headache but I ain't going to pay anything for
something that doesn't sound as good as what I've already got.

My basis for comparison has been CDs and LPs of Lincoln Mayorca and Amanda
McBroom from Sheffield and the new Paul Simon.

set /flame=off

Don't get me wrong - I'd like nothing better than for this technology to
work for a whole bunch of reasons.  It's like night and day now vs. a year
ago, and I could probably live happily with the Nak if I didn't have something
better.

/dave
56.9THORBY::MARRAWed Dec 12 1984 17:1522
	Dave -

	You've gone a long way to improve your system to it's level.
	The components you have talked about are of the finest available,
	agreed 100%.

	Considering those who cannot afford the Turntable/tonearm setup you
	have assembled.  Would the NAK be as good as this setup, and since
	CD's ARE getting better, foreseeably (sp?) be better??

	Please take into note also that the price of a very good virgin
	record is anywhere from 18$ to 50$ and wears out.  And that CD
	are also getting cheaper...

	Im not disagreeing with you at all, I've heard some very impressive
	records on my system, and not haveing a cd, can only imagine
	better.......

				dave
				----

	looking for the best from now-on...
56.10CSBCOM::PARKERWed Dec 12 1984 17:4630
I don't think so, at least not yet.  But you're correct, asking a $1300
(or $900 for the OMS-5) machine to sound like a $2200 machine ($2800 if
you include the VPI record cleaning machine ) is probably unfair.

The technology will continue to improve, but I'll be it won't be CD,
Phillips has a prototype bubble memory system that I think samples at 66k;
others are playing with ROMs of various types. No moving parts!!

If I had to live without a turntable of the quality of mine (good, I think),
then I could live with the Nakamichi in my system happily.  Knowing
what can be done with the LP (and you're right again, they're expensive),
I choose not to buy yet.  That's my real point.

I really wish it wern't so. I want that neat shiny little disk to work
and work well. It's so much more convenient and lasting.  But I also
want the best sound I can afford, ergo LPs still.

Incidentally, I do think that on 90 - 95% of all systems out there, the
Nak will do the job. Also, using the LPs is worthless without a VPI, 
Nitty Gritty or other cleaning machine to keep them in good shape.
Records rarely wear out, they get incredibly grungy, and the machines
clean them up good as new.  I've got over 1000 albums mostly from late
60's and early 70's that still sound fine. But they require care as to
cleaning and storage that sometimes trys my patience.

Hope this helps - I respect the Nak a great deal but it ain't my cup
of tea even though it's the closest I've heard yet.

/dave
56.11ELUDOM::CLARKWed Dec 12 1984 20:507
RE: .8

Watch out about using Sheffield pressing to do your LP vs. CD comparisons.
Others have expressed concern that the Sheffield CD's are not well
engineered and do not represent the same level of quality as their LP's.

Ward
56.12CSBCOM::PARKERThu Dec 13 1984 13:427
Agreed - that's why we used the Paul Simon and Dave Grusin as well
as some Boz Scaggs.  The Sheffield CDs are cut from an analogue master
made at the same time as the direct-to-disk cuts - therefore they have
at least 1 generation loss built in.

/dave
56.13XENON::MUNYANMon Dec 31 1984 15:388
Re: .8

I just got back from vacation and heard the Nak and was quite impressed.
I wasn't cutting down anything... I was just pointing out what the Kyosara
literature said it's strong points were.  I've yet to see one and was 
curious what the reaction in this file would be.

Steve
56.14CGHUB::FLEURYFri Feb 08 1985 00:392
If the performance of the NAK CD is like that of their cassette players, I can
not say enough good things about the company.  
56.15New owner of OMS-7TURTLE::TOTTONThu Mar 20 1986 17:5720
    Hello all,
    
    I'm new to this notes file, and notice this is a rather old note,
    however...
    
    I just purchased the Nak OMS-7 (and the new CR-5A Cassette deck).
    The sound is indeed fantastic, and well worth the cost (although
    I did mail order my gear and payed 80% of list price).
    
    What I found is that the differences in sound between CD players
    became much more noticable on "high end" systems (not too surprising
    of course).  For the rest of my system, I have a pair of Infinity
    Quantum II speakers, a large Nikko receiver (175 watts into
    8 ohms), and a Thorens turntable (Ma 2002e cartridge).
    
    I also found a differnce in how well the drives are isolated from
    shock etc.  The Nak is top in every respect (and consistent with
    their well earned reputation in the cassette area).
    
    	Jim Totton    
56.16JUNIOR::STUDIVANThu Jun 26 1986 01:299
I just purchased a Nakamichi OMS-7 for a fantastic price and agree that it 
is worth every cent. One of the leading factors that caused me to buy the 
NAK is a prejudice developed from owning a NAK tape deck. The sound and 
overall quality is superior to most anything I have heard. When I first 
brought the unit home my wife thought that I was crazy, but after hearing 
the results she changed her mind. 


                                                    Earl
56.17$$THORBY::MARRAAll I have to be is what You made me.Thu Jun 26 1986 12:164
    and what is a fantastic price?
    
    						.dave.
    
56.18AMBER::KAEPPLEINThu Jun 26 1986 14:424
    Probably a close-out price.
    
    I saw the new Nak CD players at the CES show.
    
56.19JUNIOR::STUDIVANTue Jul 08 1986 02:228
I was able to get the OMS-7 for about 50% of the normal price on a closeout 
deal. The newer model, OMS-7 Mark II, currently lists for $1695. Major price 
increase with no noticeable change in design. MOst of the price increase is 
attributed to the drop in value of the dollar.


                                                     Regards,
                                                      Earl
56.20New Nakamichi - check it out.CDR::COLLIERThu Jul 10 1986 02:3212
    To add maybe an incorrectly placed note, has anyone
    seen the new Nak disk players?  In particular, the
    new OMS-3 and OMS-4.  Not bad.  The OMS-4 is all the
    old Nak players were at a lower price and only a
    few differences.
       Stop by at your local store and check them out.
    For those of interest in information and possibly
    good deals (see Earl about that) on Equiptment,
    please read Note 401 and its replies.  
    		Always here to help,
    		   ...Ron...