Providing Digital Out to a Nakamichi OMS-5EII - diyAudio
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Old 7th August 2006, 03:37 PM   #1
Salar is offline Salar  Germany
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Default Providing Digital Out to a Nakamichi OMS-5EII

Hello,
a year ago, I asked for help in upgrading my 20 year old OMS-5EII with a digital output. Jobst and Ray were very kind to help me with tips and Ray even did sent me a schematic. But I am an absolute amateur! I am working as a film editor, sounddesigner, sometimes cameraman, sometimes field recordist, so I have some technical skills in keeping the gear running and how to solder tiny pieces together, but that´s it. Only a voltmeter at hand and a soldering iron.
In the meantime, i got a service manual from the Sony CDP-552ESDII, which used the same digital LSI as the Nak (CX23035) but provided digital out. (the Sony was the first consumer player in the market with digital out) So I had double information.
But some namings of the pins of CX23035 differ, I hope, it is only a matter of non-common terms 20 years ago and not a programmable LSI.
I drew a schematic based on Ray´s using scans from the service manuals and additional parts (i.e. DIT4192) in order to learn the real world layout of the pins.
Could anybody check this schematic? Again, i am an amateur...
My schematic is a .pdf but it is too big (1MB) for attaching it to this post.
So please feel free to email me:
salar at snafu dot de

About the schematic:
I am not sure, wether the connections between the Digital LSI and the digital transmitter are correct. Also, there is one octal buffer (74HC244) implemented, which might not be needed.
The modification would also need a new oscillator of 16.9344 mHz for driving the DIT4192 and being divided in two for the CX23035.
(Sony did the same with the CDP-552ESD). Even though this would be an occasion for implementing a jitter-free clock (i.e from Tentlabs), I would rather prefer a design using the original oscillator and double the frequency.
Any advice on this?
Supplying power will be the next problem (at least for me)
Once, i provided the tray of the OMS with 4 LED´s. I took the power (5V)from the circuit driving the cable(!) remote control, but this extra 80mW blew a resistor in the servo circiut after some weeks (in the moment the tray opened an the LEDs went on)
Now they run independent on a small power transformer, but the transformer only provides 3V. After this experince, I am a litte hesitant to apply some extra milliwatts to the Naks powersupply. But I can send the schematics and description of the power circuit of the Nak to anyone intersted.
In case anybody wonders why upgrading such an old player:
I like its quality! And I have two laser units as well as motors still in reserve, so this baby should work for some decades to come - hopefully with a better (modern) D/A Converter, which will be attached to the digital out...

Thanks four your kind help in advance,
all the best,
Salar
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Old 16th August 2006, 08:29 AM   #2
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Hi Solar,

Doesn't the Nak have Philips d/a converters (TDA1540) in it?
If this is the case it is possible to exchange the Saa7030 and Saa7000 with the SAA7220b. It is a bit tricky but i have done this in a philips cd304 to ugrade it to a 304mk2 10 years ago.
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Old 16th August 2006, 09:41 AM   #3
Salar is offline Salar  Germany
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Hello Lampie,
Thanks for your reply!
No, the OMS 7/5E from 1984 had TD1540.
The OMS 7EII/5EII have PCM-54KP, driven by a
NPC SM58046 digital filter
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Old 16th August 2006, 05:32 PM   #4
anatech is offline anatech  Canada
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Hi Lampie519,
I do have an older OMS-7. I'm very interested in updating this unit. Do you have any information you can send me? bhomester at gmail dot com.

Thanks for any help you can give.

-Chris
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Old 24th January 2007, 11:09 PM   #5
wsjoe is offline wsjoe  United States
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Default OMS5 and OMS7

Which laser pickup units did these units have? I heard they are impossible to find replacements.
wsjoe@yahoo.com
thanks

How do they compare against the Denons? SUch as DCD-3520 and DCD-3560? Or even lower such as DCD-1560 1520 or 2560.

thanks
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Old 25th January 2007, 01:27 AM   #6
anatech is offline anatech  Canada
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Hi wsjoe,
They used the NEC #79710002 P/U head. A true precision assembly. The head is mechanically adjustable in all three axis. The disc motor is also a very well built assembly.

Once the mechanical adjustment is made and locked (all die cast and milled pieces ) the electrical adjustment is made. This results in the most stable and cleanest eye pattern I have ever seen in any CD player. All this transport needs is a better digital filter and D/A stage than the Philips TDA1540 chip set.

Quote:
How do they compare against the Denons?
Better tracking, but poorer sound quality.
Quote:
SUch as DCD-3520 and DCD-3560? Or even lower such as DCD-1560 1520 or 2560.
Those are all excellent machines. The transport is better than average, but not as good as the OMS 5/7. The digital and analog stages are better than the Nak. Understand that Nakamichi squeezed out far better sound quality than you could imagine with these Philips parts.

-Chris (well, that's my opinion anyway)
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Old 26th January 2007, 09:50 AM   #7
zanash is offline zanash  United Kingdom
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do these units have an digital optical output?
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Old 26th January 2007, 03:47 PM   #8
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My OMS-7 does not have digital optical output- analog only.
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Old 26th January 2007, 11:16 PM   #9
anatech is offline anatech  Canada
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Hi zanash,
Quote:
do these units have an digital optical output?
No, the chip set does not support this. so none of the OMS 5/7 would have this.

-Chris
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Old 26th January 2007, 11:49 PM   #10
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You could always instal a Tentlabs X03 clock, this will then give you a very good digital output, and also at the same time improve the jitter performance of the transport, win win, at a reasonable cost.

Cheers George
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