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Old 16th February 2003, 04:58 PM   #1
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Default NAD512 CD player mod

Hi,
I'm thinking about modding my old NAD 512 CD player by replacing the OP-amps (NE5532) with better ones (OPA2604).

Is this a worthwile tweak, or is there something else that will make a bigger difference sonically?

Best Regards
/Johan
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Old 16th February 2003, 05:27 PM   #2
Chris is offline Chris  Norway
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Default cdp tweak..

I just modified my marantz cd 63 mkII. I replaced the original opamps with opa2134 (burr brown), currently I use the opa2604 whitch I like better. If mount a opamp (dil8) socket in your cpd you can easly switch opamps untill you find one you like.
I also removed the muting transistors on the output plus some electrolytic caps in the signal path. I don`t know if this is possible in the nad 512. Maybe somebody else knows?
Is the tweak worthwile? For me it was. The sound didn`t change that much. It wasn`t a wooooooowh change but it changed to the better, IMHO. The mod didn`t cost much and it didn`t take much time to do it either.

Chris
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Old 16th February 2003, 05:36 PM   #3
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Hello
Perhaps you can improve the power supply for digital and analog circuts both.
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Old 18th February 2003, 11:45 AM   #4
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Question cd tweak

Hi,
thanks for the replies.

There is a transistor close to the RCA out jacks which I presume is the mute. I don't have access to the service manual, does anyone know where I can get it?

Marlowe:
"Improving the powersupply" - you mean having separate powersupplies for the analog and digital, right? What is usually done to improve audio quality and what is most important (transformer, regulators, caps etc)?

Best Regards
/johan
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Old 18th February 2003, 12:06 PM   #5
Hamish is offline Hamish  Australia
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try the opa2132 too. i got some 2134's for a preamp, but they sound too metallic. 2132's are nice and warm/neutral.

try NAD for a service manual. they are usually pretty good about that kind of stuff.
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Old 18th February 2003, 04:49 PM   #6
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Lightbulb Output mute transistors

They are usually close to the RCA jack, bjt types /always/, emmiter connected to the signal path, collector- to the ground! Base voltage /with japaneese types one of the outermost/ drive should be around +0.7V when muted /CD off, or something.../ and under -5...-15V dc, when unmuted /CD playing/ ! My advise is to remove them!!! If you whant muting /without it there will be clicks and pops on power up/down/ better way is to use a relay!
Also check the total resistance between the last signal opamp and the RCA jacks - it shoud be lower than 200 ohms, it is the output impedance your interconnect sees. If it is high-prepare for sound-dependent-on-interconnects But do not make it under 100 ohms - the opamp may become unstable. Usually making the first-after-the-opamp-resistor about 100R, and all others - 0R /jumpers/ is quite successfull!!!
power supply -firs you can replace the filtering electrolytics with bigger ones - about 2-3 times the original value, especially on cheaper CD players. Watch out to have a docoupling cap of non-electrolytics type on every opamp/digital ICs. I don't mind to use a cheap ceramics here, nevertheless some audiphiles use only very-high-quality /and X-pensive/ Polypropylene caps. U decide!
Good luck!!!
U can also replace the DAC chips, but should be more experienced
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Old 19th February 2003, 07:37 PM   #7
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Talking Progress report

Hi,
I desoldered the 5532's and replaced them with socketed OPA2604. After checking for any shorts or bad connections I put everything together and tested it. It sounds better, not a big change, but it feels more detailed. My wife claims that it sounds a lot better though :-)

This forum is really a very good place to learn - thank you very much!


cheers,
/johan
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Old 20th February 2003, 08:33 AM   #8
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Arrow opa2134 vs opa2132

the basic difference between the two is the input offset voltage! The other difference is the price, of course! So from now on I don't believe there is a SONIC difference between the two!!
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