What is this opamp? and DAC?
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chesebert

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I recently dug out a really really old VCD machine from the basement which I have not used for ages (house cleaning) and decided to have a listen since the machine felt pretty heavy, all metal, and looks well made (I don't even remember buying this). To my suprise, the stereo output sounds significantly better than my Chaintech AV710 24/96 output through the headsave tempo (pimeta) and sr325i.

So upon opening the case I discovered that the transport itself is philips (which I assume is pretty decent), the power board is fairly well made with big heatsinks and good deal of caps (maybe change them with better quality stuff?) and on the audio board I see one DAC and 2 opamps at the output stage of the stereo.

DAC = BB 1717E
Opamp (SMD) = the top line reads: 4558, bottom line reads 829C

There are close to 2 dozen caps with various size on the audio board as well.

My question is what are those opamps and is the DAC anygood? If it's worth my time to do some modding by switching out some caps and putting a BB627 on BD adapter in place of the exisiting opamp
 
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ECM

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i'm not too familiar with the DAC, but I recently modded a sony DVD player with the same 4558 opamp. (http://www6.head-fi.org/forums/showthread.php?t=119323)

i did the usual power supply mods: bigger caps and bypass caps.

i replaced the 4558 with a BB2227 and biased it into class A with the use of some jfets. soldering a chip that small is not hard to do.

the opamp outputs were wired direct to the RCA jacks thru some Solen 5.1uF caps .

these mods really made the player sound a lot better. since your player already sounds good, it might not be a bad idea to tinker with it for better performance.
 
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amb

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The 4558 (dual) opamp is nothing to write home about. It's an old chip that is only slightly better than the ghastly 741. Search google for "RC4558" and you'll find links to its datasheet.
 
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chillysalsa

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Seems to use the PCM1717 chip:

http://focus.ti.com/lit/ds/symlink/pcm1717.pdf

It's a very basic 16 or 18 bit DAC, I think it dates back to 1995 - at least that the (c) on the first page of the datasheet. The specs are pretty mediocre.
 
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chillysalsa

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To answer your question: if you beef up the opamp output you'll more than likely just reveal how the DAC chip really sounds - which may not be such a great thing. It looks like you don't have that much to work with if you want to maximize the sound quality of this design.
 
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chesebert

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darn I thought I had a winner. ohwell maybe time to get that toshiba.
 
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skyskraper

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hey, my take is, whats the harm in trying? if you have another suitable op amp and caps lieing around, why not play around with it
ive got a dvd player thats packed up in the video stakes, i plan on messing with it when i have the chance
 
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