An article I found while looking for possible upgrades....I posted a few other links at the bottom of this post as well. Very interesting subject matter. Now I just have to see what we have in the CD-3 so we can research further. I will need your help Lee, in determining the best choice, or choices based on the technical side as opposed to the personal preference side of the equation. What do you think? Worth the effort?
Upgrading Op Amps in Audio Equipment
Precision Amplifier Wiki
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We periodically get requests for recommendations on the “best audio op amp†to upgrade op amps that a user may find in their amplifier, receiver, mixing console, microphone preamp or other audio equipment. Some comments, first:
There is no one “best audio op amp.†TI makes a number of outstanding op amps optimized for audio applications. The very best for one circuit application or equipment can may be a very bad choice for another. It requires an understanding of circuit and application details to determine what might be a best-choice op amp for a given situation or equipment.
Even after making a best choice, there are hazards in substituting op amps into existing equipment. Op amps have quirks. The circuits in your equipment may optimize the behavior of the op that is currently installed. The circuit may not be optimum or operate properly with a newer, higher performance op amp. Differences in bandwidth, phase compensation, input bias current, input capacitance, output drive capability, quiescent current, operating voltage… many factors can cause a much better op amp to perform poorly. The substituted op amp may oscillate or even fail in a circuit that was designed or optimized for another op amp.
With that said, audio enthusiast will do what they do. The recommendations below may increase your chance of success. Not all these substitutions are easy. Some may involve adapting to smaller, more modern package types. These physical adaptations can, in some circuits, cause problems such as oscillations.
Substitute at your own risk. We will not be responsible for damaged equipment, including ears. Test carefully before connecting speakers. And if you don’t like the result, don’t assume that the new op amp is actually inferior to the old one. We are not able to help further with your project. It requires circuit diagrams and hands-on testing to optimize a circuit or even determine that it is operating properly.
Note that all listings below substitute a FET op amp for another FET op amp or bipolar for bipolar. While it may be possible, there is a greater possibility of compromised performance when substituting a FET for bipolar or vice versa.
OPA627 >> OPA827 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
OPA134 >> OPA1641 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
OPA2134 >> OPA1642 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
OPA4134 >> OPA1644 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
OPA604 >> OPA1641 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
OPA2604 >> OPA1642 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
MC33078 >> OPA209* Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
NE5532 >> OPA2209* Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
RC4580 >> OPA2209* Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
RC4560 >> OPA2209* Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
RC4558 >> OPA2209* Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
MC33079 >> OPA4209* Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
TL072 >> OPA1642 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
TL074 >> OPA1644 Lower noise and distortion. Wider GBW, lower quiescent current. Not available in DIP package version.
AD797 >> OPA1611 Lower quiescent current, more stable, better general behavior. Note that circuits using the AD797 tend to be more specialized, requiring more circuit optimization. Substitution is often much more difficult. Do not be beguiled by the very low noise of these op amps. Use them in circuits designed for other op amps and you will get higher noise.
LT1028 >> OPA1611 Lower quiescent current, more stable, better general behavior. Note that circuits using the AD797 tend to be more specialized, requiring more circuit optimization. Substitution is often much more difficult. Do not be beguiled by the very low noise of these op amps. If you use them in circuits designed for other op amps and you may easily get higher noise. Beware of operating voltage. LT1028 can be operated a somewhat higher voltage than the OPA1611.
* Version optimized for high performance audio applications planned for June 2011 release.
http://audioreviews.blogspot.com/2005/1 ... -amps.html
http://tangentsoft.net/audio/opamps.html ;
And this one:
http://www.diyhifi.org/forums/viewtopic.php?f=5&t=1976
