Op Amps for a C33/C34V

[jlovda]

I have a C33 that I am "gutting" as a winter project, replacing all the caps and as many op amps and other components as I can reasonably find. I am doing this for no other reason than boredom. The unit did have some problems. This may be a backwards approach but maybe the problem will have disappeared when I am finished before I do any trouble shooting.

Has anyone found a good substitute op amp to replace an LM201N? Most 8-pin DIPs have the same pinouts but maybe someone has found a particular part that sounds best.

Thanks.

 

[UncleBingo]

Is that the one with all of the ribbon connectors? I've seen that be the cause of many a problem in that model, iirc.

I seem to remember an article about an Analog Devices op-amp that was great (albeit pricey compared to the standard chips)...
or this:
LM201N is
replaced with TI LM741CN

 

[jlovda]

The C32 is the predecessor of the C33/C34V. The internal layout and design of the C32 is different the 33/34V and I have no interest in getting involved with a 32. When the C33 was designed, all of the "mistakes" of the 32 were removed.

I am not interested in exotic op amps. I will order a few 741's from Digi-Key and see how they perform in place of the LM201's. Thanks for the suggestion.

 

[CruzBay]

I've often heard that the phono sections of those preamps had low noise versions of the standard op amp. I've always been curious if replacing all the op amps with that one would yield any improvement. (owner of a C-34V here)

I'm guessing it wouldn't matter, or Mcintosh wouldn't have bothered to stock 2 different op amps; how much more would a LN version cost?

Also, if there aren't sockets in there now, I'd install them so you could 'roll' op amps and find out for yourself.

 

[62caddy]

Is that the one with all of the ribbon connectors? I've seen that be the cause of many a problem in that model, iirc.

The ribbon cables in a C32 do not carry any audio signals. They're only used for control switching.

 

[jlovda]

It appears that op amps such as the NE5532 and 5532 only come in "low noise" versions now. In the 40 odd years that these two parts have been manufactured I would assume the process has matured to where sorting by speed, noise, etc. is unnecessary. They all meet the published specifications. There are many part number variations but they relate to the package type (SMT or through-hole) or how they are shipped for use in different types of board stuffing machinery.

On the three C34V's and one C33 I have worked on, all the IC's were in sockets. This is 80's vintage. My MX130 from the 90's had a mixture of soldered and socketed ICs.

 

[62caddy]

I've often heard that the phono sections of those preamps had low noise versions of the standard op amp. I've always been curious if replacing all the op amps with that one would yield any improvement. (owner of a C-34V here)

Unsure if this is relevant but I noticed this in the "Technical Description" of the C32 Owner's Manual:

"Active Filter Circuitry Loudness, equalizer, and band pass filters of the C 32 are all constructed with ion implanted junction field effect operational amplifiers (popularly called "Op Amps"). These new devices amplify with a 6 dB better signal to noise ratio than bipolar input op amps."

Manuals for C33 & C34 have little to say otherwise about the Op amps used in the phono stages.

 

[clinic-audio]

IC used in phono stages are NE5534AN (AN = low noise )

 

[jlovda]

Both the C33 and C34V use NE5534A op amps in the phono section. Both preamps call out MC4558 for the tone control ICs but these are no longer available. I used NE5532A in my C34V and they work fine. The only FET input op amp I found in the preamps are four LF356 used in the compressor section. They are still available.

At both Mouser and Digi-Key, Texas Instruments (TI) is the only NE5534 available, there is no "N" suffix anymore only blank or "A." The "A" part is very slightly lower in noise. The "typical" equivalent input noise figure for the NE5534 is the maximum figure for the NE5534A. The A part is about ten cents more expensive ($1.10)