Hi All,
I just stumbled upon this and thought it might be helpful and/or interesting to many here. It's an article posted on "Precision Amplifiers" forum at the TI site about Opamp rolling and the hazards of doing so, stuff I've been trying to caution people on for a long time with (apparently) little success. It's a good read, and also includes a short list of suggested substitute Opamps.
Upgrading Op Amps in Audio Equipment - Precision Amplifier Wiki - Precision Amplifiers - TI E2E Community
Mike
I just stumbled upon this and thought it might be helpful and/or interesting to many here. It's an article posted on "Precision Amplifiers" forum at the TI site about Opamp rolling and the hazards of doing so, stuff I've been trying to caution people on for a long time with (apparently) little success. It's a good read, and also includes a short list of suggested substitute Opamps.
Upgrading Op Amps in Audio Equipment - Precision Amplifier Wiki - Precision Amplifiers - TI E2E Community
Mike
There are SMT to DIP adapters available, or you can roll your own. But there can be problems in doing that with some high speed chips, excesive lead or trace length can cause instability and/or oscillation at high frequencies. As the article says, rolling opamps in search of audio nirvana is fraught with hazards that can cause all kinds of problems if one doesn't pay attention to details.
Mike
Mike
The cynic in me says it's a "good article" if you enjoy reading boiler plate CYA and infomercials. When I roll op amps, I'm not pretending to be in search of "audio nirvana," but rather just want a POS receiver to sound tolerable for under $4 -- and with OPA1642 f.ex, it does.
Now that TI has bought BB and National, do they even have any competition left...? I notice they're not recommending any National (LM-numbered) parts.
Otoh, the optimist reads: "FET for FET, and BP for BP, good to go!"
Now that TI has bought BB and National, do they even have any competition left...? I notice they're not recommending any National (LM-numbered) parts.
Otoh, the optimist reads: "FET for FET, and BP for BP, good to go!"
Are you asking the cynic or the idealist in me? Either way, your question has too many incomplete hypothetical scenarios...
My first op amp experiment did indeed result in a smoked tweeter, but since implementing the simplest of precautions (as suggested in the op amp data sheet and helpful pointers here on DIYAudio), I have had smashing success replacing old op amps with new under-$5 ones (LM4562 and OPA1642). So far, I'm winning 5-1 overall, 5-0 this millennium...
Go for it!
But do you pay attention to the important details, do you check for high frequency instability or oscillation when you replace one opamp for a different one? If you replace an "old" opamp with a more modern one, it is absolutly necessary to get the supply bypassing right, if you don't, the "increased detail" you percieve could be nothing more than increased distortion caused by instability. The human ear, Golden or not, is easily fooled.
Mike
The article is basically FUD that tries to steer readers toward TI's OPAX209 integrated circuits. Oh, except they are not available in the DIP packages that most of the old equipment uses. No problem, you can shell out even more money for adapter sockets.
It's laughable that they would suggest that anyone replace the venerable MC33079 or NE5532's with the OPAX209's, but I like their ironic notation:
The devices on the left are excellent bang for the buck and are my go-to devices for upgrading old gear. While the devices on the right have excellent specs, the bang for the buck is poor by comparison.
MC33078/79's and NE5532's will take some old device from "ho hum" to "decent and even excellent sounding unit" for a small investment.
Beyond that, any improvements with even better op-amps are a false economy and a waste of money because at this point, the big improvements in sound will not come from op-amps.
If the design and build of the device is so good that it can serve as a platform whose end-to-end signal path can reveal the difference between an NE5532 and OPA2209 (using equipment, of course: human ears are hardly that good), it would not have shipped stuffed full of @#$%-ing TL072's in the first place.
In some crummy old piece of gear, once you have that NE5532 or MC33078 in there, further improvements will likely come from better resistors in key places, better capacitors, better connectors, switches and pots, or improvements to grounding problems and EMI/RF rejection (like fixing "pin 1" issues, adding missing bypass capacitors, ferrite chokes, etc).
You're not gonna solve every problem if you just find a good enough op-amp. At some point, the noise is coming from a resistor, or from the outside world, not from the op-amp. The THD is coming from some FET switch, dirty switch contact, or ceramic or electrolytic, not from the op-amp.
It's laughable that they would suggest that anyone replace the venerable MC33079 or NE5532's with the OPAX209's, but I like their ironic notation:
Since ">>" is a mathematics/engineering symbol that generally means "kicks the **** out of", I wholeheartedly agree.
The devices on the left are excellent bang for the buck and are my go-to devices for upgrading old gear. While the devices on the right have excellent specs, the bang for the buck is poor by comparison.
MC33078/79's and NE5532's will take some old device from "ho hum" to "decent and even excellent sounding unit" for a small investment.
Beyond that, any improvements with even better op-amps are a false economy and a waste of money because at this point, the big improvements in sound will not come from op-amps.
If the design and build of the device is so good that it can serve as a platform whose end-to-end signal path can reveal the difference between an NE5532 and OPA2209 (using equipment, of course: human ears are hardly that good), it would not have shipped stuffed full of @#$%-ing TL072's in the first place.
In some crummy old piece of gear, once you have that NE5532 or MC33078 in there, further improvements will likely come from better resistors in key places, better capacitors, better connectors, switches and pots, or improvements to grounding problems and EMI/RF rejection (like fixing "pin 1" issues, adding missing bypass capacitors, ferrite chokes, etc).
You're not gonna solve every problem if you just find a good enough op-amp. At some point, the noise is coming from a resistor, or from the outside world, not from the op-amp. The THD is coming from some FET switch, dirty switch contact, or ceramic or electrolytic, not from the op-amp.
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