what electrical characteristics we should care when upgrade op-amp ? - Page 1
Forum section: electronics / beginners

author: huu_tri0101
author_rank: Contributor
timestamp: November 12, 2013, 05:24:48 am
content: I want to upgrade better op-am in my audio amplifier ( old one is JRC 4558), what electrical characteristics in new op-amp I should care when upgrade ? What characteristics need better? What characteristics need the same ?Thank you everyone.

author: madshaman
author_rank: Frequent Contributor
timestamp: November 12, 2013, 05:37:48 am
content: Noise specs and harmonic distortion for the sound.To make sure it will work:GBW (same is ideal, or a bit lower if can't match), The output swing under the old opamp's supply needs to match or exceed the old one's, also the output driving ability needs to meet or exceed the old one's.Efficiency should match or exceed the old one's.Even with this I'm leaving a lot out and might have omitted something important.Good luck!

author: tszaboo
author_rank: Super Contributor
timestamp: November 12, 2013, 06:38:28 pm
content: Quote from: madshaman on November 12, 2013, 05:37:48 amLike power supply voltage limitsAudio opamps, and opamps in general are magic. There are hundreds of parameters missing from the datasheet, which might be important.

author: madshaman
author_rank: Frequent Contributor
timestamp: November 12, 2013, 07:10:42 pm
content: Quote from: NANDBlog on November 12, 2013, 06:38:28 pmNo, I covered that:Quote from: madshaman on November 12, 2013, 05:37:48 amI am assuming the OP knows enough to check the old opamp's supply is tolerable for the new opamp; I figured it should be obvious from the above statement or there's not a good chance the OP will be able to succeed other than by accident. In any case, they know now.Quote from: NANDBlogCould you please elaborate? I think the values in most data sheets would be more than enough to pick a suitable replacement. If not, I would also like to learn what I may be missing when choosing an opamp.What parameters are missing that would lead to failure if not known?

author: free_electron
author_rank: Super Contributor
timestamp: November 13, 2013, 12:21:37 am
content: you missed an important one : same pinout and package !

author: madshaman
author_rank: Frequent Contributor
timestamp: November 13, 2013, 04:34:21 am
content: Quote from: free_electron on November 13, 2013, 12:21:37 am:-)

author: madshaman
author_rank: Frequent Contributor
timestamp: November 13, 2013, 04:38:12 am
content: Quote from: NANDBlog on November 12, 2013, 06:38:28 pmMy sardonicism sensor is broken again isn't it :-)

author: tszaboo
author_rank: Super Contributor
timestamp: November 13, 2013, 06:04:54 pm
content: Quote from: madshaman on November 13, 2013, 04:38:12 amOk, it is working againBut in general, they tend to leave out capacitive loading, effects of EMI, power off characteristics (as strange as it sounds it is actually sometimes important), channel crosstalk vs frequency, latch up behavior, THD vs load, and other significant characteristics.

author: scratch_monkey
author_rank: Contributor
timestamp: November 14, 2013, 03:07:24 am
content: My advice, for audio gear, unless the opamps are free, don't bother. Put the money towards better speakers. Or more music. The faults of modern audio amplification systems are insiginificant compared to to horrible response of any mechanical device, for example, your speakers.If you want to go really exotic, build a plasma tweeter.

author: madshaman
author_rank: Frequent Contributor
timestamp: November 14, 2013, 04:34:58 am
content: Quote from: NANDBlog on November 13, 2013, 06:04:54 pmLol. And thanks. This situation is so hard to give advice for, it's almost a situation where if you need to ask, you really need someone else who doesn't need to ask to choose for you, but it's hard to indicate this without sounding like you're trying to put the OP off.I suppose indicating that swapping an opamp isn't quite as simply as maybe switching to a new brand of windshield wipers or spark plugs or ink cartridges (and still, only certain replacements are viable) has value.

author: madshaman
author_rank: Frequent Contributor
timestamp: November 14, 2013, 04:37:21 am
content: Quote from: scratch_monkey on November 14, 2013, 03:07:24 amDon't forget the frequency response of the listening room, that will also nullify good speakers. At least with a room you're pretty much assured a linear response (not to be confused with a flat response); that's not the case with the speakers or the amplifier.

author: Monkeh
author_rank: Super Contributor
timestamp: November 14, 2013, 05:19:36 am
content: Quote from: huu_tri0101 on November 12, 2013, 05:24:48 amYou will not achieve any audible difference. Leave it alone.

author: madshaman
author_rank: Frequent Contributor
timestamp: November 14, 2013, 06:00:18 am
content: Quote from: Monkeh on November 14, 2013, 05:19:36 amOn the contrary, I believe the OP could achieve an audible, visual, olfactory *and* financial difference unless they follow your advice *or* do lots of reading and build some simple opamp-based circuits before attempting the operation; then there's a chance for no audible difference ^^'To the OP, none of this is meant as derogation, it's more a suggestion and opportunity to do some studying and learning and not have to take this advice of others as authority; particularly *bad* advice that can come from random audio forums.I can recommend some good books on sound reinforcement, amplifier design and basic electronics if you're interested. The only difference between some forum members and yourself is that they've studied these things already.