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In Reply to: RE: OP Amps, Whats Your Opinion? posted by AudioSoul on June 24, 2015 at 09:48:49
No matter what you do with them you cannot get around these fundamental limitations and in the best of cases they sound ok and in the worst they are the worst.
Follow Ups:
Let's take a step back for a second.
An Op-Amp has, by definition, very high gain and it is used with large amounts of feedback such that the closed-loop performance is determined by the passive feedback components and not the components within the op-amp.
So, if you don't like using lots of negative feedback don't use an op-amp. Simple.
Regarding too many transistors - this is an irrelevance considering the first point. A monolithic op-amp will use as many transistors as necessary to achieve high gain and whatever specs that are important. In open-loop terms any op-amp is very non-linear so using less transistors won't make it less 'bad'. This leads me to the topic of 'discrete op-amps' which, IMHO, is an oxymoron. Such a circuit may be justified to drive unusual loads but there is no justification on gain terms. If it is an op-amp it should have high gain and using discrete transistors to produce that gain does not make it more 'good'. One the other hand, if you want a moderate open-loop gain amplifier to use with a little feedback (in the style of a Nelson Pass power amp) then you probably have to design your own - but that isn't really an op-amp.
Regards
13DoW
I guess my point was that you pile on non-linear transistors and then try to fix the mess with feedback you can get something that measures well but sonically...well hey I'll let you decide.
Simpler seems to be better even for transistors as Pass has come to discover.
Cheever and some others have found that the best sound gear is the one that is the most linear, open loop and that closed loop performance is largely irrelevant soncially.
So, if you don't like using lots of negative feedback don't use an op-amp. Simple.
Regarding too many transistors...A monolithic op-amp will use as many transistors as necessary to achieve high gain and whatever specs that are important.
This is what both Brad and I have observed and why we're not fans of that approach.
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For discrete transistors I am sure that there is some quality differences although i would not know which ones are good and which ones are not.
For opamps, it is usually specific manufacturer for a given opamp so if you have specific needs then there is likely not much choice in the chip you buy. A couple of companies now are making what they call "discrete" opamps, which are not using miniaturized transistors all on a die but normal small signal transistors that are arranged like an opamp circuit. I think Burson makes one of the more popular disrete opamps.
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