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General Q about op amps
MUFF WIGGLER Forum Index -> Oakley Sound Systems  
Author General Q about op amps
jack multiple
i have seen some pretty expensive op amps on the farnell website, mostly from analog devices.

what differences would using a compatible one make in the projects we do here from Oakley? i'm certainly not implying that i'm unhappy with the modules i have, quite the opposite, am merely curious.

Has anyone ever done any aural tests.

so what sort of circuits would they be appropriate for?

Same question about resistors. would building an oakley circuit using precision resistors throughout have any affect on anything?
Paradigm X
Well, some of Tony's designs do use the more expensive/better opamps...

Must admit Im clueless.

Ive bought a number of different 'posh' opamps' based on the BOMs, but unsure whether i can swap at this stage... just do what im told at the minute!

"Horses for courses", as my mum would say.

Op-amps have many different parameters. Each op-amp will have a different set of specifications. The more expensive ones tend towards the ideal op-amp - the text book op-amp of those starter electronics courses. So this may make it seem a great idea to swap out those TL072s with something quicker, less noisy and more accurate. Well this can work in many situations but it can also lead to problems too. A crap car analogy comes to mind here - you wouldn't want to go shopping in a F1 racing car.

The general rule is 'use what will do the job and no more'. After all there is little point in following a noisy discrete circuit with a super quiet op-amp. Any gain made to the noise floor will be wiped out by the preceding circuit.

Faster op-amps tend to oscillate in a bad way if the circuit layout or circuit isn't designed to work at that speed. The op-amp may be approaching ideal but the rest of the circuit isn't. As a newbie many years ago I swapped out some slow and noisy 741s in a hi-fi amp with some OP27s. The damn thing blew up almost immediately. I later realised it had gone into oscillation and the output stage of the amp wouldn't work that fast and overheated. And an OP27 isn't that fast compared to what we have today.

So feel free to swap them around a bit but beware of high frequency oscillations and other unwanted interactions.

It's worth reading up a bit about the non ideal characteristics of op-amps. The Art of Electronics is the classic text book but there are plenty of online resources these days. I like this one:

jack multiple
thx tony thats a first class answer as usual.

Ok this next question has bugged me for about 10 years and no one has ever answered it.
So why do vintage synths sound warmer/squidgier than modern synths, even if the design is the same.
Just dont get it.
is it ageing of components? different manufacturing techniques from yesteryear/ different materials used in the components?
jack multiple wrote:
So why do vintage synths sound warmer/squidgier than modern synths, even if the design is the same.

Well that's the thing. They never are the same. Not completely.

But I'd argue for the case that they aren't necessarily that different sonically. In various blind tests done on several forums over the years, and that I have conducted over the years, it's been found that it's really hard to spot the original. Indeed, a lot of folk can't seem to spot whether they're listening to a VA or a real analogue if they can't see the instrument playing.

Part of the fun of using the older stuff isn't the sound alone but the fact that you are interacting with something that old. And for those of us of a certain age that will bring back a lot of happy memories. It's hard to discount that when you're playing or seeing it on a DVD or on stage.

Take out the benefit of the visual clues and things get way more murky. People will often talk about 'day and night' differences. I have to laugh at this. That different?

But there's whole forum topics covering this elsewhere and it goes all Mac/PC very quickly.

jack multiple
thats interesting.

i'm not going to claim to be an expert on old synths but i've had few over the last couple of years and set them up alongside modern ones,
and well the modern ones ended up on ebay pretty quick.

but yes you're right theres more to it than sound but in my basic recording gear setup( which is an old mixer,multitrack and a cd recorder and 1 fx processor) there was a HUGE difference sonically.

i think things get 'processed' so much with eq and software that the original character of the synth is lost and it just sounds the same eventually.

At the time i could instantly recognize which was which , but now listening to and old tape i did i think, jeez which one was that? harder to tell them apart. but could still tell the old from the new. new ones were just 'thinner'.

had a dopefer for a while. hated it. sold it on.

The oakleys are spot on to the sound i fell in love with and so i dont have to search anymore, which is a relief.

anyway, who cares, i've got what i wanted. finally.

thanks for answering.
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