[sdiy] Discrete Op Amps

[Neil Johnson]

Hi,

cheater00 cheater00 wrote:
> My guesses are:
> 1. Many people know op amps better than an equivalent sort of circuit with
> transistors etc and so stick to them

Discrete op-amps are a relic from the past - before today's wide
choice of op-amps there were far fewer, noisier devices with
less-than-amazing specs (e.g., 741) and discrete could still compete,
and cheaper (the economics of mixing desk design are quite
entertaining).   Some people like how they sound partly because of
their use on famous recordings from the past that some folks lust
after and want to recreate or sound similar to.

Today you've got examples like Jensen's 990, the API 2520,

> 2. It's easier to use a ready building block than to design your own

At the time of DOA use the choice came down to (a) use expensive
low-performing IC opamps (that'll be "no" then), (b) design lots of
duplicate transistor stages (tedious and slow), or (c) standardize on
a few discrete amplifier modules and get on with building and shipping
product, because that's what customers give you money for, and money
is what wages are made of.

There was an intermediate point in time when some companies (Neve, for
example) produced upgraded discrete amp modules that were based on
op-amps once they had dropped in price and were sufficiently good
enough.  The turning point was about when the NE5532 came out.

> 3. End users want to use a different character part in an existing product,
> or manufacturers want to do the same when producing simple clones

"Character" usually means some sort of distortion and/or noise.  IC
op-amps have very low noise and distortion - even the humble and
exceedingly low-priced NE5532 takes a lot of work to do better in
discrete, and the result will cost a lot more and have lower
reliability.

For more information I would start here:
http://nwavguy.blogspot.co.uk/2011/08/op-amps-myths-facts.html

Neil
-- 
http://www.njohnson.co.uk