[sdiy] Op amp notes

[Cary Roberts]

>Aren't nearly all boards, regardless of price, chock full of
>monolithics? I seem to recall that even SSLs have tons, likely
>thousands, of 5532s in them. Not to mention what must be literally
>hundreds of VCAs.

Most new stuff, yes.  API and Daking are exceptions to the rule.  There are
discrete options available for the Sony MXP3000 as well.  The stock Sonys
had the option of a discrete transformerless input and a 5534 based Jensen
transformer based mic pre.  Too bad they didn't have the discrete/Jensen
combo available.  SSLs and all other current boards are chock full of ICs
(and VCAs) so maybe that's why I don't care for the sound.  People still pay
top dollar for discrete power sucking Neve, API, and Quad Eight gear.  Just
like folks still prefere Moog, EMS, EML, and ARP designs to early 80s
integrated designs.

I'm not averse to using opamps in synth circuits - I don't think it's
warranted to use a fancy discrete amp as current to voltage converters,
buffers, etc.  And hand selecting various ICs and opamps for a circuit is a
bit different than trying to cram it on one die like CEM and SSM did.

>Well, after hearing so many list members' (justifiable) frustration
>over SSM's capricious policy of sudden-death discontinuation of their
>parts, I try to avoid using anything from SSM.

The problem is it's not just ICs but also older transitors and such as well.
There are "equivalents" but they never sound the same as the original.  Of
course, with thirty year old parts, how much of that difference is due to
age vs manufacturing differences?

>I build a lot of stuff with tubes and hybrid circuitry, so I know what
>you mean. Still, when you want to build a four-band fully parametric
>EQ, etc. monolithics make life a lot easier. MHO is that monolithics
>are fine in line-level circuits (as long as you don't use total junk).

I've become a switched filter circuit EQ snob.  I've been able to buy 100+
concentric Grayhill rotary switches on ebay for less than $1 each, and
bought a box of Grayhill parts (enough to make 300+ switches) to expand them
to three or four pole.  It doesn't get nicer than just using resistors and
caps (and inductors depending on design) to pick EQ points and using a few
buffer amps (either IC or discrete) to finish out the design.  Gyrators
don't bother me so much as many IC based EQs are constant Q not constant
power.

-Cary