On Tuesday 02 April 2013 12:46:07 Ralf Mardorf did opine:
On Tue, 2013-04-02 at 11:32 -0400, Gene Heskett
wrote:
So I used a cmos op-amp which uses very little
current at normal
signal levels. The TLO74/84 family. These were great, and could
make 29 volts P- P on a +-15 volt supply rail at around .007%
distortion.
I still own a lot of TL07* (at least a stick with some 702), it's
written that my Behringer mixer does use 4580 and it's written that the
ADA8000 does use TL072, but that the ADA8200 will use 4580.
Years ago, when I got my Behringer mixer I worried about the many TL07*
I bought a short time, before I bought the mixer. A friend confirmed
that at that time TLs were less used anymore for audio gear.
I never made ABX tests for op-amps, but IMO a lot of IC gear is able to
keep up with good discrete circuits, at least in the homestudio price
range those newer op-amps IMO do sound very good.
And I wasn't saying that it was todays cat's meow. I forgot to mention
that this was 25 years ago. Should have.
The production video switcher we used for many years, a Grass Valley Group
300-3A/B, used a grocery sack full of a slightly bigger than an airmail
stamp, custom made op-amp that Grass designed.
Of course, as the far end of the bathtub curve of time vs failure rates
approached, it lost a channel, one of those little ceramic cards had died.
I called Grass, they wanted $1500 and would not guarantee that the
remaining ones on the shelf were good. That wasn't good enough for me, so
I started scouring catalog's & calling the chip makers. I forget who came
to my rescue with a one rail 5 volt video speed op-amp with an in my hand
price of less that 2$. So I asked for samples & they sent 5, gratis.
I should have bought 50 because it was so much better and faster that it
threw the color phase noticeably off when that mixer channel was in use.
If I had sufficient stock, I would have shotgunned the other 5 identical
boards so they would have all matched again. But changing them out was a
good 3 hours a board, so it never got done, but by the time I retired, the
other 4 were in it because of more failures. Since one board then had 3 of
those in it, the color hue shift was getting to be obnoxiously obvious.
When I announced I was retiring, the first thing they did was replace it
because they knew I was the only one still living who might be able to fix
it. They paid about 100k for another brand new one from a new company, and
4 years later it was on its last legs.
Then digital needed to be done, so the building was rebuilt for a brand new
rack room and two control rooms, 3 more edit bays, 2 production offices,
and an all new area for engineering since there are now 2 tv channels, 4
programs, originating there plus a radio station. That has had its share
of 'teething' pains, but the junk seems to have largely been swept out in
the 5 years since, so its usually running pretty good. All with gigabit
ethernet, and some 10Gb in one instance, its nice to be able to move a 1
hour long program file from one box to another in 2 or 3 seconds. :)
Cheers, Gene
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