OP amp

[Andy Le Blanc]

I had a piece of gear start to go at the gig last night.

I still dont know if its the pink source or 31 band EQ. I'm hoping its the pink.

so I was looking around the net for schematics for pink, all relatively simple.

But... they all use a dual op amp...

then I remembered a note a text book I have from 1960, biological and medical electronics,

a picture of a tube based modular op amp... GAP/R MODEL K2-W...
and it happens to be up on the Philbrick company history site

theres a schematic bottom right on the page

http://www.philbrickarchive.org/k2-w_op ... _later.htm

[selloutrr]

Seems cool the only worry would be how the tubes operate as they wear out. Plus the cost of an opamp versus tube. Can tubes handle the road?

Cool post thank you!

[Andy Le Blanc]

I bet they'd be just fine with basic care...

tube drift is another thing, I'd choose non-critical applications until proven.

I guess they mfg these things from the early 50's to 1970, analog computing

I remember hearing that it would take half a day to set up a machine the size
of a semi trailer to do one simple problem, the hand held calculator was a revolution

slide rule works great but the fudge factor for significant figures is personal taste.

Op amps are every where... Be fun to explore it as a pre, a REAL tube screamer
kind of like going backwards at the same time you go forward with circuit design

[diagrammatiks]

you could always build a tube op amp man.

totem pole srpp for linear current drive.

bias that thing with vacuum diode and a throw in a constant current sink.

cascode drive an inverter to get 2 symmetrical rails.

voila baby op amp.

[Cliff Schecht]

I've got a K2-W as well as an early module that looks the same but is labeled for some sort of digital block (comparator?). Both are really cool museum type pieces but I wouldn't use them in a build or anything.