tube op-amps

[Paul Perry]

At 10:24 AM 16/07/97 -0700, Eric Barbour wrote:

>Believe me...the readers of this mailing list do NOT want to experiment
>with choppers! It would be vastly easier to use solid-state op amps.

............my point entirely..............

>There is a company in Arizona, Apex Microsystems, who makes high-voltage
>op amps. I think they are hybrid thinfilm ICs. Some can operate on
>+-150v,
>a perfect match to the tubes.

.......this is worth knowing........

>It is difficult to find these old analog-computer books
.........plenty of stuff in the pre 1960 IEEE perodicals and similar.........

>> BTW, sometimes the valve heaters are run on rectified dc with a 6v car
>> battery floating across it.....apparently this gives a more stable heater
>> supply (valve synth tip of the day)
>
>Not necessary! Unless you need to have an uninterruptable power supply.
>Conventional, well-filtered DC power is adequate. Regulation is not
>needed
>for heaters.

......well, yes, but I was trying for that "look ma, no transistors" effect
(nearly said 'no semis' then remembered that big selenium rectifier feeding
the battery)....
Actually, I remember ferroresonant transformers that formed the core of
passive AC mains regulators, also servo operated variacs that whined as they
ran up and down chasing the mains fluctuations.......

Paul Perry melb aust
sobering thought : today will be somebody else's "good old days"