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-   -   Tube op amps (http://www.diyaudio.com/forums/tubes-valves/65811-tube-op-amps.html)

SY 11th October 2005 06:43 PM

Tube op amps
 
A link to some classic papers:

http://www.national.com/rap/vacuumtubes.html

jackinnj 11th October 2005 07:17 PM

SY --

One of the people who worked on Jim Williams (williams was the editor) "The Art of Analog Design" remarked on how Williams convinced his father to purchase a Philbrick OPAMP for him -- back in the days when $250 would buy several cases of Margaux, or a Hallicrafters SR-150.

EC8010 11th October 2005 09:06 PM

Walt Jung's "Op Amp Applications" book published by Analog Devices (2002) has an absorbing history of how op-amps came about.

Rocky 12th October 2005 01:15 AM

On the subject,
http://headwize.com/projects/showfil...=opamp_prj.htm
has a pretty comprehensive reference list.

The article itself, on tubes and opamps, is good reading too.

- - Rocky

Joel 12th October 2005 02:42 PM

gain of 20,000... hmmm, not so good for a linestage...
 
Great link. Thanks Sy.

SY 12th October 2005 05:42 PM

Well, I owe ya one for those amazingly handy schematic symbols I kiped off your website.

Joel 12th October 2005 05:56 PM

I like to help the people when I can. :)

tlf9999 12th October 2005 06:31 PM

since our amps are for the most part op-amps, do those analog computers / op-amps used in missiles for example suffer from the same mishaps of our amps?

for example, what is the impact of accuracy from first-cycle distortion? or back-EMF? or ???

Sch3mat1c 12th October 2005 07:48 PM

Quote:

Originally posted by tlf9999
since our amps are for the most part op-amps, do those analog computers / op-amps used in missiles for example suffer from the same mishaps of our amps?

for example, what is the impact of accuracy from first-cycle distortion? or back-EMF? or ???


No, and no. Single ended and push pull amps are rarely of the same sort as an op-amp. For instance, gain is controlled and often, loop NFB is low (or not used at all). Op-amps work entirely by NFB, ideally having gain approach infinity (such that very nearly zero signal voltage appearing across the terminals produces an infinite output voltage). Also, since gain is so high, distortion is corrected by using ohmic resistors to define gain and thus distortion.

Tim

Devius 12th October 2005 11:21 PM

I have a doubt...

I've read the article on headwize regarding tube opamps, and I recall reading somewhere (maybe in this forum) that the usage of negative feedback in tube designs reduced the gap to solid-state designs in terms of sound. So, if I were to use one of those tube opamp designs configured for a gain of 10dB, or something like that, as a line stage would I lose the benefits of using tubes in the first place?

Sorry if this is a stupid question, but I don't know much about valves...


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