OpAmp used as Input Stage (IS)?

[djk]

"That´s even simpler."

Surely you jest!

ESP 76 not only has more parts and complexity than the RCA patent, it is totally inferior.

I suggest that you don't understand how the RCA circuit works.

Perhaps you should look at this:

http://www.audiodesignguide.com/my/Cool_Follower1.GIF

[joensd]

Surely you jest!

ESP 76 not only has more parts and complexity than the RCA patent, it is totally inferior.

I suggest that you don't understand how the RCA circuit works.

Perhaps you should look at this:

http://www.audiodesignguide.com/my/Cool_Follower1.GIF

djk, i was referring to the 300W-beast (first link in the thread) so...
the patent you´ve linked to looks real simple.
did you try it?
i always get tempted so easily with simple circuits....

Regards
Jens

[djk]

"djk, i was referring to the 300W-beast (first link in the thread) so...
the patent you´ve linked to looks real simple.
did you try it?
i always get tempted so easily with simple circuits...."

I understand now, but your link was to the ESP 76 design. No matter. The 300W design is an old one, the first time I saw this was in the early 70s from BGW. They used the 70V/µS LM318 for the opamp and a dozen 2N6259 in a tunnel for their BGW1000, 1KW bridged.

If you make the RCA circuit with MJE15030/31 as drivers, and six pairs of MJ21193/94 as outputs with the Transnova feedback scheme and ±95V you can get 1KW/2R, 650W/4R, 450W/8R from this circuit. The drivers and the bias resistors are to be fed from the ±15V opamp supplies.

For use below 1Khz we can simplify the Transnova circuit to an LM1875 for the opamp driving a 10 ohm resistor connected to ground. The MJ21193/94 pairs are connected straight to the output of the opamp.

http://www.diyvideo.com/forums/attac...?postid=182299

What we have here is a 1KW gainclone!

[sam9]

As the originator of the thread, what I was thinking og\f was something where an opamp feeds a more or less conventional VAS which feeds a more or less conventional OPS and where the global NFB connects back to the inverting input of the opamp (or the non-nerting if ones sets it uo other way'round).

I haven't had time assimilate all this info except for running a quick Spice model of the Schroeder patent which get the peculiar result of a spectrogram full of odd order spikes all of the same magnitude marching off to right as far as I cared to look. Maybe it would do for a PA system.

Someone (offline) showed me a schematic of a Carver M-400, but there was so much other stuff going on that it's a bit hard to digest. Noted, however, that he seemed to clase a local feedback loop around the opamp and then close the global loop around that.

[djk]

"Someone (offline) showed me a schematic of a Carver M-400, but there was so much other stuff going on that it's a bit hard to digest. Noted, however, that he seemed to clase a local feedback loop around the opamp and then close the global loop around that."

The early M400 had one inverting channel and one non-inverting channel.

The non-inverting channel is probably the best opamp input stage of all time, used in virtually all the Carver equipment from 1980 on.

The first amplifer that I saw that used this design was the Crown M600, around 1975.

In my mind this would be an ideal 'universal front end card', needing only a couple of resistor changes to run on any ± rails.

I would be willing to participate in a 'group buy' for something like this.