OpAmp used as Input Stage (IS)?

sam9 · 29th May 2003, 05:24 PM

I've heard of an op-amps being used as the input stage to an otherwise discrete design, (replacing the constant current source and differential amp) but I don't know how it is done. Can anyone direct be to examples, either hobbiest or commericil. I would especially like to see a schematic rather than just a statement of general principls.

Tube_Dude · 29th May 2003, 06:00 PM

Quote:

Originally posted by sam9
I've heard of an op-amps being used as the input stage to an otherwise discrete design, (replacing the constant current source and differential amp) but I don't know how it is done. Can anyone direct be to examples, either hobbiest or commericil. I would especially like to see a schematic rather than just a statement of general principls.

You have an example,here:

http://web.tiscali.it/audiofanatic3/...5003_15004.jpg

Cheers

sam9 · 29th May 2003, 06:07 PM

That URL is, alas, "forbidden". Or no longer in service.

Tube_Dude · 29th May 2003, 06:11 PM

Quote:

Originally posted by sam9
That URL is, alas, "forbidden". Or no longer in service.

Try:
http://web.tiscali.it/audiofanatic3/..._finaliSS.html

Is the 16 on the list

sam9 · 29th May 2003, 06:38 PM

Got it. Now to study it. Looks simple - that's often a sign its not so simple.

Tube_Dude · 29th May 2003, 06:41 PM

Quote:

Originally posted by sam9
Looks simple - that's often a sign its not so simple.

Clever thinking!!!

Cheers!

djk · 31st May 2003, 11:15 AM

With ±24V and an OPA2604 opamp, this circuit will do 50W/4R

http://www.delphion.com/fcgi-bin/any...53E&SCALE=0.35

If you change the feedback loop to this scheme up to 1KW may be had with suitable outputs, drivers, and supply.

http://www.delphion.com/cgi-bin/view...d/US04467288__

sam9 · 31st May 2003, 05:22 PM

Certainly a wide variety of approaches here. I find the description "Distortion-Free" a little amussing. I wonder if the patent office should treat claim for distortion-free amplifiers the same way as perpetual motion machines.

joensd · 31st May 2003, 05:32 PM

That´s even simpler.

Cheers
Jens

Andypairo · 1st June 2003, 12:38 AM

Audio Analogue products, the "Puccini" and Puccini S.E.", use opamps as input stage.

These product were reviewed as particularly well sounding, so having a look at this page might be useful... you can find the complete schematics as well as some tips to improve the commercial products...

http://www.pi.infn.it/%7Efederico/unofficial.htm

Cheers

Andrea

29th May 2003, 05:24 PM	#1
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	OpAmp used as Input Stage (IS)? I've heard of an op-amps being used as the input stage to an otherwise discrete design, (replacing the constant current source and differential amp) but I don't know how it is done. Can anyone direct be to examples, either hobbiest or commericil. I would especially like to see a schematic rather than just a statement of general principls.

29th May 2003, 06:07 PM	#3
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Forbidden link That URL is, alas, "forbidden". Or no longer in service.

29th May 2003, 06:38 PM	#5
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Thanks Got it. Now to study it. Looks simple - that's often a sign its not so simple.

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31st May 2003, 11:15 AM	#7
djk diyAudio Member Join Date: Feb 2001 Location: USA	With ±24V and an OPA2604 opamp, this circuit will do 50W/4R http://www.delphion.com/fcgi-bin/any...53E&SCALE=0.35 If you change the feedback loop to this scheme up to 1KW may be had with suitable outputs, drivers, and supply. http://www.delphion.com/cgi-bin/view...d/US04467288__

31st May 2003, 05:22 PM	#8
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	Certainly a wide variety of approaches here. I find the description "Distortion-Free" a little amussing. I wonder if the patent office should treat claim for distortion-free amplifiers the same way as perpetual motion machines.

31st May 2003, 05:32 PM	#9
joensd diyAudio Member Join Date: Dec 2001 Location: Germany	That´s even simpler. Cheers Jens

1st June 2003, 12:38 AM	#10
Andypairo diyAudio Member Join Date: Sep 2002 Location: near Milano , Italy	Audio Analogue products, the "Puccini" and Puccini S.E.", use opamps as input stage. These product were reviewed as particularly well sounding, so having a look at this page might be useful... you can find the complete schematics as well as some tips to improve the commercial products... http://www.pi.infn.it/%7Efederico/unofficial.htm Cheers Andrea

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