John Curl's Blowtorch preamplifier

[syn08]

OTOH, if I see what those IC smiths turn out in 2009, ICs get very competitive. As long as you can live with +/-15V supply, that is. For higher levels, there's still no substitute for discretes.

There are a few +/-40V opamps who, while not directly intended for audio, have quite interesting specs. OPA445 (in DIP8, JFET input, 20nV/rtHz noise, distortions in the ppm range), OPA452/453 (in TO220-7pin, JFET input, fast, 50mA output). They seem to fit pretty well a line amp application.

 

[JPV]

BTW as one would expect this list is very US centric. I would certainly consider Willy Sansen, or Rudy van de Plassche.

I would strongly recommend the reading of his book:
Analog design essentials

This is the perfect follow up of Gray and Meyer and is a real gem.

His book on non linear distortion is on my plate but I am not sure that it will bring practical aspects for audio because it treats only weak non linear distortion.

Shoud Erdi not be on the list ?

JPV

 

[jan.didden]

How long has Bob Widlar been dead? Do you know how many years? What have you, Scott Wurcer, added to IC design that was not essentially known by Harris in the 1970's? Please provide evidence, and listening feedback. Please don't say that you invented low Rbb'. We known about that since 1966.

You know John, it is a bloody shame that you still feel the need for such messages. Just lash out, right, and the hell with interpersonal relations.
How would you feel if we asked you what you have invented in audio design that we didn't essentially know after your long tailed pair in 1964?

Jan Didden

 

[syn08]

What have you, Scott Wurcer, added to IC design that was not essentially known by Harris in the 1970's?

Nothing. Scott is only a good example of those small, fast, hungry, hot blooded mammals which, according to Darwin, helped the Cretacic ruling huge dinosaurs to dissapear.

 

[AndrewT]

There are many opamps for audio these days that have output stage class A currents of over 5mA.

let's compile that list.
i.e. output stage bias current >5mA and suitable for audio.

 

[jan.didden]

A whole class of those can be found among the DSL differential line drivers. Not designed for audio, but eminently suited.
Check them out.

Jan Didden

 

[Rick Miller]

The Analog Devices AD 811 runs at 15ma with 2,500uv S/R.

 

[jan.didden]

The Analog Devices AD 811 runs at 15ma with 2,500uv S/R.

Hi Rick,

Are you the Rick Miller of the common mode chokes & stuff?

Jan Didden

 

[Rick Miller]

Yes

 

[AndrewT]

the AD811 has a quiescent current typically between 14.5 and 16.5mA.
That is not the output stage bias current. But, the bias may be >5mA. Does the datasheet confirm that?

 

[john curl]

Rick, can you post that LAMM (CES) review, here? I don't know how to.

 

[jan.didden]

the AD811 has a quiescent current typically between 14.5 and 16.5mA.
That is not the output stage bias current. But, the bias may be >5mA. Does the datasheet confirm that?

No, it's generally not in the data sheet, but I was told that about 50% of the total for the output stage is a good guess.

Jan Didden

 

[jan.didden]

Yes

Glad to meet you! 😉

Jan Didden

 

[john curl]

Jan, I am not mad at Scott, but he is being misleading about IC's. It is important that others are not given a inappropriate summary of what IC's offer. It is just like American autos. They have changed in the last 35 years in some ways, BUT are they really better?

 

[stinius]

Jan, It is just like American autos. They have changed in the last 35 years in some ways, BUT are they really better?

I think it’s only one answer to that and it is: NO
Same **** new wrapping.

 

[Joshua_G]

I did. On this point, they don't.

They do, please look again:

 

[syn08]

A whole class of those can be found among the DSL differential line drivers. Not designed for audio, but eminently suited.
Check them out.

Jan Didden

OPA847 - bipolar, 3.9GHz bandwidth, 950V/uS slew rate, 100uV offset, 0.85nV/rtHz noise, 18mA supply, probably 10mA output stage bias, distortions ppm in the MHz range.

THS4631 - JFET input, 325MHz bandwidth, 1000V/uS slew rate, unity gain stable, 7nV/rtHz noise, 12mA supply, certainly over 5mA output stage bias, distortions ppm in the MHz range.

Do it with discretes.

 

[Joshua_G]

And I use 50ma in my discrete designs. What a waste!

🙂

 

[jan.didden]

Jan, I am not mad at Scott, but he is being misleading about IC's. It is important that others are not given a inappropriate summary of what IC's offer. It is just like American autos. They have changed in the last 35 years in some ways, BUT are they really better?

He's not inappropriately given IC info. You are. You think nothing has changed in 35 years, while IC's have been leaping forward. Where have you been hiding?

Jan Didden

 

[Joshua_G]

OPA847 - bipolar, 3.9GHz bandwidth, 950V/uS slew rate, 100uV offset, 0.85nV/rtHz noise, 18mA supply, probably 10mA output stage bias, distortions ppm in the MHz range.

THS4631 - JFET input, 325MHz bandwidth, 1000V/uS slew rate, unity gain stable, 7nV/rtHz noise, 12mA supply, certainly over 5mA output stage bias, distortions ppm in the MHz range.

Do it with discretes.

I'd be more interested in comparing sound with discrete.