What are op amps?

[rogerjames]

Love your eyesight, the same as mine, being 76 years old, the best bit is at this age is everything sounds great!!! stay safe young man!!!

[gkdresden]

The opamp in your hand was an AD706. I think you use it very often for low frequency low noise input stages with higher gain (phono). I like it very much because of its low noise and very low µV offset. In fact it is a bipolar opamp but with nA input currents comparable to FET opamps. Unfortunately it is a little bit too slowly for power amps.

[gkdresden]

A little correction to your feedback resistor network: it is a voltage divider. When we consider the resistor between non-inverting input and ground as R1 and between output and non-inverting input as R2, the gain is (R1+R2)/R1 or R2/R1+1.

[christopherlangley]

I thoroughly appreciate your time and effort to share your depth of knowledge

[rompstar]

its cool that you do this / I think you are the only CEO of a audio company that does this, shows your passion for Audio!

[mehmetcemarmagan]

Hey Paul, thank you for your time and explanation, i hope you will get into more details and complicated stuff, i don't know why but i get the source of knowledge when things get more complicated. Cheers and respects...

[eddiegalindo]

you must be a lot of fun to be around !!! WOW !!! Designing something on a page ? it's got to be soooo good to understand all that you spoke about. You are the MAN !!! thank you !!!

[nachom]

Best explanation I have found. Thanks

[KaranSharmapersonal]

You are my audio GURU.🙏 Thanks sir, for teaching us all this for free, love from India.

[EthanWiner]

Your 1K and 10K resistors give a gain of 11, not 10. For a gain of 10 you need 1k and 9k.

[dell]

I can remember am article in Electronic World about building an operational amplifier with tubes, I think it used 4 dual triode tubes. I thought about building one but when I priced out the parts I just could not afford it, I was a junior in high school at the time. I think Philbrick used to sell a simplified unit that had two dual triodes on a phenolic base that would plug into a single socket..

When I got out of the army I worked for Analog Devices when they were on Binny St in Cambridge but most of my work there was on 4 quadrant multipliers. This was in 1970 and IC's were in very early days, they came into being because of the moon program with NASA and the military doing the heavy lifting for the R&D costs.

At this time high end op amps and multipliers cane in potted blocks that were about 1.5" sq and had pins coming out the bottom side. I still have some of those modules down my cellar and the sockets they plugged into. IC's were mostly used by government agencies and they were nothing like we saw later on as far as performance goes.

[gkdresden]

Bob Widlar (Irish pronounced "wide-lar") was more like an artist than an engineer. He was a genius, a little bit crazy and paranoid and he was one of the first "drop outs" of Silicon Valley. He co-founded Linear Technology which belongs now to Analog Devices. Many linear circuits from the 1970ies and -80ies came out of his brain.

[wamgoc]

Bob Pease commented a lot about Wildlar. Pease’s and Jim Williams’ books are required reading on analog design.

[clydeblair]

I wound up using a budget opamp preamp while my Hafler was on the fritz. Every bit the Hafler's equal.

[adrianmorrish]

I Ave heard reviewers say op amp swaping/rolling in a device such as the xduoo xd-05 hand held dacamp is all placebo and dosent change the sou d, what you have just told me is that changing to a burr browm/TI op amp]hich are regarded as providing g a warmer sou d is not placebo then but a valid exercise, or is the change miniscule?

[charlesnr]

Are you sure the Phono Preamp had a 709. After a year, there was a mod to change to a faster Motorola transistor which improved the sound. Though the passive eq. was soft and not dynamic for the bass. Good looking with the Wood side panels. Have to look through Audio mags. I think the unit sold for $40. And the mod was about $10. Made in your garage?

[knifeswitch]

Nice “Bob Ross” of the audio design world!

[thelonepainter]

Can you use two different brands of op amps? Like a discrete version and IC.

[davelowets]

I would guess that you biased the 709 into Class-A to make it sound better in your phone stage?

[mrmoon]

is it possible perraling two or more op-amps together (input and output)? for better stability?