John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
Wow! Laser trimming. Perhaps Scott can tell us all about the many advantages of laser trimming beyond better input offset.

Sorry, there is one glaring resemblance: neither the LF356 or the AD711 was in particular designed for audio applications.

The fact that the AD711 guarantees the distortions in the data sheet (typ. 0.0003%), while the LF356 data sheet is mum about, is of course irrelevant for the High End Audio priests.
 
I would not use an AD711 for just about anything today, but it was OK for servos back in its day. The AD797 is pretty good, in fact, excellent for instrumentation, but too expensive for most audio projects. I don't use any Analog Devices IC op amps at this time, except for the AD825 which I designed into a power amp. I like this op amp.
 
For the record, I pointed out the AD711, because it would be close in performance to the LF356 in the TIM test that I posted in Graph 1.
I thought that Scott should know where he would approximately place on the graph, if his op amp was tested in the same way, under the same test conditions. uA741? We don't use those anymore, but they were very popular back then, in the middle 1970's and they were much cheaper to buy than the LF356. The LF356 sounded better than the uA741, even in guitar amps. But that is another story. '-)
 
Why would I want to use either of those opamps, really? Neither have that great of appeal -- no slight to the AD711, just you can do better nowadays.

Daniel, this is something what I do not understand as well. I started my professional career in 1979/80, after graduating from technical university. Even in those years I needed to use much faster parts, like uA715, or LM318. I would never ever consider using those funny parts like 741 for professional instrumentation purposes. 741 had been obsolete even in 1979. Maybe audio designers had a different view.
 
Daniel, this is something what I do not understand as well. I started my professional career in 1979/80, after graduating from technical university. Even in those years I needed to use much faster parts, like uA715, or LM318. I would never ever consider using those funny parts like 741 for professional instrumentation purposes. 741 had been obsolete even in 1979. Maybe audio designers had a different view.

For the record, I used this in a recent project. Oy, oy, where would this jfet input opamp be on that already famous chart?
 
For the record, I pointed out the AD711, because it would be close in performance to the LF356 in the TIM test that I posted in Graph 1.
I thought that Scott should know where he would approximately place on the graph, if his op amp was tested in the same way, under the same test conditions. uA741? We don't use those anymore, but they were very popular back then, in the middle 1970's and they were much cheaper to buy than the LF356. The LF356 sounded better than the uA741, even in guitar amps. But that is another story. '-)

The funny thing is a AD744 with a push-pull buffer sounds the same as a JC2 line amplifier. I got the circuit from Walt Jung's opamp booklet.
 

Attachments

  • JC2linedriver.jpg
    JC2linedriver.jpg
    117.2 KB · Views: 220
Status
Not open for further replies.