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Old 16th November 2011, 11:33 AM   #17961
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Quote:
Originally Posted by john curl View Post
Look at the resistor values.
Very high but I thought they where part of the experiment as Johnson noise generators.
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Old 16th November 2011, 11:56 AM   #17962
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Hi,

Quote:
Originally Posted by simon7000 View Post
Here are two theoretical circuits. When made with real components will they have the same noise level?
Depends on the Op-Amp's and Resistors used.

Quote:
Originally Posted by simon7000 View Post
Is there any signal correlated noise?
Depends on the Op-Amp's and Resistors used.

For example, classic 5534 combined with thick film resistors would give very interesting results.

Ciao T
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Old 16th November 2011, 01:47 PM   #17963
jlsem is offline jlsem  United States
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Makes you wonder why there are so few "live" orchestral recordings. It's not that it's daunting, it's that a recording is an archival document, not a one-off performance. Add in the strict admonition to hit exactly the volumes you did at the run-through, NEVER exceeding them by even a little and what you have is a safe, sterile, performance, professionally executed, but taking no chances and not "going" with the feeling. Multiply that times 100 (or so) musicians.

Just curious, have there ever been any D2D orchestral performances that were exciting? Within the genres I favor, I can't think of any jazz D2Ds that I'd listen to more than once.
Most of if not all of the Dallas Symphony Orchestra recordings are done live and yes they are cut and spliced where the best movements from at least three performances are grouped together. The conductor usually has the say as to which movements are used and many of the recent DSO recordings are very musical and hardly sterile.

Some of the most hair-raising orchestral performances you'll ever hear are live wartime recordings of the Berlin Philharmonic made under the threat of aerial bombing and at a time when Germany was losing the war and a sense of desperation had set in. Most great art was made during times of upheaval or as they say, interesting times.

John

Last edited by jlsem; 16th November 2011 at 01:49 PM.
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Old 16th November 2011, 02:02 PM   #17964
zinsula is offline zinsula  Switzerland
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Quote:
Originally Posted by john curl View Post
Look at the resistor values.
Well in a given application of course the load seen by the source is 10x higher in the single amp approach.
If that would be ok, you may change the dual op amp design to 1k / 10k feedback resistors. shoild lower the noise, and a load of 10k should not be an issue.
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Old 16th November 2011, 02:19 PM   #17965
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Quote:
Originally Posted by jlsem View Post
Some of the most hair-raising orchestral performances you'll ever hear are live wartime recordings of the Berlin Philharmonic made under the threat of aerial bombing and at a time when Germany was losing the war and a sense of desperation had set in. Most great art was made during times of upheaval or as they say, interesting times.

John
Yes, Furtwangler's wartime 9th the chorus in particular, scarey. Many were saved on magnetophon (early tape, yes Thorsten another German invention) but technically leave much to be desired.
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Old 16th November 2011, 02:48 PM   #17966
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Quote:
Originally Posted by jlsem View Post
... many of the recent DSO recordings are very musical and hardly sterile.
But of course, they're not D2D, the musicians aren't restrained in their playing for fear of catastrophic consequences, and... they're digital. Hey, my recordings are done live, one take, but I didn't tell them to play things with exactly the same dynamics each time, and second takes were cost-free. I take it that the answer to my question is, "no."
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Old 16th November 2011, 02:50 PM   #17967
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In the end, however, great performances almost always come from orchestras with highly talented, above average musicians and great conductors. Here is a recording from the not too distant past by the Leningrad Philharmonic with Evgeny Mravinsky conducting:

Glinka - Russlan and Ludmilla Overture - Mravinsky/Leningrad - YouTube

It was made during a live concert held in celebration of Mravinsky's career where the orchestra was given an opportunity to show off its skills and nothing was left in the bag. There are many who would consider this kind of playing vulgar. I have this recording on lp and it is done very well.

Unfortunately, these days classical music performance seems overly influenced by critics who believe that correctness and accuracy should rule the day, and knowing that in the back of their minds performers do tend to be a bit too careful and sterility ensues.

John

Last edited by jlsem; 16th November 2011 at 03:09 PM.
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Old 16th November 2011, 02:53 PM   #17968
jlsem is offline jlsem  United States
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Quote:
Originally Posted by SY View Post
But of course, they're not D2D, the musicians aren't restrained in their playing for fear of catastrophic consequences, and... they're digital. Hey, my recordings are done live, one take, but I didn't tell them to play things with exactly the same dynamics each time, and second takes were cost-free. I take it that the answer to my question is, "no."
If I'm not mistaken, all DSO performances are recorded on an Otari analog tape machine. There are a few of those masters I'd like to get my hands on.

John
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Old 16th November 2011, 03:18 PM   #17969
DF96 is offline DF96  England
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Given noiseless opamps, the two amp circuit will have approximately 10dB more noise than the single amp circuit. This is because of Johnson noise from the resistors. I can't quite see the point, though.
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Old 16th November 2011, 03:23 PM   #17970
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It is an oversight on Ed Simon's part. He will change it, hopefully soon. I told him about it, yesterday. We were just checking how long it took anybody else noticed. You win the 'prize' DF96, and Zinsula, congratulations!

Last edited by john curl; 16th November 2011 at 03:27 PM.
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