John Curl's Blowtorch preamplifier part II

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#89,544
scott wurcer said:
People here use it every day as in noise power V^2/Hz or A^2/Hz. Power spectral density is a fairly basic and fundamental signal processing concept how would you suggest "using" it?
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I dont have any particular suggestion. I was hoping some interesting, maybe novel, uses could be suggested. OK. Maybe in acoustics work or maybe electomechanical systems? I found it helpful to see things brought up out of the signal or the noise which wasnt as obvious using other means.

Same with Cepstrum. Has anyone found it useful in some way for our audio hobby?


THx-RNMarsh
 
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#89,547
billshurv said:
so your study of room reflection has taken you from a narrow beamwidth dipole to a wide dispersion controlled directivity horn. That's about as far a leap as one can make in one upgrade other than the MBL Rugby balls*, and one would assume would require totally different room treatment? How have you changed things, other than cutting a bit off your sideboard?

*If I said football that would confuse the 80% of the world for whom football is not men in helmets.
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Well, it might seem that way if my T&M re speakers/room/acoustics started 2-3 years ago. But going back 45 years would be too much for here. I can only give you some 'sound bite' type info or bottom line stuff. Which would lead to endless questions and debate. The M2 comes closest to the 'perfect' system for close listening situations (Mastering). But it could be, for my use, more narrow dispersion (90) but constant power, as I am somewhat further way than I would be sitting across from a recording console in a small room with widely spaced speakers. So I have to deal with the wider than desired for my use (Not mastering) acoustically or even turn inward the speakers and more side wall absorption.... (which i do) but the other characteristics are a big step up and that part I could not do anything to improve on my own.

[I chose the 90 degree lens on a JBL LE175DLH with D130 in rear loaded horn and 075 tweeter. My early controlled dispersion system... 40 years ago]


THx-RNMarsh
 
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#89,549
i noticed, long ago, the lack of dynamic range in LP systems compared to my own field recordings. Not to even mention the much greater clarity. Maybe it was the microphones and wide dynamic range of the recorders I used. But we are closing the gap. Mics and mic preamps is where it starts.

Note the comment on dynamic range here...... on page six.


View attachment A brief history of microphones.pdf


THx-RNMarsh
 
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#89,551
RNMarsh said:
i noticed, long ago, the lack of dynamic range in LP systems compared to my own field recordings. Not to even mention the much greater clarity. Maybe it was the microphones and wide dynamic range of the recorders I used. But we are closing the gap. Mics and mic preamps is where it starts.

Note the comment on dynamic range here...... on page six.


View attachment 576468


THx-RNMarsh
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I also noted a striking difference (positive) with field recordings. I attribute it due to the fact that the signal hasn't gone through those 100 opamps in a typical mixing desk 😉

Jan
 
#89,553
jan.didden said:
I also noted a striking difference (positive) with field recordings. I attribute it due to the fact that the signal hasn't gone through those 100 opamps in a typical mixing desk 😉

Jan
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Speaking of dynamic range did I ever play you the "break" I took while doing nature recordings on an abandoned golf course. Dynamic range is only part of the answer, Harvey Gerst thought the best B&K instrument microphones still make for somewhat dull recordings.
 
#89,555
if you follow the links earlier for the schematics for the Neumann and Westrex electronics you will see some interesting stuff in the signal processing. It could be significant like crossover distortion in the amp. But with a 6 dB per octave rolloff in the playback eq. the distortion will be reduced. Lots of other interesting stuff like HF compressors as well.

However what you describe as more dynamic will really limit its "playability" on for example FM radio or even table radios etc. pretty much all released music has been "mastered" to make sure it plays well. With phono there are limits in dynamic range, low frequency output and high frequency levels so it needs lots of tweaking. Watchin a good mastering engineer do the subtle tweaks is fascinating. It takes years to learn the craft.
 
#89,557
waltzingbear said:
No Jan, its not the 100's of opamps that's the difference, its the few opamps that reside inside a compressor/limiter that's the biggest difference between field recordings and commercial product.

(vast oversimplification, but true nonetheless)

Cheers
Alan
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Well in that case it is not the opamps but the compression and limiting that goes on.

Jan
 
#89,558
I think you guys are guessing too electronics centric. The recording, mixing, and mastering is the biggest factor. People compress the frequency range to avoid a lot of information they don't associated with instruments, even though it's very telling of the instrument and environment. It's really a matter of taste.

Listen to MoFi's Megadeth: Countdown to Extinction. They played the guitars straight into auto-tuners with no amps involved. Now listen to Neil Young's Greatest hits (reprise), you can hear him play and often his guitar, and the amp is to the far right on the floor, mic'd and you can tell it's a tube amp playing heavily distorted sitting out on the side of the stage. You could also try Mambo Insuenudoe by Ryan Cooder where you can hear the live studio with minimal barriers and such (in Cuba). Very different.

Ques for how loud something is when it's as sterile as Countdown to Extinction will not be perceived as easily as other recordings with more information even if they're the same.

One of the highest ranking crest factor recordings is a snare drum smack on the Flying Cowboys album; try to pick out which one on that pretty clean album. I couldn't tell on a casual listening.
 
#89,560
from what i have seen wathing the production process I have to agree that a "production" recording with wide distribution will have a lot of tweaks based on taste, target audience and commercial judgments. I also remember hearing about the magnificent but unplayable masters.

There is a very interesting section in the Neumann calibration instructions on maximum record levels and stylus size. It explains the function of the limiters and why they are essential.
 
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