John Curl's Blowtorch preamplifier part II

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#55,221
simon7000 said:
is the most recent reference I found to a system that actually lasted until after the USSR collapsed.
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Systems under the D.o.D umbrella don’t end their life and stop existing. They are further developed, change their code names and start a new life.

If George can find more there are some very interesting engineering principles learned from this system.
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There are more and yes there are very interesting.
But please allow me to divert you –as I think that it would be far more intellectually rewarding - to some early work on engineering principles:

https://ia600304.us.archive.org/5/items/vitruviustenbook00vitruoft/vitruviustenbook00vitruoft.pdf

🙂
George
>Edit: For other formats: https://archive.org/details/vitruviustenbook00vitruoft
 
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#55,223
gpapag said:
Systems under the D.o.D umbrella don’t end their life and stop existing. They are further developed, change their code names and start a new life.

🙂
George
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Yes but folks think you are paranoid if you show interest in some of the secret stuff.

This is a nice older satellite photo of an interesting installation. Note the tall round thing is not a fence. (The short round one probably is the fence.) It is part of an antenna system! The scale indicates the frequency range.

Pavel could probably explain its' purpose.
 

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#55,225
Wide-Aperture Direction Finding (WADF) Circularly Disposed Antenna Array (CDAA).
These enormous antennas arrays contain dozens of monopoles arranged in a circle with diameters ranging from 50m to over 150m. Such systems used a capacitive switching goniometer to electronically select each antenna and produce highly-accurate azimuthal headings with sub-1-degree precision. These arrays were placed throughout the United States and networked extensively to provide accurate headings for any high frequency radio signals detected.
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NSGA Homestead, Florida - Photos taken during 1970 - from Ken Halliwell (former CTM1)
 
#55,228
#55,229
Just about any of the Crown D-Series power-amplifiers (i.e., D-75, D-150, DC-300 stereo amplifiers) from the early 1970's would present most of the problematic sound attributes of TIM; they're all readily available on EBay from about $150-$300, so auditioning the troublesome topology (5-9 gain stages in series, wrapped in massive quantities of NFB) is easily at hand... 😀
 
#55,231
can't find a readable schematic but the service manual does claim a op amp is used for input - that would be a early 1970's op amp

and that the output Q are zero bias Class B


not sure what that means to anyone trying to design a good amp in 2014, having the benefit of Self and Cordell's Books, 4 decades of JAES, WW(while it was still good), Jan's Linear Audio, discussions here that have actual technical content....
 
#55,234
jcx said:
can't find a readable schematic but the service manual does claim a op amp is used for input - that would be a early 1970's op amp

and that the output Q are zero bias Class B


not sure what that means to anyone trying to design a good amp in 2014, having the benefit of Self and Cordell's Books, 4 decades of JAES, WW(while it was still good), Jan's Linear Audio, discussions here that have actual technical content....
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LM301 I think.

EDIT - My bad parts list has uA739/49 somewhere in the circuit.
 
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#55,238
mullardel34 said:
Just about any of the Crown D-Series power-amplifiers (i.e., D-75, D-150, DC-300 stereo amplifiers) from the early 1970's would present most of the problematic sound attributes of TIM; they're all readily available on EBay from about $150-$300, so auditioning the troublesome topology (5-9 gain stages in series, wrapped in massive quantities of NFB) is easily at hand... 😀
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70's , so whats the excuse today ...... 😀
 
#55,240
No music. This amplifier made no music. Not to say that it wasn't sonically impressive at times, but the music got lost somewhere between input and output.

Sonic spectacle and musical accuracy don't always go hand in hand, but this was a textbook case. It's clear that Crown wanted to change its image with this amplifier, and it did. Gone was the bright, hard quality of earlier years, replaced by a dark, thick, grainy character that obscured all the finer details of the musical performance. No matter which digital processor, preamplifier, or interconnects I used, the quality remained the same: thick, woolly, and opaque, with a brittle, forward midrange. I auditioned all three samples, but the results were the same. Dual-mono operation did nothing to improve the situation; in fact, it sounded somewhat worse.
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That's fairly positive?😀
 
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