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In Reply to: RE: I'm only talking about power amps. posted by gusser on July 08, 2017 at 15:55:00
Gusser, I'm curious to know, though, what kind of amplification and processing stages a typical audio signal will have gone through, in a modern recording studio and CD production plant, on its way from the studio microphones to the output of the home-user's CD player.
Would the amplification stages typically be op-amps, with lots of feedback? Could you walk us through the steps the signal might typically follow, between the microphones and the CD player's output? That would be really interesting.
Today most work is done on digital workstations. The large mixing consoles with multiple flat screens are just control surfaces talking to a bunch of commodity PC's over Ethernet. The audio processing is all via AES in and out - so much for all the SPDIF jiter scares! AES and SPDIF are virtually identical - especially in terms of jitter performance.
Now the microphone preamp before the ADC is analog of course and mostly an OPAMP design. There are some studios that use discrete transistor mic preamps and some even tube preamps. But beyond the ADC, the audio remain digital, in fact a computer file. Tape is long gone except again for tiny esoteric operations. All storage is via hard disk and that data is shipped and modified around a lot including between facilities over the public internet - encrypted of course.
In the 1980s, large mixing consoles were all OPAMP. Hundreds of them in a 128 input board. Anywhere from two to ten stages per module. I once cared for a Neeve console that had 128 inputs and the internal bussing was wide standard ribbon cable. They ran balanced +/-/G across a 50 wire cable with no twists either. No crosstalk and no noise. It just shows what is possible with god engineering as Neeve is well known for. So much for esoteric audiophile cables! If any of that hype was true, Neeve would have used them. Cost was no object on his products.
The 1970 was the rein of discrete transistor OPAMPS. And they were not as good to spite what some audio magazines want you to believe.
Thanks for the summary of the path from the microphone; very informative.
Presumably there is quite a bit of analogue processing after the DAC in the home CD player? Low-pass filtering to block the digitisation artifacts, and so on? Op-amps, typically?
What I'm thinking, then, is that probably at the two ends of the chain (microphone amplifier, and output stages of the CD player) the typical setup will involve op-amps, with the usual very large negative feedback applied. I'm just wondering where that leaves the people who argue that negative feedback is a bad thing.
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