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In Reply to: RE: Listen for yourself posted by cpotl on July 07, 2017 at 11:56:14
Why are there no commercial applications for SET amps? What amps were used when the recording mixer did his work?
Follow Ups:
Wait a minute: The analog record circuitry in the classic Ampex 351 tube tape recorder was all single ended. Its internal playback electronics were push-pull.
Edits: 07/07/17
Of course lots of 1950/60s studio and broadcast line level gear was single ended and it worked just fine.
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.
Chris
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.
Edits: 07/10/17 07/10/17
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.
Chris
After listening to a fair group of SE amps, I have yet to hear one I wanted to build, except for geetar amps.
For stuff SE needs, like gapped OPT's there is some benefit to the linearizing effect this has on the sonics delivery. I may try gapped PP at some point if I can live with the reduction in LF performance the drop in overall primary L gives. Since I run electronic cross overs, this could be sooner than later...
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Bi-amping is your friend: I run parallel single ended 2A3s above 160Hz and McIntosh push-pull tubes in the bass.
"Bi-amping is your friend"
I totally agree.
Gapped transformers and good bass performance are, IMO, mutually exclusive.
The gap reduces the inductance, the reduced inductance causes the loadline to become elliptical (in the presents of low bass) and all the frequencies follow that elliptical loadline increasing the HD.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Yah, it is a fight...for the bass amps, I think I want as much as I can get. Anything else above that, the gapped core sonics are not to be despised.
It does not take anything like a SE, full Class A idle current worth of a gap to be of use. Just enough gap to knock 10% off is quite worthwhile. it is likely one of the reasons I like cut C-cores; their effective gap is much larger than an interleaved stack of E's and I's.
I think I need some 49% Ni cut C's...
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"Why are there no commercial applications for SET amps? What amps were used when the recording mixer did his work?"
Indeed, this gets to the nub of the question. When someone chooses to use either a tube SET or PP amplifier, or an SS amplifier, in their home stereo system, they are just making a selection that sits at the end of a long chain of totally "conventional" SS amplification and processing stages. If this last step of the chain makes a big difference, it seems likely that it is because of what it is adding, rather than what it is not adding, to the signal that has been fed into it.
I have never understood why this is a controversial point, but somehow the suggestion that the SET amplifier is adding colourations that are "pleasing," "nuanced," or whatever, seems not to go down too well sometimes!
Chris
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