Incredibly impractical as you increase the number of channels. Requirements on parasitics (leakage capacitance) too stringent. Resulting increase in impedance also needs attention.5v333 said:
Bus Source Impedance (w / opamps)
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As said, with good control of impedance and grounding, you can get "lossless" mixing.
Well actually half the power of a single source is absorbed by the other sources, not the load.
The parasitics eat you up for more than a small number of sources.
And what the heck is the problem?? We are Audio Techs! The thing that separates us from plain Telephone Workers is that we work directly with Amplifiers. We are usually over-supplied with amplification.
Well actually half the power of a single source is absorbed by the other sources, not the load.
The parasitics eat you up for more than a small number of sources.
And what the heck is the problem?? We are Audio Techs! The thing that separates us from plain Telephone Workers is that we work directly with Amplifiers. We are usually over-supplied with amplification.
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I described it in a magazine article back in 1980, and I'm sure I have cut and pasted a schematic block here at least once, maybe more. It was used in production in an AMR console series back in the '90s...5v333 said:
Summing more stems in the digital domain actually gives you more signal or more resolution depending on how you crunch it. Even my lossless current source summing had a cumulative noise build up from the active synthesized current sources adding incoherently, but it was respectable for analog technology a few decades ago.
JR
ruffrecords
Well-known member
JohnRoberts said:
The bruise on your forehead must be quite sore by now JR.
Cheers
Ian
JohnRoberts said:
Not going to argue that but it's not so easy when you don't have the digital know how and hardware to do it
abbey road d enfer said:
Yes - it's hardly practical in implementation.
Still interesting in concept though
It had almost healed but there are always newbies who haven't heard my old stories.ruffrecords said:
Coincidentally last weekend I got a PM (on another forum) from a guy in Portugal with questions about how to put back together an old AMR 32x16 Production Series basket case he got from a friend for $0.. Still getting service calls 25 years later, but that's what I get for admitting I designed it on the WWW... :
JR
5v333
Well-known member
JohnRoberts said:It had almost healed but there are always newbies who haven't heard my old stories.
Coincidentally last weekend I got a PM (on another forum) from a guy in Portugal with questions about how to put back together an old AMR 32x16 Production Series basket case he got from a friend for $0.. Still getting service calls 25 years later, but that's what I get for admitting I designed it on the WWW... :
JR
Dont worry i just thought it sounded inovative and interesting. Not looking for a design to build just been thinking alot latly about the summing concept in analogue/digital.
I spent decades thinking about the difficult parts of console design.5v333 said:
Almost on topic for this thread is that a passive summer with make up gain will pretty much require the same amount of gain as the noise gain of virtual earth sum amp with the same number of stems. My current source approach overcame that Nx noise gain, but I repeat at this point it is academic, or moot.
JR
5v333
Well-known member
yes time to leave the thread for the original topic.
