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SM58 but better

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Re: SM58 but better

Postby ef37a » Wed Nov 18, 2020 7:12 pm

Arpangel wrote:
ef37a wrote:Skeet pre amp? You said you had some you could not get working?
Send one over and I might be able to fix it up for son!

Dave.

Dave, if you visit Mikes obituary here at SOS, you’ll see two boxes featured in the article, one is a live surround panner, and the other is a complex 8.1 surround plus height mixer, preamp "thing"!!! That has eight of his mic amps built into it, I just need to figure out how to acces them, I suppose you could extract the circuits, but I couldn’t do that, as these are reminders of Mike.
He always made his circuits on bread board, I could take one out and try and figure it out, or, if we ever meet up Dave, you could have a go yourself!

:thumbup:

Well Tone,' with ALL props to the Great Man I doubt there is anything in his pre amp designs that is not already known. Had I still the eyes and the energy I would love to have a crack at an ultra-low noise design almost certainly using an input transformer*. We are however always limited by Mr Johnson and his blasted noise!

*NOT for any "warmf" or "saturation effects" (they don't) but for the 'free' gain and RF immunity.

Dave.
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Re: SM58 but better

Postby N i g e l » Wed Nov 18, 2020 8:12 pm

ef37a wrote: We are however always limited by Mr Johnson and his blasted noise! .

& what of Barkhausen noise ? triggered by the signal but generated from magnetic domains flipping over randomly.
I often wondered if this was significant or had a "dithering" effect.
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Re: SM58 but better

Postby ef37a » Wed Nov 18, 2020 8:27 pm

N i g e l wrote:
ef37a wrote: We are however always limited by Mr Johnson and his blasted noise! .

& what of Barkhausen noise ? triggered by the signal but generated from magnetic domains flipping over randomly.
I often wondered if this was significant or had a "dithering" effect.

Strewth Nige! I have not seen mention of Barkhausen noise for a good two decades.

I am not sure it would be a problem in audio transformers? Causes modulation noise in tape I think where there are relatively few magnetic domains?

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Re: SM58 but better

Postby Arpangel » Thu Nov 19, 2020 9:21 am

ef37a wrote:
Well Tone,' with ALL props to the Great Man I doubt there is anything in his pre amp designs that is not already known. Had I still the eyes and the energy I would love to have a crack at an ultra-low noise design almost certainly using an input transformer*. We are however always limited by Mr Johnson and his blasted noise!

*NOT for any "warmf" or "saturation effects" (they don't) but for the 'free' gain and RF immunity.

Dave.

You’re right Dave, about the design, but as I said, he adhered to whatever he was using, and didn’t cut any corners. But, he was always talking about how he used a "virtual earth" circuit in his designs, and how it was essential to some aspects of the performance, he was a big fan of whatever that is.
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Re: SM58 but better

Postby Hugh Robjohns » Thu Nov 19, 2020 10:54 am

He was referring to 'virtual earth summing' which is a very useful property of op-amp circuitry (it can be done with other technologies too, but it just happens to be particularly easy and effective with op-amps).

The negative feedback around the op-amp effectively maintains the input terminal at 'earth' potential. Any number of inputs can be connected through mix resistors to that input terminal and, because it is effectively always maintained at earth potential, there is no possibility of any interaction between the different connected inputs, but their signals can be combined.

This is important where the inputs come from channel faders, say, because it ensures that moving one fader wont affect the signal levels received from the other channels.

This is not the case with, for example, a passive mixing setup, or some other topologies! In a passive mixer changing one fader setting will alter the impedances to ground for all the other channels, and thus some interaction between sources becomes inevitable. Hence the significance of the technique, and the particular relevance to Mike's weird and wonderful multi-channel designs where input sources were routinely feeding multiple outputs via multiple faders.

There was nothing magical or advanced in what Mike was doing. He was just using op-amps in the way they were intended to be used.
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Re: SM58 but better

Postby Arpangel » Thu Nov 19, 2020 11:15 am

Hugh Robjohns wrote:He was referring to 'virtual earth summing' which is a very useful property of op-amp circuitry (it can be done with other technologies too, but it just happens to be particularly easy and effective with op-amps).

The negative feedback around the op-amp effectively maintains the input terminal at 'earth' potential. Any number of inputs can be connected through mix resistors to that input terminal and, because it is effectively always maintained at earth potential, there is no possibility of any interaction between the different connected inputsbut their signals can be combined.

This is important where the inputs come from channel faders, say, because it ensures that moving one fader wont affect the signal levels received from the other channels.

This is not the case with, for example, a passive mixing setup, or some other topologies! In a passive mixer changing one fader setting will alter the impedances to ground for all the other channels, and thus some interaction between sources becomes inevitable. Hence the significance of the technique, and the particular relevance to Mike's weird and wonderful multi-channel designs where input sources were routinely feeding multiple outputs via multiple faders.

There was nothing magical or advanced in what Mike was doing. He was just using op-amps in the way they were intended to be used.

Thanks for that thorough explanation Hugh, I finally "get it"!
Mike did explain it to me a few times, but he always assumed I knew more than I did!
And I’m a bit slow on the uptake regrading these things, so he used to just break off his explanation if he saw my eyes closing!!
What I really liked about Mike was his ability to "improvise" with electronics, I’d say "wouldn’t it be great to do this?" something virtually unheard of or impossible, and he’d disappear into the kitchen (workshop!) and about two hours later he’d have it on a bit of bread board, his knowledge of what would make certain things happen to other things in circuit design was incredible.
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Re: SM58 but better

Postby Hugh Robjohns » Thu Nov 19, 2020 11:27 am

Arpangel wrote:...his knowledge of what would make certain things happen to other things in circuit design was incredible.

As Arthur C. Clarke wrote: “Any sufficiently advanced technology is indistinguishable from magic”
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Re: SM58 but better

Postby Arpangel » Thu Nov 19, 2020 1:01 pm

Hugh Robjohns wrote:
Arpangel wrote:...his knowledge of what would make certain things happen to other things in circuit design was incredible.

As Arthur C. Clarke wrote: “Any sufficiently advanced technology is indistinguishable from magic”

That’s the problem Hugh, I used to believe in magic when I was a child, then as I grew up I realised it was just an illusion, and technology is all we have.
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Re: SM58 but better

Postby blinddrew » Thu Nov 19, 2020 2:31 pm

Arpangel wrote:
Hugh Robjohns wrote:
Arpangel wrote:...his knowledge of what would make certain things happen to other things in circuit design was incredible.

As Arthur C. Clarke wrote: “Any sufficiently advanced technology is indistinguishable from magic”

That’s the problem Hugh, I used to believe in magic when I was a child, then as I grew up I realised it was just an illusion, and technology is all we have.
You just need to take it one stage further and appreciate that it's pretty much the same thing and it's all we need. :)
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Re: SM58 but better

Postby Arpangel » Fri Nov 20, 2020 9:32 am

blinddrew wrote:You just need to take it one stage further and appreciate that it's pretty much the same thing and it's all we need. :)

There are still a lot of things that cannot be explained, scientifically, or technically, where does instinct actually come from? it certainly doesn’t come from evolution, I’m not a Darwinian, why do we want to survive? who instigated that? what is love? we cannot and will not, be able to explain the fundamental questions about life that we all want to know, science is good at the superficial stuff, the utilities, the material would, but the real stuff still goes unanswered, and these are things we can’t touch, see, or feel, but they affect every one of us.
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Re: SM58 but better

Postby ef37a » Fri Nov 20, 2020 10:09 am

Arpangel wrote:
blinddrew wrote:You just need to take it one stage further and appreciate that it's pretty much the same thing and it's all we need. :)

There are still a lot of things that cannot be explained, scientifically, or technically, where does instinct actually come from? it certainly doesn’t come from evolution, I’m not a Darwinian, why do we want to survive? who instigated that? what is love? we cannot and will not, be able to explain the fundamental questions about life that we all want to know, science is good at the superficial stuff, the utilities, the material would, but the real stuff still goes unanswered, and these are things we can’t touch, see, or feel, but they affect every one of us.

I prescribe a year's subscription to New Scientist. If you read that honestly and with an open mind you will realize that the world of science is not just a cold, hard purveyor of 'facts' but many scientists are indeed trying to 'unpick' some of the very elusive emotive things you mention.

Altruism, empathy..LOVE if you will certainly do have a survival value! Selfish, psycopathic bastards are quickly discovered and ejected from societies. (yes, I firmly believe "they" will get their comeuppance one day!)

I find the discoveries of science make this wonderful world all the MORE 'magical '. Far more so than the bollox expounded about 'how it all happened' by religious dogma.

We don't NEED to be told to be kind and generous, it is those that are not that are flawed.

Dave.
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Re: SM58 but better

Postby Tim Gillett » Fri Nov 20, 2020 11:31 am

Hugh Robjohns wrote:
Arpangel wrote:...his knowledge of what would make certain things happen to other things in circuit design was incredible.

As Arthur C. Clarke wrote: “Any sufficiently advanced technology is indistinguishable from magic”

Yes to those who dont understand the technology. The person most qualified to judge the abilities of an alleged expert is... another expert in the same field.
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Re: SM58 but better

Postby Arpangel » Fri Nov 20, 2020 1:33 pm

ef37a wrote:Selfish, psycopathic bastards are quickly discovered and ejected from societies. (yes, I firmly believe "they" will get their comeuppance one day!)

Dave.

Many years ago I believed that people were basically good, but as I’ve lived my life, I simply cannot believe that, given the things I’ve seen and experienced during my time on this earth, in fact, I now believe completely the opposite.
Very early on I started being drawn to certain philosophers and artists that fall into that way of thinking, William Burroughs, Bukowski, artists like Francis Bacon and Picasso, bands like The Velvet Underground, all people that observed what human life is like on it's underbelly.
Now I find all that way too depressing, and I’m on to another stage of my life, escapism, I no longer want to be reminded of reality, it’s too disturbing, I’ll settle for nice fluffy clouds a seat in my conservatory and a large gin and tonic.
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Re: SM58 but better

Postby CS70 » Fri Nov 20, 2020 9:06 pm

[quote="Arpangel"] it certainly doesn’t come from evolution, I 'm not a Darwinian/quote]

What you decide to believe or not has nothing to do with what is...
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Re: SM58 but better

Postby N i g e l » Fri Nov 20, 2020 9:58 pm

CS70 wrote:What you decide to believe or not has nothing to do with what is...

Tell me about it ! ..........


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