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Electronic devices : How cold is dangerous?

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Re: Electonic devices : How cold is dangerous?

Postby Logarhythm » Wed Nov 27, 2019 11:31 pm

ef37a wrote:
MOF wrote:The self noise stat’s should be excellent in Antarctica, it could start a new trend - studios at -40C.

Actually, if you do the math (Google calculator) you have to get a hell of a lot colder than that to make any real difference to component noise.

Dave.
In a previous life I ran experiments taking various electrical measurements in systems cooled to -273.12C (30mK) and can confirm this had a very positive effect on noise levels. Anyone want to invest in a new line of studio thermals so thick that they double as acoustic treatment? :mrgreen:
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Re: Electonic devices : How cold is dangerous?

Postby Martin Walker » Thu Nov 28, 2019 12:19 am

Logarhythm wrote:In a previous life I ran experiments taking various electrical measurements in systems cooled to -273.12C (30mK) and can confirm this had a very positive effect on noise levels.

You'd think that might put off some folk from buying some vintage tube-based mic preamps, wouldn't you? :beamup:


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Re: Electonic devices : How cold is dangerous?

Postby ef37a » Thu Nov 28, 2019 8:52 am

Martin Walker wrote:
Logarhythm wrote:In a previous life I ran experiments taking various electrical measurements in systems cooled to -273.12C (30mK) and can confirm this had a very positive effect on noise levels.

You'd think that might put off some folk from buying some vintage tube-based mic preamps, wouldn't you? :beamup:


Martin

The Pedant stikes again! Valves, triodes at least are pretty quiet themselves, it is the anode loads that cause the trouble. Everything else being equal a 100k typical triode load is 10dB noisier than the 10k or so you find in discrete transitor cirduitry.

Cheaper 'cashing in' valve pre amps tend to use the high impedance, high mu ECC83 when you really need high gm and lower circuit resistances. Techniques such as cascoding and bootstrapping can deliver low noise valve pre amps. Transformers help as well of course.

On cooling again? Looked it up. Get down to -196C, liquid N2 and you gain less than 6dB!

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Re: Electonic devices : How cold is dangerous?

Postby Hugh Robjohns » Thu Nov 28, 2019 11:47 am

ef37a wrote:Actually, if you do the math (Google calculator) you have to get a hell of a lot colder than that to make any real difference to component noise.

Quite so.

At a nominal 20C (and with a 20Hz-20kHz measurement bandwidth) the thermal noise contribution of a 150 Ohm source -- the nominal impedance of a typical microphone -- will be -130.9dBu.

So a perfectly noiseless mic preamp can never have an EIN value (rounded to) better than -131dB when connected to a real microphone. And since the electronics in the preamp will inevitably add a decibel or three of self-noise, the best mic preamps will typically have EIN's of around -127 to 129dBu.

If you ever see -131dBu or lower, the specs have been cheated in some way! Often by measuring with a dead short across the input, rather than a defined source impedance. NB. Some (particularly US) specs use a 200 Ohm source for the EIN measurement, in which case the theoretical thermal noise value is -129.6dBu (same temp and bandwidth conditions).

So what happens if you go somewhere cold? Well, the electrons don't run about as fast, so there's less thermal noise energy. As a result, the thermal noise contribution from the same 150 Ohm resistor at, say, -40C (with the same measurement bandwidth) would be -131.9dBu -- a whole decibel lower! Whoopydoo! :lolno:

And if you went to -100C it would reduce further to -133.2dBu.

If you could justify the expense and the waste of a rare resource, bathing the studio in liquid Helium (-269C) would get the EIN value down to -149.4dBu, or using more affordable liquid Nitrogen would get it to -136.6dBu. Your recordings might well sound cold and clinical though... :wtf: :wave:

But overall... temperature really doesn't play a very significant role in the self-noise figures when you're dealing with relatively low circuit impedances. It obviously had greater efect if the circuit impedances are orders of magnitude higher - -as they typically are in valve circuitry, for example!

In general, though, changing the source impedance has a far bigger effect, and if the EIN is -130.9dBu for a 150 Ohms source, changing that to a 50 Ohms source reduces the thermal noise figure to -135.7dBu... which is a far more dramatic change than any amount of playing with the thermostat could ever do! :lol:
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Re: Electonic devices : How cold is dangerous?

Postby Rich Hanson » Thu Nov 28, 2019 12:31 pm

Hugh Robjohns wrote:If you could justify the expense and the waste of a rare resource, bathing the studio in liquid Helium (-269C) would get the EIN value down to -149.4dBu, or using more affordable liquid Nitrogen would get it to -136.6dBu. Your recordings might well sound cold and clinical though... :wtf: :wave:

You'd need a good pullover or two, too :bouncy:
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Re: Electonic devices : How cold is dangerous?

Postby Wonks » Thu Nov 28, 2019 12:48 pm

"Don't touch anything in the studio, Anything you touch, you keep. Frozen skin and fingers on our equipment isn't a good look for the next studio clients".
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Re: Electonic devices : How cold is dangerous?

Postby ManFromGlass » Thu Nov 28, 2019 2:11 pm

New entrance door installed here recently. It has an aluminum threshold. The temperature was below zero when I put on my slippers sitting on the wet entrance rug and proceeded outside. The slippers instantly glued to the aluminum while I kept going. :problem:
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Re: Electonic devices : How cold is dangerous?

Postby Wonks » Thu Nov 28, 2019 2:59 pm

Maybe you should have got an aluminium threshold instead. :D
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Re: Electonic devices : How cold is dangerous?

Postby Sam Spoons » Thu Nov 28, 2019 3:14 pm

Obviously English ones are inherently better than American :D
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Re: Electonic devices : How cold is dangerous?

Postby Wonks » Thu Nov 28, 2019 3:24 pm

Sam Spoons wrote:Obviously English ones are inherently better than Canadian :D

FTFY
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Re: Electonic devices : How cold is dangerous?

Postby Sam Spoons » Thu Nov 28, 2019 3:25 pm

I was referring to language differences actually :tongue:
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Re: Electonic devices : How cold is dangerous?

Postby Wonks » Thu Nov 28, 2019 3:30 pm

It is one of the Canadian/English differences, as well as American/English differences.
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Re: Electronic devices : How cold is dangerous?

Postby Sam Spoons » Thu Nov 28, 2019 6:03 pm

We spelled it first :D
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Re: Electronic devices : How cold is dangerous?

Postby ManFromGlass » Thu Nov 28, 2019 6:19 pm

Avoiding the influences of the giant to the south, now that your monarchy has allowed us our own constitution, is a non-stop slog. Where is Mi5 to protect us?
If I hear the word "foyer" pronounced like foy-er one more time. . . . . . . :protest:
eh?
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Re: Electronic devices : How cold is dangerous?

Postby MOF » Thu Nov 28, 2019 6:26 pm

All this controversy from one throw away comment :D , though at the back of my mind I was also thinking about the Sony C-800g microphone which has a peltier heat pump to keep the valve at the optimum temperature https://pro.sony/ue_US/products/lavalie ... nes/c-800g
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Re: Electronic devices : How cold is dangerous?

Postby Wonks » Thu Nov 28, 2019 6:30 pm

Any thread that doesn't stray off-topic within the firsts page can't be a very good thread.
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Re: Electronic devices : How cold is dangerous?

Postby blinddrew » Thu Nov 28, 2019 6:52 pm

"Wonks' Law".
It's like Godwin's Law but without the Nazis.
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Re: Electronic devices : How cold is dangerous?

Postby ef37a » Thu Nov 28, 2019 7:22 pm

blinddrew wrote:"Wonks' Law".
It's like Godwin's Law but without the Nazis.
Eee said it! Ee's out! Stone 'im!

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