G7 mic 1g resistor wattage?

[CMB]

Hi, my first post! I´m about to build a Gyraf G7 microphone and I wonder if different power ratings of the 1Gohm resistor will affect the performance of the microphone? That is, will it make a difference if I use a 1 Watt resistor instead of an 0.25 W resistor? I have always thought that the power rating was just how much power it can handle before it starts to break down, and that it is never wrong to choose higher values of the power rating, other than of course size and cost. But then I read something that Gyraf wrote, "1.000.000.000 Ohms at 0.75W that is one hell of a voltage it will soak..!". What does that mean? I also read something about a "ballast resistor" in an laser application were they also talked about the importance of choosing, not only the right value of the resistor, but also that the value of the power rating should not, of course, be to low, but also not to high!

So, all you educated intelligent, probably not so beautiful , but still intelligent people at this site: Does it matter, considering the sound and performance of the mic, if I build it using a 1G/1W resistor instead of a 1G/0.25W resistor?

Thank you!

Martin, Sweden

 

[Guest]

[quote author="CMB"]That is, will it make a difference if I use a 1 Watt resistor instead of an 0.25 W resistor? ..... if I build it using a 1G/1W resistor instead of a 1G/0.25W resistor?
[/quote]

Large resistor have large parasitic capacity and
maybe modify sensitivity of mic by some 0.0001 dBs.
But practically nothing changes.

And pure theoretically. If you use 1G resistor as bias (for tube or FET), there
is DC current flowing trough it. And the bigger resistor - the bigger plurality of current flowing trough it - the bigger 1/f noise.

But don t worry. This phenomenon is far under your topology´s thermal
generated noise


xvlk

 

[gyraf]

Thanks for the good answer, xvlk! :thumb:

I wonder what working voltage you'd need to dissipate 1W in a 1G resistor - my calculator freaks our when I try figuring out.. :razz:

Jakob E.

 

[Walrus]

[quote author="gyraf"]Thanks for the good answer, xvlk! :thumb:

I wonder what working voltage you'd need to dissipate 1W in a 1G resistor - my calculator freaks our when I try figuring out.. :razz:

Jakob E.[/quote]
31.623kV
According to my calculator! :shock:

 

[gyraf]

that's freakin' sumtin'!!! :shock:

 

[jensenmann]

In my teens we checked such things. We took the HV amp of a TV, tuned it with some selfmade HV caps in a voltage tripler and generated a lot of blue radiation in some tubes :wink: I guess you call that Röntgenstrahlung.
Not the best experiment if you want to live long and get healthy kids but that was fun, indeed :grin:

 

[Michael Krusch]

[quote author="Walrus"]31.623kV[/quote]

How does it sound if the capsule is polarized with that voltage?

I guess they do a 1W series with different restistance but the same housing, so will also have a 0 Ohm resistor with 1W.

 

[bcarso]

Actually larger-sized resistors will have lower 1/f noise, all other things being equal, since the current density is lower.

 

[seavote]

ok i understand a high voltage resistor can cause unwanted capatence(did i spell that right). so is there any negative effect,besides size, to using a capacitor with a much larger voltage rating. the only 1u polyester cap for my g7 i could find was 630v. it will fit but is it a bad idea to use it? i thought it was ok

 

[gyraf]

the only 1u polyester cap for my g7 i could find was 630v. it will fit but is it a bad idea to use it?

If you can cram it in there, I don't see any problem. Parasitic capacitance would probably only be a problem at the small polystyrene caps at the input of the circuit.

Jakob E.