Microphone Directionality

  • Thread starter Thread starter Farshock
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I've had a private response which suggests the difference might be caused by the "miller effect" do to capacitance and how tube circuits and transformers deal with gain in their relative stages vs. solid state mics and how you would have to set the gain of the amp before implementing the capsule. That might explain everything. Needless to say I am on the path of agreeing with you. My education on the subject continues, which is an after effect I am grateful to go through and how it is responsible for revealing certain aspects with which I had no prior understanding. This is turning out to be a great thread for me.
 
John Willett said:
Ahh - you got here before me.

I was just about to mention that is was the possibility of the valve itself being microphonic.

Especially as it was noticed mainly with quiet, distant sounds and the gain would have been high.
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Normally that would be a good explanation, but I do test every component for microphonics as I do a build. I even check capacitors for microphonics (and have found quite a few). I think the Miller effect is the most likely culprit.

BTW, secondary tests showed it may have been the directionality of my main room I test mics in. After I really started tweaking gain on the mics, the less noticeable the differences were.
 
dgatwood said:
Regarding tube mics, part of the difference there could be microphonics. Tubes do, to some extent, act as microphones in and of themselves. To the extent that any noise might be coupled from the floor through the mic stand, I could see this affecting the sound in ways that would not be obvious from a simple plot—particularly if we're talking about low frequency noise.
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Nice theory... to check the reality, take one of your favorite tube mics, instead of capsule connect some 50pF capacitor to emulate the source and then put in front of screaming singer and try to record through your favorite setup.

Report back what did you hear.

Best, M
 
Marik said:
Nice theory... to check the reality, take one of your favorite tube mics, instead of capsule connect some 50pF capacitor to emulate the source and then put in front of screaming singer and try to record through your favorite setup.

Report back what did you hear.
Click to expand...

Can't do that. My favorite tube mics don't have 35 cent Chinese tubes. :D
 
PhilGood said:
I've had a private response which suggests the difference might be caused by the "miller effect" do to capacitance and how tube circuits and transformers deal with gain in their relative stages vs. solid state mics and how you would have to set the gain of the amp before implementing the capsule. That might explain everything. Needless to say I am on the path of agreeing with you. My education on the subject continues, which is an after effect I am grateful to go through and how it is responsible for revealing certain aspects with which I had no prior understanding. This is turning out to be a great thread for me.
Click to expand...

Miller effect wouldn't change directionality. I would guess it is relatively rare in FET mics as a big chunk of the Chinese are using some variation of the "Schoeps" circuit, which has no gain, and the Europeans seem like they tend to use cascodes, although I have hardly made a complete study of such mics. I imagine tubes could suffer depending on the circuit, a single triode plate follower could be problematic.
 
Marik said:
Nice theory... to check the reality, take one of your favorite tube mics, instead of capsule connect some 50pF capacitor to emulate the source and then put in front of screaming singer and try to record through your favorite setup.

Report back what did you hear.
Click to expand...

Hey, don't be giving away the secret to my sound!;):D:drunk:
 
mshilarious said:
Miller effect wouldn't change directionality. I would guess it is relatively rare in FET mics as a big chunk of the Chinese are using some variation of the "Schoeps" circuit, which has no gain, and the Europeans seem like they tend to use cascodes, although I have hardly made a complete study of such mics. I imagine tubes could suffer depending on the circuit, a single triode plate follower could be problematic.
Click to expand...

Would the gain of the tube and the output level of the transformer contribute? I noticed that even though I set the peaks to match, the meters did not respond identical on the dynamics all the time. Just the peak levels.
 
PhilGood said:
Would the gain of the tube and the output level of the transformer contribute? I noticed that even though I set the peaks to match, the meters did not respond identical on the dynamics all the time. Just the peak levels.
Click to expand...

It's a function of grid capacitance * gain. If you change the load on a transformer that is the plate load, that will change gain.
 
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