09-11-2023, 02:46 PM
(This post was last modified: 09-11-2023, 02:51 PM by Mike Watterson.)
Measuring the resistance with cap/cable unscrewed, so just a resistor across the output. Zero Ohms between spud on cap to end of cable.
After writing initial description I decided the only thing that made sense was if the battery + goes to internal spring (wired via on/off to red wire of capsule) and battery - goes to spud in centre of screw on rear cap. So as per my second post I tried it and it works much better.
Odd that spud isn't on internal end and spring on screw on cap. There is no + or - marking! I should put a warning label?
The capsules always have the FET inside on any electret capsule I've ever seen. Normally red is to + battery via resistor and out via capacitor, or nothing at all (PC /soundcard/laptop/phone/tablet supply via resistor). This arrangement puts battery in series with output and load resistor across equipment input.
But after considering it, obviously I've been fitting the battery the wrong way round for 25 years. Gives about 12 dB more signal now with + to internal spring and - to the spud on screw on cap with cable (and likely a 680 Ω resistor inside it).
Now what happens if I accidentally turn on +12V, +24 or +48V phantom power? I guess the recorder (or desk I haven't got) sees 690 Ω load (approximately 70mA @ 48V, 17 mA @ 12V) and electret capsule sees phantom volts added to battery volts!
However I have nothing that uses phantom power. Neither the Zoom H4n nor Zoom H6 manuals have a spec for current limit on phantom power. Wikipedia suggests 2mA or 10 mA or 2x 680 Ohms for 12V and 2x 6.8K Ohms for 48V as source resistances, but as the mic is unbalanced, it's 680, 1.2K and 6.8K. The resistances would limit voltage to about 6V at 12V and about 5V at 48. I could simply connect cable without mic and measure volts centre spud to screw cap outer. Perhaps I should, just to know. Odd that the manuals and web FAQ only list phantom settings (48, 24, 12 and off). See https://sound-au.com/articles/p-48.htm (Link to Electrets in article is broken)
This seems comprehensive on Electrets
http://sound-au.com/articles/mic-electret.htm
After writing initial description I decided the only thing that made sense was if the battery + goes to internal spring (wired via on/off to red wire of capsule) and battery - goes to spud in centre of screw on rear cap. So as per my second post I tried it and it works much better.
Odd that spud isn't on internal end and spring on screw on cap. There is no + or - marking! I should put a warning label?
The capsules always have the FET inside on any electret capsule I've ever seen. Normally red is to + battery via resistor and out via capacitor, or nothing at all (PC /soundcard/laptop/phone/tablet supply via resistor). This arrangement puts battery in series with output and load resistor across equipment input.
But after considering it, obviously I've been fitting the battery the wrong way round for 25 years. Gives about 12 dB more signal now with + to internal spring and - to the spud on screw on cap with cable (and likely a 680 Ω resistor inside it).
Now what happens if I accidentally turn on +12V, +24 or +48V phantom power? I guess the recorder (or desk I haven't got) sees 690 Ω load (approximately 70mA @ 48V, 17 mA @ 12V) and electret capsule sees phantom volts added to battery volts!
However I have nothing that uses phantom power. Neither the Zoom H4n nor Zoom H6 manuals have a spec for current limit on phantom power. Wikipedia suggests 2mA or 10 mA or 2x 680 Ohms for 12V and 2x 6.8K Ohms for 48V as source resistances, but as the mic is unbalanced, it's 680, 1.2K and 6.8K. The resistances would limit voltage to about 6V at 12V and about 5V at 48. I could simply connect cable without mic and measure volts centre spud to screw cap outer. Perhaps I should, just to know. Odd that the manuals and web FAQ only list phantom settings (48, 24, 12 and off). See https://sound-au.com/articles/p-48.htm (Link to Electrets in article is broken)
This seems comprehensive on Electrets
http://sound-au.com/articles/mic-electret.htm
