This is probably a stupid question. I know what the idling voltage is on my phono stage output coupling cap to the volume control in an MFA luminescence. What I want to find out is how much AC voltage is on there when a record is playing so I can determine the total voltage, particularly during loud passages. My plan is to connect my meter via alligator clips to each end of the cap and play a record with only the turntable and preamp on, manipulate the volume control and measure. No power amp. Cartridge is a Benz Ruby. Is there any danger to the cartridge doing this?
Much simpler to measure output voltage, then calculate voltage across cap - which will, of course, vary with frequency.
Going back to your actual question, you do realise that the DC voltage and the AC signal voltage don't add up - the cap just sees the DC voltage unless you have lots of infrasonics coming through?
Going back to your actual question, you do realise that the DC voltage and the AC signal voltage don't add up - the cap just sees the DC voltage unless you have lots of infrasonics coming through?
I was going to add that the only AC voltage across the coupling capacitor is of a lower frequency than designed. So if an amplifier designer requires the 3dB point to be say 30HZ then the R*C*2pii point is calculated to stop or block lower than required frequencies from passing through by allowing the LF AC to dissipate in the coupling capacitor. It works the other way as well, a cap accross the output to ground will block HF as the capacitor acts as decoupling, shorting the HF to ground.
I hope that makes sense.
I hope that makes sense.
The answers here make me think I should have asked a different question. The DC voltage across the cap in question is 190 volts. I want to change the cap to one that is rated at 250 volts. I thought that to be safe, I had to have an idea of what the AC voltage at peaks would be. That is, would something playing very loud raise the total voltage to over 250 volts, thereby threatening the cap?
Running capacitors at the rim of their working voltage is not wise for several reasons.
Audiosignal at line level will be negligible, don't worry about that. When you power up the max supply voltage can be over the coupling cap. Choose the working voltage at least at the PS voltage, although the actual voltage might be lower.
Audiosignal at line level will be negligible, don't worry about that. When you power up the max supply voltage can be over the coupling cap. Choose the working voltage at least at the PS voltage, although the actual voltage might be lower.
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