R/E/P > Klaus Heyne's Mic Lab

regulated power for tube mics-- impact on sound?

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soapfoot:
Is regulated power as a positive or not in tube microphone power supplies?

How much does the load resistance presented by the microphone vary during normal operation?  Is it small enough to be negligible?

Is there any benefit (or downside) to a regulated supply?

ssltech:
Can you be more specific?

Regulated AC supply into the tube mic PSU, or regulated DC PSU?

Keith

soapfoot:
Sorry, regulated DC PSU.

ssltech:
Ah, gotcha.

The dominant consumption in terms of current is usually the heater. Since this doesn't change much with signal, I'd imagine that it's largely insignificant. -That doesn't preclude regular checks though.

For my own microphone, I'm building a slightly 'improved' power supply in that it will have -among other things- a relay in the HT line BEFORE the C/R/C/R/C ladder, energised by a current sensing circuit in the HEATER feed.

That way, if the mic is unplugged, the PSU voltage won't rocket upwards. -Since that's incorporated, it may as well be regulated and adjustable, since that adds very little to the difficulty, with modern designs.

I'm also contemplating a constant CURRENT drive for the heater, which is much kinder on startup.

Of course in this design, the heater is being fed along a separate conductor. -If you think about how the heater is fed in a U47 circuit, significant variations in AC voltage can alter the way that everything is balanced, so that particular design is likely to be 'differently-sensitive' compared to a design with the heater fed separately.

A regulated HEATER voltage with unregulated HT is a third combination to consider.

Keith

soapfoot:
I have a lot to learn about power supply design.  I know the basic building blocks, but I need to learn more about regulation and how to work toward a target voltage.

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