noise: re Dynamo Regulator Help

Johny Radio johnyradio at
Mon Jul 22 00:44:04 UTC 2013

Henner Zeller h.zeller at
Sun Jul 21 22:07:55 UTC 2013 wrote

 >>If it is a DC motor, it will output DC with a bit of noise.
--it clearly outputs an oscillation. Isn't an oscillation always AC, 
even if it's offset above zero, and never goes negative?

 >>60000 RPM, which is way higher than what typical small motors usually
--it takes 30+ volts on the power supply of the OTHER DC motor (which is 
used to spin the shaft on the "oscillator" motor)

 >>Before connecting to the amplifier, use the multimeter to measure 
that the AC voltage is in the order of 1V, which is a typical input.
--cool, will try

 >>It is the voltage or the DC part of the voltage that is killing your amp.
--i did try a 100uf series cap on one of the terminals. Did not protect 
the amp.

 >>If you voltage is _way_ to high (which I suspect is happening here), 
then you can blow the input stage, because you send too much current through
--um, current? or voltage?

 >> the resistor you have 'on the outside' forms a voltage divider with 
the input impedance. If they are in about the same order of magnitude, 
you get half the input voltage.
--then shouldn't the series resistors i used give me significant 
overdrive protection? They seemed to have no affect.

 >>It does sound you operated the motor way out of its specs.
--in what way?

 >>a DC motor does _not_ generate a sine wave, at best it returns a wave 
that you would get as the result of rectifying a sine wave; that is what 
the commutator is for. If it is an AC motor, then you get a sine wave.
--on the scope, it sure looks sine-like. But also weird.


Johny Radio

Stick It In Your Ear!

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