[time-nuts] Low noise power supply recommendations

Will Matney xformer at citynet.net
Wed Jun 15 11:49:23 UTC 2011


Correct, and by adding the series resistor for higher impedance, the
voltage regulation at the zener value is raised from 10 volts to some value
higher. I actually remember a variable bias control to a tube using a
similar circuit, except the fixed resistor was a pot. He shows using this
on a shunt regulator also on the following page. How much unstability this
causes at the value given is unknown without actually building the circuit
and testing it, but one shouldn't use a series resistor with a zener this
way. I remember Rich Measures and myself speaking of this a few years back.

One thing that's not mentioned in the article is that certain resistors can
cause noise by themselves. Good articles on this are in some power supply
and voltage reference App Notes from both Linear Tech., and National.



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On 6/15/2011 at 6:59 PM Bruce Griffiths wrote:

>Will Matney wrote:
>> As far as the power supply is concerned, I think I am going to go with
>> Ni-Cad batteries, and regulate the voltages. I think what they had was
>> nothing more than four step voltages from the battery supply, going from
>> 6 (7), 12, and 24 Vdc, or X2 of the other. From what I saw in the
>> earlier, an easy zener with emotter follower regulator should do the
>> by the comparison with batteries. They used some resistance in series
>> the zener to reduce noise, but it did decrease the stability somewhat. I
>> have seen this used in some old bias regulation circuits for tubes years
>> ago.
>A somewhat misguided idea, they really should have used an RC low pass 
>filter between the zener and the output transistor base.
>The filtering effect is the same but without significantly decreased 
>stability over that of an unfiltered zener..
>> As far as the noise, I also wondered about this, as ESI used a current
>> limited DC power source to do the same thing, and it was ran off the AC
>> line.
>> Thanks,
>> Will
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