noise: re Dynamo help

jim jim at
Mon Jul 22 04:00:48 UTC 2013

    assume some AC voltage coupled to a 
transformer. If the transformer is 1-1, 
then the secondary will present the same 
voltage swings as the primary windings. 
    Note that a transformer has a current 
limit, essentially a function of the 
insulation on its windings as well as the 
saturability of its core and winding 
    Note also that a transformer has 
frequency limits, which may be a small or 
large range as well as very low or full 
audio or very high (e.g. radio) frequency 

    For starters you can probably get 
away with using a power transformer, 
and you can use its labeled primary as 
a secondary (and its labeled secondary 
as the primary). One typical power tranny 
is a step-down transformer, taking 120 VAC 
in and putting out 12 VAC, which makes it 
a 10-1 step-down transformer, or, wired 
in reverse, a 1-10 step-up transformer. 
    A trick: get two identical transformers 
and wire their secondaries together, then 
input an AC voltage on one tranny's primary 
and you'll get that same AC voltage on the 
other tranny's primary windings (remember 
that the secondaries are wired together). 

On Sun, 2013-07-21 at 17:46 -0700, Johny Radio wrote:
> jim jim at 
> Sun Jul 21 21:43:25 UTC 2013 wrote
> >>A different approach, assuming AC from the  "dynamo", is to feed it
> to a transformer, even a 1-1 tranny, and feed the audio amp with the
> tranny secondary (with recitfier 
> and conditioning circuitry between the secondary and the amp's power
> input stage). 
> -- interesting, will try! How would a 1-1 tranny affect my signal?
> Johny Radio
> Stick It In Your Ear!

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