[sdiy] transformer buffering, terminology lost - simple question and live in

[Scott Gravenhorst]

>hallo,
>
>i'll be playing at bonobo in sendagaya (near yoyogi station) in tokyo for
>a few nights in the coming weeks.  if anyone wants to drop in and see this
>radical serge rebuild they're welcome to.  it'll be 100% live analog
>improvisation, probably along the lines of black devil disco club and
>delia derbyshire.
>
>had a quick question.  i've mounted a bunch of 1 to 1 600ohm or 1000ohm
>audio transformers in the hyper?-serge and want to get inverted outputs as
>secondaries to the main outputs (jacks and front panel are already setup
>for this).  Anyway, being slightly handicapped as i am, i didn't realize
>that by multing the signal over to the transformer, i would lose the
>output on the original non-inverted signal, because of course, the
>transformer coil is run to ground.  do i need to use op-amps to buffer the
>signal or can a simple shunting resister drop the current flow enough that
>impedence is close enough for both outputs to work.. 

I'm wondering what you mean by "shunting" resistor.  Did you put the resistor in
parallel with the transformer's primary?  If so, this won't limit current into the
transformer primary except if the loading on the OpAmp's output is above spec.  A series
resistor will limit the current, but doing so will also limit the output of the
transformer's secondary.   Two transformers of the same type with primary windings in
series and with the proper series resistance might be able to give you both an inverted
and noninverted version of the signal that will have closer to equivalent output levels.
 I'm also not sure if the driving circuit you attached to the primaries likes an
inductive load.

I'm also curious why you've used a transformer, maybe there's something else going on
here you've not stated, but if I need both an inverted and noninverted version of a
signal, I'd use an OpAmp inverting voltage follower to produce the inverted version. 
This way, the loading of the original signal will be negligable and will be available
elsewhere in the system.  I think that the spectrum and probably delay of the signal
available through the transformer will be affected more than by using an OpAmp.

Did you do this because a transformer is a passive component with no need of a power supply?


>I tried resistor's
>from 1ohm to 100kohm and didn't have much luck, so i'm wondering do i need
>to buffer with a cap, anyway it's getting complexier than i expected.
>
>any suggestions and any interested locals please come out, the place i'm
>playing looks like the star wars bar.  if you can read symbols you're
>welcome to play the machine later in the night.
>
>-a



-- ScottG

-------------------------------------------------------------

-- Scott Gravenhorst
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