[sdiy] Quadra phasor clone questions

[harrybissell]

RE: the 10uF....

you don't need the DC path after the cap... but it is common practice
if that point can be connected to the external world or conditionals
like
a switch contact.

The far side of the cap will float to whatever level it 'likes'...which
may not
be ground. Then if you change the load.. it will thump.

I didn't look at the schematic lately... one other variation is if the
capacitor
feeds a non-inverting opamp input... it MUST have a resistor for the
bias current
path (but not for the cap)

H^) harry

Tim Ressel wrote:

> Hey,
>
> I've been taking a good look at Juergen Haible's
> Quadra Phasor clone. I'm a bit confused over the input
> circuit. First there is an attenuator of about 6.5 to
> 1, followed by an amp with a gain of 2.6. It seems to
> me this serves to increase the noise in the system.
> After the 1st amp there is AC coupling with a 10uF
> cap, but there is no DC path to ground after it. I
> think this will cause clipping for inputs with narrow
> pulses.
>
> Any insights?
>
> Other than these little puzzles, I am going ahead and
> building one of these.
>
> Thanks!
> --tim
>
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