[sdiy] Quadra phasor clone questions

[jhaible]

> 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.

Yes. But it's not as bad as it seems. Other parts of the circuit
ar way more noisy. If you don't mind the signal inversion,
just use an inverting adder with virtual GND summing node
instead.

> 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.

Right. Just add a resistor to GND. It may even be there in the PCB
layout.

JH.