"Arny Krueger" wrote in message
...
"Iain M Churches" wrote in message

"Arny Krueger" wrote in message
...
"Iain M Churches" wrote in message


I would be interested to know the phase response
of a high end SS amp (OK, I know, they are ALL high end:-)
at 20Hz and say 20kHz, or more points if the info is
available.

Look at the amp's frequency response curve and use what you know
about the Hibert transform or simply draw Bode diagrams to estimate
the amp's phase response.


The phase measuring equipment to which I have access is built
by Feedback Electronics in the UK.
It can be used in two ways, depending on whether
or not you have the additional digital meter for direct readout.

The test signal is supplied by an oscillator which has two outputs,
both with attenuators for level matching.
Without the meter unit, one proceeds as follows;
Connect output 1 from the oscillator to one input of the scope
which is in the XY mode. Adjust output level 1 of the oscillator
to give a satisfactory diagonal deflection on the scope.

Connect output 2 to the input of the device under test.
Connect the output of the DUT (via a dummy load if required)
to input 2 of the scope, and adjust the oscillator output level
to give a similar deflection in the other diagonal plane.

Then connect both signals to the scope. The resulting display
will be an ellipse. Output 2 of the oscillator has a variable
phase control, which can be adjusted until the ellipse
collapses into a straight diagonal line.
Then, read off the phase angle indicated on the
skirt of the phase control knob, and you have the answer.

If you have the digital readout unit, measurement is even simpler,
and the oscilloscope is not required.

Connect output 1 from the oscillator to input 1 of the meter unit.
Connect output 2 to the device under test.
Connect the output of the DUT (via a dummy load if required)
to input 2 of the meter unit. The latter can measure the phase
angle between a pair of signals with a 30V difference, so a 60W
amp can be measured with ease.

A led shows which signal is lagging or leading, and the digital
readout gives the phase angle. Easy and fun:-)

Iain