In article JQlWa.36368$Ho3.6629@sccrnsc03,
All Ears wrote:
You could also add a Zobel RC network, it will effectively short any high
freq. noise on the speaker cables.

Sorry, "Ears," that is NOT what a "Zobel" network is. Not in the
least.

A "Zobel," so named after one Otto J. Zobel, is network that
implements a complex conjugate of another network. That is, a
circuit might have a non-resistive impedance. A complex
conjugate is a circuit that, combined with the original circuit,
results in a resistive impedance. Be assured that a Zobel
circuit DOES NOT "effectively short any high freq. noise on the
speaker cable." That is NOT what a Zobel does, despite
ill-informed claims by some to the contrary.

A common use for Zobel-type circuits in audio is in speakers. A
driver present a non-resistive impedance. In its most basic
form, the impedance presented by a driver looks like a circuit
consisting of a resistor in series with and inductor inseries
with a parallel RLC resonant circuit (this RLC circuit is the
electrical equivalent of the speakers mechanical resonance).

WIthout a resistive load, it is impossible to achieve certain
response functions from passive crossover filter networks.
However, by applying the kind of circuit Mr. Zobel describes,
the non-resistive load presented by a driver can be made to look
resistive.

But the high-frequency decoupling and bypass circuits used on
the outputs of amplifier ARE NOT, most definitely are not
"Zobel" circuits.

For more details, you might want to take a look at US Patent
1,557,230, granted to Otto. J. Zobel on Octover 13, 1925,
assigned to the American Telephone and Telegraph company, titled
"Complementary Filter." It clearly describes the implementation
of conjugate filters, and clearly does NOT describe what you're
talking about.

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| Dick Pierce |
| Professional Audio Development |
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