VAC PA35/35 - Manual (Page 9)

TIPS & ADVICE
A Word About Impedance Matching
We strongly suggest that you experiment with the three available impedance connections for the best sonic
match with your system. Since no loudspeaker represents an unchanging impedance at all frequencies, it is
impossible to assert with certainty which output tap is appropriate to use. In many systems an amazing
difference in sound will exist between the various impedance taps.
Most loudspeakers vary away from their "nominal" impedance, which is why experimentation is essential. We
often find that matching a speaker's minimum impedance is more important than matching its nominal (average)
impedance.
If you bi-wire your system (run separate speaker leads from the amplifier to the high and low frequency
transducers) you may discover that two different impedance taps work best. For example, with early Martin
Logan Sequel II we find that the bass speaker is best matched with the 4 ohm tap, while the electrostatic panel
is best controlled by the 2 ohm tap. To achieve this connection, the black leads of both speaker cables connect
to "G", the red lead for the panel connects to "2", and the red lead for the woofer connects to "4". With later
Sequels we use the 4 ohm connection for both drivers.
Contrary to popular misconception, no power is lost due to unused output taps.
TIPS & ADVICE
A Word About Triode Amplification
Triode amplification is the oldest form known. From the engineering perspective, the triode mode has the
following characteristics:
1) Somewhat more distortion at low power levels
2) Somewhat less distortion at moderate power levels
3) Reduced maximum power output
4) Output impedance matching is less critical
5) Increased natural damping factor.