Polarity
It is important to observe correct polarity. One side of the speaker wire will have some sort of mark: either
printing, a raised ridge on the insulation or a different color of conductor. This permits you to know which
wire you had connected to the + and which to the - speaker terminals so you can do exactly the same at the
power amplifier terminals. Polarity is marked separately for both stereo and bridged connections.
Mono Speaker Connection
When you bridge the left and right channels, you connect your speakers to the combined bridged channels
differently. You bridge by using only the left red + terminal and the right red + terminal. The red + terminals
have alternate markings for bridged mono connection. In the bridged mode the right channel's red terminal
b, and the left channel's red terminal becomes -. Do not use either of the black - terminals. You may
also use a single standard 3/4" (19mm) "dual banana" plug for the mono bridge connection to the two inner
red + terminals.
Mono Bridge Switch
Simply select Mono (up) or Stereo (down) as marked on the rear panel. The power should be switched off
before moving this switch. If you accidentally leave the Mono Bridge switch in the Mono (up) position, you
will find stereo output will be very weak and distorted.
Safe Operation Note
You may use 4
Ω
- 8
Ω
rated speakers for stereo operation. Lower impedance loads are not recommended, as
they may cause overheating and trigger one of the protection circuits.
You may use 4
Ω
rated speakers for mono bridged operation only if you don't intend to run your HCA-600
at high levels for extended periods. We recommend an 8
Ω
minimum mono load.
This 8
Ω
restriction results from the mathematics of the bridging circuitry. In the bridge mode each channel
of the amplifier functions for only the + or - half of the musical waveform. Thus, each channel “sees” only
half of the speaker's impedance. Use of an 8
Ω
speaker means that the load for each channel is 4
Ω
. For a 4
Ω
speaker, the impedance would be only 2
Ω
per channel.
Dual "Half-Stereo" Operation
For a sonically superior high power alternative to mono bridging, you can enjoy the best possible sound by
using a pair of HCA-600s, and operating each unit on one channel rather than bridged mono. You will gain
substantial reserve power, since only one channel is now drawing upon the power supply.
While you will not obtain the full 150 watts at 8
Ω
available in mono bridging, you can obtain approximately
80 watts at 8
Ω
, or 100 watts at 4
Ω
. The audio signal is not required to travel through the additional phase
inverter circuits required for mono bridging, and the resulting clarity will more than compensate for the
slightly lower available power.
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