Parasound HCA 806A Mono Bridging - Channels 3+4 and 5+6, Minimum Impedance Precautions

Mono Bridging — Channels 3+4 and 5+6

When you bridge channels 3+4 and/or 5+6, your speakers are connected to the bridged channels differently. You bridge by using the red + terminals of the adjacent channel pairs only. Note that bridged connections are made horizontally rather than vertically and that the upper red + terminals have separate markings for bridging. In the bridged mode, channel 4 (and/or 6) output is positive and channel 3 (and/or 5) output is negative.

Unbridged speaker connections can be made with standard 3/4" (19 mm) dual banana plugs. However internal space required by the high current protection relays prevent the bridged terminal pair spacing to be close enough to accept 3/4" (19 mm) dual banana plugs. Single banana plugs, spade lugs, or bare wire termination are required.

Select MONO BRIDGING (up) or SEPARATE (down) as marked on the rear panel. Switch the power off before moving either of these switches. If you accidentally leave either switch in the mono bridge position, the stereo output will be very weak and distorted.

For bridged operation of channels 3+4, use only the input jack and level control for channel 4. For bridged operation of channels 5+6, use only the input jack and level control for channel 6.

Minimum Impedance Precautions

You may connect loudspeakers with a 4 Ω or 8 Ω nominal impedance for unbridged operation. Your HCA-806A is capable of driving speakers with occasional impedance dips well below 2 Ω. However, Lower nominal impedance loads are not recommended and may cause overheating.

The HCA-806A is designed for a minimum 8 Ω nominal impedance for each speaker connected to bridged channels 3+4 or 5+6. Use of lower impedance at high listening levels may cause overheating or trigger one of the amplifier's protection circuits.

These restrictions result 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 resulting load is only 2 Ω.

Use Good Speaker Wire

For best results, you should never use speaker wire thinner than 16 AWG and keep the length of speaker wire as short as possible to maintain a high damping factor and avoid deteriorating bass response.

AC Power Connections and Audiophile-Grade AC Cord

Before you attach the AC cord, make sure the HCA-806A power switch is in its off position. Your HCA-806A includes a detachable audiophile-grade AC cord. We recommend that you use only this cord and make a direct connection to the AC wall outlet.

Do not connect the amplifier to the accessory AC outlet on your preamplifier. The current draw exceeds the ratings of most preamplifier’s power switches and power cords and could cause premature failure of the switch.

DC Trigger Connection

This connector provides a way to trigger your amplifier on with an external DC voltage source ranging from + 9 Vdc to +12 Vdc. With the main power switch on the off (down) position, the amplifier can be turned on with voltage from any external DC source such as the +12 Vdc trigger from the Parasound P/SP-1500. Since it is optically coupled, the DC trigger only requires 15 mA of current to activate the circuitry and turn on the amplifier.

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