user manual
TFS-780
TFS-780 user manual
Page 45
equipment. For example, if two adjacent channels are fed from the same line but are driving
different speaker impedances, the meter readings will differ to reflect the extra loading on
one channel, even if the input attenuator settings are identical.
Output Connections
Two pairs of 4mm terminals are provided on each channel. Each terminal accepts a 4mm
plug at the rear; in the AMP-780 rack MDP (dual banana or Pomona plug) connectors are
used for convenience. If an amplifier is replaced in the rack, ensure that these are
reconnected in the correct polarity.
Damping Factor
The TMC amplifier outputs provide a high damping factor, typically 400 times at low audio
frequencies. This damping helps the amplifier to control the loudspeaker drive units,
provided that the resistance of the intervening cables and connectors is very low. The sonic
benefits of high damping factor are most pronounced at bass and low-midrange frequencies
(i.e. 10 to 600Hz) providing a subjectively
tighter
sound as a result of the improved
reproduction of transients.
Amplifier damping factor is degraded by high resistance in the loudspeaker circuits; i.e. thin
conductors, long output cable runs and tarnished, corroded or loose connections.
Damping factor is maximised by installing cables containing conductors of large cross-
sectional area, and by specifying connectors with heavy-duty contacts and waterproof
covers. The cable sets supplied with TFS systems are manufactured to a high specification
with these considerations in mind.
Which speaker impedance?
In most active speaker systems, the nominal speaker impedance is close to the minimum
value (with continuous signals) and rarely more than half the minimum under transient
dynamic conditions. The TMC-750 and TMC-1250's normal 4 Ohm rating refers to nominal
impedance ratings, and already allows for short term worst case dips to around 2 Ohms.
Long Speaker Lines
Whenever loudspeakers are connected to power amplifiers by long cables (above 20'/6m),
there is invariably an increased risk of high frequency instability. It is aggravated by the
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