Additional Information; Power Amplifiers; Anti-Clipping Circuit; Combos - TRACE ELLIOT AH1000-12 Guide D'utilisation

ADDITIONAL INFORMATION

POWER AMPLIFIERS

The power amplifier sections within these Trace Elliot products are high efficiency advanced
MOSFET designs. They are designed to withstand rigorous use and include protection for over-
temperature, over-current and short-circuits.
Although designed to run comparatively cool, the high power versions do contain fans. These blow
cool air from the outside across critical components and back out through the vents. Therefore, the
vents on the front and rear or sides of these units should not be obscured. Please bear this in mind if
you intend to rack-mount or flight-case your amplifier.

ANTI-CLIPPING CIRCUIT

To prevent prolonged power amplifier clipping which, apart from sounding highly offensive, is the
easiest way to destroy speakers, the power amp sections are immediately preceded with a two-stage
circuit to control the signal level from the preamp. The rear panel of each amplifier will show two
RMS power ratings, one for transients and the other for steady-state signals. The circuit is inactive
until the power level reaches the lower rating. At this point the first stage of signal amplitude
control is applied. This works like a fairly slow compressor that is relatively unobtrusive and will
gently control the signal level to keep it from clipping the power stage. To catch transients, a
second stage is applied at the higher power level. Between the two stages the signal level is
controlled to keep clipping to a minimum without the circuit being too audible in affecting
dynamics. The 12 Band products incorporate a valve as part of this circuit.

COMBOS

Various combinations of preamp, power amp and speaker configurations are available within the
range. The particular combination of your unit will be marked on the front panel.
All the amplifier sections are designed to deliver their full rated power into 4 ohms. Therefore a
combo fitted with a 4 ohm internal speaker (e.g. 715) will deliver the full power into its own
enclosure. Although capable of driving extension cabinets, the connections on the rear mean that
the user has to disconnect the internal speaker before connecting to an extension cabinet.
Combos fitted with an 8 ohm internal speaker (e.g. 715X, 1215, 1210) will deliver approximately
50% – 60% of the rated power into their own enclosure. Connecting to an 8 ohm extension cabinet
will bring the overall impedance down to 4 ohms and will therefore deliver 100% of the rated
power. The connections on the rear of these combos allow an extension cabinet to be connected
while keeping the internal speaker connected. This arrangement is ideal for using the combo on its
own at rehearsals, recording sessions and smaller gigs, then connecting an extension cabinet, such
as a 1518 or 1028H, to give more power when required at larger gigs.
Combos fitted with switchable high frequency horn attenuation (e.g. 715X, 1215, 1210) benefit
from the user being able to set the horn on full, half or disconnected. The setting will depend on
playing and music styles, preamp settings and personal choice.
On 12 Band units, when using the VALVE drive at high DRIVE settings it is advisable to
experiment with the setting of the horn attenuation. Generally for more traditional warm or
overdriven bass tones the horn should be set low or off.
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