ETI Sound Systems, INC US-1200 Stereo Amplifier User Manual


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B-52 US Series Professional Power Amplifiers - Instruction Manual
THE BEAUTY OF POWER
US SERIES AMPLIFIERS
in limiter circuitry for improved performance when
overloading.Thelimiteractivatesat“clipping”when
the output voltage reaches the power supply voltage
rails. Without limiters, the output voltage will grossly
distort if the signal elevates beyond this point. The
signalwaveformisattened(“clipped”),producing
excessivehighfrequencydistortionnotpresentinthe
originalsignal.Thismakesmusicsound“dirty”and
increases stress on the high frequency transducers,
significantly shortening their life span (most loud-
speaker manufacturers will not honor warranties if
highfrequencydriversare“burnt”duetoaclipped
signal overload). Clip limiters effectively solve this
problem by compressing the signal at clipping. US-
Series amplifiers use intelligent clipping circuitry to
protect both the loudspeakers and amplifier.
NOTE: US-1200 and US-1800 amplifiers have
a built-in limiter circuitry which is constantly
activated. The US-3000 and US-4000 amplifiers
haveanexternalswitchlocatedontherear
panel, which activates and deactivates the clip
limiters. B-52 recommends the clip limiter switch
onboththeUS-3000andUS-4000remainON.
YoumaychoosetoturnOFFthelimiterswhen
using the US-3000 and US-4000 to power
subwoofers.
SETTING UP YOUR US-SERIES AMPLIFIER
CLIP LIMITER: Clipping is the result of an amplifier running into a power supply limitation.
Themaximumoutputvoltagethatanyampliercanproduceislimitedbyitspowersupply.
Attemptingtooutputavoltagelevelthatexceedsthepowersupplyvoltagerailsresultsina
atteningeffectofthesignalcausingittoclip.Aclippedwaveformexhibitsseveredistor-
tions, making it sound harsh. The clip limiter detects this condition and reduces the gain to
minimize the amount of overdrive. To preserve as much of the program dynamics as possi-
ble,thelimiterreducestheaverageprogramleveluntilthepeaksbarelyclip.Eachchannel
hasitsowncliplimiterandyoucanswitchitONorOFF(onlyonUS-3000andUS-4000).
The clip limiter allows brief clipping which is not detectable to the ear. It activates when a
clip condition repeats, to avoid prolonged distortion. When driving full-range speakers, clip
limiting reduces the high frequency distortion caused by low frequency overload. It also
protectshigherfrequencydriversfromexcessoverdriveandharshclippingharmonics.
NOTE:YoumaywanttokeepthelimitersOFFwhenconnectingtheUS-3000and
US-4000 to power subwoofers.
HPF (High-Pass Filter): High Pass Filters (HPF) are also known as low-cut filters. HPFs
ontheUS-Seriesamplierscutoffsignalsbelow50Hz.Asaresult,bassreproductionis
optimized, since ultra-low frequencies, which most speakers cannot reproduce anyway, are
eliminated and more power becomes available for the reproduction of the remainder of the
music signal.
NOTE: You should set the filters to best suit the frequency response of your speakers as
somespeakersareparticularlysensitivetoover-excursion.The50HzltersontheUS-Series
amplifiers work well with most full-range speakers.
NOTE: FormostsubwoofersandinstudioapplicationskeeptheHPFintheOFFposition.
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