Protection
Every model in the B Series incorporates pro-
tection features. The HPA B-Series front panel
Protection LED indicates the activity of the relay
speaker connection circuitry in each channel.
When the protection LED turn on, this circuitry
is active, and all connected speakers are muted.
Initial power-up ; For approximately five sec-
onds after initial power-up, the protection
circuitry is activated and the speaker outputs
are muted. If everything is operating normally,
you will hear an audible click at the conclusion
of this brief period, as the protection circuitry is
deactivated and the B Series begins delivering
signal to connected speakers. It is normal for
the Protection LED to fade gradually after the
amplifier is powered off.
Thermal Protection ; Abnormally high heat sink
temperatures will engage the Protect circuitry
for the overheating channel only. An output relay
disconnects the speakers until normal tem-
perature range is restored. During this time, the
Protect LED will light.
To guard against this problem, make sure the
B Series receives adequate ventilation on all
sides and that both the front and rear panels are
unobstructed. If the power transformer gets too
hot, its thermal switch will disconnect all of the
secondary power and disconnect both channel
outputs.
Short circuit ; If output is shorted due to faulty
wiring, the thermal circuitry will automatically
protect the amplifier. If this will occur, the load
will be disconnected by thermal protection cir-
cuitry (also output relay opens).
DC Voltage Protection ; If an amplifier channel
detects DC voltage at speaker output, the out-
put relay immediately open to prevent speaker
damage.
Subsonic Frequency Protection ; Built-in High
Pass Filter provides subsonic frequency protec-
tion for each channel.
Current limiting Protection ; At the amplifier’s
full power limit, or clipping point, the limiter
circuitry will be activated. This is indicated by
illumination of the Clip LED. The channel gain
is automatically reduced, protecting the speak-
ers from the high power. This circuitry may be
activated by uncontrolled feedback, oscilla-
tions, improper equipment gain setting. And this
circuitry is virtually transparent in operation and
full signal bandwidth is maintained.
Any time the Protection LED lights up (except
for initial power-up during approximately five
seconds), there is reason to be concerned. If
this occurs, turn the amplifier off immediately
and check carefully all wiring and external
equipments in order to locate and correct the
condition.
Protection
