🚀 go-pugleaf

Jimmy CHAN wrote:
> 
> We have just purchased one CROWN Macrotech MA-600 and one MA-1200 for
> our JBL 4982 speakers in our church.  We got an annoying "POP" sound
> when we turned on or off the AC power of MA600 which is used for driving
> the high frequency of the speakers and the MA1200 is used for driving
> the woofer of the speakers.  We have pulled down all the fader for the
> mixer already and power of mixer kept on when we turned off the power
> amplifier.
> 
> The pop sound comes from the MA600 only.
> 
> Is it normal?  Will it hurt the speakers? Any method to kill the POP
> sound.

It's not 'normal' and if there's a DC component it may damage the voice
coils in the speakers. You can wire a DC-blocking cap in series with the
high frequency driver to reduce the possibility of damage. I'm sure 
someone with more recent circuit experience will post appropriate
values,
but you want a non-polarized capacitor with a 200V or so rating, and
the capacitance needs to be selected with regard to your crossover
frequency.

> Both amplifiers are brand new.
> 
> The technical staff of CROWN replied that it it normal and there is no
> relay for the output of the power amplifier.

I don't think it's acceptable, but I've had similar experiences with
several Crown amps, and no real technical answers from Crown. I make it
a practice not to connect speakers until the amp's had time to
stabilize.
I realize that's not a realistic option for you in a fixed installation.

--
Heath Roberts  heath@nortel.ca   ESN 255-2078 or (919) 992-2078
Operating Systems Integration/Nortel Global Enterprise Services
TDY to RTP UNIX Systems Commissioning and Consolidation