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Gallien Krueger Fusion 550 pop issue

J

John Lovell

Jun 20, 2020
6
4
#1
Hi guys, I have a GK Fusion 550 that has a minor issue. At switch on there is a huge "rifle shot" pop through the speakers. With all controls to zero and standby on, the sound still occurs.

I took it to a local tech who replaced a number of possible suspect components such as thermistors and capacitors but not able to fix the problem. There appears to be a DC voltage applied to the speakers to cause a very loud "crack" on startup.

Anyone have the same issue and if so, how was it fixed?
 
#4
Same here. Mine is more a low volume "thump" once the amp fully cycles on power-up. The one suggestion I have is, you could mute the amp and then turn on the power. That might solve the issue, it might not.

I believe this amp is still featured on GK's current model's page. Wouldn't hurt to reach out to them for advice.

EDIT: You can try replacing the speaker cables and trying a different cab to see if it makes a difference.
 
#6
John Lovell said:
Hi guys, I have a GK Fusion 550 that has a minor issue. At switch on there is a huge "rifle shot" pop through the speakers. With all controls to zero and standby on, the sound still occurs.

I took it to a local tech who replaced a number of possible suspect components such as thermistors and capacitors but not able to fix the problem. There appears to be a DC voltage applied to the speakers to cause a very loud "crack" on startup.

Anyone have the same issue and if so, how was it fixed?
Click to expand...

Many solid state amps have an automatic mute. When the amp is turned on, the circuit applies a mute to the input of the power amp, until it stabilizes. The mute is also applied instantaneously when the amp is turned off until the power supply has a change to bleed down a bit.

Here's and example of the circuit from a GK RB series amp.
upload_2020-6-25_19-1-16.png


The "Fault" tab on the right monitors voltage in the power amp. The "GRN POWER ON" and "RED PROTECT" leads at the bottom drive green and red status LEDs on the front panel. On the left side, the "MUTE1" tab energizes a Mute circuit on the Power Amp module, which generates "MUTE2" for the tweeter amp.

My QSC PL236 amps have a similar circuit but it seems to be way more complicated.

The problem could also be unrelated to muting.
 
#14
I am going to send it to the local Aus repair centre soon to get it fixed soon. I have purchased a new GK MB500 lightweight D Class amp, nowhere near the quality for the fusion, but sounds good and portable. I will post the outcome of the repairs in due course.
 
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