What is this Amp design called?

packer · 28th February 2009, 09:06 PM

I have an FBT MAXX 4a powerd speaker which keeps blowing FETS (Q3). See page 3. I have never seen this design before.
especially passing audio through digital Gates See pre amp section.

I would like to know what the design is called and then search for some theory on operation. Also I would like to know what voltages to expect at each junction.

Even with a lamp in series with the ac in it shorts Q3, D5 & U2

The circuit was too big to Upload so link below

SCHEMATIC DOWNLOAD

All help would be be most appreciated.

infinia · 28th February 2009, 10:13 PM

Hi
It looks like a Class D amplifier output stage.
It's basically a pulse width modulated power switch with a low pass filter.
U2 is a MOSFET driver with high side and low side gate drive.

Check Q4 and for any low impedance on outputs.
If OK, check with O-scope after disconnecting the 60V drain supply.
EDIT>If the otherside is working, use it for a reference.

Cheers

Cal Weldon · 1st March 2009, 12:11 AM

Mission accomplished, thread closed as requested.

28th February 2009, 09:06 PM	#1
packer diyAudio Member Join Date: Oct 2006	What is this Amp design called? I have an FBT MAXX 4a powerd speaker which keeps blowing FETS (Q3). See page 3. I have never seen this design before. especially passing audio through digital Gates See pre amp section. I would like to know what the design is called and then search for some theory on operation. Also I would like to know what voltages to expect at each junction. Even with a lamp in series with the ac in it shorts Q3, D5 & U2 The circuit was too big to Upload so link below SCHEMATIC DOWNLOAD All help would be be most appreciated.

28th February 2009, 10:13 PM	#2
infinia diyAudio Member Join Date: May 2005 Location: Californication	Hi It looks like a Class D amplifier output stage. It's basically a pulse width modulated power switch with a low pass filter. U2 is a MOSFET driver with high side and low side gate drive. Check Q4 and for any low impedance on outputs. If OK, check with O-scope after disconnecting the 60V drain supply. EDIT>If the otherside is working, use it for a reference. Cheers __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

1st March 2009, 12:11 AM	#3
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Mission accomplished, thread closed as requested. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

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