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Output Transistors/Ultimate Power Amp?
Output Transistors/Ultimate Power Amp?
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Old 14th July 2009, 02:50 PM   #1
alanandlexie is offline alanandlexie  Wales
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Default Output Transistors/Ultimate Power Amp?

Hi everybody, I'm planning on building a combo amp based on 3 of the following circuits:http://sound.westhost.com/project27.htm#bass

One will be a Bass channel, the other 2 will be guitars.

Now my question is probably dumb but I just can't find the answer. I want to add more output transistors to share the power in the power amp, but I haven't a clue how to modify the circuit. It's going to be used pretty aggressively and I don't fancy having just two output transitors for each 'channel' as it were.

Woudl there eb a better design of power amp I could try? Would I be able to put all 3 pre amps into a single large 3 channel power amp?

I'm pretty good withelectronics but not had any real involvement with amps, only fairly simple circuits involving model railways.
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Old 14th July 2009, 07:20 PM   #2
EchoWars is offline EchoWars  United States
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Try here: http://www.sound.westhost.com/phpBB2/index.php
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Old 14th July 2009, 08:48 PM   #3
nigelwright7557 is offline nigelwright7557  United Kingdom
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Location: Carlisle, England
You would be better going for a more powerful design.

The driver stage needs to be powerful enough to drive the extra transistor pairs.

I designed my own 900watt amp with 3 pairs of MOSFET's on the output and it is very loud. I use it for disco and guitar use.
PCBCAD51 pcb design software. 2018 version out now with lower prices >> http://www.murtonpikesystems.co.uk
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Old 15th July 2009, 10:00 AM   #4
AndrewT is offline AndrewT  Scotland
Join Date: Jul 2004
Location: Scottish Borders
for PA duty, you have to decide what power output you need.
Borrow some amps and experiment to find your requirements. Listen to feedback from your audience. Do you have a soundman/roadie you can rely on?

Is 100W into 8ohm sufficient for your needs?

If you decide on a power output make sure your PA can adequately drive 4ohm speakers if you ever decide to connect them up or double up the cabinets you use.

That gets you to a minimum requirement of 180W into 4ohms.
Even that is low for PA duty with 94/96dB/W/m PA speakers.

If you need reliability, then use ONsemi mj15003/4 or mj21192/3
These are both 250W 200degC devices on big fan cooled heatsinks.
With lots of protection features built in to keep the amps working all night.
regards Andrew T.
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