WAT TO DO ??????????? MOSFET OR BJT FOR A 1200W RMS AMP @ 4E - diyAudio
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Old 29th September 2010, 06:12 PM   #1
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Default WAT TO DO ??????????? MOSFET OR BJT FOR A 1200W RMS AMP @ 4E

AS I HAVE HEARD THAT MOSFET HAS A TENDENCY OF GOING IN OSC IF LARGE NUMBER R PARALLELED ..... BUT ALSO THAT MOSFET R MORE FORGIVING THAN BJTS........AND ALSO THAT MOSFET AMP IS ALWAYS LESS EFFICIENT THAN A BJT AMP OF SAME SPEC....
I AM CONFUSED WHAT OUTPUT DEVICES SHOULD I USE FOR 1200W AMP @ 4E ,,, AND WHAT OUTPUT TOPOLOGY QUASI OR COMPLEMENTARY.........
HELP ME GUYS...........


REGARDS
PHOENIX
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Old 29th September 2010, 06:29 PM   #2
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Sheesh turn caps lock off!!

What is the application ? for home use you rarely need a bigger amp that 50 watts per channel and maybe 150W for a normal size sub.

For an amp above 400W its better to buy a PA amp from Behringer or other budget company than to build one.

Amplifiers above about 500W contain lethal voltages and should not be built by a novice.

I'd say start off with simple stereo amp built from a pair of LM3886, there are kits available for cheap.

If 1kW is a requirement, buy a PA poweramp.
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Old 29th September 2010, 07:26 PM   #3
Arius is offline Arius  United States
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To OP:

It sounds like you want to build your own 1200W@4R amp, but lack the proper EE skills.

Tekko's advice is right on. You'll need an amp riding on +/-110V rails at least. Such a project is not for a novice.

If you must proceed with your intent, both MOSFETs and BJTs can be used. The SuperLeach is a good starting point, you'll have to up-rate the design to suit your rails. MOSFETs will also work, provided you take proper precautions with the gate drive.

You might also want to consider a 600W@4R amp designed to operate continuously into a 2R load. Take 2 of them and bridge it to get 1200W@4R. That'll make your rail voltages easier to cope with. Don't expect very hi-fi performance out of that.

Disclaimer: Do not do this at home
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Old 29th September 2010, 08:16 PM   #4
CBS240 is offline CBS240  United States
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For that kind of power, forget linear audio, go with class D.
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Old 30th September 2010, 10:08 AM   #5
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Quote:
Originally Posted by Tekko View Post
Sheesh turn caps lock off!!

What is the application ? for home use you rarely need a bigger amp that 50 watts per channel and maybe 150W for a normal size sub.

For an amp above 400W its better to buy a PA amp from Behringer or other budget company than to build one.

Amplifiers above about 500W contain lethal voltages and should not be built by a novice.

I'd say start off with simple stereo amp built from a pair of LM3886, there are kits available for cheap.

If 1kW is a requirement, buy a PA poweramp.
frnds i have a lot of EE experience ..... i have made amps >500W rms . I just needed to know which is better Mosfet or BJT in terms of high power amps.
And just for the word.....I have made all the following amps with my own pcb design...
1. 6.1 channel amp using STK4211V & TDA2030
2. STUDIO SE by dr Bora
3. Legend stage mk2 by dr BORA
and many other small chip amp projects....

regards
phoenix
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Old 30th September 2010, 10:19 AM   #6
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Neither is better, it is down to the way the devices are used that makes and amp better or worse.
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Old 30th September 2010, 12:58 PM   #7
AndrewT is offline AndrewT  Scotland
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Quote:
If 1kW is a requirement, buy a PA poweramp.
Quote:
Originally Posted by CBS240 View Post
For that kind of power, forget linear audio, go with class D.
agreed.
Cheaper to buy than to build.
Linear amp capable of 1200W into 4r0 requires ~210Vdc to 230Vdc across the supply rails!!!! What are you planning for capacitors?
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Old 30th September 2010, 07:47 PM   #8
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i think I should settle for 500W rms @ 4E, 1200W seems way to high for normal use . I just wanted to complete my HT system .
so wat should i use BJT or Mosfet...........
ANd how many pairs....????????

regards
phoenix
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Old 30th September 2010, 07:58 PM   #9
LAJ is offline LAJ  United States
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Default I'd go BJT.

Because have you seen how much those TO3 FETs cost? They're way more than bipolar for the same dissapation. Also you will need a larger heatsink for FETs.
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