400W Power Amplifier

[AraNubanti]

Hello! I'm new to this forums and also quite new to DIY amplification too, the only experience I have is with vacuum tube guitar amps that I have built with my band. The next project we're going to take on is that we need a 2-channel Power Amplifier with the output of 400W-600W, so that it can be used on minor outdoor / hall performances. So I was wondering if anyone here has any ready schematics and projects that have turned out good, fitting to our purposes?

[taj]

Here's a very good option for your purposes.

Quasi's amplifiers

..Todd

[nigelwright7557]

I would go for a BJT amplifier or a complimentary MOSFET output stage.
The quasi isnt symetrical.
One side has much more gain than the other.
Its fine for a very high power amp where you cant get p channel transistors.

[AndrewT]

Originally posted by nigelwright7557
The quasi isnt symetrical.

exactly, so what.

Originally posted by nigelwright7557
One side has much more gain than the other.

are you sure.

[runebivrin]

Originally posted by taj
Here's a very good option for your purposes.

Quasi's amplifiers

..Todd

Probably quite sufficient as far as power is concerned, and fairly simple designs. For the intended use I would be very hesitant to use anything that didn't include short circuit protection and thermal protection.

[nigelwright7557]

Originally posted by AndrewT
exactly, so what.are you sure.

Yes.
What would have been the p side has much more gain.

The n side is simply buffered with an emitter follower.
The p side has an inverter which has gain.

I have yet to be succesful with a quasi design.
Mine just oscilated and blew itself up.
And that was a bog standard design I followed.

Its bad enough trying to stabilise a symetrical amp never mind a none symetrical one.

So for a beginner I would suggest a complimentary design.

[mrwireless]

One of the amps in Randy Slone's book "The Audiophile's Project Sourcebook" is capable of 400W. It uses the double-die L-Mosfets to reach that power output. Using normal mosfets the same design (with a few component changes detailed in the book) gives 200W.

Apparently it's a very good amp indeed, i'm building the 200W version currently. PCB artwork and schematic in the book.

[sakis]

Originally posted by nigelwright7557



Yes.
What would have been the p side has much more gain.

The n side is simply buffered with an emitter follower.
The p side has an inverter which has gain.

I have yet to be succesful with a quasi design.
Mine just oscilated and blew itself up.
And that was a bog standard design I followed.

Its bad enough trying to stabilise a symetrical amp never mind a none symetrical one.

So for a beginner I would suggest a complimentary design.

let us suppose for a minute that what you say is correct then you have to explain why the first Qsc and pevay cs series where made with the exact same topology ....

no matter everything else peavey cs series was supporting conserts and musical events for years before modern designs comes up....


finally ....my input .... i have so far builted 3 of the brother of quasi in power 180-300w depending on the number of outs and rail voltage all of them are used for small pa application and so far they manage realy zouper

only last night friend and costumer asked to use one with his own speakers for a party .... i give him a big one the
300+300W with
1500W trafo
120 ma bias /
70+ rails /
75.000+75.000 mfd/
10x MJW21194 per ch/
45 cm of heatsink per chanel plus
tunel ventilation with 2 x 7.5cm double ventilators per chanel

to my surprize ( poped in to the party for a drink ) my friend was driving the most stupid speaker available in the market
Bought from MAkro super markets
including 2x15" woofers without any xover
including 5 8x8 cm piezo tweeters also i think without any xover
including 1.5 " piezo driver + horn also i think without any xover ....

i said to my shelf that by the end of the night either tweeters or amp is going to be history after driving this so stupid load for full power all night ....

well nothing happend .... full power for many hours always very next to cliping no serious temperature rising speakers presented a load i think lower than 4 ohms ( but i can never tell ) and by the end of the night all the piezos where still working ....

any comments ????

[Wavebourn]

Assembled class D PCBs are available from ePay and from internet stores.

[sakis]

Originally posted by Wavebourn
Assembled class D PCBs are available from ePay and from internet stores.

if you follow my procedure you will realize that you might end up with a board that costs bearly 30 euros all included regarding semis passives and pcb

now if this is one of your targets .... then Yes you got your shelf a very fine amplifier

where i buy semis from cost me something like 1 euro each ...the real original japanese stuff ...

now this was the original target on building a quasi ....it just hapend to proof a very nice amp .... beyond construction and design issues