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?
AndrewT said:
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.
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.
Apparently it's a very good amp indeed, i'm building the 200W version currently. PCB artwork and schematic in the book.
let us suppose
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 ????
nigelwright7557 said:
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 ????
if you follow
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
Wavebourn said:
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
I doubt you could build an amplifier for cheaper than a used semi-pro amp unless you have some really great surplus sources. Case, heatsinks, transformer, and filter caps are all expensive items if you're buying them new. It might even be cost-effective to buy a new Behringer amp for parts rather than buy those bits separately.
runebivrin said:
Agreed (at least for the short-circuit protection). That's the rub with most DIY designs, which severely limits the choice of projects for "non-audiophile*" use. (for lack of a better term)
Most DIY designers here do not consider short circuit protection worthwhile as a project component, I assume because of an impact on the sound quality.
nigelwright7557 said:
Nobody has complained of Quasi's amplifier designs being unstable to my knowledge, and they were a very popular project at one time. If one follows his plans and instructions, there should not be a problem. I would not be afraid of this.
..Todd
The Leach SuperAmp includes a VI limiter and is pretty powerful if I remember correctly. And it has a symmetrical output topology.
I'm just throwing ideas out there.
----------------------
"The energy stored in the eight apacitors was about 250 joules. This is enough energy to lift a 25 pound dog over 7 feet off the floor."
Heh, I always get a kick out of reading that. It's good to know for those times when Fido refuses to jump up into the back of the car.
----------------------
..Todd
I'm just throwing ideas out there.
----------------------
"The energy stored in the eight apacitors was about 250 joules. This is enough energy to lift a 25 pound dog over 7 feet off the floor."
Heh, I always get a kick out of reading that. It's good to know for those times when Fido refuses to jump up into the back of the car.
----------------------
..Todd
nigelwright7557 said:
Not all designs are equally "scaleable". QC designs typically are not. You can't just go adding more and more voltage and more and more output transistors - they go south faster than complementary output stages when you do. Somewhere around 5 or 6 pairs is about the limit for a QC or CFP triple. For doubles, you could probably get away with 10. Triple complementary EF's have worked with as many as 20 pairs. The nearest I can figure as to why is that the fake PNP side can't tolerate distributed impedance between the rail, the emitters of the lower bank, and the low side of the VAS. And the more beta you put in the output stage the worse it gets. The old Flame Linears got unstable with high beta outputs. With good bypassing and not a lot of stray inductances, I can get them to work fine. But make it big enough and you can't anymore. With EF's I can put all kinds of junk in the collector leads of the outputs and not go unstable.
Re: let us suppose
That load is a piece of cake for that amp. Try +/-85V, 6 pairs of MJ15024/025, three pairs of 8 ohm speakers and one pair of 4 ohm. Clipping like mad. The amp didn't care.
I would have expected the tweeters to give up the ghost without a crossover. Piezos can only handle 35V RMS, and that amp should put out way more than that. You just weren't playing it loud enough.
sakis said:
That load is a piece of cake for that amp. Try +/-85V, 6 pairs of MJ15024/025, three pairs of 8 ohm speakers and one pair of 4 ohm. Clipping like mad. The amp didn't care.
I would have expected the tweeters to give up the ghost without a crossover. Piezos can only handle 35V RMS, and that amp should put out way more than that. You just weren't playing it loud enough.
AraNubanti said:
Hi AraNubanti,
If you are interested in my amps may I suggest the Actrk600 for use as a PA amp. This amp uses an all N-channel output stage without suffering from the shortfalls of a true quasi-comp configuration. This allows you to use cheaply available N channel mosfets.
This link takes you to the middle of the relevant thread and shows one constructors project.
http://www.diyaudio.com/forums/showthread.php?postid=1303252#post1303252
It has occured to me that this linked thread title is incorrect. This is not really a quasi-complementary amp. I wonder if I can change it (with Mod intervention?)
Cheers
Quasi
Re: Re: let us suppose
i wonder if you know what is a clip detector circuit ????
and also what is the power provided by the particular quasi when you see the clip blinking ....
it seems to me that you have a thingy with my approach ....but that is ok i cannot be bothered
(5 years ago when i had much less expirience with diy designs had produced some small amplifiers my shelf and repaired many of various quality and power ....i come in to the forum looking for a simple design that produces average power 150w or so stable relaible ....and so on and on ...Then dr Bora come up with his design Legend 4 which is very very similar to the citation 12 but with four outs and so on ... BY mistake i thought or missunderstand that is amp was capable of 60+60 volt rails ...with 4 IRFP 250..... it was simply a joke never possible to work ....
but with an easy load not too many peaks and good cooling the amp operated for a few hours before fire . with this rail voltage produced almost 175 w but no ccs any where ....bootstraps here nad there simply impossible
what ia m trying to say is that i belive that the truth as for most things lies in the midle .....either overdesign or underdesign is not a solution ...somewhere in the midle is the truth )
wg_ski said:
i wonder if you know what is a clip detector circuit ????
and also what is the power provided by the particular quasi when you see the clip blinking ....
it seems to me that you have a thingy with my approach ....but that is ok i cannot be bothered
(5 years ago when i had much less expirience with diy designs had produced some small amplifiers my shelf and repaired many of various quality and power ....i come in to the forum looking for a simple design that produces average power 150w or so stable relaible ....and so on and on ...Then dr Bora come up with his design Legend 4 which is very very similar to the citation 12 but with four outs and so on ... BY mistake i thought or missunderstand that is amp was capable of 60+60 volt rails ...with 4 IRFP 250..... it was simply a joke never possible to work ....
but with an easy load not too many peaks and good cooling the amp operated for a few hours before fire . with this rail voltage produced almost 175 w but no ccs any where ....bootstraps here nad there simply impossible
what ia m trying to say is that i belive that the truth as for most things lies in the midle .....either overdesign or underdesign is not a solution ...somewhere in the midle is the truth )
I have built another quasi and found it works very well.
I suspect in the previous amp MOSFET driver transistors might have cooked and blown up the output MOSFETS.
It could be anything as i had hooked into a none quasi amplifier board and made changes to it. The output definitely oscilated and the amplifer overheated and died.
Oh well learned something new. Onward an upward.
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