900W H-class PA Amp with Limiter

[engel dela pena]

apex,
good day sir
i'm happy to inform you that i already have a working balanced input
thank you for sharing
i have an old quasi mosfet amp but unbalanced input only
now i can use your circuit and my amp to avoid power loss due to long speaker cable because it is now balanced
thank you

 

[apexaudio]

if no nsl in circuit and i use only led
will it serve as clip indicator and will my fuse react immediately after clipping
before my speaker burn or before amp power output burn[/QUOTE]

U can use led as clip indicator, fuses will not react after clipping, fuses react after power output burn.

 

[apexaudio]

apex,
good day sir
i'm happy to inform you that i already have a working balanced input
thank you for sharing
i have an old quasi mosfet amp but unbalanced input only
now i can use your circuit and my amp to avoid power loss due to long speaker cable because it is now balanced
thank you

Is this your PCB design?

 

[apexaudio]

Hello Apex and to all another DIYer

look my schematic attachment, VI Limiter 1 and VI Limiter 2



Whats your opinion,.... ?

which VI Limiter is better to protect the amp or better for powerful deep Bass and protect the amp ?

I like to feel deep heavy bass without smoking amplifiers

BGW did use in his legendray 750 B/C amps in the late 70 and 80s VI Limiter 2
and the bass was heavy and very deep without defective amplifier with continous overloading amps every weekend

A lot of newer amps especially Class D Amps dont had this deep bass and 3 QSC EX 4000 was overheating after 2 hour deep Techno, but 3 old Vintage 750 B was playing without problems all night long with JBL Subbass Speakers in RLA (Richard Long Sound System) without PA LIMITER we did test QSC before 12 years... the nightclub was closing on 31.12.2000....but the old BGW working since today in new installation for heavy deep bass... We did test old BGW with Powersoft Class D Amp about 2 x 1500 W 4 OHM before 5 years ....no way for Powersoft CLASS D V/s Vintage BGW Amp in deep bass, Class D Amp was clipping without deep Subbass feeling....I was shocked because spec from Class D is 3 times more output power

Newer 750 BGWs lilke Model 750G and a lot of chinese Class AB amps use VI Limiter 1

Finally: the Quasi NMOS Amp is sounding excellent and has the same deep subbas feeling like Vintage 750s... Class D really no way...a lot of DIYer know it....

I think about to add Class H and change QUASI Design to complentary BJT output for high Subbass output power...not good news to hear class H with quasicomplentary output is impossibile because Sound with N Mosfet Output stage is excellent... and free from Secondary Breakdown output device Faults

U can use Limiter circuit
http://www.diyaudio.com/forums/solid-state/162043-mosfet-amplifier-irfp240-irfp9240-17.html
post #161, it is like VI Limiter 1 but diferent value.

 

[engel dela pena]

Is this your PCB design?

yes i use dual op amp and make it stereo balanced input
thanks for sharing

 

[engel dela pena]

can i use 5k resistor for max vol(5k pots not to use)
i want to control the volume from amp existing volume control

 

[wg_ski]

Hello Apex and to all another DIYer

look my schematic attachment, VI Limiter 1 and VI Limiter 2



Whats your opinion,.... ?

which VI Limiter is better to protect the amp or better for powerful deep Bass and protect the amp ?

I like to feel deep heavy bass without smoking amplifiers

BGW did use in his legendray 750 B/C amps in the late 70 and 80s VI Limiter 2
and the bass was heavy and very deep without defective amplifier with continous overloading amps every weekend

A lot of newer amps especially Class D Amps dont had this deep bass and 3 QSC EX 4000 was overheating after 2 hour deep Techno, but 3 old Vintage 750 B was playing without problems all night long with JBL Subbass Speakers in RLA (Richard Long Sound System) without PA LIMITER we did test QSC before 12 years... the nightclub was closing on 31.12.2000....but the old BGW working since today in new installation for heavy deep bass... We did test old BGW with Powersoft Class D Amp about 2 x 1500 W 4 OHM before 5 years ....no way for Powersoft CLASS D V/s Vintage BGW Amp in deep bass, Class D Amp was clipping without deep Subbass feeling....I was shocked because spec from Class D is 3 times more output power

It's not so much a fault of what type of VI limiters are employed, but where the limit threshholds are set. If you've been keeping up with other threads around here, I'll tell you what amps I think are "alike plague". Ones that have +/-90 (or even higher) rails and no rail switch to keep the dissipation down with only 3 or 4 pair of plastic outputs, two stages of current gain with and only 20mA from the VAS to drive it all, powered by an eight pound 750VA toriod, with maybe 12,000 uf in total capacitance. Then they go and claim 2000 watts a channel. No bass, they overheat and shut down. You want class D? Remember, they're going to size that little switchmode supply for the avearge current draw at 1/8 power and hard limit. That's what you get with a $1000 class D amp. Put out even 1/3 duty cycle at 25 Hz - and that little supply says there's a short somewhere and cuts back. Sure, you can build one (or more correctly, Eva could) that will sustain the 4500W output you need but that's one big expensive supply. Which is why Labgruppens, Crest pro, and Macrotech I tend to be a wee bit on the expensive side.


End rant....

 

[apexaudio]

can i use 5k resistor for max vol(5k pots not to use)
i want to control the volume from amp existing volume control

Just use signal from 100R, no need for 5k resistor.

 

[andrewlebon]

hi apexaudio
greetings waiting for nsl 32 how many output pairs can be added
to circuit will output power increase can this circuit work in 2 ohms

thanking you
andrew lebon

 

[apexaudio]

hi apexaudio
greetings waiting for nsl 32 how many output pairs can be added
to circuit will output power increase can this circuit work in 2 ohms

thanking you
andrew lebon

Another three output pairs and circuit will work in 2 ohms.

 

[event horizon]

Hi apexaudio, i have finally found a simple way to impliment a fast switch for the rail switches Looks like the job can be done in about 200ns & with no direct connection.

I'll be using a single LM319N fast dual comparator per amp, these are open collector outputs. Each comparator will drive a FOD3180 2Amp gate driver, as these are opto isolators there will be no connection as you can see Coming here sooner or later....

Thanks again for the inspiration

Mark.

 

[apexaudio]

Hi apexaudio, i have finally found a simple way to impliment a fast switch for the rail switches Looks like the job can be done in about 200ns & with no direct connection.

I'll be using a single LM319N fast dual comparator per amp, these are open collector outputs. Each comparator will drive a FOD3180 2Amp gate driver, as these are opto isolators there will be no connection as you can see Coming here sooner or later....

Thanks again for the inspiration

Mark.

Mackie in SWA1801 have optodriver for mosfets, maybe U find more inspiration there.
Regards

 

[engel dela pena]

apex;
just for clarification
what kind of ldr is this one?
why this one can't be use as limiter?

 

[apexaudio]

apex;
just for clarification
what kind of ldr is this one?
why this one can't be use as limiter?

NSL32 is opto-ldr, ldr with integrited led diode. There is four pins + and - (litle circle is -) from led diode and two pins from resistor. When led light resistor value incrise and atenuate input signal, that how limiter work. On your picture is just ldr with two pins, U can use this ldr as limiter with clear red led diode put together in black pipe.

 

[apexaudio]

thank you verry much
ldr and led parallel connection
led positive to schematic of nsl with dot?

Not parallel. Led - is dot on NSL32. Ldr pins are conected opsite from led pins there is two holes. Circuit diagram can also help U to understand.

 

[engel dela pena]

apex,
should the clear red led placed at nsl with dot (as for component lay out)
and the ldr to two holes in the middle of 22uf caps and nsl

 

[engel dela pena]

thank you

 

[apexaudio]

apex,
should the clear red led placed at nsl with dot (as for component lay out)
and the ldr to two holes in the middle of 22uf caps and nsl

Yes hole are for ldr, but led and ldr must look each other, and isolate from daylight with something black.

 

[engel dela pena]

thank you,as the saying goes
HE WHO THAT ASK IS A FOOL FOR A MINUTE,
BUT HE WHO THAT DO NOT ASK IS A FOOL FOREVER.
thank you

 

[engel dela pena]

andrewlebon,
hello friend,
how is your h900?
looks like only nsl is missing
i wish i can give my ldr to you
too much waiting for nsl?
find ldr like this and clear red led
and follow apex instruction
good luck on your h900