1kW MOSFET amplifier

[Aussieamps]

Greetings Gentlemen

The 1kw amplifier does indeed use IRFP240 and IRFP9240 devices
The +-110 volt rails drop down to 96 volts under load.

If you wish to see the design for this amplifier you only need to visit my site and download the PDF file for the AV800 amplifier.
It is basicly the same amplifier except with fewer o/p devices.

The new web address is www.aussieamplifiers.com

Any other questions? just let me know I will do my best to answer them...

Warm regards

Anthony Holton

[AudioFreak]

it wouldnt be such a bad idea to make 2 smaller amps of say 300W in 8ohms based on this amp then run them bridged into an 8ohm speaker.... you should get around 1200W into that 8ohm load and it would give a much bigger safety margin on the o/p devices..... i'd just run each amp with say 16 o/p devices (8 x IRFP240 and 8 x IRFP9240) with a big power supply. All said and done this should be enough given that this is a low bias Class AB design.

[Kilowatt]

It would if you plan on bridging the 1000W amps

[Aussieamps]

Greetings once again...

To reply to Audiofreak.

When bridging any amplifier into say 8 Ohms, only double the power o/p is realised. In theory it should be 4 times the power o/p. but in practise because of power supply loss and amplifier inefficency it is only 2 times.

So a 300 watt into 8 Ohm amplifier when bridged will develop only 600 watts into 8 Ohms.

The 1kw and AV800 amplifier can easierly be bridged with no additional circuitry, because both amplifiers have balanced i/p stages. One only has to use the inverting i/p of one of the modules and the non-inverting i/p on the other then connect the load across the active o/p's of each amplifier module.

The AV800 Module when bridged produces 900 watts RMS into 8 Ohms and over 1600 watts RMS into 4 Ohms....

I have heard of no failures with this amplifier.


I hope this helps....

Warm regards

Anthony Holton

[AudioFreak]

Originally posted by Aussieamps
Greetings once again...

To reply to Audiofreak.

When bridging any amplifier into say 8 Ohms, only double the power o/p is realised. In theory it should be 4 times the power o/p. but in practise because of power supply loss and amplifier inefficency it is only 2 times.

So a 300 watt into 8 Ohm amplifier when bridged will develop only 600 watts into 8 Ohms.

The 1kw and AV800 amplifier can easierly be bridged with no additional circuitry, because both amplifiers have balanced i/p stages. One only has to use the inverting i/p of one of the modules and the non-inverting i/p on the other then connect the load across the active o/p's of each amplifier module.

The AV800 Module when bridged produces 900 watts RMS into 8 Ohms and over 1600 watts RMS into 4 Ohms....

I have heard of no failures with this amplifier.


I hope this helps....

Warm regards

Anthony Holton

Well i cant agree with that sorry...

If you bridge 2 amps the voltage across the speaker should double and if you double the voltage you double the current which gives 4 times the power .... you've then just got to make sure that the power supply and the o/p's are upto the job.

[Aussieamps]

Have you ever built an amplifier in bridge mode?

I can tell you I have built dozens of them and not one of them produced 4 times the output power, regardless of how big the power supply was or how many o/p devices it had.....

The AV800 amplifier has a 2KVA transformer with a 100,000uf bank of caps and it doesn't produce 4 times the power o/p in bridge mode...

[Kilowatt]

I'll have to partially agree with AudioFreak. Two bridged OPS's will provide almost twice the power into twice the impedance as one normal OPS, because the voltage doubles. Theoretiacally 4 times the power into the same load, but that would be like hooking up each amp to half it's nominal recommended load, In which case, I would agree with Anthony that you would not get 4 times the power. We all know that amps do not produce twice the power into half the load. As far as two bridged AV800s with a sufficient power supply and OPS doing 1600W into 4 ohms and not 8, That doesn't seem right, is that a typo? All I know for sure is that bridged amps normally produce twice the power into twice the impedance. Why wouldn't they? They would each see the nominal load (half the load used when bridged). Maybe it's different with the AV800, I don't know.

[AudioFreak]

Originally posted by Kilowatt
Theoretiacally 4 times the power into the same load, but that would be like hooking up each amp to half it's nominal recommended load, In which case, I would agree with Anthony that you would not get 4 times the power. We all know that amps do not produce twice the power into half the load. As far as two bridged AV800s with a sufficient power supply and OPS doing 1600W into 4 ohms and not 8, That doesn't seem right, is that a typo? All I know for sure is that bridged amps normally produce twice the power into twice the impedance. Why wouldn't they? They would each see the nominal load (half the load used when bridged). Maybe it's different with the AV800, I don't know. [/B]

Yeah i agree with what you have said .... most amps cant double there output into half the load but they can come very close!.... Anothony is proposing that amps produce the same power into half the load just with less voltage and more current ... this would give twice the power when bridged.... many many many amps do far better than this.

I also know many amps that when bridged can produce twice the power into twice the load but do not have the current capacity to supply double that into the original load...

A 2kVa transformer with 100,000uF is not that big for a 800W amp...

[Aussieamps]

OK

Bridging works like this in theory.

You have an amplifier which has say a 2kw power supply.
Its power o/p into 8 Ohms is 100 watts RMS (28.4 VAC @ 3.55 Amperes RMS= 100.82 watts RMS)
If you bridge this same amplifier into an 8 Ohm load in theory you should get twice the voltage across the 8 Ohm load (56.8 VAC RMS @ 7.1 Amperes RMS = 403.28 Watts RMS)
Or 4 times the power o/p

If you then half the impedance or load on this bridged amplifier to say 4 Ohms. In theory you should get twice the o/p power again.
(56.8 VAC @ 14.2 amperes = 806.56 Watts RMS)
Which is 8 times the power o/p into 8 Ohms on an non-bridged amplifier or 4 times power o/p @ the same impedance of 4 Ohms.

Now this is assuming ideal amplifiers and power supplies with no losses what so ever

In practice this doesn't happen....

If you look at any commercial amplifier which operates in bridge mode, they only ever double their power o/p into any given load equal to the non bridged load...

My AV800 amplifier produces over 870 watts rms into 4 Ohms non bridged. In bridge mode it produce about 1600 watts rms into 4 Ohms with a 2KVA transformer. Into 8 Ohms bridged it produces about 870 watts. which is about double its power o/p into 8 Ohms of 450 watts RMS.

The only commercial amplifier that could possibly come close to 4 times the o/p power would be Crown amplifiers. Which use Grounded Bridge Technology and even then they a subject to power losses and produce 4 times the power o/p or greater by driving into impedances of 2 Ohms or less...
Another amplifier would be Krell and not even Nelson Pass amplifiers x1000 can produce 4 times the power o/p in bridge mode using just two single module amplifiers into 8 Ohms...

I am willing to be corrected here, But I just don't see it...

regards

Anthony Holton

[Kilowatt]

AudioFreak:
Hmmm, he is, isn't he. That's of course just not true, unless half the power is wasted as heat, because we all know that an amplifier's OPS does not function like an output transformer in this manner (lowering the voltage, increasing the current). So, I wonder why the AV800 can not put out more than twice the power into the same load, even when bridged. Most amps definately can.

Anthony, were these bridged output ratings actually measured in bridge mode in the real world, or just assumed based on measurments taken from non-bridged operation? If so, why is it that bridged AV800's only do 900W into 8 ohms, 1600W into 4 ohms?