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Duo 23rd May 2003 07:36 AM

Ideas for parts in insanely powerful amp?
 
Hey everyone. This is totally insane. But I intend to render my
design of a line of high power amplifiers.

There will be 6 models in the line.

ZN50 = 50W @ 8ohms
ZN65 = 65W @ 4ohms
ZN300 = 300W @ 4ohms
ZN450 = 450W @ 4ohms
ZN500 = 500W @ 4ohms
ZN2000 = 1000 X 2 @ 4ohms / 2000W X 1 @4ohms

I would like some ideas as to good output transistors to use in these amplifiers.

The ZN2000 already has a complete power supply that I built which will suffice for up to two ZN2000's before reaching its limit.

The PSU output voltage is regulated at +/- 50V so that I may facilitate about an 80V swing in bridge mode.

This means that the transistors don't have to be high voltage, but they must be high in current.

Any suggestions for transistors that will be good as outputs in all these units? They will all be built with the same bandwidth capability and thus need a good high frequency transistor that will have a good slew rate. The transistors will operate in push-pull class AB.

Any ideas??

2000W too insane???:bigeyes:

TheFettler 23rd May 2003 04:59 PM

I think you might be asking a bit much to expect 1 or 2 Kw from +/-50v rails.
This pretty much precludes the use of Mosfets due to the extra driving voltage swing you'd need , which is a shame 'cos they are quite cheap for high current outputs.
to get 1Kw from these rails you would need to swing about 20A almost rail-rail discount any losses, which in reality would probably mean closer to 30A allowing for output driver losses.

I was told not to be optimistic when I said I wanted 500w from +/- 70v rails..... maybe the smarter folk in the group can give a better answer.

Ray

sam9 23rd May 2003 06:06 PM

I pulled up a spreadsheet I made a while back that relates desired output to transformer requirements. It seems to work at low to moderate powers so I can't say for sure the extrapolation is 100% valid. Nonetheless, here is what it tells me:

For 500W/ch @ 8ohms you need a transformer rated 72-0-72, 1,400VA (2-channels). 2,800VA if the load will be 4 ohms.

It doesn't say directly what you need to get 1,000W/ch @ 4 ohms - Watts don't really double just by attaching a 4ohm speaker. I would guess to get 1kW @4 ohm you need the equivalent of 700w/ch @ 8 ohms, which yields an 85-0-85 4kVA transformer (2-channels). And of course many parallel output devices.

As an aside, the same spreadsheet says you will want 140,000uF smoothing capacitance per RAIL.

An additional nice benefit is you can use those cool huge gold plated fuses that I see in the catalogs for automotive sound.

jan.didden 23rd May 2003 06:15 PM

Re: Ideas for parts in insanely powerful amp?
 
Quote:

Originally posted by Duo
Hey everyone. This is totally insane. But I intend to render my
design of a line of high power amplifiers.

There will be 6 models in the line.

ZN50 = 50W @ 8ohms
ZN65 = 65W @ 4ohms
ZN300 = 300W @ 4ohms
ZN450 = 450W @ 4ohms
ZN500 = 500W @ 4ohms
ZN2000 = 1000 X 2 @ 4ohms / 2000W X 1 @4ohms

I would like some ideas as to good output transistors to use in these amplifiers.

The ZN2000 already has a complete power supply that I built which will suffice for up to two ZN2000's before reaching its limit.

The PSU output voltage is regulated at +/- 50V so that I may facilitate about an 80V swing in bridge mode.

This means that the transistors don't have to be high voltage, but they must be high in current.

Any suggestions for transistors that will be good as outputs in all these units? They will all be built with the same bandwidth capability and thus need a good high frequency transistor that will have a good slew rate. The transistors will operate in push-pull class AB.

Any ideas??

2000W too insane???:bigeyes:

Think big! I hear they have a used nuclear power plant for sale shortly in North Korea. That'll take care of most of your worries....:bigeyes:

Jan Didden

PS You may want to skip the 50, 300 and 450W versions. They are barely differing in perceived sound level to the 65 and 500w versions respectively.

Duo 23rd May 2003 08:49 PM

Thanks for all the replies.

Firstly, I know 45volt rails sounds quite small. The point is, to get 2000W into 4ohms, I will be bridging two amplifiers that each have rails of 45volts. This means around 90V swing into the speaker.

Secondly, the reason for so many different models of amplifiers is that there will be very different requirements and uses for each model.

I know, 450 and 500 is an extremely small difference, but the amps will have different designs and features.

Really, I might just make a model for 500W instead of one for 300, one for 450, and one for 500.

I still have to conceptualize a bit.

Anyway, any ideas for high current and medium voltage audio output transistors? I'm definitely looking for high quality here!


Thanks.

kevin gilmore 23rd May 2003 09:49 PM

With 50 volt rails especially unregulated ones you will not
be able to reach your design specs.


My uberamp uses regulated +/- 65 volt rails and in bridge
form with 48 output transistors can only put out 800@8
or 1600@4.

Think Mj21195/mj21196. Lots of them. With +/-75 volts
and 60 output transistors you will still barely get to 2000@4.
The SOA will be extremely close.

thylantyr 23rd May 2003 09:58 PM

I picked the aussieamplifiers.com av800 as my choice
for DIY monster amp. It was tested at 550w@ 8 ohm,
1100w @ 4 ohm, 1600w @ 2 ohm, 2 ohm being short term
test, +110V rails, 20 output stage transistors. (1kw version)

The PCB layout I'm doing has different versions,
24, 28, 40, 60 output transistor per channel.

Realistically, the 60 will not be made by me, maybe
if I lose my mind some more, I will try the 40 version.

These are non-bridged power ratings.

Bridged mode = scary power , the power supply is your
bottleneck.

I'm almost done with my reference pcb layout for the
24 and 28 version. Almost done integrating various
protection circuits into the basic av800 design,
been testing the circuits on the bench for a few weeks.

For 1 ohm or 0.5 ohm continious operation driving
monster woofers of modern era, you might want to venture
into the land of class T or D.....

/// monster amps are fun ///

/// smoke test ///

/// kabooom ////

sam9 24th May 2003 02:11 AM

Hmmm.... just realized you need to pay attention to the choice of rectifier. The standard 35A metal cased bridge rectifier will be right on the edge. Better plan on two per channel.

Duo 24th May 2003 03:14 AM

Hmm, I guess that the transistors won't really reach such rails at that current draw will they? I can easily raise the rails.

The rails can be as high as +/-110V so anything works!

Solid Snake 28th May 2003 02:00 PM

TIP35/TIP36's are great, look them up. Not bad at all for $1.25.


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