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Old 18th June 2007, 03:29 AM   #1
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Exclamation Searching for a minimum 400W@8 ohms amp project

A friend of mine got a 15 inches and required a 400W beast to drive,with Class AB MOSFETs output stage,any suggestion???

Thanks!
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Old 18th June 2007, 03:53 AM   #2
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Mono only? I'd suggest that you're into seriously dangerous voltages and power with that thing. Why not grab a pro power amp and bridge it?

Or maybe this thread might help.

Did you search DiyAudio?
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Old 18th June 2007, 03:57 AM   #3
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Nice thread but all I require is a Class AB design with 'dangerous voltages and powers'.
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Old 18th June 2007, 04:08 AM   #4
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Default Is this for a sub?

.
If so then the 12 FET version of this amp will do it.
http://www.diyaudio.com/forums/showt...050#post991050
You'll need an 800va 67v 0v 67v* transformer and humungous DC section.

Layouts available here http://www.adam.com.au/cgpap/QuasiWeb/index.htm

Select the "Actrk400 / 600" link. The 12 FET version will deliver just over 400 watts RMS into 8 all day with adequate heatsinking (a lot). Might even do 4 ohms with lighter duty i.e; sub amp.

* = unloaded.

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Quasi
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Old 18th June 2007, 04:15 AM   #5
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Build Quasi's N-channel Mosfet amp. Depending on whether your friend's 15" driver is 8 or 4 ohms, configure the amp for 200 watts into that impedance and then bridge to get to your 400 watts mark. It is a very stable amp, even into 2 ohms and the voltages you will be working on are pretty low.
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Old 18th June 2007, 04:32 AM   #6
quasi is offline quasi  Australia
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Quote:
Originally posted by Samuel Jayaraj
Build Quasi's N-channel Mosfet amp. Depending on whether your friend's 15" driver is 8 or 4 ohms, configure the amp for 200 watts into that impedance and then bridge to get to your 400 watts mark. It is a very stable amp, even into 2 ohms and the voltages you will be working on are pretty low.

I think Samuel means the amp in this thread.
Power amp under development
Yep a proven and stable amp with over a hundred modules built. But I want someone to build the first one of the other one.

A bridged pair would do the job easily though. In any case do not to run an Nmos500 at anything over 80v rails.

Cheers
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Old 19th June 2007, 02:53 AM   #7
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Many many thanks!Any more,guys???
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Old 19th June 2007, 04:09 AM   #8
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Quote:
Originally posted by quasi


But I want someone to build the first one of the other one.

Cheers
Quasi, I am willing to build it provided you assure me that you have completed simulations and are satisfied in every respect. This is because I don't have too much time these days to troubleshoot the amp, just in case it is not optimised as yet.

What is your gut feeling. Should the boosted +ve voltage amp sound better than the Nmos?
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Old 19th June 2007, 06:48 AM   #9
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Hi Samuel,

I have built the 6 Fet version of the amp and have tested it, but only on the bench. Whilst it seems to be "excellent" it has not been in service yet.

Having said that I have built a 10 FET version of that amp that is similar in design. It uses the extra +ve rail but uses a cascode second stage with with FETs providing a fixed voltage across the driver transistors. This amp performs well, but not as good as the Nmos series.

So if you're after a proven design that has stood the test of time, build an Nmos350 or Nmos500.

This begs the question though, has anyone built any of the amps found here? Another quasi-complementary design
I do know a couple were built earlier in that thread.

Anyway sorry about hijacking your thread Leolabs.

Cheers
Q
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Old 19th June 2007, 07:26 AM   #10
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Quote:
Originally posted by quasi
Hi Samuel,

I have built the 6 Fet version of the amp and have tested it, but only on the bench. Whilst it seems to be "excellent" it has not been in service yet.

Having said that I have built a 10 FET version of that amp that is similar in design. It uses the extra +ve rail but uses a cascode second stage with with FETs providing a fixed voltage across the driver transistors. This amp performs well, but not as good as the Nmos series.

So if you're after a proven design that has stood the test of time, build an Nmos350 or Nmos500.

This begs the question though, has anyone built any of the amps found here? Another quasi-complementary design
I do know a couple were built earlier in that thread.

Anyway sorry about hijacking your thread Leolabs.

Cheers
Q
How do you further qualify "excellent". Are the sonics better than the Nmos series?

You may be aware that I have built the Nmos with 6 FETs and powered with +-63volts DC (with some modifications). This may not qualify as Nmos350 but I was just offering to test an assured schematic, taking the lead, so to speak.

Tell us a little more about "excellent" and I will give it a try with 10 FETs and +-84 volts (+94 for input stage) since I have such a torroid rated at 1.1KVA and a dozen IRFP264s.
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