150 Watt / 8ohm @ 30V or 55V with good efficiency? - diyAudio
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Old 20th February 2005, 02:04 PM   #1
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Default 150 Watt / 8ohm @ 30V or 55V with good efficiency?

hi!

i already searched A LOT around the forum but couldn't find something specific.

i'm going to build an amp for my subwoofer with about 150 watt into 8 ohms. class b or ab with a fet design.

with chipamps it was easier for me to find something because there are a few popular chips. but with solid state it's really difficult to choose something(n-fet, mosfet, hexfet, bipolar fets .....). to this end i hope someone of you can help me

what i want:
- 150 W / 8 ohms
- 30V or 55V power supply (i can't get any powersupplies between these values or above 55V). i think 55V would be ok?
- good efficiency because it's better with cooling and i also don't need a huge power supply. also costs are not so high then.
- no kit ...

perhaps someone knows a design for me(perhaps also with a pcb layoud)?
aussieamps or project 68 (sound.au.com) seems interresting to me... but i don't know if they would have a little much power for me. 180 watt or so would also be ok

thx
greez
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Old 20th February 2005, 02:07 PM   #2
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150 watt in 8 Ohm on 30 Volts ?
Bridged ?
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Old 20th February 2005, 02:57 PM   #3
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hm....i think i would rather use a non-bridged thing.

i also think 55V supply is better for that application?!

this amp will get a monoblock for active driving the sub
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Old 20th February 2005, 03:03 PM   #4
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30 volts is only good for less than 100 watts/8 ohm.

Without a second powersupply the max you can expect with a fet output stage on a 30 volt supply is 70-75 watts.
With a 55 volts powersupply 180 watt will work, or a bit more.
Depends on the size of the transformer.
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Old 20th February 2005, 03:06 PM   #5
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You can try Rod Elliots new p101

www.sound.westhost.com

thats a mosfet amp which at 55v+- dc should get you about 150 watts.

also, if you can reach him, Anthony Holton's av400 would suit you as well

www.aussieamplifiers.com

but i don't know if he's receiving emails right now...good luck

-Matthew K. Olson
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Old 20th February 2005, 03:10 PM   #6
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Hi didifeed.

This will doo the trick too:
NAIM 250 clone
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Old 20th February 2005, 03:27 PM   #7
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ta get 150W(sinus) on 8ohm you need 63V (unregulated) rail voltages, made by a 90V-CT trafo.

+/-55V is enough for 115W(sinus) on 8ohm.

there is no hearable difference between a 115W and 150W power, so you can do the trick with the +/-55V rails.
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Old 20th February 2005, 03:44 PM   #8
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i thought the 30 and 55 volts are ac values ?
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Old 20th February 2005, 04:54 PM   #9
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first of all thx to all of you

hm....should be ac.

115 is a little bit low. i thought of some spare watts. so 150 or a little bit more would be fine.

has anyone tried these amps at 55/30 volts? bcause i'd really like a design that works..... i don't really like the try(trail) and error principle

greez
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Old 20th February 2005, 06:42 PM   #10
edl is offline edl  Hungary
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hi!

you, wrote that your psu's are giving 30 and 55volts.

so:
-are these values AC voltages of a trannys secondaies?
-or are they stabilised psu's?
-or they coming after a graetz-bridge and filter caps?
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