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Old 6th September 2011, 05:18 PM   #1
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Default Simple Killer amplifier

Im thinking of building one of the Simple Killer amps. specificaly the GB300D, but i need ampere more than Watt. I heard I could get it to deliver more ampere with running less voltage, though it then would be able to give less Watt. Anyone that can explain this more? Must i configured in any other way?

I can go down to about 200W maybe even 150W.

I have a set of Bower and Wilkins CM1 speakers and listen mostly to big classical orchestras and then these speakers need ampere more than watt.

For the other parts i was thinking of using 2x 500Va Triad Magnetics toroids, that is supposed to be able to give 10amp in 48v, but they also custommake lead out voltages. And for Capacitors i was thinking of 2x SKA GB300S boards, and last a softstart as i only have 16amp fuse in the wall shared with other powerreq. stuff...

Tnx
Espen B
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Old 6th September 2011, 05:58 PM   #2
Bone is offline Bone  United Kingdom
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These are 8 ohm speakers and the manufacturer recommends between 30 and 100 watts for them. so any 100 watt amplifier should be OK. I wouldnt go above that else they could be destroyed!
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Old 6th September 2011, 06:13 PM   #3
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lol. I have a friend that ha been running them biamped with 2 rotel rb 1080 for years and they havent been destroyed yet. And even the store that i bought them in want me to run them with a 200w amp. when i think about it all of the people I have asked about when questioned about a suitable amp, they have said i should run 100w at minimum. As I dont run full volume the only difference they told me was mostly control.
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Old 6th September 2011, 06:42 PM   #4
Mooly is online now Mooly  United Kingdom
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Try this to see how much power you really do need,
So how much power do you really need for domestic listening ?

It will give you a ball park figure if nothing else.

B&W's... my 703's are 8ohm (well that's what they say) but actually dip to 3 ohms.
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Old 6th September 2011, 06:59 PM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Trumpetman89 View Post
Im thinking of building one of the Simple Killer amps. specificaly the GB300D,
but i need ampere more than Watt. I heard I could get it to deliver more
ampere with running less voltage, though it then would be able to give less
Watt. Anyone that can explain this more? Must i configured in any other way?

Tnx
Espen B
Hi,

It depends on how if any protection circuits fitted work, if they are fitted.

Simply put the SOA (safe operating area) of your output devices depends
on VxI, max voltage and max current. Reducing rail voltages increases
the max current that is still in the SOA, so essentially optimum rail
voltages depend on the load impedance of the speakers.
With no protection always lower the rails for lower impedance than 8 ohm.

Amplifiers with VxI protection circuits will compensate for lower rail
voltages, allowing more current, amplifiers with simple current only
based protection won't - your typical chip based AV channel.

rgds, sreten.

e.g. as a simple example take a simple basic 100W 8 ohm amplifier.
Applying a 2 ohm load might blow it up.
If you halve the rail voltage then you have a 2ohm 100W amplifier,
as it has twice the current (for same VA tranformer) as power
is Isquared*R or Vsquared/R, so in principle just get it ~ right.
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Last edited by sreten; 6th September 2011 at 07:11 PM.
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Old 6th September 2011, 08:26 PM   #6
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Ok. So if I use half the rail voltage to about 35-40v (its speced for +-75v) on the 300w amp I would have about 75-100w in 8 ohm if 2ohm is 300w and 4 ohm is 150-200w, or am I thinking wrong?

My speakers is nominal for 8 ohm but on B&Ws website it can dip down to 5.1ohm, but i found a review a while ago that said it could go down to 3.1ohm when playing extremely big parts in big orchestra recordings. And I mainly listen to orchestra, when not instrumental jazz.

I didnt think of using any "external" VxI protection if there arent any built into the SKA modules. Should I have this?

I seldom use any high volume when listening but i know for a fact that the speakers need a lot of push and power to show their best. Once I heard a blindtest with two amplifiers of same type and as alike in soundcolour as possible, but one was 50w in 8ohm and the other 150w in 8ohm, and there was a remakable difference.
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Old 7th September 2011, 07:37 AM   #7
Mooly is online now Mooly  United Kingdom
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The impedance dip in a speaker has nothing to do with the type of music or how loud it is.

The dip is frequency dependant,
Loudspeaker Impedance
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Old 7th September 2011, 07:57 AM   #8
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Ok. Then i must have misunderstood.:-\ but will the amp also be more stable in lower impendance when running lower voltages on the rails? And will my estimates be about right when considering Watt and railvoltages? If i get it down to about 100w when running half voltages ill be on the safe side with bower and wilkins's recommended amount of watt :-)

Last edited by Trumpetman89; 7th September 2011 at 08:03 AM.
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Old 7th September 2011, 09:03 AM   #9
repeet is offline repeet  Australia
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Why not ask Greg on his forum, he's always keen to help. I'm pretty happy with the GB150D's I built and his kits are certainly high quality for the money.
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Old 7th September 2011, 09:08 AM   #10
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Nice. I didnt know he had a forum
Tnx
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