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Old 19th April 2014, 10:49 PM   #1
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Default Output power - high voltage or high current?

Hi!
I consider myself as a newbie, although I've been making DIY amps for some time. Last night, I started thinking about voltage vs ampere at the output (to the speaker) on the amplifier.

As I've understood it; the voltage will push the cone out or in, and the ampere is how much power or force it have. That means you'll get much more "punchy" and quick bass with more amps.

I've seen some huge chipamps at ebay, capable of delivering ~500w at 8ohm. they have a maximum operating voltage of +- 40v, but will deliver huge amounts of current to the speaker. What if you have an 18" long stroke subwoofer. wouldn't +- 40v be way too small for such speaker? I know that the current is the thing that "really" matter, but you can't max out you speaker if the voltage is too low?


Is it "better" (on large speakers) to have +-36v with a peek of 10A to the speaker, or +-60v and a peek of 6A?
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Old 19th April 2014, 11:20 PM   #2
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It is the speaker impedance and power that you use to work out what amplifier you need.
Amplifiers usually come in watts and into a certain impedance(s).
i.e. 500 watts RMS into 4 ohms.
So for this you can use 2 off 250WRMS speakers that are 8 ohms in parallel.

There is the age old and controversial question about amplifier power and speaker power.
Personally I prefer to make the speakers much more powerful so they are harder to destroy with big volume from the amplifier.

Last edited by nigelwright7557; 19th April 2014 at 11:22 PM.
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Old 19th April 2014, 11:48 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

Understand resistance R = V/I, V = IR and I = V/R.

Power is VxI = I^2R = V^2/R = watts.

60V and 6A implies a load of of 10R.

36V and 10A implies a load of 3.6R.

The power is the same but the latter in reality is
far more practical with real speakers impedances.

rgds, sreten.
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Last edited by sreten; 19th April 2014 at 11:50 PM.
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Old 20th April 2014, 12:03 AM   #4
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Hi
I see a couple of very different threads to the original post.

On the pure electronics aspect of voltage or current issues for an amplifier, the previous poster is correct. It is great that you are building stuff, to move more into the understanding of design it seems to me that a deeper understanding of electronics would be great for you.

When I was a kid there were some good intro books I read, though they would be horribly outdated now, "understanding electronics" or some such. I would expect other members could recommend some online material.

I suggest this as in a power amplifier/speaker system. Volts, amps and watts are intimately related mixed in with a real mess of the speaker impedance.

On the subject of "sound" that is a whole different thing. A very subjective domain for which I rather doubt a technical basis exists - though even that might be disputed. I would endeavour to keep subjectivism separate to objectivism -or design.
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Old 20th April 2014, 12:10 AM   #5
jcx is offline jcx  United States
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some multiway loudspeaker crossovers cause impedance dips at certain frequencies - dipping to 1/2 the name plate speaker Z is impolite but happens, even worse infamous examples exist

but the current demand with special signals that pump the energy storing impedances and then abruptly reverse phase can be up to 6x the name plate Z calculated I

a basically competent audio amp needs to at least be able to drive 2x the current of the nominal power rating at the rated speaker load Z - briefly if not continuously
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Old 20th April 2014, 12:30 AM   #6
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The ratio of voltage to current doesn't really matter, the only thing that matters is the amount of power that is going to the speaker. High voltages and low currents are usually used in places where there's a great distance between the speakers and the amp.
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Old 20th April 2014, 11:25 AM   #7
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Thank you so much! Of course it depends of the speaker impedance!
my old JVC amp was capable of delivering +-60v to my 4ohm subwoofer, but after I replaced it with a +-35v gainclone, I can play louder, and the stroke is longer because of higher current.
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Old 20th April 2014, 12:12 PM   #8
tvrgeek is offline tvrgeek  United States
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Hans,
Hans, You still have a bit of understanding to do.
Pl ayes louder" What does that mean? For a knob setting it is louder? That may be only the gain of the amplifier. There are many many factors here. All things are never equal.

The stroke is longer because a higher VOLTAGE was applied to the coil. It will draw whatever current is required to supply that voltage unless the power supply is not capable of supplying that much current, in which case the voltage drops and the amplifier clips.

There are many good starting out tutorials on electronics on the WEB. Old books are fine as the laws of physics don't change. It is a bit too involved to learn in a Q&A forum.
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Old 20th April 2014, 12:20 PM   #9
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I'm sorry. The old JVC amp couldn't deliver much current, compared to to my gainclone. I have a 10" subwoofer, and with the gainclone the stroke is much longer that with my old JVC amp. I guess the stroke was smaller on the JVC because it couldn't deliver enough current (it was rated from 6-16 ohm, and my sub is 4 ohm)
Since my subwoofer is only 4 ohm, it will draw more current, and a high current amplifier is well suited for this subwoofer I guess.
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Old 20th April 2014, 12:28 PM   #10
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Quote:
Originally Posted by hansibull View Post
Hi!
I consider myself as a newbie, although I've been making DIY amps for some time. Last night, I started thinking about voltage vs ampere at the output (to the speaker) on the amplifier.

As I've understood it; the voltage will push the cone out or in, and the ampere is how much power or force it have. That means you'll get much more "punchy" and quick bass with more amps.

I've seen some huge chipamps at ebay, capable of delivering ~500w at 8ohm. they have a maximum operating voltage of +- 40v, but will deliver huge amounts of current to the speaker. What if you have an 18" long stroke subwoofer. wouldn't +- 40v be way too small for such speaker? I know that the current is the thing that "really" matter, but you can't max out you speaker if the voltage is too low?


Is it "better" (on large speakers) to have +-36v with a peek of 10A to the speaker, or +-60v and a peek of 6A?
Hi,
What you are talking about is DAMPING factor. That is what gives you punchy and quick bass. Do not contaminate your head with voltage and current. Looking for good amp with good bass? Search for Damping factor around 1000. In general, damping factor is output resistance, in more general is how amp can operate the driver and reduce all parasite oscillation.
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