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Paralleled Amplifier Wiring

Hi, I have a small stereo amplifier which came with two tiny 4ohm 3watt speakers. I'd like to combine the two channels of the amp in order to drive one, slightly larger, 8ohm 4watt speaker. The amp is of the non-bridgeable type, so I assume parallel wiring would be required - combining the two outputs together. I have read that small resistors are required in parallel configuration, to enable proper current sharing between the amplifiers, as without them the two amps would fight each other and overheat. Can anyone tell me the correct values for these resistors, and where they should be placed?

thanks, jamie.

--

PS. If your name is Dave Plowman, do not reply.
Reply to
j r powell
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How very rude ... d :-\

Arfa

Reply to
Arfa Daily

How very rude ... d :-\

Arfa

Reply to
Arfa Daily

Well... he follows me around usenet and trolls me.

Reply to
j r powell

On 7/21/2010 6:55 AM j r powell spake thus:

slightly

resistors

between

Have you tried simply using a pair of 8-ohm speakers with the amp? Chances are they'd work (less power, but shouldn't harm the amp).

--
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with the flaunting of well-defined muscle, wrapped in flags.

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Reply to
David Nebenzahl

I have, but then the audio output is too quiet for my requirements.

Reply to
j r powell

I'm not being sarcastic -- but how do you know that paralleling the outputs will produce a significant increase in power? Ignoring the very pertinent question of how to do this /correctly/, the most you could get is a 3dB increase, which is plainly audible, but hardly a large increase.

Reply to
William Sommerwerck

A small increase is better than nothing.

Reply to
j r powell

No, it isn't. Not when it requires a lot of work, and will be only slightly audible.

"Forget about the whole thing." -- The Lady from Philadelphia

Reply to
William Sommerwerck

Fitting resistors is hardly a lot of work. I just need someone who knows their stuff, to answer my original question.

Reply to
j r powell

On 7/21/2010 6:10 PM j r powell spake thus:

So, William, what is the correct answer here (value of resistors)? I'm curious now, too.

--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)
Reply to
David Nebenzahl

slightly

their

I don't see where I'm obliged to provide an answer, but here's what I believe, to the best of my understanding...

Assuming that both channels have the same output impedance, and the output levels are closely matched, then (if the outputs are directly paralleled) there will be /no/ current flow from one channel into the other, and the total amount of current that /could/ be delivered will be doubled. But if the load impedance remains the same, there will be no increase in current flow and no increase in volume level. You would need a speaker of half the impedance to gain more power.

I think that's correct. Anybody want to agree or disagree?

Reply to
William Sommerwerck

Well, you sure don't want to use resistors to match it. Any gain would just be converted to heat.

ASSuming the impedance's were the same and you paralleled the outputs, you would need a 1.5 to 8 ohm transformer to match the speaker.

But I agree with the first premise, it's hardly worth the 3 dB you might gain.

T

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Reply to
tm

puts

nt

The increase will be 0. Changing from 4 ohms to 8 will cut the power in half because the voltage stayed the same and the current cut in half because of the impedance change. Paralleling the amps raises current capacity - which you don't need - and does nothing to increase the voltage. In fact, your resistors will reduce it slightly. You need a bigger amp.

G=B2

Reply to
stratus46

"j r powell"

** The only way to go here is to use "bridge mode".

Parallel wiring of the outputs is not only 100% useless it will almost certainly destroy both amplifier channels.

** Complete crap.

There is such of lot of it on the net you know.

.... Phil

Reply to
Phil Allison

I made a mistake -- for some reason I assumed this was a tube amp. (I don't know why.)

Regardless, if the output levels are closely matched, one amp /will not/ pump current into the other. But to gain any increase in power, you'd have to use a lower-impedance speaker.

There is also the possibility that, even with the levels matched, the amps might not "like" looking at each other.

"Buy a decent amplifier that delivers the power you need." -- The Lady from Philadelphia

Reply to
William Sommerwerck

On Jul 21, 7:28=A0pm, "William Sommerwerck" wrote: > I made a mistake -- for some reason I assumed this was a tube amp. (I don't > know why.) >

You are VERY WRONG on this.

Virtually a certainty.

This is good advice.

G=B2

Reply to
stratus46

Why? You haven't changed the output voltage. If the amps are solid state, their source impedance is much lower than that of the load, so there wouldn't be any significant increase in current flow (that I know).

Reply to
William Sommerwerck

.. and, assuming both outputs are _exactly_ in phase,

Jonesy

Reply to
Allodoxaphobia

The power limit might not be the amplifier output stages, but the common power supply. So, you'd just connect to the left channel and ignore the other.

Alternately, you could transformer-couple and put the left and right channel outputs in series (not parallel), to get good drive into an 8 ohm speaker. Transformers, though, aren't cheap. Doing this only gains you 3 dB, it's scarcely worth the effort.

More efficient speakers (two of 'em, not one) is the preferred solution if you don't like what you've got.

Reply to
whit3rd

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