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From: William Sommerwerck on 21 Jul 2010 21:53
>>>>> 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.

>>>> A small increase is better than nothing.

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

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

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

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?


From: tm on 21 Jul 2010 22:09

"William Sommerwerck" <grizzledgeezer(a)comcast.net> wrote in message
news:i288c2$65c$1(a)news.eternal-september.org...
>>>>>> 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.
>
>>>>> A small increase is better than nothing.
>
>>>> No, it isn't. Not when it requires a lot of work, and will be only
> slightly
>>>> audible.
>
>>> Fitting resistors is hardly a lot of work. I just need someone who knows
> their
>>> stuff, to answer my original question.
>
>> So, William, what is the correct answer here (value of resistors)? I'm
>> curious now, too.
>
> 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?
>


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





--- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: stratus46 on 21 Jul 2010 22:18
On Jul 21, 5:56 pm, "j r powell" <nos...(a)invalid.xy> wrote:
> "William Sommerwerck" <grizzledgee...(a)comcast.net> wrote in message
>
> news:i283ln$l13$1(a)news.eternal-september.org...
>
> >>> 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).
>
> >> I have, but then the audio output is too quiet for my requirements.
>
> > 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.
>
> A small increase is better than nothing.

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.

G²
From: William Sommerwerck on 21 Jul 2010 22:28
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


From: stratus46 on 21 Jul 2010 22:38
On Jul 21, 7:28 pm, "William Sommerwerck" <grizzledgee...(a)comcast.net>
wrote:
> 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.

You are VERY WRONG on this.

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

Virtually a certainty.

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

This is good advice.

G²
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