130 watt valve amp

[mentalmuso]

I have a 130 watt valve amp for guitar, and it only has one 12 inch 8
ohm speaker in it.
i wanna add an extension cab to it, which has two 12 inch 8 ohm
speakers in it.
The amp can be switched from either 4ohm or 8 ohm. i understand with
the configuration of having three speakers at 8 ohms i am not going to
be able to achieve a 4 or 8 ohm load.
Any suggestions? can i run an odd ball impedance like 6 ohms?

[Phil Allison]

"mentalmuso" > wrote in message
oups.com...



** Kiwi Groper Alert !!!!!!!!!!


>I have a 130 watt valve amp for guitar, and it only has one 12 inch 8
> ohm speaker in it.


** Not a Music Man HD130 ?


> i wanna add an extension cab to it, which has two 12 inch 8 ohm
> speakers in it.
> The amp can be switched from either 4ohm or 8 ohm. i understand with
> the configuration of having three speakers at 8 ohms i am not going to
> be able to achieve a 4 or 8 ohm load.
> Any suggestions? can i run an odd ball impedance like 6 ohms?


** Just run the 4 ohm extension cab alone.

Bound to be well louder than the one in the amp.




......... Phil

[Ian Iveson]

mentalmuso wrote

>I have a 130 watt valve amp for guitar, and it only has one 12 inch 8
> ohm speaker in it.
> i wanna add an extension cab to it, which has two 12 inch 8 ohm
> speakers in it.
> The amp can be switched from either 4ohm or 8 ohm. i understand with
> the configuration of having three speakers at 8 ohms i am not going to
> be able to achieve a 4 or 8 ohm load.
> Any suggestions? can i run an odd ball impedance like 6 ohms?

What about the power distribution to the speakers? Won't you end up with 80 per
cent of the power going to the single speaker?

Perhaps you should consider connecting just one of the speakers in the
extension?

cheers, Ian

[Patrick Turner]

mentalmuso wrote:

> I have a 130 watt valve amp for guitar, and it only has one 12 inch 8
> ohm speaker in it.
> i wanna add an extension cab to it, which has two 12 inch 8 ohm
> speakers in it.
> The amp can be switched from either 4ohm or 8 ohm. i understand with
> the configuration of having three speakers at 8 ohms i am not going to
> be able to achieve a 4 or 8 ohm load.
> Any suggestions? can i run an odd ball impedance like 6 ohms?

The only simple safe way to use the amp is with the single 8ohm speaker
in the amp in the cab connected to the 8ohm outlet,

OR

leave the speaker in the amp cabinet disconnected and
use the two speakers in the external cabinet connected in parallel and
both connected across the
4 ohm outlet, which gives a 4 ohm load for the 4 ohm outlet.

Using all 3 speaker in parallel gives a load of 2.7 ohms and when
connected
to the 4 ohm or 8 ohm outlet may produce smoke and silence from the amp.
Too low a load will cause the amp to fry itself, so don't parallel all
your speakers.
( Don't be tempted to series ALL the speakers either, since the external
speakers
won't have the similar impedance as the amp speaker. And the sound won't
be very loud
since the total Z would be 24 ohms, and Loudness relates to P = Vsquared /
Z. )

Alternatively, the two speakers in the external cab could be SERIESED to
make a 16
ohm load which could then be paralleled with the amp speaker of 8 ohms to
make a total load
of 5.3 ohms which can be connected to the 4 ohm outlet.
This would give you a quiet foldback speaker...

This means the amp speaker will produce most of the sound.

If the power rating of the 2 external speakers is higher than the single
amp speaker then only use
the pair in the first option with 2 in parallel without the amp speaker;
they will most likely go louder than a single
speaker.

Double check what you are doing, since if you don't understand, or think
you do
when you really don't, then smoke will be a very probable result.

Patrick Turner.

[Lord Valve]

Hey, Metamucil - this ain't the psychic Friends Network.
You got a MAKE and MODEL NUMBER there, Sparky?
You'll get much better answers if you do.

Lord Valve
Not Clairvoyant

mentalmuso wrote:

> I have a 130 watt valve amp for guitar, and it only has one 12 inch 8
> ohm speaker in it.
> i wanna add an extension cab to it, which has two 12 inch 8 ohm
> speakers in it.
> The amp can be switched from either 4ohm or 8 ohm. i understand with
> the configuration of having three speakers at 8 ohms i am not going to
> be able to achieve a 4 or 8 ohm load.
> Any suggestions? can i run an odd ball impedance like 6 ohms?