# Marshall Class 5, Extension Speaker...



## Bruiser74 (Jan 29, 2010)

Hi,
The Class 5 has a 16 ohm extension speaker out...
I have a 2x12 cab rated at 8 ohms that i want to 
use with the Class 5.
Can i do this or is there some risk?
Also/or, can the Class 5 be modded to have an 8 ohm speaker out??

Thanks!
B


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## JSX/6505 (Nov 18, 2007)

No, you can't plug an amp with a higher impedance rating into a cab with a lower impedance rating. 
Not sure if if the amp can be modded. Maybe the speakers can be rewired to 16 ohms? Another person may be able to help with that.


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## greco (Jul 15, 2007)

This topic comes up quite often.

It is my understanding that that you can have an impedance mismatch without risk *unless* you run the amp at loud volumes for exteded periods of time. The main concern is that you might shorten the life of your output tube(s) to some extent.

You could mod the amp by putting in a transformer of the correct specs and that is tapped for 4, 8, or 16 ohms impedance. Possibly there are other mods that could be done, I'm not sure.

You could also change out the speakers to be able to wire the cab to 16 ohms. I assume that you have either 2 x 4 ohm speakers or 2 x 16 ohm speakers in the cab now.

Wait to see the comments of other forum members. 

Cheers

Dave


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## Bruiser74 (Jan 29, 2010)

Thanks guys, i wouldnt normally even try this as i have enough common sense not too fool around
tube amps and electrical in general. I have read on the MLP forum some opinions that suggest exactly
what you said dave...keep the volume down and it should be ok.
my 2x12 cab is my main cab (actually only cab) and i dont want to mod it, but would rather look into\modding the
Class 5 instead. There are 2 16 ohm speakers in there now, 60watts each.
I will check with the amp guy and see if he can do it fairly cheaply.

Thanks!
B


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## greco (Jul 15, 2007)

Bruiser74 said:


> Thanks guys, i wouldnt normally even try this as i have enough common sense not too fool around
> tube amps and electrical in general. I have read on the MLP forum some opinions that suggest exactly
> what you said dave...keep the volume down and it should be ok.
> my 2x12 cab is my main cab (actually only cab) and i dont want to mod it, but would rather look into\modding the
> ...


If you end up deciding on getting a new transformer that is a suitable replacement and tapped for 4, 8, and 16 ohms on the secondary, you will always have lots of options for the future. However, the cost of the transformer and installing it might be a prohibitive. Please let me know if your amp tech has any other ways of solving this.

However, lots of folks run tube amps and cabs with mismatched impedances and don't think twice about it. Tube amps are apparently very forgiving.

BTW...What is it like to "live in Paradise" (so the old saying goes).

Cheers

Dave


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## ThePass (Aug 10, 2007)

I like these little amps......was looking at one in waterloo that was green. Very nice.


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## tbellisario (Apr 14, 2010)

Actually it is the output transformer and not the power tubes that suffer with an impedance miss match.
Most amps can take a 100% miss match with no effect. What this means is that if you have a 16 ohm output you could go down to an 8 ohm load but not 4 ohms.
If your 2 x 12 cabinet has two 16 ohm speakers they are wired in parallel to make an 8 ohm load.
If you start messing with the main speaker output whatever you do don't turn on the amp without a speaker attached even for a few minutes. Very bad for output transformer.
Some people are really parinoid about this, its up to you.


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## Bruiser74 (Jan 29, 2010)

Living in Paradise is alright lol.
I will let you know what the tech says about it, he may have some things kicking around... or maybe not.
The amp is decent as it, but starts to 'fart' with the volume up...and it is quite loud. I think it would
be really good with my cab. I really like it at moderate volumes with an OD pedal or two in front, great tones with a TIM or OCD.
As you may gather, i am no tube amp expert, just like to play em...but i know what NOT to do with them
so i never turn one on without a speaker attached and i dont touch anything inside! lol
Cheers
B


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