Marshall Valvestate - speaker and stuff

[chagzuki]

Please forgive the vulgar display of ignorance that follows. I really know next to nothing about electronics.

I have a marshall valvestate 8040 and I've read on other sites that the stock speaker is crap. It's a 4 Ohm speaker and I've read in the marshall handbook that when connecting an external speaker one shouldn't use anything below that in impedance. Therefore I assume I can replace that speaker with a Vintage 30 8 Ohm: is that correct? I've also read that the Vintage 30 is a very 'efficient' speaker and therefore will be louder than the stock one. Is this something different from speaker sensitivity? The sensitivity of the stock speaker and the v30 is approximately the same and I can't think what that statistic would refer to other than the loudness of the speaker.

I'm also seeing contrary views on whether or not the single valve is in use in the clean channel. The common view seems to be that it is only employed in the boost channel, but not everyone agrees. I don't understand circuit diagrams so perhaps someone here wouldn't mind taking a look at this:

www.drtube.com/schematics/marshall/8040.gif

and clarify that issue.

Cheers and also hello.

[JohnH]

On those earlier Valvestates, the valve is only used on the Overdrive channel, and the diagram confirms that. You can use an 8Ohm speaker in place of 4Ohms, in a solid state power amp like yours, and the Vintage 30 is a good one, but I dont know how the sound will compare to the stock speaker.

I have a V30 in my DSL401, a big improvment, and it got even better after I'd cranked it for a couple of hours to break it in.

cheers

John

[chagzuki]

Thanks for the fast reply.

As for the sensitivity thing, am I right in thinking that if the speakers are of similar sensitivity they ought to be close in loudness?

[JohnH]

Yes Id say you are right about sensitivity and loudness. The V30 is particularly loud compared to many other speakers due to its large magnet, with a sensitivity of 100db (sound level measured in a standard way with a particular power and at 1m distance).

On the other hand however, if the current speaker is 4Ohm, a new 8Ohm speaker will not draw as much power from the amp, meaning it would be slightly less loud.

My guess is that these two effects will balance out and you wont notice much difference in overall loudness.

John

[chagzuki]

That's good as in this case louder is not better. Thank you, appreciated.