Postby ClubAndCountry » 09 Oct 2009, 06:58
I'm not sure I like the idea of hardwiring the speaker like this either. Two reasons:
First, it prevents you running anything - like an attenuator - between the amp and the internal speaker, and it prevents you using the amp's own internal speaker via the headphone jack as a built-in attenuator as SteveD suggested. (This used to be a feature on the Studio 15, too.) Second, by running the speaker signal through the switch in the extension speaker jack and also the speaker/headphone switch, there are now two potential contact failure points instead of only one if the speaker simply plugged into a jack and needed to be manually disconnected to run either headphones or an external cabinet. It's not a big issue, but jack switches are a common cause of problems on many amps - they're definitely less reliable than the contact between a jack and a plug. It would have been simpler - and saved the cost of the switch, although also adding the cost of the plug - to just provide two jacks, one for the speaker and the other for the headphones/low power output.
Not a big deal, I just think it's preferable to maximise the options while minimising the number of contact points in the signal path. Any tech will confirm that bad contacts in jack switches are a substantial proportion of all repair work - easy to fix, but annoying. And in cases where it involves a speaker-level signal in a valve amp, potentially serious - if it does go bad and leave the circuit open you could blow the output transformer. (This is a known cause of OT failures in the DSL/TSL amps where the switch in the 16-ohm jack interrupts the signal path when using the 8/4-ohm jacks, for example.)
Presumably it would be possible to remove the hardwiring, fit the speaker with a standard cable and plug, and plug it into the extension speaker socket (or the headphone socket).