You can't damage the amp with speakers rated at higher power.

You didn't speak directly to the technician, did you? There's nothing to support such a claim and I would disregard it. It must be a misunderstanding between technician and support guy.

As far as impedances go, there's no impedance matching for modern solid state amps (it's just pointless and expensive). If the amp says 8 ohms, that means plugging in a 4ohm speaker can overload it, which will sound nasty after certain power output. If it's got separate outputs for different speaker impedances than I would suspect current feedback and you would need to match the labels.

Thanks phatt, quite like the website. I think this link in particular http://www.lenardaudio.com/education/13_guitar_amps_3.html should be a "Read before you post" as it will save a lot of explanations.

Quotewhy the 1x12" would be the choice of most people

What people choose is very subjective and rarely related to anything tangible. I've come to the conclusion that most people define sound with very ambiguous terms, which in my mind brings only confusion. I haven't got a different way to describe it though, so I guess we'll have to manage somehow.

I would assume it's the bass response, since that's the benefit of a larger speaker. If you look at the frequency response of jensen mod speakers http://jensentone.com/mod_index.php and compare the mod6-15 and mod12-110, the lower cut-off frequency isn't that much different in the 12", but the impedance peak is more prominent. Since valve amp (and some ss) gain depends on speaker impedance, the gain around peak is higher for the 12".

Also I would expect the 12 inch to be louder, but you can find large speakers with 90db spl.

Don't forget the large speaker looks cooler

And here in the UK the smallest speaker I could find was the 6" jensen (everything else is 8 inch minimum and I don't think it would be much different in the US).

This does look great. I'm a bit of a minimalist and I just love small guitar head amps.

I made a small "travel" cab 26x23x17cm (10x9x6.5 inches) and fitted it with the same 6 inch Jensen MOD speaker. I just love this little speaker. It's great value for money, so I strongly recommend it!

I haven't played it with a valve amp yet, but I did try it with a current feedback ssd amp. The low E string sounds just great...

My main worry with brushless DC motors would be EMI... haven't tried anything myself though.

Has anyone had any experience with that?

I don't understand this at all.

In my view the whole point of solid state amps is to save money. The most expensive components in tube amp is usually the output transformer, which usually costs several times the rest of the components. If you just look on sowter's website, the cheapest one is about £100 http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_PUSH_PULL_OUTPUT_16.html (guitar OTs are cheaper though).

If we disregard the tone effects of an OT (I haven't read a sophisticated article regarding this subject so far), there are two aspects of a tube power amp - overdrive behaviour and output impedance.

The impedance is so EASY to implement in a SS amp (I bet someone's already posted a link to this http://sound.westhost.com/articles/guitar-amps.htm#s3) and is actually widely used.

The other aspect is overdrive behaviour. I've read articles saying that FETs operate like Tubes (which is a stupid statement) and therefore valve circuits can just be copied and components replaced.

What's similair between the two types of devices is that they have very low transconductance and, unlike BJTs, it isn't as strongly dependent on quiescent current (in a BJT gm=Ic/VT and in a MOSFET, for example, above the threshold voltage it is fairly constant).

I tried making a MOSFET gain stage using a BS170 biased with a quiescent current of about 150mA (which is quite high for a preamp). The output waveform (on an oscilloscope, not SPICE) looked pretty much like that of a tube gain stage. But when I played a guitar through it it didn's sound good at all. I decided to look at the spectrum of the output from the gain stage. What I noticed is that there was a strong second harmonic (which everybody goes on and on how desireble and tube-ish it is), but there was also a noticeble 9th harmonic. I tried to find an ideal overdrive value, but there wasn't one. It just doesn't work with single discrete mosfets.

I've wandered off a bit. My main question is - what's the benefit of all this?

A downside will be that all of your return currents will be carried by the ground connection and not sinked by the centre tap of the transformer. The neutral is for safety, it's not suppose to carry currents. The ground is connected to the centre tap just to offset the windings. In a bipolar power supply the centre tap sinks return currents from the load.

If you need more info I think http://en.wikipedia.org/wiki/Ground_and_neutral clarifies the situation.