Blackstar HT Club 40

[sunshine_bassman]

I have a Blackstar HT Club 40 that the customer wants a cleaner clean sound. We calculated 27 clean watts before breakup. Is that par for the course on a 40 watt amp?

[nickb]

I have a Blackstar HT Club 40 that the customer wants a cleaner clean sound. We calculated 27 clean watts before breakup. Is that par for the course on a 40 watt amp?

Most guitar amps are measured at 5-10% THD. Clipping is quite evident at those levels so 27 watts clean seems about right. Your customer can either get a more powerful amp, fit a more efficient speaker and/or add a second speaker.

[g1]

I tend to agree with nickb, but I'm going to be contrary here and say maybe something is wrong.
It's not hard to get 40W clean out of a pair of EL34, so why not. I know it's a different model, but I measured a HT20 Studio yesterday and got 19W before clipping. To me, it doesn't make a lot of sense to have a 20W version, and a 30W version.

Are you looking at it with a scope? If so, set it up so you are getting 40W clipped (measure with AC RMS voltmeter) and post a pic of the scope image.
Also, the literature says it should be biased for 50mV across D36. (something has to be plugged in to the input jack when biasing)

[The Dude]

What does the amp's B+ measure?

[SoulFetish]

I have a Blackstar HT Club 40 that the customer wants a cleaner clean sound. We calculated 27 clean watts before breakup. Is that par for the course on a 40 watt amp?

Can you post a schematic there, Sunshine?
(couldn't resist )
If there is an effects loop return, you can try and inject signal into this junction. Traditionally, these bypass some of the preamp stages and can provide a more direct input to drive the output stage in case you are experiencing preamp clipping. Even in some "clean" channels, the preamp will clip before the output stage.
Of course, the logical question then becomes "how can they quote a power output which really can't be achieved in the normal operation?"
I'll tell you!.. I really don't know.