Originally Posted by markw51
Yes and its the same trebly sound. So that's a signature sound of Vox AC?
The AC4 is quite different to the AC15 is quite different to the AC30.
The common characteristic is no negative feedback, otherwise they are very different amp circuits. The AC30 is not a 30W version of the AC15 (although it started out as two AC15 in one box :) This no-NFB gives richer harmonics and a characteristic mid-range, definitely not hi-fi. A number of British amps went this way.
The AC30 is the one that got the Top Boost (TB), it can give it a breaking-glass quality but it does not lack bass. The AC15 was always intended as a stage amp, the AC4 as a little practice amp. Part of the AC4 problem is lack of grunt, at higher volume we need far less bass boost (it's our hearing). It is a perennial problem of small amps, the better ones don't suffer it - they are voiced correctly.
One thing that may be important is the speaker. An ext cab is generally designed to be played loud and not voiced to bottom-end at low volume. A trebly little amp may benefit from a woofy speaker like the Greenback, which is unusual in that it is rich and plummy at low volume but tightens up and has a clear top-end at high volume. Makers generally fit a cheapish high-volume sound-reinforcement stage speaker, which sound great at stage volume but have little bottom-end at low volume.