Blackstar Ht-5 Guitar Combo

Blackstar's Artisan amps, reviewed in Guitar & Bass last summer, have become firm favourites with a wide variety of players, both famous and less so. The HT-5 is following in their footsteps, but instead of the wide-open plug-in-and-blast applications favoured by the bigger models, it's catering to the growing demand for very low power valve amps, popular in home studios based on hard-drive recording gear. There's hot competition from directly-connected PC modellers, but many recording players favour the amp/mic/A-to-D method for its authentic Sun Studios liveliness, even if results are a little less predictable. So small valve amps are very much today's order of business, and recently bigger amps are also sporting power selectors that allow half-power or less, some going below the one-watt mark.
Far from being a simple single-ended version of the Artisan 15 - which, given the 15's popularity, it must have been tempting to produce - the HT-5 is a brand new design with some original and interesting technical touches. It incorporates in its preamp much of the circuitry from the HT valve-driven pedal series, coupled to a novel power stage that uses an unusual twin triode push-pull arrangement for power rather than the conventional single-ended pentode power valve. The reason, Blackstar says, is that it sounds closer to a big class AB amp being driven to its limit, and there's a good deal to support their philosophy. Push-pull has an inherently different harmonic spectrum to single-ended operation in overdrive, and can sound less nasal and narrow-banded. Those seeking clarity without resorting to feedback circuitry often advocate the use of triodes, although these valves demand more from the power supply for a given amount of output power. Interestingly the HT-5 uses an exotic valve, the 12BH7, better known as the power-driver pair in the Ampeg SVT bass amp, in a fixed-bias set-up with a high supply voltage that has fed into the amp's name. Triodes used as output valves are also notoriously drive-hungry, and Blackstar has adopted a Music Man/Peavey-like configuration of driver transistors to provide enough swing where a conventional driver valve would lack the required oomph.