Blackstar Repair – HT40


Recently, a Blackstar amp repair was brought to my workshop in Newark. The amp was an HT40 (the Club 40 combo) in working condition, but the owner wanted to try a new set of EL34 power valves in the amp. He selected a matched pair of Tung Sol with slightly higher gain (according to my valve tester) than then outgoing stock Ruby parts.

However, whilst checking the amp over my valve tester highlighted a fault in one of the Sovtek preamp valves, so I’ve replaced this with a JJ ECC83S.


There’s an interesting and fairly unusual element in these Blackstar HT amps – they appear to use a transistor Phase inverter (you can see it in the image at the top), so all the 4 gain stages in the 2 12AX7 preamps are used purely for gain in the preamp circuit. They sound great. This unit doesn’t use the DPR circuit that I mention on that page.

Anyone who knows me as a player, rather than a tech will know I’m a bit of a Blackstar amp fan. I play a Blackstar Series 1 50W head (recently upgraded from a heavy Blackstar Series 1 45 combo). I almost bought one of the these HT40s actually!blackstar-valve-amp-bias

If you have a blackstar repair, please get in touch!