Biasing a Blackstar Artist 30 amp. (fixed-bias)

Discussion - Artist Series amplifiers. The New Classic.
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angelfire
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Joined: Fri Sep 23, 2016 1:33 pm

Fri Sep 23, 2016 1:47 pm

Reference Artist 30, is there a trimpot for bias adjustment? If so, where is it located? Thanks for any help you can offer. Best wishes, Chris.

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thephantum
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Joined: Wed Jan 29, 2014 6:42 pm
Location: Virginia, United States

Fri Sep 23, 2016 10:02 pm

If it's similar to other Blackstar tube amps it has two trimpots: one for the overall bias adjustment and the other to balance that adjustment between the output tubes. They are most likely labeled "BIAS" and "BAL".

angelfire
Posts: 5
Joined: Fri Sep 23, 2016 1:33 pm

Sun Oct 02, 2016 3:43 pm

You are absolutely correct with regard to two trimpots labelled bias and bal, on the circuit board, approx. in the middle of the board. They look like small cogs, with a screwdriver slot.They are a sort of cream colour. To bias this amp I understand dissipation is 30 watt, plate voltage is 490, setting is 36-38ma for 60% average bias setting. With regard to the bal pot, does this equalise both tube readings exactly after setting the bias pot as close as it will go?
Chassis removal is very straightforward for biasing and valve changing.

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thephantum
Posts: 1273
Joined: Wed Jan 29, 2014 6:42 pm
Location: Virginia, United States

Sun Oct 02, 2016 4:05 pm

Correct. The Bias pot allows you to dial in the total bias current across the pair and the Bal pot let's you balance that Bias between both tubes. Keep in mind, that calculation is per tube: so your overall bias reading should be 72-76 mA, with 36-38 mA at each tube.

Personally, I think those numbers are a little cool. I would go warmer (closer to 70%)....but again, that's just a personal preference.

angelfire
Posts: 5
Joined: Fri Sep 23, 2016 1:33 pm

Mon Oct 03, 2016 11:06 pm

Thankyou very much for your input & guidance. I`m new to blackstar amps & am very pleased with this Artist. Modulation works well through the loop & I am using an old orange lovepedal eternity in the front end for boost/gain as required. One small point, Blackstar might put in the user manual that to activate power amp the input socket needs to have a lead plugged in. It fooled me into thinking the amp was faulty with no output as I was warming up the valves on standby & only connecting guitar with lead just before use. Hence, no output for a couple of mins while the power amp sorted itself. Blackstar deal with this under ` no sound ` in their support forum, but it would help if it were in the book. Once again, thanks for sharing your knowledge. Best wishes, Chris.

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