Artist 30 valves.

Discussion - Artist Series amplifiers. The New Classic.
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Posts: 1
Joined: Thu Jan 11, 2018 12:45 am

Thu Jan 11, 2018 12:54 am

Hi, just bought an Artist 30 yesterday.
Are the valves all biased to exactly the same amount in the factory or will some be hotter and some colder?
I was wondering what make are the valves in the Artist 30?
When it comes to changing them, how to I bias it? Taking it out of my flat to a tech isn't an option.

Thanks, Stefan.

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

Thu Jan 11, 2018 4:31 am

I don't own one so I don't know what valves are in there. Most Blackstars are coming with TAD's from the factory, so that would be my guess in the Artist as well.

As far as actually biasing the amp it's just like any other Class AB amp in push pull config. There's lots of threads on here describng how to do it (I've written a few of them).

The catch is that there are no true bias test points inside Blackstar amps, so I highly recommend using probes. That way you can get accurate measurements and eliminate guesswork.

Now, in my experience, Blackstars are biased to a set amount for that particular model. So they take the theoretical plate voltage of that amp model, calculate a conservative percentage of max dissipation and set bias to that.

However, the actual plate voltage will be vary from amp to amp and tube to tube. So while bias might be set the same across that model, how hot or cold the individual amps are will vary.

For example, my HT20 was biased from the factory at exactly 50mA per bottle. So they assumed a plate voltage of 300V and set it to 60% of max plate dissipation...which is considered cool. Same thing with my HT50. It was set at 35mA per bottle, which assumed a plate voltage of 450 and a max dissipation of 60%.

In both cases the amps ran at higher plate voltages, bu still tended to be on the cool side (less than 70%).

...but don't assume they set yours at 60% of theoretical. My HT-5 was set at 6mA from the factory which is 75% of theoretical. So it all depends on the model.
WARNING: Tube amps contain LETHAL voltages, even long after they have been unplugged. If you are not familiar with how to safety work on high voltage circuits, then PLEASE don't die...take it to a tech.

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