Just got new replacement tubes (2 x JJ EL34L power tubes 2 x JJ 12AX7 ECC83 preamp tubes) so I could get rid of the old ones. I'm really eager to just start playing since I got a new tremolo in the mail. Is it necessary to bias the tubes with a multimeter?
I have no idea what tubes your amp comes with stock but if you replace with the same type (i.e. el34 to el34 or 6l6 to 6l6) then you should generally have no problems with biasing. If you want the absolute best tone out of your amp you may want some minor adjustments but there isn't always a need.

And preamp tubes dont get biased so youre set.

Hope I helped and a senor member please check my facts here.
*insert witty statement here*
Quote by ginger ninja102
how does one bias an amp anyway?

I have a Bugera that has a convenient bias knob. Don't know how Blackstars work in the biasing realm, though.
Quote by ginger ninja102
how does one bias an amp anyway?

generally an amp will have a nice knob like the aforementioned Bugera, a fixed bias like the 6505+ 112, or an adjustable bias via internal trim pot somewhere on the undersideof the chassis such as many older fenders. (someone feel free to correct me if I'm wrrong on that one) But adjusting the knob/pot adjusts how hot or cold the tube runs. Hotter generally sounds better and konks out your tubes faster, while colder generally does the opposite. Too far either way causes problems though, which is why you should know your specific tubes ideal range and be able to test it with a multimeter. Fixed bias is stuck for your one stock tube. Unless modded with one of the other options.

EDIT: I'm *assuming* the blackstar has an internal trim pot, and could very likely be wrong.
*insert witty statement here*
Last edited by metalhead352 at Mar 12, 2012,
I'm pretty sure all Blackstars are Cathode based so there is no actual need to bias them. They can be made to sound better by biasing them though and I'm fairly certain there are internal trim pots for this.
Well reviews say that the stock are 2xECC83's and 2xEL34's so I guess mine are fine to go. If anyone has any more information please post other than that thanks to the people who have already posted.

Much appreciated man
I have yet to deal with a Blackstar amp, but a quick google search lead me to this site: http://blackstaramps.forumotion.com/t915-ht-40-bias-information

It seems though that all Blackstars are cathode biased (I cannot confirm this). So, any bias adjustment would just be for sound, not protecting tubes.

A little more info I just came across. At least in the HT-5, only the preamp is cathode based. Dave says the output tube should be properly biased by a technician.