Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on October 02, 2011, 11:38:37 am

Title: Blackstar Artisan 30 Head
Post by: plexi50 on October 02, 2011, 11:38:37 am

This amp sounds muddy as can be at most setting. When cranked it sounds unusable. Why are they using a EF86 tube for the first stage in this amp? Being a high gain amp from what i can see wouldnt it be better to have a 12AX7 in the first stage. It really is lacking any drive and sounds like a blanket over a speaker. Does anyone else have any experience with this amp?

This is the 3rd amp my customer has gotten from them to replace the previous 2 bad sounding ones

Title: Re: Blackstar Artisan 30 Head
Post by: DummyLoad on October 02, 2011, 01:22:35 pm

EF86 is not the first stage, it has a 12ax7 stage preceeding. Search this forum for blackscar. I reverse engineered two blackstar amps - the artisan 30 and the artisan 15.

--DL

Title: Re: Blackstar Artisan 30 Head
Post by: plexi50 on October 02, 2011, 03:50:52 pm

I found a bad EL84 that was shorting out. Another case of should have checked the tubes first. I found your thread DummyLoad  and saved the schematics for both amps. Thanks

Title: Re: Blackstar Artisan 30 Head
Post by: DummyLoad on October 02, 2011, 05:37:01 pm

now that you have replaced a bad tube, has your opinion changed on the sonics? with the EF86 channel i found i liked the bass contour at the next to the last treble setting and the tone about 3/4 up. i also remember them as boomy amps. the all triode channel was my favorite overall. the EF86 channel is not bad, however, IMO the matchless DC30 ckt. is a much better implementation of the EF86.

peace.

--DL

edit: 
those amps bias the EL84s really hot. make SURE you use a well matched quad and watch for red-plating. i modded the one i had after it ate a second quad of tubes. i lost money on that amp. i'll spit on the next one that comes my way. IMO they have reliability issues because of their hot bias. on another forum one member was on his 4th amp. the best thing you can do to that amp is tame the bias with a higher value cathode resistor - mod is in that thread and on the schematic.

Title: Re: Blackstar Artisan 30 Head
Post by: plexi50 on October 02, 2011, 06:42:12 pm

Yeah i feel like a dummy for not checking them first. I like the bass contour. The amp is boomy. Yes i will remember to watch the new tubes for redplating when i get the new ones in. The has it's own flavor. Why do some amp builders bias thier amps too hot? It just stands to reason that it would be better to bias them on the colder side rather than full throttle

Title: Re: Blackstar Artisan 30 Head
Post by: macula56 on October 05, 2011, 05:13:25 am

I searched for your previous thread and all that comes up for Blackscar is this thread. has it been removed?

Title: Re: Blackstar Artisan 30 Head
Post by: John on October 05, 2011, 05:54:27 am

http://www.el34world.com/Forum/index.php?topic=11923.0 (http://www.el34world.com/Forum/index.php?topic=11923.0)

Should be it.

Title: Re: Blackstar Artisan 30 Head
Post by: PRR on October 05, 2011, 09:38:15 pm

> all that comes up for Blackscar is this thread.

"Search this forum for blackscar."

DL can't type right. BlackSTAR, light in the night sky, not the old soldering-iron wounds on our typing fingers.