Blackstar Artisan 15 - warmer tone

[Bernd]

Well, to put an end to this thread:
Finally I have changed nothing except the speaker which I had done before.
My settings that I find usable (guitar plugged directly into amp) :
channel I, low input at mid volume for fender amp style tones, ch. II, high input at full volume 15W and a marshall powerbrake to reduce the volume a little. In this way the sound is warmer and not so bad, mainly my drummer likes it. It could be a little more creamy to my taste.

Bernd

[zenlife05]

Hi Guys,
I'm new here. I arrived here looking for an answer about the type of biasing in the Artisan 15. I have read everything I could Google up and got four answers. The problem is that they are all different. This is without a doubt the most knoweldgable group so far, so, Is the A-15 cathode biased, fixed or adjustable?
Thanks for being here, and my tech will love the schematic.
BTW, I replaced the tubes with new production Tung-sol Gold pins in the pre amp and new production mullards in the power section and it lost some of the bright edge that it had when I bought it. I had a cabinet made for it and loaded it with a G12H30 and a Blue Alnico.
The thing sounds amazing, warm rich and creamy.

[J M Fahey]

Answer it yourself.
With amp on, no signal, what DC voltage do you read on power tube cathodes?
And on grids?
If grids negative, cathodes grounded: fixed bias.
If grids grounded and cathode positive: cathode bias.
We expect voltages consistent with tube types; we are talking on the order of 20V, not millivolts.
Hope it helps.

[zenlife05]

My Apologies,
I must have wandered into the wrong place here. I have zero background in electronics. I can replace my tubes, fuses, and speakers, but once the chassis is open, I'm lost.
I was just hoping someone would be kind enough tell me what kind of biasing this amp uses so I would know weather or not I need to take it to a tech everytime I replace the tubes.
Thanks

[guitarmike2107]

Its cathode biased. You can replace the valves yourself but check them to ensure they are not red plating or screens glowing

[zenlife05]

Thank You much for the help. I like swapping tubes to find different timbres, tone and responses and have had no problems, but I read on a tube store site that rebiasing was required for this amp and started worring a bit. I do recall reading somewhere, while looking at this amp, that it's cathode biased. I feel much better now. I 'd hate to do any damage to this gem.

[Bernd]

EL 84 types - Finally I got further

Some time has passed now and I got a little further. I want to share this:

In order to obtain a warmer tone with this amp I started to use it only at full volume and put a powerbrake at the end to reduce the volume. What I didn't like was that the amp was still too touch sensitive, the tone didn't feel good in the fingers.
On my search for a solution I started to look for other types of the EL 84 power tubes: the amp came with Electro Harmonix which give the amp a lot of headroom. My decision for a trial went to JJ's EL 844 which are said to be a low powered version of the EL 84.
And it did give a change: the powertubes seem to be an important part to influence the tone of this amp. The amp sounds a little dirtier now, when being cranked they produce a lot of crunchy highs, a nice singing tone and they give the compression that I was looking for. The tone feels good now in the fingers, the only thing is that the tone is a little thin now.
Maybe someone has other suggestions for EL 84 types with low headroom but a fat tone. I saw that there are not so many on the market.

Bernd

[wickerd]

No definit tried and approved solutions so-far, ii own one and want full rich tone.

A proper compressor/limiter fixes the agressive bite.

Options left to explore now.
Switching the speaker helps, any ideas apart from the canabis rex?
Switching the bright caps /switchable is something definitly worth exploring, i''ll give guitarmike2107 idea a go together with my friend (he's the electrotech)
10n for C6 and C24. from the new plots you can see that those caps affect the low mid roll off point.