Bassman 100 biasing?

[ThatBassistDude]

So I've got a question... I took my bassman 100 to band practice for the first time today, and I don't quite think I'm getting enough clean headroom as I should be getting. I just got it back from getting new caps on Monday and just a basic tune up, as well as a new set of matches JJs tubes. I was told that since the tubes were matching, I probably wouldn't need to get it biased. But seeing as though I'm getting a Lemmy like tone with both channel volumes at about 6, I think I do need them biased. I've been told that was a bassman 100, I should have tons of loud clean tone... What do you guys think?
Here's the amp in question....
Thanks![ATTACH]313416

[mattbass6945]

did you have them done at a shop or by a tech? seems to me they should have biased them if they were installing power tubes.......

[ThatBassistDude]

Originally Posted by mattbass6945

did you have them done at a shop or by a tech? seems to me they should have biased them if they were installing power tubes.......

I got it done by a really well knows tech around north Texas that works at a music shop close to me. And the tech didn't put the tubes in, they came in after I got the amp, and he was going to charge about $100 to bias them.

[mattbass6945]

if you don't mind me asking, who was it? i'm in ftw.....

[T-Bird]

Hi.

Originally Posted by ThatBassistDude

I've been told that was a bassman 100, I should have tons of loud clean tone...

It's all very relative obviously, but whomever told You that has IMHO entirely different view about the quantity of a ton than most of the people who have or has had the said amp.

I've had both the 100 and the 135 and neither was very loud if kept clean. Not even with 412+215 Marshall stack.

Originally Posted by ThatBassistDude

What do you guys think?

Swapping power tubes without biasing them is a job half done if You ask me.

Tubes being matched by some fashion or other does not negate the need for checking/re-setting the bias.

Regards
Sam

[mattbass6945]

i'm no engineer, but it is my understanding that anytime the power tubes are replaced, they should be biased.

[mattbass6945]

beat me to it sam!

[ThatBassistDude]

Originally Posted by mattbass6945

if you don't mind me asking, who was it? i'm in ftw.....

Forget the guys name, but the tech at Craig's Music in Weatherford.

[ThatBassistDude]

When I do get the tubes biased, can I expect more clean headroom than I'm getting now?

[mattbass6945]

ahhhh.....ok. no experience with him. they're tubes, they're gonna break up when pushed. lemmy's tone is pretty hairy though! get those puppies biased and rock that amp!

[B-string]

Six (out of 10) is pretty much were you should be out of clean amp power. That said I have in my experience found JJ 6L6's to distort pretty easy (and require higher negative bias). Winged "C"'s would have been a MUCH better choice for staying clean. Any NP (New Production) tube set IMO should be biased as the old set point was for the more generous valves of old.

[ThatBassistDude]

Thanks for all the help guys, I'll definitely get this thing biased ASAP. I'll playing it at lower volumes in the meantime be bad for it? Sorry, I'm kinda new to all tube gear, I've played mostly hybrid stuff...

[Tim1]

I have owned several Bassman 100s and 135s. It was always my experience that they ran out if clean headroom far too early for any significant volume.
Now the new Bassman 100T is a totally different story........
And yes, I have always believed that you should rebias the amp when changing power amp tubes.

[B-string]

Originally Posted by ThatBassistDude

Thanks for all the help guys, I'll definitely get this thing biased ASAP. I'll playing it at lower volumes in the meantime be bad for it? Sorry, I'm kinda new to all tube gear, I've played mostly hybrid stuff...

If you see any discoloring of the plates of the tubes (the black metal part you can see from all sides inside the glass) stop using the amp. If the plates stay black you are okay to run the amp and the use will get you a more stable adjustment when it is corrected.