So, lets discuss bias point for a minute.

[black_out]

So, I just got some tubes in the mail for my Laney that is llloonnnggg overdue for a re-tube. Just wondering...what are you dudes biasing your tubes at? I've been biasing mine @ 70% but I'm thinking about trying to go a little hotter...like maybe 75% or something. How far can I go before I'm risking immediate damage to my head? I don't really care if I shorten the life of the tubes. I could probably swing re-tubing twice a year if I really had to, assuming the tone was better.

[RAGER]

Somebody will probably point out that 70% is a general starting point but to really get exactly what you want you'll need a scope which I don't have so I start @ 70% and use my ears.  But to answer your question about longevity, I think that is subjective to the quality of the tubes you;re using and what the b+ is and what that tube can handle and some other factors somebody more versed will point out.

[black_out]

Somebody will probably point out that 70% is a general starting point but to really get exactly what you want you'll need a scope which I don't have so I start @ 70% and use my ears.  But to answer your question about longevity, I think that is subjective to the quality of the tubes you;re using and what the b+ is and what that tube can handle and some other factors somebody more versed will point out.

What could the scope tell me? Anything that my Webber Bias Rite couldn't? Sorry, I know just enough about this shit to be dangerous. Appreciate the advice.

[RAGER]

I'm kinda the same way.  But the scope will tell you precisely where the crossover is.  the mathematical way isn't really that accurate but a general starting point.  But that may be splitting hairs as I've never used a scope and heard the difference.  Techs with scopes scoff at our method.

[Hemisaurus]

Not true, I use a scope, and I use a meter, and you can even use your ears.

What you see on a scope is the perfect bias point, in the original sense of bias. Biasing was to turn the tubes on to the point that crossover distortion is removed, that being the distortion when the positive going tubes switch off, and the negative going tubes turn on, or if you prefer the pushing tubes stop pushing and the pulling tubes start pulling. If you read the tone-lizard article, you'll see it's that little dingle where the signal crosses the zero line. You'll also read about the fact true pentodes probably shouldn't be biased that hard, and you need a little nick there.

Nowadays, people use crossover distortion as part of their tone and true biasing is probably only of interest to the hi-fi guy.

I read an intersting article about tube pre's with a variable heater voltage, I wonder if the same could be applied to amps, you could get a wealth of tonal difference from that as well, I'd imagine.

To answer the original question, opinions vary, and equipment varies, some output transformers could melt if you run them full on (or hard) too long (ie. what you get from overbiasing) as they are only designed to peak at that power for a few seconds. If you want a tone difference, try underbiasing instead

[black_out]

Not true, I use a scope, and I use a meter, and you can even use your ears.

What you see on a scope is the perfect bias point, in the original sense of bias. Biasing was to turn the tubes on to the point that crossover distortion is removed, that being the distortion when the positive going tubes switch off, and the negative going tubes turn on, or if you prefer the pushing tubes stop pushing and the pulling tubes start pulling. If you read the tone-lizard article, you'll see it's that little dingle where the signal crosses the zero line. You'll also read about the fact true pentodes probably shouldn't be biased that hard, and you need a little nick there.

Nowadays, people use crossover distortion as part of their tone and true biasing is probably only of interest to the hi-fi guy.

I read an intersting article about tube pre's with a variable heater voltage, I wonder if the same could be applied to amps, you could get a wealth of tonal difference from that as well, I'd imagine.

To answer the original question, opinions vary, and equipment varies, some output transformers could melt if you run them full on (or hard) too long (ie. what you get from overbiasing) as they are only designed to peak at that power for a few seconds. If you want a tone difference, try underbiasing instead

I guess I really just want it to break up more. I can dime this thing and it barely breaks up at 70%.

[black_out]

I guess I shouldn't say barely breaks up..it's just not as raunchy as I'd like.

[Hemisaurus]

Overbiasing isn't going to help you here, you need more gain or tubes with an earlier breakup in your preamp.

I can suggest ways you can gain up each stage, if I knew what amp we were talking about, but it's probably a whole lot easier for you to order some early breakup tubes. I don't know where you get your tubes, but a lot of dealers offer early breakup or high gain tube sets, eurotube for one.

https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=118&sub_category_id=149

[VOLVO)))]

Since we're talking about biasing, do I have to check the mA of each socket, or can I adjust it using the reading from one? I finally got tubes for my 800... kt77s, mmmm.

[Hemisaurus]

I know I told you before, in one of these damn threads

You check every socket, and adjust for an average, watch the video again.

[black_out]

Since we're talking about biasing, do I have to check the mA of each socket, or can I adjust it using the reading from one? I finally got tubes for my 800... kt77s, mmmm.

Hemi can probably answer your question better than I, but I think that depends on how closely matched your tubes are. I check all four, but the tubes I get from tubedepot.com always come out within less than a mA of each other. I would imagine that if they weren't so closely matched, you would have to find a balance between the tube that reads the highest and the tube that reads the lowest.

Let me know how you like those kt77s. I've been thinking about throwing some in the Laney just out of curiosity.

Edit: Hemi beat me to the punch.

[black_out]

Overbiasing isn't going to help you here, you need more gain or tubes with an earlier breakup in your preamp.

I can suggest ways you can gain up each stage, if I knew what amp we were talking about, but it's probably a whole lot easier for you to order some early breakup tubes. I don't know where you get your tubes, but a lot of dealers offer early breakup or high gain tube sets, eurotube for one.

https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=118&sub_category_id=149

Never tried the JJs in my amp, but everyone that I know who's used them wasn't impressed.

This might all be null anyway. I picked up a 5751 preamp tube to throw in the v1, too. I popped that in the other day, and while I haven't had a chance to really lay into it, it's changed the whole character of the amp for the better. Before, I would dime the master volume and keep the gain around 2 or 3 because it sounded harsh to my ears with the gain up any higher. The more I think about it, the addition of the 5751 will hopefully allow me to crank the gain more with out it sounding fizzy and harsh. I'm definitely gonna pick up some more 12ax7s to experiment with in the v1 spot now, too. Shit just to see.

I was always aware that changing the v1 could have a profound impact on an amp, I just never experienced it first hand. used to be I had to fucking WORK to get a decent eq out of this amp...it was always glassy, and it was kind of a struggle to balance it out. Now there isn't a bad sound to be found out of it. I guess I'll see how it sounds Sunday, which is gonna be the first chance i get to really turn it all the way up, and make a decision from there.

[VOLVO)))]

He doesnt check 'em all in the video, dickhead!  im just making sure. Why arent you on vacation?

[Hemisaurus]

Am too, its just too damn hotbright now