Valve bias - Your opinions

[bum]

Hi there, I have a Blackstar HT Stage 60 which I really like.
I'd like to put some nicer tubes in there but I am now reading about the amp needing biasing and that I should take it to a certified Blackstar shop.
So, I guess my question is, how do you guys approach this? What went from a simple swap has now gone to taking my amp 50 miles and leaving it at a certified shop.

I'm really interested to hear peoples opinions on this

 

[JCarno]

When I got into tube amps, I knew nothing about them accept to turn them on, off and play them.
Then I started hearing about biasing power tubes and thought, "oh my, I'll never be able to do that!!"
So I started doing some searching and reading and went and bought myself one of these:Dual Bias Tester Probe for Vacuum Tube Guitar Amplifier by AMP-HEAD
I've never taken any of my amps to a tech for biasing. So not only has the tester payed for itself, I also have the satisfaction of making sure it is done right and to my liking.
Do your research on your particular amp and I'm sure you'll be able to do it yourself.
I can't stress enough to research research because if done incorrectly, it can cause more problems than it's worth. Also, always buy "matched" tubes.
Good luck and have fun!!

 

[JohnnyN]

I got me a probe and a couple of multimeters, so I can do it myself. Taking the necessary precautions to avoid being electrocuted with high voltage of course

 

[kevinpaul]

I did not bias for years because I did not know about it. I would change tubes and off we went. Now I have a bias prob set and test, adjust and worry. I like it before when I was just in the dark and things worked fine.

 

[JCarno]

I got me a probe and a couple of multimeters, so I can do it myself. Taking the necessary precautions to avoid being electrocuted with high voltage of course

Oh yea, you'll need a good multi meter too

 

[JCarno]

I did not bias for years because I did not know about it. I would change tubes and off we went. Now I have a bias prob set and test, adjust and worry. I like it before when I was just in the dark and things worked fine.

What do you worry about? It's kinda set it and forget it. I do recheck every now and again just to make sure there hasn't been any drifting from the tubes breaking in.

 

[bum]

Thanks for the replies, it was pitched to me as some kind of voodoo, I didn't even know you could buy a tester.
I'll have to read more, now I know that it is doable!

Edit: I was looking at these:

https://www.watfordvalves.com/product_detail.asp?id=3011

In your honest opinions, would I even need to do the bias if they are specced out for the amp?

 

[JohnnyN]

Thanks for the replies, it was pitched to me as some kind of voodoo, I didn't even know you could buy a tester.
I'll have to read more, now I know that it is doable!

Edit: I was looking at these:

https://www.watfordvalves.com/product_detail.asp?id=3011

In your honest opinions, would I even need to do the bias if they are specced out for the amp?

I think Fender have (or had) colour codes on their output valves (for amps with fixed BIAS resistors), so when replaced with same colour code no need to replace the BIAS resistor.

But most often - and particularly with aftermarket valves you have to check and adjust if necessary. BIAS can be set far from ideal even from the factory these days.

 

[sonar]

You don't need a probe and I'd pass on one unless it can read both ma and plate voltage, which very few do. A digital multi meter and a little math will do the same thing. If you're not into math there are free online calculators.

If you really got into amps and biasing you'd be better off buying a used scope.

The most important part is knowing safety precautions. Reading voltage could potentially be the most dangerous part of servicing tube amps.

 

[cybermgk]

Thanks for the replies, it was pitched to me as some kind of voodoo, I didn't even know you could buy a tester.
I'll have to read more, now I know that it is doable!

Edit: I was looking at these:

https://www.watfordvalves.com/product_detail.asp?id=3011

In your honest opinions, would I even need to do the bias if they are specced out for the amp?

Depends on the amp.

Some Amps require a resistor to be changed to adjust the bias.

Others, place an adjustable resistor, a small pot or pots to adjust. It is these latter that are not to hard to adjust with a bias probe.

From what I have read the HT Stage 60 uses a bias pot.

 

[bum]

OK, cool thanks guys.
I may get the kit and have a place fit them, this is all a little beyond my skill level with electronics (zero)

 

[JohnnyN]

OK, cool thanks guys.
I may get the kit and have a place fit them, this is all a little beyond my skill level with electronics (zero)

Yeah better safe than sorry, and it does take some research to get the knowledge
Maybe a bit of trial and error too, but there is no room for that when it comes to safety precautions!

 

[cherrysunburst00]

I'm too intimidated to mess with fixed bias amps (with the exception of Carr amps which are simple enough that I would try). Cathode biased for me all the way

 

[THDNUT]

Bias, schmias, just put the tubes in and go. The worst that can happen is your tube life is shortened a little bit. Tubes don't cost that much these days. If the bias current is a little high your amp will be louder.

 

[EndGame00]

I don't know if Blackstars amps have a bleeder circuit which discharge the filter caps when the amp is powered off.... If it doesn't, you're gonna have to discharge them yourself before touching any of of the amp's inside components....

 

[cherrysunburst00]

I LOVE that cavalier attitude. I really dig AZ as well as...TEXAS!!

Pleased to be your (slightly eastern) neighbor

Bias, schmias, just put the tubes in and go. The worst that can happen is your tube life is shortened a little bit. Tubes don't cost that much these days. If the bias current is a little high your amp will be louder.

 

[JCarno]

Bias, schmias, just put the tubes in and go. The worst that can happen is your tube life is shortened a little bit. Tubes don't cost that much these days. If the bias current is a little high your amp will be louder.

And if it's too low it will sound like ****!!

 

[bum]

Yeah. I'll pay someone to do this.
I don't want to die, but more importantly I don't want a quieter amp

 

[frankv]

Since we are talking about biasing tube amps I have a set of tools that I would loan out if anyone is interested. PM me and we can work it out. I have the plate voltage measuring tool and I have the dual bias tool for current. All that is need is a multimeter.

 

[JCarno]

I just noticed that the tester I linked to is different than the one I have.
Mine does have a switch to check the plate voltage.
Apparently they stopped adding that feature.
Mine is the Amp-Head Dual Bias Tester MPD. I can't seem to find it on the site anymore.