The Definitive valve / tube change guide

[joshukov]

boxofspiders.....can you remember some of the reasons he recommended not biasing? just curious as I've never heard that before. Also if anyone else could chime in what harm can be done without biasing...can it hurt the amp or just the tubes themselves?

[majikmojo]

yes...i would like to hear the reasons also
i can think of none

[boxofspiders]

He mentioned that on lower wattage amps that it becomes less important. I think he said something about the tubes being designed to carry a much higher wattage. I'll have to dig deeper into my crappy memory to remember the rest of the conversation, sorry about that. He also said, "just make sure you watch for the browning of the tube label . if it gets to brown too fast we might need to bais the amp." And he said to use my ears, if something doesn't sound right then we'd need to find out why and do some biasing. When I turned it on, it sounded great. The popping and growling of my old failing tubes was gone.

[gypsyblues73]

I read an article from an "techie" type a couple of weeks ago where he was getting into the reasons why and/or why not to bias an amp, and although I can't remember all the details (especially since most of the tech-speak went way over my head) he essentially stated that for a lot of practice-size/medium-size amps, biasing is completely unnecessary and people have come to perpetuate this myth that all amps have to be biased when you change the tubes, when actually they don't.

[flyingbanana]

Hi everyone. I thought I would chime in since I just replaced all the tubes in my HT 40. I did not check the bias before the swap, but afterward, the bias was around 40. Do obviously I needed to make the tubes run hotter. I adjusted the bias knob until I got to 51, and backed it off until it was a hair over 50. The tubes I used were the ones from Mesa Boogie. I used their EL34 str 447's and also their 12ax7's. The amp kicks some serious tone out now.

Even before it began sounding like a lousy fuzz pedal, I could tell it was sounding a bit weak. If the original tubes were actually running cool, that might explain a lot. Now, the gain is smooth and the bass is tight. Really opened the amp up. I may try rebiasing a bit hotter...maybe to 55 or so and see how things run. I think there's room to play with.

To cap off, I think these things always need to be rebiased. You never know when your amp might be running weak and under performing. Crank up the bias to the recommended figures, but be safe doing so. If you plan carefully, and take precautions when sticking your tester in there, you'll be ok.

Ymmv obviously, if there's any doubt, just take it in to have it done. It's a 5 minute job.

[majikmojo]

interesting your one of the few on here i heard of running the amp a little hotter banana...
most folks seem ok with the factory bias but i think it is a little cold
i run my stage 60 hot as well and it definitely made the gain sound better to me too...
didn't seem to effect the clean channel that much but the OD channels sound better to my ears

[flyingbanana]

interesting your one of the few on here i heard of running the amp a little hotter banana...
most folks seem ok with the factory bias but i think it is a little cold
i run my stage 60 hot as well and it definitely made the gain sound better to me too...
didn't seem to effect the clean channel that much but the OD channels sound better to my ears

From what I gather, the Mesa tubes...however rebranded they are, are what Mesa wants to put in their own brand of amps, because that is the only way they can reasonably guarantee that the amps will run on the side of cold versus to hot and burn things out. That said, I wonder if their tubes will also cause other amps to run cool. So...if people are throwing these in their amps and not getting awesome tones, they are going to need to warm them up to at least recommended specs for the particular amp. In the case of the HT40, the few places I have read about it say about 50 on the bias. Some circuit boards will say 50 on them, but mine didn't say anything. Not sure if it was an earlier model, or if they quit putting the specs right on the boards.

I'm exhausted right now...hope I made even a little sense.

[MikeD]

OK...since it´s coming to be the time that my tubes need changing I´v been looking for some opptions that might work for me...as said the original author of the threads tube combo is exactly what I´m looking for sound wise...classic rock...AC/DC OD1 and a better OD2 but I´ve had issues finding a tube dealer stocking the tubes he uses here in europe......so heres what I´ve put together

http://www.karltone.co.uk/index.asp?function=CART

winged c´s in the pwer
JJ´s in V1/V2
Elektro harm. in V3

any thoughts and or reccomendations to where else to find tubes would be greatöly appreciated

[boxofspiders]

OK...since it´s coming to be the time that my tubes need changing I´v been looking for some opptions that might work for me...as said the original author of the threads tube combo is exactly what I´m looking for sound wise...classic rock...AC/DC OD1 and a better OD2 but I´ve had issues finding a tube dealer stocking the tubes he uses here in europe......so heres what I´ve put together

http://www.karltone.co.uk/index.asp?function=CART

winged c´s in the pwer
JJ´s in V1/V2
Elektro harm. in V3

any thoughts and or reccomendations to where else to find tubes would be greatöly appreciated

That's a good selection of tubes. Only thing I would change would be to skip the Electro Harmonix in V3 and go for another JJ or Jan Phillips 5751 (to tame the insane amount of distortion).

[MikeD]

would the 5751 go in v3 replacing the 82 then.....little bit of a puzzle trying to figure out tubes so I figured I´d go the sae route and go by the numbers on the tubes

[quote=)
"boxofspiders"]

OK...since it´s coming to be the time that my tubes need changing I´v been looking for some opptions that might work for me...as said the original author of the threads tube combo is exactly what I´m looking for sound wise...classic rock...AC/DC OD1 and a better OD2 but I´ve had issues finding a tube dealer stocking the tubes he uses here in europe......so heres what I´ve put together

http://www.karltone.co.uk/index.asp?function=CART

winged c´s in the pwer
JJ´s in V1/V2
Elektro harm. in V3

any thoughts and or reccomendations to where else to find tubes would be greatöly appreciated

That's a good selection of tubes. Only thing I would change would be to skip the Electro Harmonix in V3 and go for another JJ or Jan Phillips 5751 (to tame the insane amount of distortion).[/quote]