Changing Tubes on Vacuum Tube Amplifiers : How to Set Bias for Right Power Tube of Amplifier

Posted by  in Friday, March 26th 2010   
Topics: Pro Audio    
expertvillage asked:


Learn how to set the bias for the right power tube when changing the tubes on a vacuum tube amplifier in this free video. Expert: Jeff Naylor Contact: www.Mtroniks.com Bio: Jeff Naylor is the owner and operator of Mtroniks Engineering in Mesa, Arizona. Filmmaker: Eric George

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25 Comments

andy92811 said in March 27th, 2010 at 7:12 pm    

What should the mA rating be on each tube?

SirCorn said in March 28th, 2010 at 10:35 am    

I’ve gotta a dummy load for ya…

imasspeons said in March 31st, 2010 at 6:04 am    

How about biasing a real Marshall amp instead of one of the newer ones with cheat ports on it?

Cwildenradt said in April 2nd, 2010 at 12:47 am    

I just had to do it. I HAD to see how you could post a 59 second video about biasing power tubes.

I mean, seriously?

zlutz814 said in April 4th, 2010 at 8:26 am    

Expert villagers are black toothed idiots…
thanks for the 0:59 second waste of time

markyellowseries3 said in April 4th, 2010 at 4:50 pm    

expert village **** ***.

this vid is called ‘ How to Change Tubes on Vacuum Tube Amplifiers : How to Set Bias for Right Power Tube of Amplifier’

It neither told me how to change tubes, or set the bias.

epic fail.

i might as well post a video titled ‘ how to build a time machine’ then show a shot of how i made my cheese sandwich, just like expert village (idiot).

domdabombabc said in April 7th, 2010 at 8:03 am    

Do you have to do this when you put new tubes in the amp or can you just put them in?

RORYzRIGHT said in April 9th, 2010 at 1:06 am    

good one rex ill remember that next time im climin off your mom. ive already done it *****.

AgaricusRex said in April 10th, 2010 at 7:59 pm    

leave the tech to the men

AgaricusRex said in April 12th, 2010 at 8:42 pm    

bitches should be in the kitchen

RORYzRIGHT said in April 15th, 2010 at 7:13 am    

I have an 1970 ampeg svt tube head.Can anyone point me to a video that shows how to set the bias on it . Thanks!

reginaldbowlsiii said in April 16th, 2010 at 3:53 pm    

No kidding.. Expert Village should be banned from YouTube.

opel47 said in April 17th, 2010 at 5:21 pm    

the blu-ish glow inside the tube happens to be ions that are reacting with air that has gotten inside the tubes….this would indicate a less than perfect vacuum but like imprint audio said, this is not abnormal, but if you havent replaed your tubes for a while and you play often, you might want to change them for preventive maintenance’s sake. out.

endserenading00 said in April 18th, 2010 at 11:17 pm    

it is fucking impossible to watch these videos in order. how frustrating.

stigcoma said in April 22nd, 2010 at 8:44 am    

dude this is cool…nice clip.thx

ImprintAudio said in April 23rd, 2010 at 6:36 pm    

Depends on who you talk to. Most people wait until their tubes start to make funny noises. Pre amp tubes can last years and power tubes depending on bias setting last a year or so, depending on how often the amp is used.

oldGNRfan23 said in April 25th, 2010 at 7:19 pm    

How often do you need to replace tubes? Is it pretty often or…? Any help there would be great. Thanks in advance!

ImprintAudio said in April 28th, 2010 at 10:49 am    

Great video bro!

ImprintAudio said in May 1st, 2010 at 3:55 pm    

Blue is normal and not all tubes exibit color so NO you don’t need to replace your tubes. You only need to replace them if you hear hiss, pops, or other noises.

6661VengeanceHarlot said in May 5th, 2010 at 12:19 am    

i have a B-52 ST-100 and i opened up the back to heck the tubes. and when i turned it on, i noticed that all the power tubes turn a blueish color. and one of them didnt light up blue at all. does that mean i need new tubes??
please help??
im not a pro with tube amps..

aziker said in May 7th, 2010 at 5:31 am    

Great job, Jeff! People should be lining up on Main St. in downtown Mesa to use your expertise.

insektuo said in May 10th, 2010 at 8:33 am    

this *****!!

Charliemusslewhite said in May 10th, 2010 at 4:21 pm    

Sorry, but I didn’t get that. You said there is NO adjustment pot at the right side, so what did happen? The current adjusts itself magically? Not very well made how-to video.

ectskater said in May 13th, 2010 at 10:43 pm    

Oh yeah, the amp sounds great for 15 min, then gets brown sounding. Hmmmmmm?

ectskater said in May 16th, 2010 at 3:56 pm    

Thanks for posting this info.
I have a Hughes and Kettner tube 50 head that I am replacing all of the tubes in it.
It has (2) EL34′s for the output, and (3) 12ax7, the head has reverb, so I imagine one of the tubes is a driver for that signal path.
In any case, I would like to know if you have any tips on doing the bias to it, I can’t find any info on the spec for it from H&K, so I am hoping if it can’t be biased,(fixed?), that the tubes will be OK.
God Bless- Joshua

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