How to Bias Your Guitar Tube Amp 

I managed to switch my tubes with this video and set the bias myself. Thanks for being very thorough and giving safety warnings, which I think a lot of videos out here lack. It was actually very easy to do. My amp sounds like new again 👌🏾😄

“I’ve got one hand in my pocket, and the other is biasing.” - Alanis Morrisette

I wanted to drop by and say "thank you" for this informative and easy-to-follow tutorial. This saved me some time on restoring my amp, and I learned something new. Thanks again! :)

EXCELLENT!!! So glad you did this tutorial. I didn’t want to take my HRD to a tech for such a simple maintenance task. You shed light on the mystery.

Thanks for the knowledge, this makes it much clearer for me. I always thought that if I didn't set the bias pot to the "absolutely correct" spot (that could only be derived at through an engineering degree) I would blow the amp up entirely. Thusly, I would until recently only buy solid state amps because I didn't want to get someone else to bias my tubes. Now I am learning to do it myself, and this vid provides a nice piece of the puzzle.

Kennis, want to say thank you for sharing your knowledge on this. I just bought a FHD and it was so flat and dead sounding. Bought a set of matched JJ's and with your help got them biased to were I am so happy now! What a difference :)

Thank you for the education on biasing the power tubes. I have a Hot Rod Deluxe and I'm replacing all the garbage GT's with JJ's (both preamp and power) but never knew anything how to check the bias. Looks simple enough, thanks for the video and safety tip!

Thank you for this! Your short video was more helpful than anything I’ve read in the forums.

super helpful and straight forward video! looking forward to getting amongst the tubes in my deluxe and having a go

Ahh man THANK YOU!! Have been wanting to switch from SS to tube but this whole bias thing kept me from doing so. Finally got myself a HRD iii and could not believe this is all there was to it!! Thank goodness I have the potentiometer!! Thank you!!!!

Good stuff Kennis. I'm acquiring a USA HRD that most likely needs to have a total tube overhaul, and I'm just glad biasing can be done relative quickly and easily. Having no prior experience because all my other tube amps either have fixed bias (Mesa Boogie ROV25) or are self-biasing (THD Bivalve 30), so this video is super useful!

Most excellent! I wish all how-to videos were as well done and to-the-point as this.

really appreciate your effort to make these guides. Very well explained!

Thanks for the tutorial!!! Didn't know it was something I could do by myself...Amp sounds GREAT now!!!

Remember driving thru Mississippi in the 70's. Bias was set high there. Great vid, thanks.

Straight to the point and brought across very well, no Guru secrets like I always thought were involved, Thanx Kennis.

Great vid. All the information I wanted and none of the filler. Thanks for the info.

I love your videos! Very informative, clear, and concise. Thank You!!

Thanks Kennis. Great job making your tutorial easy to understand.

Great video tutorial. I really enjoyed the way everything was explained. Keep up the good work.

Cheers! Seems a lot easier than I expected! Good idea hand in pocket rule.

Thank you for a very instructive video. Changed tubes in my Fender HRDx and set bias to 71....it's like a new amp....

Very explicite, helpful and friendly help sir! I'm changing my tubes for the first time today (Traynor YCS100).

Just a few clarifications .. Unless your amp is horribly defective (and blowing fuses) the circuits ARE already biased .. What you're doing is adjusting, measuring and/or optimizing the existing bias voltage/power dissipation. Secondly, one must be careful with that term "self bias". "Self Bias" DOES NOT means that you can adjust the bias yourself. Self bias is also known as Cathode Bias. It's referring to the the tube creating it's own bias by virtue of the cathode being lifted from ground via a cathode bias resistor. Outside of replacing the bias resistor with one of a different value, you cannot adjust this bias scheme. The other common method of biasing the output tubes is called "Fixed Bias". This method frequently utilizes an internal potentiometer that allows one to adjust the bias voltage to the output tube(s). This is called fixed bias.

Great video for someone who knew nothing about biasing tubes! Thanks!

Great video, really cleared up my confusion with biasing. Thank you.

Thanks! This works for my Fender Blues-Deluxe Reissue as well - same test point and pot locations.

Great video. Exactly what I was looking for. Thank you.

Excellent video - professionally done !!

Awesome info Kennis. Thanks for making this.

You have explained so far better then anyone else.

On an interview the tec guy for Angus ACDC said he runs the valves hot.bias high a bit on the edge...which explains Angus,s eq only on 3 bass treble & mids...great info Thanks...you have saved me a few quid...and amp down time.

Great video! Thank you, for this! About too go bias my hrd, and now i know exactly what too do

Great video! Very informative and easy to follow.

Great video. Fender sets this amp at 60mV. Raising it to 70mV gives a better sounding gain. Higher bias shortens valve life.

That bias point is total cathode current.. A little screen current (5%) is included in that number.. So a number like 70mV at the test point is ~ 66mA plate dissipation for two tubes or 33mA for each tube. The B+ voltage with a cold bias (60mV) is 431V. A little OT loss and you have 429V plate. Multiply Volt with mA and you get the plate dissipation at idle. This is 14.16W or 47.2% of max plate dissipation for a 30W 6L6GC tube.. That is too cold,, you want to be above 50% to avoid crossover distortion. Between 50% and 60% is a good number for the hot rod.. Going higher and you will loose a lot of headroom and spank in the bass.. Lets run the bias to 80mV at the test point.. deduct 5% as screen current = 76mA of total plate dissipation.. Multiply with you plate voltage which should be a little lower as you are drawing more current at idle.. So lets say it has dropped to 424V (80mV) from the previous 429V (60mV). Now you get an idle plate dissipation of 16.11W which is 54% of max dissipation.. That should be a good bias... With the Hot rod deville you want to have a lower mV number at the bias test point as the voltages are higher in that amp.. With 60mV at the test point and correct wall voltages and a pair of 30W 6L6GC tubes you should get around ~484V on the plates.. Doing the same math you get that 60mV is 57mA plate dissipation (I assume 5% screen curent). Plate dissipation is (0,0285A x 484V) = 13.8W dissipation (or if screen current is even lower) around 14W which is 46.6% of max dissipation.. Again a little too cold.. Bring it up to 55% if you have a strong 30W 6L6GC tube..

thanks man , you took some worry out of my life lol now my amp sounds great and has been running good.

Perfect, thanks. Makes sense and I just happen to have a Hotrod Deluxe so I may just tweak before tomorrow's gig.

I've got one of these amps, so this video was very helpful. Thanks very much

Thank you for posting this video. This really helped me feel more comfortable changing out the power tubes from 6l6 to 6v6 for my Hot Rod Deluxe!

thanks for "the hand in the pocket rule", as a self taught electronics experimental person, never heard that one before

Thank you , that was really educational and concise ,, it helped .

Very Nice introduction to biasing. Thanks!!

Thanks for this... I recently purchased a new Fender Blues Deluxe to replace a 15 year old model that quit working. The new one breaks up/distorts at 1-2 where as the old one would begin to break up at 4-5. I need the amp to play clean (jazz/traditional blues) with my hollow body guitars. This was a good video, a starting point to get the new amp set up to match the old one.

I'm gonna bias my Fender HotRod Deville 212 tonight, thanks to this movie!!

Thanks, very informative and good job explaining.

That was very informative. Thanks!

Great video. Exactly what I needed to know. Thanks for posting. Subbed.

Nice video as always thanks Kennis

Thanks for the good instructional videos

Very easy to follow. Thank you! Never BIASed my Hot Rod Deluxe in 4 yrs I own it. The meter was showing 55. Damn!!

Best bias video on ytube. Also helps that mine is the blues reissue which is basically the same amp your biasing.

i just got that very amp second hand , your video was very helpfull thaks alot!!!!

Thanks for clear information!

Really helpful video. Thanks!

Great video. Thank you. Just getting into this

sooo awesome. definitely help me a lot!

very useful video. That is just great. Thanks a lot.

thanks dude, this really helped!

Two hands will direct a lethal dose of current thru your heart and stop it. You are done for.

Greatly done and very informative

Cool, man, thanks. Appreciate the vid. Don't forget, people, you can get a serious shock if you touch the wrong place back there.

Man, Ive been paying 75$ an hour for someone to do this. Thanks man, this is simple.

thanks Kennis. I've been playing guitar for years but just take the amp for granted. recently I bought a Blues Jr to run in stereo with my HR DV because i felt things were "lacking". great combo though... Changing out my stock power tubes for the first time as well so I'll look to see if my HR DV 212 has the bias option. Sound like I may have some fun. great info, cheers.

This is really easy! Thanks

Helpful. Good video, thanx

Thank You great tutorial.

this is great, thank you for this video

very good video, thanks for posting

Great video. Thanks!

Big thanks for that video!

Really helpful. Thank You

"What does that even mean" ... a question which should be addressed pointedly at all irritating muso/tech know-it-alls. A handy tutorial as well. Thanks.

Hello Kennis. Thanks for your very well done informative videos that you do I just got a Bugera v22 and it's got an RCA jack with a biasing potentiometer feature in the back that's accessible without having to open the amp up Upon reading forums and watching a specific how to video on biasing the V22 I have to say that I'm now more lost than I was before getting all of this FYI with the exception of your explanation here I am just wondering if you might be able to simplify for me whether or not the feature on my amp is an effective way to bias it and if there's a general setting bias number for my specific amp or tubes (el84s)once I do decide to upgrade my power tubes Again I really enjoy and appreciate all you do here on youtube so naturally superior as a teacher! Better yet "a mentor"

That works out real well if one has an adjustment and test point. I haven't looked in my Carvin so I can't say how it's set up, everything sounds fine but it is a older amp so I expect to be servicing it soon, my Bugera is suppose to self baising.

Apart from most of this being incredibly 'Average Joe' standard, I did cry a little when he switched the power and standby switch immediately one after another, then stated to let it warm up. Let it warm up with the the power on and the standby off.

Great video! Thank you!

thanks for you info straight to the point A+

Thanks for the awesome video. Nice having amps with only a pair of power tubes and three pre amp tubes. Saves a lot of $$$ come tube time ahem Mesa Boogie Mark Series.

This video is a little biased.

Outstanding Class ... Thank you.

Tanks men great work i never understand the concepts and what to do, and you explain so easy, you'll save a little money with the technician LOL

Thank you so much! I have Blues Deluxe Reissue I remember it looking the same internally. Any suggestions on cost effective power attenuators? I live in a small apartment...

Thanks for the information

Thanks very helpful video

Great vid thanks!

Great video !!! really helpfull.

Tube info worth weight in gold! Tech Schools need to copy Kens delivery and info “train”.

Very clear thank you!

great stuff for us. thanks

Great stuff

Thanks for the great tutorial! I'm wondering about lowering power? I have a Fender Concert Reverb with a 1/4 power switch. Is there any way to get this thing to 15 or 20 watts safely? I've heard of running on input 2 as well as 6V6 tubes? Different pre-amp tubes? Thoughts? Experience?

great video

Great stuff thank you

Very nice, thank you.

Very helpful.

Very informative video. Thanks man. If you have 4 power tubes, when checking the bias test point would the minimum be 120 instead of 60? Or is 60 just for this specific amp?

Wow great how-to explanation. Is this about same for the Hot-Rod Deville 4x10 2x12 the 1st ones.

Thanks You De- Mythed Biasing. Great explanation!

Good one, thank you!