How to Bias Your Guitar Tube Amp

[@sldaley5692]

I'm 76 years old and 'been messing with analog and digital electrical projects since the 1950s, when my grandfather showed me (more or less) how a simple radio worked on the inside. Got into rock music in the '60s, playing sax and keys along with a number of guitar players in many bands. All their amps used tubes, which were still a mystery to me, as to how they worked. I got pretty good as an amateur, with solid state transistor projects including mic preamps. And I've known that there WAS such a thing as "biasing your tube amp" but I'VE NEVER KNOWN THE THEORY BEHIND IT much less HOW TO DO IT until watching YOUR VIDEO! Thank you very, very much for your well presented lesson and vivid demonstration. So I did get into playing guitar along the way, and now look forward to replacing my guitar amp tubes the proper and safe way!

[@iblesbosuok]

Throughout my short life, there has always been an 'engineer figure' who usually serves every artist community. The 'engineer figure' is more of an artist, must meet directly with the owner of the device to be handled so that she or he can handle the device according to the personality of the device owner. In every artist community that I have met, there is always an 'engineer figure' like that. I am sure you can also find an 'engineer figure' like that in your community.

[@sarayontheroad]

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 👌🏾😄

[@Take-the-Ticket]

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.

[@corywhite9944]

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! :)

[@rerawho]

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.

[@lightinme217]

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 :)

[@javierf55]

Great explanation, thanks. I followed your suggestion to set it at 71 and the result was so good for me.

[@Roomfulofgear]

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!

[@dbltap3332]

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!!!!

[@Mr75044]

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.

[@johnmarkelewicz5495]

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!

[@eweegeewa]

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

[@mikecordell4111]

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!

[@CR3W1SH03S]

Not recommended. www.tdpri.com/threads/6v6-and-6l6-interchangeable.52593/

[@vertebralremains379]

You put 6V6 tubes in to replace 6L6s? I hope you get 5 minutes out of them. And I don’t really understand why anyone would want to do that in the first place?

[@Jonathan-mt9up]

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

[@69zenos1]

Ive got one hand in my pocket and the other one is jerking my girlfriend off

[@Thegoldtop57]

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

[@MrAnders1976]

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..

[@jamesknakiewicz3615]

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

[@allengarrow6295]

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

[@rhythmrockets3583]

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.

[@RiffLair]

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

[@MrBenjaminveng]

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

[@Mark-vq7nh]

You have explained so far better then anyone else.

[@jonkwest0928]

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

[@StevieBassFingers]

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

[@hyedenny]

No, actually it's a crappy video, full of incorrect information.

[@elcochipit]

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

[@LewisShieldsUS]

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

[@nickjimenez6138]

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

[@rokspodcast2571]

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

[@Nimrodsland]

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

[@chrismcloughlin163]

"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.

[@billybishop911]

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

[@Z0ul0u]

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

[@funnyharleyman]

If you replace the old tubes with the exact same ones, do they still need to be biased? Thanks, Garry.

[@bakerXderek]

Greatly done and very informative

[@mattmatt222333]

What do you not do? CHEAH!

[@invin7215]

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

[@susannahtomlin6003]

What your adjusting is the bias voltage. It's best to bias it by miliamps, to do that you have to go in series with the B+ to the tubes and use a different setting on your meter. By biasing to a set voltage your current draw will vary from tube to tube. When u find a brand of tube u like u want them to run the same after a change and even tubes of the same brand will vary on current draw because of differences in internal resistance. So by ohm's law the same bias voltage with a different internal resistance will yield different current draw. Not saying what your doing is wrong just what the tube is drawing is the important factor.

[@Feedbackboy1]

+Susannah Tomlin : the voltage reading is fine as it is typically measuring volt-drop across a 1 ohm resistor, either within the bias probe base or in this case, on a purpose designed measuring point on the PCB. In this way, it obviates the need to put your multi-meter in series (always a hassle) with THE mV range relating directly to the mA range.

[@rjmcmooseknuckle]

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

[@danadlewis]

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

[@arsenalfanrichi]

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

[@guitardo100]

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.

[@nardvandinterenmusic]

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

[@Andre-jm7pu]

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

[@OuttaHere7]

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

[@TheIkaika777]

This video is a little biased.

[@mr.awesomeness9601]

UNDERRATED COMMENT

[@ransom77]

Quite!!

[@notofimportance]

That's pretty funny 😂

[@Steve-f7m]

😂 Dad joke of the day !!

[@wfhstudio]

lol

[@RobRileyGuitar]

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

[@kickerpunter]

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

[@azmike3572]

The music on this is mixed bit too loud to hear you easily. But do tubes have to be re-biased before reinstalling if they were removed for shipping?

[@tangotango256]

I've got a 1984 Laney AOR 100 h with new Mullard EL34s and it sounds a bit flat and cold power Trans died ... and had to send it to Atlanta for repair ... my Groove tubes gone and the mullards in their place ... imagine my disappointment as it's been a year since it was "fixed" and I didn't look and bought a spark 40 to jam on ...I've ordered a set of GT #8 matched Quad EL34Ss that have been sitting in a closet in California since the 90s coming my way ... Hopefully they'll sound better and bias a smidge hotter for that sweet sound I miss so much .... Great vid BTW gonna shortcut like you did and bypass all the crazy math 470 vdc x .0632 ma is about 29 wats per tube X4 voltage drop is 1. 18ish per pair at the anode connection... wish me luck !!! 😂

[@viniciusmarcilio3194]

Should I turn the volume and master knobs all the way down first?

[@Starkster50]

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.

[@dr123hall]

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

[@SRR420]

Really good video also thanks for hitting on the safety side of things not many do that

[@guitarwiz2000]

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

[@RuneBlackBackup]

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.

[@artofnoly9754]

Damn good presentation Kennis. Good work. I'm a VOX AC-30 man myself... Beatles fan.... and I watched your vid on biassing because a power toob just shat in my AC-30 CC1. I knew that, because the main input fuse blew its stack. You've taken the mystery out of biassing (in broad general terms). I'll give it a go myself when I get a new set of valves. Thanx again Man! P.S. please buy a non-conductive set of screw drivers... for the sake of your longevity. Thanx Kennis.

[@33stratman]

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

[@benlloyd3155]

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.

[@mugginsdot]

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"

[@noahtysonhighlonesome8117]

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

[@shckltnebay]

Best bias video on ytube. If you dont have a real Fender tube amp.

[@christopherdupont1124]

Awesome info Kennis. Thanks for making this.

[@AntonioRockGP]

Nice video thanks! Will try it. Now my question: if it's about how it sounds why use the multimeter at all? Why not just plug the guitar and tweak the Bias by ear just like you would any other knob on the amp?

[@jimg5413]

Very Nice introduction to biasing. Thanks!!

[@guspdm]

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

[@adelorme4468]

Great video Kennis! Well done and explained. Several years ago, I biased my Fender Hot Rod Deville 212 while swapping from the 2x 6L6s to 2x KT66s and landed around 80. The amp sounded absolutely great for years but I've learned recently that going "too hot" (over 75) can have the negative effect of shortening your tube's life. Recently, I've experienced some unexpected volume and headroom drops at odd times while jamming, and just the other night, during a gig, it flat out volume dropped and stayed low all night. I had to crank it to 6-7 to have any useful sound (which if you know the 2x12, is a crazy high volume for a small room). I have a question for you: are unexplained volume drops a symptom of dying/tired tubes? (NOTE - I've removed other variables such as my pedal board etc... and have isolated it to my amp). Forgive my ignorance - this has been my only tube amp in 20 years so I lack the experience with other tube amps and troubleshooting.

[@mrrll2007]

Could be that one of your power tubes is blown.

[@louisverrone2341]

Can a Fender Deluxe Reverb be self biased as well or should i take it to tech? Thank you for taking the time to to make these videos. They're really great!

[@Cluless02]

Excellent video - professionally done !!

[@bbalestier]

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...

[@johnslawncaretips4103]

Great video if one of the pre-amp tubes blows do I need to change the whole set

[@germansanchez3577]

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

[@anilyazar_]

Very clear thank you!

[@jesse5694]

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

[@PapaDavid98]

Agreed. I made the mistake of that and no joke the tip of my index finger is burned/ melted off because of touching something wrong. Be careful guys.

[@brianh4625]

How is it that some amps have "fixed bias" and claim not to require biasing, e.g., my Mesa Roadster.

[@brianh4625]

Very nice tutorial, by the way.

[@moonbustin]

Thank you for this! I don't wanna take my tube amp to the expert because they're hella heavy for me to carry around 😂 plus it's fun doing this, DIY at home

[@dogbreath203]

Thanks Kinnis! I'm wondering if the 70mV setting is across the board - or for 6L6s - or for the Deluxe. I've got a Hot Rod Deville 212 and wonder if the 70mV would be the same for my amp? Also, my Fluke 75 has a DC 300mV setting, but not a 200mV. I'm thinking it would still put me in the right range. Thanks for the video and advice.

[@jonno63]

hey ken very descriptive video, where is the self bias setting potentnmeter and self testing point on a 59 reissue Bassman? thank u for your videos

[@mauriciogambini]

Thanks for all great info. I’d like to replace the original power tube from my Vox AC4C1 for a Mullard and,Honestly, I’d prefer not to bias it if I don’t need it.once my amp has only one power tube, do I need to bias it ?If i don’t bias it (just replace) how can I check if it is working properly ? Which are the evidence of bad functioning (that it should boas-noites it) ?Thanks !!

[@daleweber2579]

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

[@mauricehason]

Excellent guide, thank you! I have exactly the same amp and when turning on the standby switch I hear some cracks for the first few minutes and then they disappear. Does this has anything to do with the power tubes?

[@kdawson020279]

In short, it can. There's some leftover products from manufacturing that can cause some noise. That said, if it persists, try tube shields especially in your preamp stage and check for environmental sources of electromagnetic energy. I would expect properly biased tubes to quit having break-in issues after you've biased them then flogged them for a good days' work or so. How long that takes is dependent on how hot they are biased and manufacturing and how much you play. Some amps just crackle from worn pots and microphonics. Tl;dr: Yes, but if it persists look elsewhere for the crackle.

[@rockstarim]

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

[@BARSPR]

Very helpful. Do a re cap tutorial???

[@manchiloco]

i really like your tutorials,you're easy to listen to and learn,have you ever looked into an orange amp? do you think it's gonna be similar to bias like you did on vid? thanks

[@freddytravale4958]

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

[@NeilMcMusic]

Hi Kennis, great video! .. i have the fender hot rod deluxe western version are they the same as the normal hot rod deluxes? I'm going to replace the valves myself but confused on the term "self-biasing" does that mean you can put the power tubes in and they bias automatically ? or do you still have to bias them? ...do you also ever need to change the 3 little valves? your videos are really helpful thanks.

[@lespaul462]

Great video! Very informative and easy to follow.

[@Steve-wz5pz]

You are leaning on the metal chassis with your left hand, adjusting the bias pot with a uninsulated screwdriver with your right. A recipe for 'thoughts and prayers'.

[@zay3741]

Would you be able to do an instructional video on biasing a blues Jr 3?

[@billwilliams6338]

KENNIS RUSSELL, 1.) When you're biasing the power tubes in an amplifier circuit how do you bias the compression of the power tubes the 1dB compression point of when the power tubes start to compression? because its say to bias tubes at a 30mA bias current per tube to be safe but how do you know when the tube is compressing? 2.) Most Power tubes 6L6,EL34 use a B+450vdc on the plates, if you increase the B+ to +600vdc would this increase the AC ripple but why would it increase the AC ripple? i would think it would decrease the AC ripple because more B+ voltage mean less current draw from the power tubes.

[@tombyrne4377]

I have a Fender Deville 410, practically identical to your amp in the video. I went to Radio Shack and bought a milli volt reader w digital display but never got a reading anywhere similar to your video. Can you tell me what the exact model millivolt reader did you use? I would purchase one of those.

[@shyammohabir8283]

Thanks for the Video. Why you need to bias your tube Amp: Resistors, capacitors and tube values deteriorate with time. It changes the amp output tube characteristics in terms of current, voltage drop and power dissipation. Bias is really realign these values to tube specs for optimum performance. I highly recommend you check out Uncle Dougs bias video.

[@kissrocks45]

No need to check plate voltage, just use the meter? Since im using the clean channel on my blues deluxe and I need head room, a moderate setting say 71 might be best for head room huh? Thanks a lot!

[@preciseaudioblog]

Hi, great video. I have a Bugera V22 Infinium (with auto bias). It bursts the power tubes in days. Could be that auto bias is damaged? Thank you.

[@Armalite015]

Thanks for the good instructional videos

[@AMH4brothers]

On what setting do you have the multimeter on? Thanks for such a great informative video!

[@silasfatchett5693]

You set it to DC volts. If it's not auto-ranging, set it to read mV (millivolts). My meter has a 200mV range, and since I'm expecting to read 60 to 80mV, I'd set it to that.

[@KrispyCoins]

Nice video as always thanks Kennis

[@WBWhacker3]

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?

[@BoyanDechev]

Dear Kennis, Thank you for the great video. I own a Fender Hot Rod Deluxe III and followed your video closely. Everything is set correctly with the multimeter (200m DCV) but I only get 30mv from the bias testing point. When I turn the wheel it goes from about 10mv to 55mv. Do you know what the problem here could be? I'm using an almost brand new pair of JJ 6L6s that replaced the original Groove Tubes.

[@midnightraiin4035]

thank you. do power tubes need to be replaced at the same time and if so , why ?

[@stefanhamilton8713]

Thanks, very interesting. I have a laney vc-30 and the clean channel is very quiet compared to the drive channel. This happened after a guy revalued it. Would I have a bad valve in the preamp?

[@fyrcrack1]

I am not an amp guru or anything but you need to let the tube heaters warm up for a couple of minutes before you turn the standby switch on. Is the 70 mv you speak of divided by the 2 power tubes or is it 70 mv each?