How to Bias Your Guitar Tube Amp

[@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 👌🏾😄

[@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

[@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.

[@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..

[@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.

[@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! :)

[@TheIkaika777]

This video is a little biased.

[@mr.awesomeness9601]

UNDERRATED COMMENT

[@ransom77]

Quite!!

[@adrianmay_multiinstrumentalist]

That's pretty funny 😂

[@Steve-f7m]

😂 Dad joke of the day !!

[@wfhstudio]

lol

[@eweegeewa]

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

[@OuttaHere7]

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

[@javierf55]

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

[@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 :)

[@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.

[@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!

[@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!

[@allengarrow6295]

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

[@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.

[@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.

[@Mark-vq7nh]

You have explained so far better then anyone else.

[@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!!!!

[@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....

[@jamesknakiewicz3615]

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

[@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.

[@elcochipit]

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

[@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?

[@invin7215]

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

[@Thegoldtop57]

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

[@Z0ul0u]

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

[@nardvandinterenmusic]

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

[@bakerXderek]

Greatly done and very informative

[@mattmatt222333]

What do you not do? CHEAH!

[@rokspodcast2571]

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

[@StevieBassFingers]

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

[@hyedenny]

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

[@dr123hall]

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

[@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!!

[@funnyharleyman]

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

[@danadlewis]

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

[@shckltnebay]

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

[@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.

[@nickjimenez6138]

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

[@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.

[@Andre-jm7pu]

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

[@billybishop911]

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

[@castleanthrax1833]

If you were wondering about the "one hand rule" the reason is this. If you have only one hand in your amp and get shocked, you have a chance of surviving, as the current will hopefully bypass your heart on it's way to the ground. Two hands in the amp and the current will likely go to ground via your heart resulting in death. These things are EXTREMELY DANGEROUS, even if you know what you're doing.

[@aaronm.1998]

60,900 deaths per year do to tube amps.

[@vertebralremains379]

@@aaronm.1998due

[@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.

[@jimg5413]

Very Nice introduction to biasing. Thanks!!

[@RobRileyGuitar]

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

[@Nimrodsland]

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

[@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.

[@SRR420]

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

[@jonkwest0928]

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

[@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 !!! 😂

[@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?

[@rjmcmooseknuckle]

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

[@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.

[@germansanchez3577]

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

[@christopherdupont1124]

Awesome info Kennis. Thanks for making this.

[@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.

[@LewisShieldsUS]

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

[@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...

[@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.

[@kasperkap]

Run to radioshack and buy some... That dated the video a bit :) Great info

[@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???

[@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 !!

[@Cluless02]

Excellent video - professionally done !!

[@johnslawncaretips4103]

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

[@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

[@guitarwiz2000]

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

[@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.

[@thezosokid]

Noob question, Do Hand wired amps such as a JTM 45 would have a bias test area/switch?

[@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.

[@kissrocks45]

Hi, no need to check the plate voltage huh when using the meter? I have a blues deluxe but running pedal through the clean and it works well. BD biases the same way and around 70 to 80? thanks!

[@ezandman6804]

Kennis means knowledge in my language dutch... Thank you for the information

[@Packy11920]

My amp is class A Orange Rocker30. It doesn't come with Effect loop. Do you know how to install effect lube into my amp? Thank you

[@midnightraiin4035]

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

[@danelectr]

Hi, I have a question. I have a laney irt60 212. I read the manual and it say V1 12Ax7 for the pre amp and V10-11 6l6 for the power. Im confused with the versioning the V1 and V10-11. Does it matter? I cant seem to find the versioning in the tube store. Can you please explain what it means? Thanks

[@cat6oo]

V1 indicates the first pre amp tube in the chain(position), the model number for this tube is a 12ax7, I am assuming V10-11 is a potion number, the tube type is 6L6. Hope this helps

[@danelectr]

+cat6oo got it. Thanks

[@badurskiroffli176]

I have a Fender quad reverb, where could I get info on how to replace the tubes and set the bias ? Is it also possible to fix the vibrato effekt on my own ?

[@sleepyd1231]

Hey my guitar amp's bias has been dropping quickly, every 1-2 weeks I have to re-bias. any ideas? Ive never changed tubes before. It's a hot rod deluxe, I've had it for a year(brand new), and I play about 3 to 4 hours a day.

[@michaeltownsly1493]

+Dylan Ost Dumb dumb...your tubes are fucked

[@Armalite015]

Thanks for the good instructional videos

[@33stratman]

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

[@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!

[@guspdm]

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

[@danielg9810]

Thanks for clear information!

[@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.

[@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.

[@lespaul462]

Great video! Very informative and easy to follow.

[@enodude59]

Do you know if the Fender Supersonic 22w has adjustable bias? I don't find a test point. Thanks.

[@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

[@zay3741]

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

[@daleweber2579]

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

[@kickerpunter]

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

[@noahtysonhighlonesome8117]

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

[@mlmancus]

Could you assume you have a bad set of tubes if you are getting a low reading when biasing? I got a brand new set of JJ 6L6gc's for my Hot Rod. Attempted to bias after replacing them. Set to 200m, I was reading between 33.0 at the lowest and 68.0 at max, after warming up the tubes for 15 minutes. I put in the old Stovek tubes I was replacing, read between 59.0 and 114.0.

[@viniciusmarcilio3194]

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

[@whoisthenext1]

One question, Kennis. About an amp with bias test point like this, do you read cathode voltages both sum ? Thank you.

[@rampage222555]

No sum. In most amps with 2 test points, what you have to do is read the voltage at each test point and bias with regards to the one that reads the highest. If the bias reading between the tubes is too different(more than 2-3mV on the meter) then you have mismatched tubes and would probably want to get a matched pair. there are cases where amps have two test points and inside they have 2 bias pots, but these are rare.

[@whoisthenext1]

rampage222555 Yes, I got it. I thought there was just one test point, like some amps. Thank you.

[@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?

[@karlnaicker4527]

This was great man.. The guy who does my amps is really expensive...

[@karlnaicker4527]

About $130 to put in 2 JJ 6L6gc's

[@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.

[@albertn872]

Would I have to bias or not if I switch one broken Marshall EL34 tube with a TAD JJ EL34 Tube in my Marshall 9200 Dual Monobloc amplifier?

[@zeke5989]

This is a great video, but how do I bias a Super Reverb Reissue that doesn't have a bias test point? I tried to get a reading on the volt reader but I couldn't get any consistency.

[@silasfatchett5693]

In the Hotrod Deluxe (and many modern amps) there is a one ohm resistor inserted between the cathodes of the output tubes and ground. By measuring the voltage across this resistor, you are actually measuring the current through the tubes. Many older amps do not have this resistor fitted, and according to the schematic, the original Super Reverb (AA763) is one of them. Biasing your Super Reverb involves rummaging around in those lethal voltages, and is a job for someone who knows what he/she is doing.