Two Types of Tube Amplifier Hum and How to Determine the Source

In this video, I discuss two types of hum found in tube amplifiers, how to easily differentiate between the causes, and how to effectively remedy the situation. The technical aspects of this discussion are explained in basic, comprehensible language. I hope you find it to be both interesting and informative. NOTE: The frequencies stated in the video (60Hz and 120Hz) refer to 60Hz primary AC. If your AC source is 50Hz, then the frequencies would be 50Hz and 100Hz.
If you enjoy videos featuring classic vintage amps, jukeboxes, gear, and down-to-earth technical talk, then please subscribe to my channel. You will gain immediate access to over 65 additional videos, and you will be notified each time a new video is posted.
Thanks for watching !!!

[@UncleDoug]

PLEASE NOTE: I posted this video primarily to assist in determining if the hum was created in the power supply (120Hz) or elsewhere in the circuit (60Hz). A faulty tube can cause the 60Hz hum, as in this video, but there are literally hundreds of other possible causes. Indeed, there are internet sites that offer helpful lists of these possible causes. Please consult them if you have ruled out the power supply or a tube as the cause of the hum in your circuit. Good luck.

[@donh01965]

Would that make the tube unusable in every application? Could it be usable in say test equipment or other non amplifier items?

[@Angelum_Band]

I would like to thank you for your explanation it made so much sense and resolved my problem. BTW 61.74Hz is a low B so if hear a flat B in your spectrometer ap you know where it's at.

[@fuzzyhi5621]

Where you located I was wondering if I could send you an amp to fix?

[@UncleDoug]

@@fuzzyhi5621 Please message me at my FB page: Uncle Doug's Vintage Amps.

[@RiotHomeRecording]

@@UncleDoug What about buzzing? Is that a tube thing or more of a grounding issue in your experience.

[@hackit25]

I just came across this video trying to figure out the hum in my tube amp. Great info!

[@TheOldOakSyndicate]

You got some of the best "How To/Electronic Amplification" videos on KZbin! Keep up the good work Uncle Doug!

[@UncleDoug]

Thanks so much, OOS. Rusty and I really appreciate the kind words :) ^. .^

[@wildthing3026]

Uncle Doug I think that you are an amazing technician. ....and a great person to share your knowledge...just love your videos...many many feel just like I do....

[@curtisowens6413]

Absolutely the best!

[@GoochGoocherson]

Excellent information as always! I am absolutely addicted to watching your videos since I found your channel. I have only recently gotten into tinkering with tube amps and converting tube radios. Largely influenced by a video you did converting a J.W. Davis PA amplifier into a guitar amp, being that I have the model 405 Davis amp, I was intrigued at the thought. Thank you again from the bottom of my heart for preserving this knowledge and passing it on for generations of people to use.

[@UncleDoug]

You're quite welcome, Josh. Good luck with all your projects.

[@kenq7948]

I'm getting exactly this sound on my fender bassman amp. Thanks a lot for the advice. Much appreciated.

[@UncleDoug]

You're welcome, Ken. Good luck with the repair :)

[@MrLespaul1963]

Uncle Doug...thank you for being so informative and helpful. I've been a musician (mostly electric guitar) for 35 years. I've been a gear head and DIYer as long. You've really broadened my understanding by taking what I understood from the theoretical to the practically. See, my day job I'm a pharmacist and have zero formal training in electronics. Everything I know is self taught and its served me well. I've been wanting to build a tube amp from scratch and have hesitated, until now and thanks to you opening up my understanding, I'm ready to take the plunge. I'm looking at the P1 from the AX84 collaborative group. As to this video, as soon as you said it wasn't from the filter caps, my first thought was the heater grid being involved. Your MOA for the heater grid involvement makes perfect sense and I learned that the filter cap AC hum is st 120 Hz...I had never thought about the quality of AC hum from the filter caps being double. I understand the how. The why just had never crossed my mind. Again thank you.

[@UncleDoug]

You're welcome, Kirk. Rusty and I are self-taught also, so we're quite glad to hear that our videos are helping you gain knowledge regarding tube electronics. Best of luck with your amp-building project.

[@curtvincent3728]

Hey Uncle Doug! I really feel compelled to comment that I really, really appreciate you making these videos. You go over a concept slowly and you repeat that concept several times (it takes 7 times for a concept to penetrate our thick skulls) and your diagrams are very clear (old school, but that's fine, tubes are old school!). Give Rusty a treat, he is one hell of a guitar player too!

[@UncleDoug]

+Curt Vincent Thanks so much for your very nice comments, Curt. Rusty and I really appreciate them. P.S. He says thanks for the treat :)

[@rondobondo6600]

Uncle Doug I just want to thank you for all of the time that you spent for us In making awesome and informative video's .I just wanted you to know that I appreciate all of your hard work....

[@UncleDoug]

That's great to hear, RB. Thanks !!

[@twirlyboggs]

wow, that helped me confirm what was happening on my amp. I was getting thqt 60 cycle hum on it, and after the 5th preamp tube swap, it's now gone! I may try another online store for my tubes and see if i get quieter ones. I also thought about getting 12ax7WA's too. Your videos ROCK!!!

[@UncleDoug]

Thanks so much, TB. I have chased hum for years, replacing all sorts of components before finally discovering that it was simply a noisy tube (usually a pre-amp tube like a 12AX7). Another strange discovery is that sometimes a tube that hums in one amp is quiet in another.....probably dependent upon which of the two triodes in the 12AX7 is actually noisy. Regardless, the tone of the hum is definitely a great clue to its source. Best of luck !! :))

[@twirlyboggs]

you are truly full of knowledge~ funny u said that about diff amps / same tube, because one of my amps just seems to never have noise after rolling preamp tubes - never really thought about it tho~ i love making thought connections, thanks!

[@UncleDoug]

You're welcome, TB. I guess some circuits are more sensitive to noisy tubes than others. Again, thanks for your great input :))

[@djfrank59]

Once again, you and David have the best videos out here! If I ever get the incentive to clean up and organize my shop, I'll make some tech videos as well, what stops me from cleaning up the shop is, I may not be able to find anything then :)

[@UncleDoug]

Thanks, Frank.....and sometimes you find the missing item you lost back in 2008 :)))

[@djfrank59]

I probably order things I already have (LOL) :)

[@UncleDoug]

....and when I find them, I mistakenly think that the order has arrived :)

[@TroyLeonardO]

I CANT GET ENOUGH OF YOUR VIDEOS!!! FANTASTIC INFO!! THANK YOU!

[@UncleDoug]

You're welcome, Troy :)

[@nathanwatrous1519]

This video is a sanity saver. I restore Bogen Amps. I have a challenger cab on my bench right now. I recapped the whole darn thing. After that there was still a 60 hertz buzz. This buzz was present no matter what I did with any of the controls. I noticed if I turned down the voltage on the variac, that the buzz would calm down. So I tried a voltage dropping resistor network on the heater circuit. Didn’t change the buzz. I even ran the heaters off of 6 volt battery to see if that would help. Nothing, still the same. So I did some research and came across this video. So I started pulling tubes, long behold the phase inverter, a 5C4, was the culprit. These tubes are dirt cheap, so I have some on order. Thank you so much Uncle Doug!

[@UncleDoug]

That's great news, Nathan. I'm glad the video was helpful :)

[@UncleDoug]

Mick, your question had no reply capability, so I'll answer it here. Whistles are usually due to oscillation. It can be at the input, where there is usually a 50K to 70K resistor between the input and first tube grid to eliminate it (may have failed or be missing), or due to a slightly microphonic tube. While the amp is on, try lightly tapping on each tube with a chopstick to see if the sound appears or changes. Hopefully, this will reveal the source of the sound. Good luck.

[@babybearkill1]

Hey Doug, All glues by JBL are provided by Moyan. I worked for the Australian distributor as the tech and that's what's supplied www.cpmoyen.com Go check em out, they also supply the dope

[@UncleDoug]

Thanks, BBK. This information would probably be more useful under the Speaker Repair video. I'll add your link to that video description.

[@babybearkill1]

It was the most recent post so I popped it here

[@jeffbeck6501]

Great info. I think dimmers can also cause problems. I have rarely had no hum on my amp. In big clubs in big old buildings downtown with those damn beer signs everywhere, I have had so much hum at times, that one time I pull off the ground to unground the amp to get less noise, as I had to do at home for recording to reduce the hum and it worked well. The only problem was that during my first song of the first gig of a big band that I had joined, playing in front of a full house of 500 plus fans, the singer walked over to me on stage right and put his hand on the back of my neck while he was holding the microphone and SHAZZZZAAM BAM POOF. He just about electrocuted me and I fell back on to the floor. He did not feel the shock, nor did he see me fall backwards onto the stage floor. He went back to the other side of the stage while focusing on his singing while I was half dead trying to hold a first position A chord with one finger the best I could while recovering from the shock. After the singer had walked over to stage left he turned around and saw me, the new guitar player, playing the guitar parts while laying on the floor. He never knew I got shocked. The first thing that popped into his mind was "kind of hamming it up, aren't ya?" was what he was thinking about me. It took me at least 30 seconds to slowly get back up. I never unplugged the ground at a show after that. And in fact, when I sang and played guitar, I would add a jumper from the mic cable ground to my foot pedal ground. I used car jumper cables. Otherwise, your mouth can get shocked really badly while singing. The singer never knew that I had gotten shocked til after the show. But he had a clue because later on toward the end of the show, I was playing a solo with a wah pedal and could not leave my pedalboard, and the singer came back over to touch me on the back of the neck again, and I was shaking me head, no no no no no. He seemed to pick up on that. So it almost happened twice. I would not have survived a second jolt of club power mains. And to add a bit more carnage, in the middle of the show, while running around on stage in the high energy show band, I slipped on a plastic bag left on the stage from some bags of bananas we threw out to the audience. I took a hard fall to that stage. And our hottest dancing girl announces to the audience live that she is leaving the band to boot. What a crazy night.

[@UncleDoug]

Good grief, Jeff, a few more nights like that and you might be better off quitting the music biz while you can still walk away. What a harrowing experience. Yes, I too believe that light dimmers can cause electronic "noise".

[@jeffbeck6501]

Nah, just another day in the office for me.

[@jeffbeck6501]

And it is pretty you replied to my comments. You are perhaps the #1 guy or one of them at what you do. It is really nice the info you share, and how it gets put on to video for forever, and many people for forever can learn from it. I did not know anything about anything until people like you started uploading videos to youtube. My hats off to all people that do that.

[@UncleDoug]

You're welcome, Jeff. I'm glad the videos are helpful and appreciate your nice comments :)

[@1Dcorace]

Do you ever check house power with a simple receptacle tester to see if you have ground? I see some pretty bad house power in older buildings. No ground, reversed polarity, all kinds of good stuff. I carry a APC power conditioner, I'm not sure it's made any more, but that has helped in the worst situations.

[@joeyshuster8569]

I appreciate your time put in to this video! This helped me diagnose the bad filter caps in my lowrey organ

[@UncleDoug]

Glad to hear it, Joey :)

[@allendodd4844]

Your dry humor and Rusty's attitude really make the information more fun. This is one of my favorite youtube channels.

[@UncleDoug]

Wow, thank you, Allen. We appreciate your kind words.

[@professorhardknock]

Rusty looks like a Norwegian Elkhound. Great dogs.

[@UncleDoug]

We're not sure about his true origin, Prof. His Australian accent made us think he was a Queensland Blue Heeler, but he loves to ski, so Norway is possible :) :)

[@harbselectronicslab3551]

Yep I can confirm that.....I am from Oz and he is definitely a Blue Heeler for sure......we love our cattle dogs down here......he is a lot like my old mate "Bluey" who I had to put down at the age of 16 years a few months back......it was the hardest thing I have ever had to do , but he was in a lot of pain, and I didn't want to see him suffer. I dont know how anyone can go through life without a dog.......they are just the best.

[@charlesmatthias9459]

@@harbselectronicslab3551 God Bless You Harb!Been thru that and it's the hardest thing a Dog/animal- lover will ever go thru!

[@crunchchannel9391]

I pushed the subscribe button because i dont want any one offended.

[@UncleDoug]

+Rondo McBower Thanks, Rondo. Rusty gets real cranky when he's offended :)

[@frankfinegan425]

Uncle Doug can you do s video of how to choose a driver tube for a given power tube?

[@vicoilsteems9764]

Rondo McBower Trump loves you.

[@lonnieo4676]

me2...

[@iangray7410]

How remarkably brave of you !

[@dallasrode9653]

I should add I am just trying to learn about tube amps in the last few months. I knew I was hooked when I learned that AC and DC cohabitate inside the same circuit. Love this youtube channel, really great simple to understand learning. Thank you very much Uncle Doug!

[@UncleDoug]

You're welcome, Dallas.

[@deluxetone]

Excellent as always. Thanks for all the great information.

[@UncleDoug]

You're welcome, DT.....glad you liked it :)

[@jeffmclowry]

I'm deeply offended. lol You're so funny! I love your videos...

[@UncleDoug]

Greetings, Jeff, and thanks for the kind words. Glad to hear that you're enjoying the videos. I try to toss in a little humor once in a while to pep things up :)

[@UncleDoug]

Brian R, your comment had no reply capability, so I'll answer here. Does the amp hum with nothing plugged into it? If so, it's the amp. If not, it's probably your cable (try a different one). 1.) If the hum changed when you touched the strings, it would mean that the bridge and strings are not grounded properly. It doesn't, so they must be OK. 2.) If the hum obeys the VC, then its cause is before the VC in the circuit: input jack not making good contact with cable, faulty cable, lots of electrical noise in the room, badly routed wires, noisy pre-amp tube (switch it and see if hum changes). 3.) There is no way to differentiate ground loop hum from other sources of hum. Unless you have changed the wiring within the chassis, then a ground loop would not simply appear. They are usually caused by a fault in the circuitry design, particularly in the way that components are grounded. It would have always hummed.

[@Brobb772]

Thanks for your quick response. 1) Im not sure if its the guitar cable or not, but I'm thinking not likely? I tried with 2 different chords and hum occurs with both - but i guess it could be possible, just seems less likely 2) I've never messed with the tubes before but maybe i could try and start with the pre-amp tubes; and if i get stuck take it in to a repair person -- whats a reasonable price to pay somebody for replacing tubes?? 3) i can't remember if its always hummed or not. it seems like it has, but i can't really remember because when i lived in apartment i played it pretty quiet and not as often. Now i live in a house and can turn it up. So i don't know if its a fault in the amp design or not. 4) The house from the 60's and its possible the wiring isn't good in the house, and there are a few street lamps down the street that have a hum to them (a couple hundred feet away?), but i dont know what i would do about that..? Theres something online called an Ebtech Hum exterminator ($50 - $75) that plugs into the outlet, but i dont if that addresses my problem or not. Do you know what problem this product addresses?

[@UncleDoug]

You might be better off just taking it to an amp tech and get his opinion on the nature and source of the hum. In some tube amps, slight hum is a normal occurrence. It would probably end up costing less money, time, and frustration to get it checked out by an expert.

[@randyheath8566]

Makes a lot of sense to me Uncle Doug. I have a Koch Multitone amp head that is humming, so now I know what to check. Thank you very much for the Lesson. Love your Channel and you ❤

[@UncleDoug]

Check the frequency of the hum, Randy. Good luck.

[@Mr3DBob]

Lifesaver, Uncle Doug! I have a humming Princeton right now, so as soon as I get to watch this whole video, I'll know where to start on diagnosing my vintage FPR.

[@UncleDoug]

We're glad the video was helpful, Robert. Best of luck with your diagnosis.

[@djfrank59]

I've encountered the 60 cycle hum problem many times with 12AX7's especially with the Chinese tubes...There are times you have to swap out a few to find one that's quiet...I've also had situations where I would slightly re dress the heater wiring and the hum would vanish...

[@UncleDoug]

I'll try the re-dress first next time.....it's cheaper than switching tubes :)))

[@bullet0657]

Uncle Doug Hi Doug what do you guys mean by Re-dress.I am a noob when it comes to electronics but i would like to learn now that i have all these old guitar amps. Thank You.

[@djfrank59]

These as well as other amplifiers have both AC and DC wiring passing around throughout the amplifier...most amplifiers with the exception of a few others, have AC tube filament lines. AC hum can enter the signal by the wires passing close to DC or signal wiring and pre amp tubes which will induce hum; also due to the sensitivity and gain of the pre amp tubes...that's another reason why they contain metal shields...However, under the chassis, if AC heater wiring passes too close to the grid connections of the preamp tubes, AC hum can easily prevail...Dressing of the wiring is a matter of moving them at a slight distance as not to touch signal or DC wiring...This is another reason why if you notice that the filament wiring is twisted paired...If filament wiring is placed in a strait line, it can act as a dipole antenna and is subject to RF (radio signals) getting into the amp's signal path...I recently repaired a Fender amp for a customer who was picking up AM radio stations in his amp...

[@UncleDoug]

I guess that's better than picking up radio station transmissions with your fillings :) Thanks for the great info, Frank !!

[@rich1051414]

Yep, I have a preamp that has started to hum, and it uses chinese 12AU7's. The odd thing is, the hum value is not directly connected with the volume knob, but it gets louder around 75% volume then starts going down again after that. Very strange.

[@knuckle47]

Uncle Doug, thoroughly enjoy your videos. Thanks for the effort that goes into all of them. I know I am better for learning this.

[@UncleDoug]

+luthier47 You're welcome, L47. It's great to hear that the videos are helpful and appreciated :)

[@georgeonerato575]

Thanks Doug. Fixed my issue on a preamp without driving myself crazy. Your the man

[@UncleDoug]

That's good to hear, George. Thanks :)

[@122Music1]

We need more mentors like this in the world. Great post U.D... Thanx

[@UncleDoug]

You're welcome, 122 :) Thanks !!

[@aaronfidelisrecine]

Just fixed up a small amp with a 60 cycle hum. Filter caps had tested fine on the BLUE esr so I remembered your video and now im tube swapping. Thank you again for your videos! They are truly helpful and inspiring.

[@UncleDoug]

You're welcome, Aaron. I'm glad you're finding the Blue ESR meter to be helpful. Without it, you probably would have simply replaced all the filter caps......and still had a hum. I hope the tube switching helps. Good luck with your repairs.

[@mdillo2]

Great lesson, and exactly what I needed, thank you Uncle Doug!

[@UncleDoug]

+mdillo2 You're welcome, MD :)

[@LuosRestil]

Thanks so much for this! I didn't even realize that the annoying 60 cycle hum from my Hot Rod Deville wasn't normal. A simple preamp tube swap has entirely eliminated it, and now I know what to have my ear out for when the capacitor gremlins come to call. Incredibly helpful.

[@UncleDoug]

LuosRestil You're quite welcome, LR. It's great to hear that the video was helpful. Best of luck :)

[@d-labelectronics]

Love your vids. Good to know a fellow amp repairman. Great work sir. TD

[@UncleDoug]

Thanks so much, DL. Coming from a fellow tech, your approval means a lot.

[@VERBANDTREM]

Thank you so much! I'm really enjoying and learning from your videos (especially the Princeton restoration)

[@UncleDoug]

You're welcome, Jesse.

[@larrydering1598]

Had to revisit this great info video. You have the best on the web. Thanks Doug.

[@UncleDoug]

Thanks so much, Larry. Welcome back :)

[@Aijse]

Thanks for the examples of the hum at different frequencies!

[@UncleDoug]

You're welcome, Aice.

[@jmv668]

Love your channel and tube amps ❤️

[@Kiddomike]

I just got a new tube online and for some reason when I plugged it into my amp it produced a hum similar to a 60Hz hum. This is a very helpful video.

[@UncleDoug]

We're glad the video was helpful, KM :)

[@grilledcheeseeater3443]

Uncle doug your probably my new favorite content creator. great detail. and you get more veiws than you have subs regularly. which means your content is top notch

[@UncleDoug]

Thanks so much, GC :)

[@sigdaddy7377]

I will try the stabilization ideas. Thanks again, and again, and again-- these videos are great!!

[@UncleDoug]

+sigdaddy You're welcome, Sig, and good luck.

[@michaelyoung6986]

Epiphany moment💥 I came here after a random unrelated rabbit hole and found an answer I've been looking to understand for years. Thank you.👍

[@UncleDoug]

Glad to hear it, Michael.

[@sedici888]

I recently purchased an old Klemt M40 from ebay, and of course it had a Hum. I was going to try and fault find the device, and was going to concentrate on the caps. After watching this vid, the 50hz hum pointed me towards the valves. I replaced the valves, and the hum is pretty much gone. Thankyou so much for this, and all of your informative videos.

[@UncleDoug]

I'm glad the video was helpful and aimed you in the right direction, Sedici. You're welcome :)

[@the_hero_less_few4398]

Thanks so very much for the informative video!

[@UncleDoug]

The_Hero_Less_Few You're welcome, TH....glad you liked it :)

[@JS-vh4yq]

Absolutely stellar information. Thank you Doug. I just picked up a used SUHR PT100 SE for a decent price. When I turned it on there was what I believedto be a 60 cycle hum (will be confirming that very in the morning). There is also a large amount of hiss that increases as the output level is increased, especially on the higher gain channels. I suspect one or more 12AX7's.... Thanks again for sharing your wealth of knowledge!

[@UncleDoug]

You're welcome, O. Good luck with your repairs.

[@lennyb783]

Uncle Doug You are like the honey on my peanut butter. I just listen to the fist talk and at 72 years I have been away from school and you make me want to go back. I enjoy the info and want to thank You for your time.

[@UncleDoug]

+Leonard Nixon You're welcome, Leonard, and thanks for the very nice comments. Rusty and I have posted well over 100 videos, so you have lots more to watch. We welcome you and hope you enjoy them :)

[@tim2468]

One of the fun things about this work is solving puzzles. You're a great puzzle solver!

[@UncleDoug]

+Tim Tim Thanks so much, Tim. One of the biggest rewards associated with technical challenges like this is the pleasure you get from solving the puzzle, and the pride you feel whenever you can turn an inert pile of smoking wire and components back into a functional device.

[@jetblakink]

This channel is so good!… Wish I had it as a resource couple decades back!

[@UncleDoug]

Thanks, JB :) We do too.

[@31309586]

Thank you, I'm making a JCM800, it is the first amp I've ever made, and this is a very important information. Regards from Argentina.

[@UncleDoug]

You're welcome, GG. We're glad the information was helpful.

[@m.c.alejandrolizarragaliza637]

Nice video, you make that all tube stuff appear more easy to understan!

[@UncleDoug]

+M.C. Alejandro Lizárraga Lizárraga Thanks, Alex. That is our intention.

[@brettmcnaueal1951]

Very well explained Doug. Always good to start with preamp tubes when it comes to hum. I’m not sure how many techs out there that would start with replacing capacitors to get rid of hum, and only come to find that even after they have replaced the filter caps, the hum is still noticeable. Microphonic preamp tubes can be a nuisance as well, as they usually check out okay, but can be very problematic when installed.

[@UncleDoug]

Thanks, Brett, for your nice comments and helpful input :)

[@evanmcfevan3211]

Great video uncle Doug. Thanks for the valuable lesson!

[@UncleDoug]

You're welcome, Evan.

[@1986yamahafazer69]

Man I wish I learned this decades ago. No time like the present! Thanks again for the lesson.

[@UncleDoug]

Happy to help, YF.

[@anthonyvee]

How informative! thank you, i'm 62 years old I wish i had a neighbor like yourself with the knowledge that you possess, so i can learn from the beginning... never too late to learn i believe and videos like yours show how important, exciting and interesting tube technology was and is...thank you and stay well.

[@UncleDoug]

Thanks so much, Anthony. We appreciate your kind words and wish you the very best.

[@kefka4203]

What an awesome video; such valuable knowledge gained from this! Thank you.

[@UncleDoug]

You're welcome, K. Glad it was helpful :)

[@robzecc]

I just fixed this problem thanks to your video! Thank you

[@UncleDoug]

Glad it helped, Rob :)

[@hqmuvids9127]

Thank You very much for your video! I didn't know what was wrong with my amp. That was it! BIG THANKS!!!

[@UncleDoug]

You're welcome, HQ :)

[@curtismuma1931]

Frecking awesome! Lov your insight. Keep up the great work. And the information

[@UncleDoug]

Thanks, Curtis. We will :)

[@billmckenna7056]

Thanks again Doug, super helpful info, i had this issue some months back with a brown virbrosonic. took me weeks on head scratching before i randomly tried a new driver 12ax7. Never knew this about ac bleed between tube elements.. you are a great teacher😂👍🏻

[@UncleDoug]

You're welcome, Bill. Yes the internal capacitance between the AC filament and the cathode can cause havoc without being detectable as a short. About the only way to fix the problem is through tube substitution.

[@anthonyhitchings1051]

thanks for demonstrating the two hum frequencies

[@UncleDoug]

Thanks for realizing the whole purpose of the video, Anthony. Many, many viewers have simply read the title and then asked for long-distance repair suggestions to cure their hum issues.

[@ryanybos]

Thanks for the time saving information Uncle Doug !

[@UncleDoug]

You're very welcome, Ryan.

[@marcelziul]

Thanks for taking the time to make such great videos! This one in particular really helped!

[@UncleDoug]

You're welcome, Marcel. I think it explains something that many people don't realize, and it can provide a quick, selective diagnosis of faulty filter caps.

[@marcelziul]

+Uncle Doug definetly; you steered me away from a wild goose chase. Turns out this was the issue with a supposed NOS 12AT7. Thanks again.

[@UncleDoug]

You're welcome, Marcel. One nice thing about a tube being at fault is that it is the easiest of all such problems to fix :)

[@copytekk]

This was super helpful. Thanks Uncle Doug!

[@UncleDoug]

Glad to hear it, Aaron :)

[@TheMorphicResident]

This video saved me a trip to the tech. Couldn’t figure out where the hum was coming from but this video made me realize it’s 60 cycle and likely a tube issue. Seems like I tried everything until I swapped out the 12AT7 reverb driver and then silence.....thank you!

[@UncleDoug]

You're welcome, CB.......glad the video was helpful :)

[@russmills5103]

Video made 10 years ago saved me all kinds of time. Had almost the same problem, only difference is mine was effected by the master volume, but identical sound. The very first preamp tube I replaced fixed it. Thanks!

[@UncleDoug]

Glad the video was helpful, Russ :)

[@SPWoz]

Thanks - I was going to replace filter caps - but now I will start with changing out tubes (I certainly have the 60Hz) ... I appreciate the advice. Great videos - I am just learning, and your videos really help.

[@UncleDoug]

That's good to hear, SP. Good luck.

[@camielkotte]

You are the best! Thank you a bucket of tone!

[@UncleDoug]

Thanks so much, Camiel.

[@jamesjameson2369]

I would just like to say a huge thank you for this vid...after putting up with hum for a while I got a friend who knows a bit about it and said the problem was anything from capacitors to output tranny..after watching this vid I remembered I had a problem with a 12ax7 and had changed..Hum happened ever since so just changed and hum is gone..cheap fix on my Laney lc50..many thanks.

[@UncleDoug]

That's great news, James. Congratulations on a successful repair.

[@jeremyb2108]

Thank you so much for making this video. You just saved me $120 for my local amp repair shop just to look at it. Let alone providing me an answer.

[@UncleDoug]

You're welcome, AJ. It's great to hear that the videos offered practical, helpful information.

[@joelewisband879]

I am so thankful for you and your video's You have helped me thru many nights of insomnia...😎👍👍☕🙏

[@UncleDoug]

We're here for you, Joe :)

[@danilosuarez4887]

im a number 1 fan of uncle doug. very informative. thank you.

[@UncleDoug]

You're welcome, Danilo. We appreciate your nice comments.

[@rcjward]

Thoroughly valuable information!

[@UncleDoug]

I'm glad you appreciate it, Ronny.

[@gordonperkins6268]

Love your videos, some of the most interesting and informative videos ive seen.Personally Id like to see more of the algebra ex plaining the application to and from component to component via Schematic and equation in rellevance to the assembling order. You perhaps one i dont know about

[@UncleDoug]

Thanks, Gordon. I'll keep your suggestions in mind for future videos.

[@davea.8499]

Again, this is awesome info. It helps me with a project I am working on. Thanks

[@UncleDoug]

You're welcome, HA :)

[@randorider2801]

Hey Uncle Doug! Thanks for the free education!

[@UncleDoug]

You're welcome, RR.

[@jcpsaravia]

Hi Uncle Doug!! Nice information you have been posting!! I have learned a lot!! Greetings from Costa Rica!!

[@UncleDoug]

+Juan Carlos Perez It's always nice to hear from our international viewers, Juan. Rusty and I are glad the videos are helpful and wish you the very best.

[@IoneiTheBand]

Thanks for this video! Helped me narrow down an issue with my amp.

[@UncleDoug]

Glad it helped, Ionei.

[@weldingfabricationrepair6331]

great video, information and example. very understandable thank you for sharing your knowledge and understanding.

[@UncleDoug]

You're welcome, WF&R. Thanks for your very nice comments.

[@user-tw7ef7vk1q]

Thank you. you just solved my problem. My Fender Blues junior had really loud 60 hum noises.. now, I solved this problem and just subscribe your video!

[@UncleDoug]

That's great to hear. We're glad the video was helpful :)

[@Talisman21]

Extremely helpful. Thankyou so much!

[@UncleDoug]

Glad to hear it, T :)

[@sonnygutierrez3979]

Very informative, great video! Thank you very much uncle Doug!

[@UncleDoug]

You're welcome, Sonny :)

[@Kalkaekie]

Very helpful video. Thanks for sharing !

[@UncleDoug]

You're welcome, Kal. I'm glad you enjoyed it.

[@JesusIsLordofMybeing]

Thanks so much Doug!! Very valuable information sir.

[@UncleDoug]

You're welcome, JT.

[@catfishfry336]

Thanks Doug!!….as usual outstanding lesson and well received!…..Thank You…

[@UncleDoug]

The pleasure is all ours, Catfish :)

[@kevinking2468]

Thanks Uncle Doug. Welcome Back!

[@UncleDoug]

It's good to be back, Kevin

[@zachjarrett8730]

Thank you! Great troubleshooting step that can be employed early on to save a lot of headaches.

[@UncleDoug]

Thanks, Zach. It's not a cure for all hum issues, but it is a good first step :)

[@Songwriter376]

Hello and just wanted to say thanks for this very helpful channel.

[@UncleDoug]

You're very welcome, ZoT :)

[@lofstrandsverkstad]

Thanks! I'll try replacing the death cap and or building a tube rectifier. Been watching your videos, soon all. Man, you are doing a great deed (is it called that?)! Will get back to you with what helped and with an explanation of possible.

[@UncleDoug]

You're welcome, Anna. Good luck and be very careful with shock hazards.

[@emadismusic]

Excellent! Very interesting and informative!

[@UncleDoug]

Glad you enjoyed it, EM.

[@jambalaya7647]

A 60 Hz hum through its speaker even when the amp is on standby stumped me for a bit, Uncle Doug, until this video illustrated what the problem is not, and helped suggest what it likely is - electromagnetic coupling from the power transformer to the output transformer. Now to dope out the how of the what.. Your videos are both helpful and entertaining, Uncle Doug. Thank you for making them.

[@UncleDoug]

Try placing a fairly thick, grounded steel partition between the two transformers, if possible. It should reduce, if not eliminate, the problem. Even if it only reduces the hum, it will prove your theory. You're welcome for the videos :)

[@louisegilmour4366]

Ive recapped... retubed.... in an effort to try to remove a hum that existed on standby and the on position, slight hum with no volume control difference.... turns out to be a combination of a new speaker baffle with the speaker moved closer to the power transformer and a larger magnet.... electromagnetic coupling .... thanks !

[@49bednar]

Hi again Doug, Just built a 5F1 kit. Works great but has a hum, which I now know is a 60 cycle hum. I was prepared to live with it until I saw this video. It also has a fairly loud screech at full volume. Your video gave the idea and courage to poke around the 12AX7 socket. I found that pin 2 was a bit loose and as I fiddled with it, presto...no screech and almost silent. Miracles will never cease in the tube world. Thanks again for your great work. George

[@UncleDoug]

You're welcome, George. It's great to hear that the video was helpful. Best of luck with your projects :)

[@moilimyacoub4580]

Woooow rhank you @uncledoug for this video. As I was just testing a BOGEN Tube preamplifier from 1963 and all Variac test passed but thenwhen I was testing the pre-amp.. I was hearing that kind buzz/hum continuous from the chasis of the amplifier. But when listening to music and raising the volume that buzz/hum sound didn't affect the volume and I was asking myself what could cause this. Now this clarify more about the myth or how to check these kind of situation. Thank you and keep up the great work sir ;-)

[@UncleDoug]

You're welcome, MY. Best of luck with your project.

[@ess2586]

Huge help Uncle Doug....trying to decrease the hum in my 5E7 Bandmaster build and I did not know if it was 60 or 120 until you compared the two....it's definitely 60 cycle and now I know what to troubleshoot. thanks!

[@UncleDoug]

You're welcome. Thank you for using the video in the way it was intended, to help with elimination of hum based on its frequency.

[@jeremywatson3882]

Really helpful, many thanks Doug

[@UncleDoug]

Glad to hear it, Jeremy :)

[@UOttawaScotty]

Excellent video, very interesting problem !

[@UncleDoug]

Thanks, US.

[@michaelpukmel9175]

Thanks Doug, great vid, great info.

[@UncleDoug]

You're welcome, Michael.....glad you liked it.

[@TheTuckmorgan]

Thank you for posting. I've been wondering if the tubes in my 67 reverb needed to be replaced. They're still rockin. Again, thanks for the post

[@UncleDoug]

If they still work, keep using them, Tucker. People change tubes way too often and for no good reason.....at least in my humble opinion.

[@20thcenturyboy85]

Thanks for this informative video!

[@UncleDoug]

You're welcome, CB :)

[@BadToad1963]

Very useful information. Thank you.

[@UncleDoug]

You're welcome, Clark.

[@mrGoesto11]

Little gems of information that have helped me along in my little hobby (obsession).

[@UncleDoug]

We're glad to hear it, Mr. G. :)

[@dwightjt]

Yes indeed Uncle Doug Don't guess diagnose. Many year's ago as a pro. Mechanic certified. I saved me and my customer's Money by diagnosis Not guessing. Your a wise ol man. Love your vids. I have learned more from you in tube Electronics than anywhere else or Books. Thanks for sharing The way you do. Dwight.

[@UncleDoug]

Thanks so much, Dwight. We appreciate your kind words.

[@davidwindstrom2472]

Thank you SO MUCH. Believe it or not, this just happened to me with a 5751 (12AX7 replacement) NOS tube. I was going crazy testing ground loops, upstream components and cables, and was getting ready to send the amp in for repair. After watching your video, I pulled the single input 12AX7 (5751) I had recently rolled in, and problem solved. I couldn't believe it. What an obscure problem. Also interesting..the hum was only in the left channel (dual triode), and there was also a scratchy crackling in the volume control (fairly new amp). The hum did not increase with the volume though. Wild. I'm assuming the increasing volume increasing grid voltage masqueraded as a dirty volume control.

[@UncleDoug]

I'm glad the video was helpful, David. Congratulations on a successful repair.