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

[@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.

[@julesl6910]

Doug, I can't tell you how many times I've shared this video with friends and others in need. Distinguishing the pitch of the two hums is instrumental in troubleshooting so many problems. All Hail Doug, and Rusty.

[@UncleDoug]

I'm glad to hear that the video was helpful, Jules :) Thanks !!

[@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!

[@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 :)

[@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.

[@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.

[@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 :))

[@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.

[@jamesmfreire]

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

[@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 :)

[@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.

[@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 :)

[@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

[@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.

[@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 !

[@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.

[@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 :)

[@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.

[@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.

[@kingdom-art7672]

brother, I want to THANK you for what you've done. I hope that my comment encourages you. I took apart my preamp and just slightly pushed it to the left! and boom! the humming/crackling was gone, eradicated!!!! I love you man!!! and your right! you did save me time and money! love you bro

[@kingdom-art7672]

pushed the tube*

[@UncleDoug]

+Thomas Johnson That's great news, Thomas. You can tighten up the socket a bit (use a tiny screwdriver and carefully bend each of the contact "circles" into smaller diameters) to eliminate a re-occurrence. It's good to hear that the videos are helpful :)

[@kingdom-art7672]

+Uncle Doug yes sir! bless you man I'll keep that in mind if I come into this problem again. thankd

[@UncleDoug]

You're welcome :)

[@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!

[@DjPaulDeLeon]

Holy crap...I now know whats with one of my radios that I restored and still got the hum....thanks!!

[@UncleDoug]

You're welcome. Good luck :)

[@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 :)

[@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.

[@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.

[@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 :)

[@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.

[@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 !!

[@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 !

[@dwightjt]

You know Uncle Doug. You seem to be a kinda Rare breed of person When you come across a problem you make A video about it Educationally as if you didn't know all ready But I'm sure you are learning to as you Go along. I hope I'm Not puffing up your head. But your a humble man. Your teaching does not jump back and forth And create confusion. It's organized and Interesting. I think you Are helping a lot of People. And saving people money. I worked in quality Asurance before I retired 2 years ago Now I get to drink a beer And sleep in HaHa. During my inspections of auto parts one of the supervisors found out about my back ground Years of experiences In electonics electricle Wiring and mechanics Repair. And offered me a position to build Powe supplys to Test electrical parts like the head lights on the Chrysler 200 and 300 automobiles so Eventually I had to install solid state Relays and electronic Control module's For the 300 HID headlight projector Movements for testing. I built 32 power supplys for 100 to 300 Dollars a piece instead Of the contracted out 17,000 dollar a piece universal power supplys. I had chinese and Korean people wispering to me That I was saving to company hundreds of thousands of Dollars Of money I guess a good way to make friends I wish I was still there. It was a lot of Fun for me. So Uncle Doug I know quality When I see it and you are It. I had to repair them Often, the inspectors On the line twisted my Hand wiring around Untill they would break down so I made a few Spairs to replace one or two while I made Repairs on the units Used on the line then return it to keep the line going. Time saver Instead of stoping the line. It was fun soldering all those Hand made harnesses. Love your good work By. Dwight.

[@UncleDoug]

Thanks for sharing your life experiences, Dwight, and for your very nice comments :)

[@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 :)

[@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.

[@IllusiveSwampMoose]

Thank you! I know this video is 10 years old but it was it was clear, to the point, and extremely helpful in troubleshooting my old reel to reel

[@UncleDoug]

That's nice to hear, SM. I'm glad :)

[@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 :)

[@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 :)

[@jamesromano3567]

I restore old electronics and this stopped me from trouble shooting the capacitors in my 1958 Harman Kardon Allego monaural amplifier. Had a 60 cycle hum that was constant and turned out to be the 6V4 fullwave rectifier. But then i still had a hum lower in volume. It varied with the volume control and it turned out to be the phonograph preamplifier 12AX7 tube. Thanks!

[@UncleDoug]

You're welcome, James. The frequency of the hum can really help determine the source. I'm glad the video was helpful.

[@jetblakink]

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

[@UncleDoug]

Thanks, JB :) We do too.

[@stillcrazyafteralltheseyea1379]

I'm an electronics technician by trade, although I don't specialize in audio. Especially tube audio, which its it's own special mixture of voodoo and electrical witchcraft. I like to listen to things like this every once in a while to see if the author is dangerous, really knows his stuff, or is full of hot air.... I want to say your video was so full of hot air I had to leave the room...... but I can't. You were right on point with everything you said, as far as theory goes. But what was really cool is the way you explained it, both with the sig gen AND the little explanation on paper. Nice job. I'm actually going to watch more, because even salty old dogs like me can pick up little things we either forgot or didn't know in the first place. Keep it up, and thank you ! Peace, Matt Gee

[@UncleDoug]

Nick Gregg Greetings, Nick, and thanks so much. I was getting nervous as I read your comment, fearing that I was about to get my electrodes handed to me, but it definitely ended well. I'm flattered that an experienced tech would approve of my videos and look forward to future (hopefully positive ;) comments.

[@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 :)

[@122Music1]

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

[@UncleDoug]

You're welcome, 122 :) Thanks !!

[@brettgallagher6951]

Hi: Got my 30 watt amp build all straightened out. Hum was definitely not the power transformer. Had to fix the grounding layout and ground bus. Also found loose connections for the screen grid circuit and grid stopper resistors. Lots of loose connections. When I originally built the amp, think the soldering iron was not hot enough and I was using the wrong soldering iron tip. With a hotter iron and screwdriver tip, was able to get the connections very tight and strong. Amp works great now!! No more hum and buzz problems as I was previously having. The tone has also improved and the amp seems to have more output power now.

[@brettgallagher6951]

Thanks again for the great videos and helpful advice!!! Brett Gallagher / TubeGuy1975

[@UncleDoug]

@@brettgallagher6951 You're welcome, Brett. I think that figuring out all the mistakes we made during a build is probably the most educational part of the process.

[@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 :)

[@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.

[@cdelonline]

I got a akai m8 tape reel to reel and took out the amps and to stand alone as preamps. I had 60 hum/ hiss forever and recapped the hole thing witch got a bit quieter and replaced el84 tubes. It has an other power tube in there I've been going bananas trying to figure out this hum. And your video saved me. I will replace remainder tubes tomorrow . Thanks and hope my hum goes away

[@UncleDoug]

I hope the tube replacement solves the problem, CD. Best of luck.

[@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 :)

[@emadismusic]

Excellent! Very interesting and informative!

[@UncleDoug]

Glad you enjoyed it, EM.

[@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.

[@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.

[@joemicoletti]

You are a true blessing, Uncle Doug -- thank you!

[@UncleDoug]

Thanks so much, Joe :)

[@bullet0657]

Hi and thanks for pointing this out.I have silvertone 1474 that has this 60 cycle hum and no amp tech around here could find the problem so i will re check my tubes one at a time. they checked the tubes on a tube tester and they all came out good to very strong.Thank you for post things like this Uncle Doug this will save people time and money.

[@UncleDoug]

You're welcome, Edwin. Thanks for watching and for posting an excellent comment. As you saw in the video, a tube tester can often give a false impression of tube quality. It simply doesn't check all the parameters.

[@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.

[@TroyLeonardO]

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

[@UncleDoug]

You're welcome, Troy :)

[@keithhatton1975]

Uncle Doug, much appreciated, I was about to swap all caps. My hum, as you pointed out is a 60 cycle... valves I'm coming for ya.

[@UncleDoug]

I hope the video saves you some time and money, Keith.

[@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.

[@Aijse]

Thanks for the examples of the hum at different frequencies!

[@UncleDoug]

You're welcome, Aice.

[@qua7771]

Excellent. I just finished a fairly elaborate amp build, and got all paranoid about a 60Hz hum I'm getting. I'm also getting some undesirable distortion. I measured every component prior to installation, and double checked my solder joints to avoid this sort of thing. I'll swap tubes in the morning. Thanks.

[@UncleDoug]

Thanks, AR. Good luck with the repair.

[@qua7771]

@@UncleDoug Hey it worked! The whole time I thought I had a power supply problem, and would have to pull the board again. Your video saved me a bunch of time. The problem was the PI 12ax7 long black plate Raytheon that worked fine in another amp V1A. Odd! I replaced it with a new production long plate Mullard. The ghost note, (inter-modulation distortion) is gone. I'll have to donate. Thanks.

[@UncleDoug]

@@qua7771 That's great news, AR. Congratulations :)

[@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.

[@michaeldowning796]

Thanks Doug!!! Just got a Marshall head on the bench that has 60mhz hum and the customer said he just replaced all the tubes so just as you said I was thinking caps but inspecting them they look ok Now Im going to go through all 11 tubes on this thing (Marshall 6100LM, 7 - 12AX7's, 4 - 6L6's)....

[@UncleDoug]

Remember that tubes are only one possibility, Michael.

[@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.

[@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.

[@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.

[@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.

[@1986yamahafazer69]

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

[@UncleDoug]

Happy to help, YF.

[@heyartbailey]

Thanks for posting this! Just got done recapping and rebuilding a Bogen CHB-100, and was left with a pronounced 60 cycle hum. Rechecked all my work, outside foil orientation, etc. Saw this video, and put in a fresher 6EU7 and 6C4...bingo. There's still the slightest bit of hum there, gonna try to find a 12AX7 in my stash. This amp wasn't made with love and care, so it might just be something I have to live with, but I know I'm not going to even notice it when it's got Hammond organ screaming thru it.

[@UncleDoug]

You're welcome. I'm glad the video was helpful. One other thing to check is lead dress, Art. Use a wooden chopstick and move the pre-amp wires around.....see if any of them affect the hum.

[@bootlegapples]

Thanks UncleDoug .I'm doing my first conversion,a console tube amp to guitar amp,and after modifying it to accept a guitar I am getting a fair amount of hum when I turn the bass up..even with no guitar plugged in.I will do the 60 vs 120 cycle hum listening test.

[@UncleDoug]

+bootlegapples If the hum began after your modification, be sure that your input jack(s) are self-grounding, that your input circuit is properly wired and includes correct-value grid leak and grid stopper resistors (see my latest video series), and consider using properly-grounded shielded cable for all signal connections between jacks and the first tube grid. Good luck.

[@UltimateEnd0]

I have had the 60hz hum when I bought my "Bravo Audio V2 Class A 12AU7 Tube Multi-Hybrid Headphone Amplifier". I installed a gold lion tube before even trying the original tube. I also have it hooked up to a digital to analog converter from my computer.

[@UncleDoug]

Is there a question?

[@UltimateEnd0]

@@UncleDoug What is causing the 60hz hum? Is it the stock 1.5amp power supply charger causing it? Should I replace it with a 3amp one?

[@UncleDoug]

@@UltimateEnd0 I wish I could magically diagnose this issue long distance, but it's simply not possible. I'm afraid you'll have to either do on-site troubleshooting.....or get some qualified help. Good luck.

[@LongJim]

This is great info. I just checked out a Montgomery Wards Airline 6000 which exhibits a hum, but still produces sound. I shied away from buying it, fearing it had bad caps. It sounds like 60 cycle, so it may just be a bad tube. Thanks Uncle Doug!

[@UncleDoug]

You're welcome, Jim. There are many other causes of 60Hz hum, so keep that in mind.

[@jameswatkins7263]

Checking out an amp head tomorrow at my local guitar shop. They said it had a bad hum. So I hit this video up again to listen to the difference between the 60 and 120Hz. Remembering that 60 tubes and 120 caps. Lol

[@UncleDoug]

Use the hum as a bargaining tool, James. No matter what, it will cost money to fix.

[@baron_orm]

I experienced this very issue with my 2008 Blackstar HT-5 Combo, heard the 50Hz (I'm in the UK) and wondered about input caps or tubes. Replaced the single power amp tube and it removed the hum completely :)

[@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 :)

[@larrydering1598]

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

[@UncleDoug]

Thanks so much, Larry. Welcome back :)

[@mrGoesto11]

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

[@UncleDoug]

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

[@AmIonArock]

your video made since to me, and I think your excellent in teaching. your saying different tones mean different things. i am very new to working on my tube amp, which is a alamo dart. I went from no sound at all ... to a hum sound that gets louder when turn up the volume! It was very exciting . Now i have convert that hum sound to REAL: sound.

[@UncleDoug]

Greetings, AA, and thanks for the kind words. It sounds like you're making some progress. Best of luck !!!

[@The_Absurdistt]

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.

[@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.

[@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 :)

[@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 :)

[@randorider2801]

Hey Uncle Doug! Thanks for the free education!

[@UncleDoug]

You're welcome, RR.

[@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 :)

[@emanoelraiffnobrega7419]

Hi, Mister Doug. Congratulations for this video. I have a Fender 68' Custom Vibrolux Reverb (PCB) with reverb on both channels and it has a 60Hz hum that intensify when I turn up the volume, especially on the second channel. I look inside and touch with a chopstick the pins 7 from V1B, V2B, V4B and V6B and when I touch these pins, the hum intensify (especially V2B and V4B). This new Fender 68 Custom Vibrolux Reverb has 10k resistor atached to the grids from tubes V1, V2 and V4 I can't understand why these resistor, but I know they are not responsible for the hum. There is another noise from full-wave bridge rectifier I listen but not comes from speaker. It comes from the ceramic capacitor connected besides each diode. Whe I put my ear near the bridge rectifier, the buzz noise is more present. Fender email me the schematics for this amp. If you want it, I can email to you. I am a brazilian guy. Sorry for my english, it is not so good.

[@UncleDoug]

Your English is fine, Emanoel. If the hum responds to the volume control, then it must be originating before the VC in the circuit. This will narrow down your search. Try switching pre-amp tubes to see if it makes a difference. Good luck.

[@emanoelraiffnobrega7419]

Uncle Doug Thank you! I will do that. But the other noise, it comes from the snubber capacitors in parallel with rectifier diodes. Is this buzzing normal?

[@hydorah]

Working on a Laney AOR 30 at the moment has every kind of hum you can think of! It did have a couple of microphonic ECC83s. replaced all four it hums less now. It now has the higher pitched hum that increases with volume. Interesting with the reverb engaged it gets louder still. I'm replacing the big filter cap first then I'll see where I'm at. I've got a schematic so if humming persists in the reverb section I know where I'm poking! Your vids continue to be a great resource and I'm learning... little by little

[@UncleDoug]

Good luck with this frustrating problem, Hy.

[@hydorah]

@@UncleDoug Thanks for the good wishes. My Capacitor arrived. The old old one was marked 50uF (greek mu) a couple of times, with a printed colour code legend and a common ground which told me it contained to 50uF caps in one can - Very helpful. The new one was marked 50M + 50M (not nearly as helpful) but which I think, thanks to you (?) I was able to work out was another can containing two 50uF caps. Anyway got the thing install and bingo! Hum is now reduced to expected levels! Happy days! I'm now enjoying my first ever 6v6 amp. Cheers!

[@UncleDoug]

@@hydorah Congratulations on a very successful repair, Hy. Thanks for sharing your triumph with us :)

[@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 :)

[@robzecc]

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

[@UncleDoug]

Glad it helped, Rob :)

[@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 :)

[@Kenoleptic]

Very informative, thanks. I found this after listening to a Wurlitzer P-12 (I recently acquired) that has a bad hum. The amp also has a hum adjustment control, that doesn't help much...actually as it "reduces" the hum intensity, the hum seems to "pulsate". I noticed the speaker has what looks to be a transformer attached to it, but no idea what that does as I am new to the amp world. I do not see it in the schematic. I have a replacement speaker that is supposedly off of a P-12 and it does not have the transformer. I'm hesitant to plug a different speaker in as I'm not sure if I could damage the amp. Anyway, thanks again for taking the time to make these types of videos!

[@UncleDoug]

Ken O The hum in the P-12 amp is probably from leaking filter capacitors, Ken. The hum adjustment balances the center-tapped voltage to the amp tubes, reducing hum in the tubes, but will not be able to eliminate filter cap hum. The transformer on the speaker is the output transformer and is essential for the speaker and amp to function. The speaker is also probably an electrodynamic speaker with electromagnetic field coil, which is part of the power supply of the amp. This is a special speaker constructed specifically for this amp circuit. It's possible, but quite difficult, to make the modifications necessary to substitute another speaker.

[@joemcgraw5529]

45 trolls really? your at the wrong channel this guy knows what hes doing ,kids jeez ,sorry doug ,much respect to you really!!!

[@UncleDoug]

Thanks so much, Joe. Don't pay attention to the drooling idiots with the thumbs down.......no one else does :)

[@Raiders757]

I didn't want to offend anyone, so I subscribed. Great info by-the-way. despite having played guitar since 1980, I am new to tube amps. I bought a used Haze 40 and replaced the tubes a few months ago. Sadly the first set of tubes I got kept blowing the fuse out. The replacement set works great, but when I made my first attempt at biasing them, I think I had my ground hooked up wrong. It may have been touching something, becasue I couldn't get them to even out. Anyhow, I ended up with a lot of crackling sounds, and a low pitched hum. I discovered the error of my ways when I opened the amp back up and now have the tubes biased to 38. Sadly I still have the constant hum, Btu the crackling sound is gone for rhe most part. I checked everything, guitar, pedalboard, and despite having an original Rockman Smart Gate (bought new as a young a lad), the hum is still present. I was thinking it might be something within the amp, but now I am wondering if it's my tubes. The amp sounds great, but the hum kind of worries me. I am still hoping that it might be some sort of outside interference. My practice area is around a lot of devices. Stereo, PC, and the room is right off the kitchen with microwaves, coffee pots, etc...

[@UncleDoug]

Rusty is very pleased to hear that you subscribed :) Re the amp, I assume that the 38 refers to the mA of plate current, but this is not an accurate way to bias an amp. Please watch my video on how to bias a DE amp by adjusting the plate dissipation. As far as the hum, it sounds like you may need to get it looked at by an experienced tech. Best of luck.

[@jr_8712]

Very good information; thank you much. I was wondering what was causing that hum in my jukebox amplifier.Now when I'm done work I'll have to try swapping some tubes out.

[@UncleDoug]

You're welcome, Justin. We hope it works for you.

[@jr_8712]

Alas, unfortunately this wasn't the cause or solution for my hum; I hadn't realized prior that it does get louder with an increase in volume.

[@Souldoubtrocks]

Thanks UD. I’ve been chasing 60 cycle hum on my old acoustic amp. The volume increased with the volume knob up. So I figured it was on the preamp side. Thanks to you this ex navy sheet metal mechanic is playing with electricity. Lol.

[@UncleDoug]

That's good to hear, Mark, but be very careful when doing so.

[@Souldoubtrocks]

@@UncleDoug yes sir. Always.

[@1thess523]

I believe this is what's happening to my blackstar 👍. Ordered a new set of preamp tubes yesterday.

[@UncleDoug]

You can test your theory by switching the existing pre-amp tubes around within the circuit......or simply substituting fresh tubes, one at a time. Good luck.

[@MrBluesina]

Nice tutorial, i learned something here. just a minor correction, two 100uF caps in series gives effectiveness of a 50uF cap with double the voltage capacity.

[@UncleDoug]

Thanks, Mr. B, and you are completely correct. I apologize for the oversight and will correct it.

[@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.

[@catfishfry336]

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

[@UncleDoug]

The pleasure is all ours, Catfish :)

[@southsilicondan1776]

Tears in my eyes ... my fender champion 600 has a perpetual hum... I'm going to try your recipe...(let you know and Thanks in advance...) Daniel.

[@UncleDoug]

Good luck, Daniel. I hope you're able to solve the problem :)

[@davepastern]

Thanks Uncle Doug! I have a pair of Opera Consonance 845 monobloc amps - they run 5687/e88cc/845 valves in each monobloc. The Right channel has been humming for a month now (amps are 4 years old, haven't hummed before). It sounds like a 60hz hum to me. The 3 valves in the Right channel are probably 4 or so years old (I bought the amp 2nd hand). I'm not noticing any change if brightness if the 3 tubes, or colour changes. No change in volume capability in the Right channel either, or obvious frequency changes. Both channels sound the same, other than the Right channel has obvious hum. Adjusting the hum pot doesn't do anything at all. I checked the bias last night, and the Right channel was spot on at 4.5VDC as per manufacturer's specs (Left channel was low at 3 VDC or thereabouts and is now fixed). I'm not really knowledgeable on electrical stuff, it's mostly double dutch to me lol. I would logically think that it's best to get replacement 5687 and e88cc valves and see if that fixes the hum, would you agree? The 845 valves are harder to get in Australia and far more costly, so would have to wait a month or so until I could afford to get them from overseas. I guess if it still continues to hum, then it's something else, possibly internally in the amp and that would mean a valve tech to look at it. What are your thoughts?

[@UncleDoug]

mrtheoden Greetings, Theo. I work on vintage guitar tube amps and am not well versed in HiFi, but will try to help you. I believe the two monoblocs are power amps, and are driven by a separate 2-channel preamp. The hum may be coming from the preamp. To find out, simply reverse the inputs and see if the hum stays with the monobloc (indicating that it is to blame) or follows the input (implicating the pre-amp). If it's the pre-amp, then try switching tubes between the two channels, one at a time, to see if the hum follows a tube. If so, then it is your culprit.

[@deluxetone]

Excellent as always. Thanks for all the great information.

[@UncleDoug]

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

[@denismpoiriersr3339]

I liked the video so much I couldn't help adding my 2 cents to help others with this issue. What would be fun is to apply DC filament voltage on just that tube in that location to put the final proof of the cathode/filament capacitance coupling theory.

[@UncleDoug]

+Denis Poirier Thanks again, Denis. I rely upon knowledgeable viewers, like you, to contribute to and improve the overall video content. I still have the tube, so further testing and confirmation of capacitance could be done. If the outcome is interesting, I'll add it to the video description.

[@copytekk]

This was super helpful. Thanks Uncle Doug!

[@UncleDoug]

Glad to hear it, Aaron :)

[@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.

[@rádiosantigos1958]

That explanation was a live saving one! Thanks, now I know that the hum is not coming from my new electrolytics that I have just installed on my old radio. Now, I will look elsewhere.

[@UncleDoug]

Glad it helped, RA. Best of luck finding the source.