Tube guitar amp hum solution - $0.00!!!
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- Опубликовано: 5 дек 2020
- After 9 months of trying to resolve the hum in this awesome Vox V125 amp, I discovered it was as simple (and free) as this... 'one weird trick'. 😂
Most amp hum diagnosis checklists tell you to check and usually replace the tubes first. The argument is that tubes commonly fail and that they are cheap to replace. Sure, they are a major point of failure in a tube circuit, but nothing is cheaper than tightening your power transformer bolts. 😄 It's at least worth a shot.
The reason for the hum in this case is because the E core transformer (EI) is made up of laminations of thin metal plates. Since they conduct magnetism, if they are slightly loose, the magnetic flux of the transformer (oscillating at 50 or 60Hz) can cause them to vibrate. Annoyingly, this will induce electrical noise into the secondary windings and cause noise that not even the freshest, highest capacity power supply capacitors will be able to filter out.
In my case, I was able to feel the chassis physically vibrating when the amp was powered up.
I hope this will help someone else who's been hunting that hidden source of hum in a guitar amp.
All the best!
Dax. 
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Metal wrench, using both hands, amp powered on. I can't think of a single thing that could go wrong.
🙄
It’s safe
Too many white peoples anyway
Good Man!! ...doing this fixed the hum issue I was having with my Marshall vs100, thanks a lot for posting this 'one weird trick!'!
That's fantastic news. So glad to hear it helped. :)
Mate, saved my ass! I had the loudest fender amp in creation. Did exactly what you did and got the same fantastic result. NO NOISE WHATSOEVER JUST CLEAN GUITAR . Yahoo!
Hey @stringfish100, that's great to hear. Glad it was useful to you. Hopefully it's saved you some time and cash.
Wow, I have a beautiful tweed twin amp, high power, 3 years old that now is making some hum and it sounds like transformer... I will check it out before I take it to the technician...Thanks for sharing it. Cool video!!
More likely to be your output tubes, but this can't hurt to check. Good luck with it!
Lol! Congrats, love this vid.
No Money!Just a lot of Time vested,to find out!Glad you figured it out!Cool 4 U!Take care,now!
My guess is that one of your preamp tubes are very microphonic, so it picks up the vibration of the power transformer. When you tighthened the screws, the laminations and everything on the transformer gets tighther together and the vibrations cancel each other out. I suggest checking your pre amp tubes for microphonitivity!
Nah, tubes were the first thing I tested. In fact, I even borrowed tubes for a test from another unit of the exact same model of amplifier. The noise was being induced onto the power rails and you can't get clean output with dirty power.
@𝐒𝐨𝐯𝐞𝐫𝐞𝐢𝐠𝐧 𝐀𝐜𝐨𝐮𝐬𝐭𝐢𝐜𝐬 But did you actually watch the video and listen to the explanation I gave? It was the E-core power transformer delaminating after 40 years of service. That's a lot of hot-cold cycles.
I disagree, it’s adequate grounding. Mine has a similar issue. I have 4 separate grounds going to each of the 4 lugs on the PT. Its volume dependant and on both normal and vibrato channels. A similar crackley hum can originate in a preamp tube if the grid is too close to the filament. In that case just replace the bad tube. However tiger is improving the contact my torquing up that loose connection. Thank you
Sorry, not Tiger but Daxmakes
Transformer laminations should never be the slightest bit loose. They should always be as tight as possible when running. That is a good way to wear out a transformer and or cause failure, higher current draw which in turn blows fuses.
That is why it is not a good idea or design to mount transformers using the laminated plate bolts.
In theory if it is done correctly there will be no problem but after many years of use and with the bumps and hits and hot and cold that a guitar amp is exposed to, the bolts will slowly over time loosen. Metals expand and contract at different rates and different temperatures. That is the first thing i will check on an amp i am servicing. Visual inspection of components and solder joints and tighten all nuts and bolts, pots, groung connections. Before i even check a fuse or turn it on.
At any rate i know this is an old video but i noticed during your video the bolt that you were tightening first appeared to strip while tightening it. If that is the case buy a new nut and bolt and replace it. Also what can be done is remove the transformer buy longer bolts and a few extra nuts with lock or bite washers install the bolts first tight to the transformer use mild grade locktight then install the transformer to the chasis adding two more nuts and isolation washers or grommets on the bolts to prevent slipping and a buffer for vibration. Otherwise everytime you have that amp open to clean pots or whatever maintenance you are doing always snug up all the bolts while doing so.
One other note use a smaller wratchet to prevent over tightening and stripping or stretching the bolts
Cheers good video will help alot of people i am sure
My deluxe is making that noise now. Changed original tubes to NOS ones, rectifier red plated so immediately pulled them but with original ones back in it hums now. Might try this tomorrow
I know I am pretty randomly asking but does anyone know of a good site to watch new series online ?
@Anders Briar i dunno try flixportal. you can find it through google:P -flynn
@Flynn Braylon Thank you, I went there and it seems like a nice service :) Appreciate it !!
@Anders Briar no problem xD
Awesome! I have one doing the same thing and suspect the transformer. I’ll give it a go!
Good luck! Let us know how you go with it. Also, be careful inside tube amps, they have voltages in excess of 400V and they don't mess around or say sorry!
Does the hum increase/decrease when you turn the volume controls? Mine is
@@dirtyboy3544 That means the problem is 'upstream' of the power amp stage, so tightening the transformer won't help.
It's probably tubes (it's always the tubes 😂).
@@puzzlefactorysoundstudios I put the original tubes that were in there when it was nice and quiet a few minutes before back in after trying the NOS ones and now it hums
@@dirtyboy3544The NOS tubes are probably not well matched or you need to adjust your bias.
Large power transformers in building substations have to be “set up”, there is a procedure where you adjust the frame out to minimize the vibration which is what causes the hum, so, you have a mini sub station. Lol
Ahh, that's fascinating!! Thanks for sharing that knowledge.
I think its a ground issue. Tightening the two pieces of chassis together perhaps altered a ground loop path.
Cool little amp! I love amps like this.
It IS a cool amp, but though at 100W, not so little! 😃
The issue was definitely not grounding because that wouldn't cause physical vibration in the chassis.
@@puzzlefactorysoundstudios Loose transformer vibrating, and it's picked up by a microphonic component?
You could prove this theory by lightly tapping on components with a plastic tool while the amp is powered. You'll know immediately if the component is microphonic.
@@vhfgamer Who do people insist on suggesting possible (but wrong) solutions after I've already shown what the exact problem is and how to solve it?
@@daxliniere Maybe because your solution is invisible?
One question: your power transformer has isolation washers on bolts? (fluctuation above the chassis) or the transformar laminations have a continuity to the chassi? and , another one: the hum noise follow your master volume? Thanks for sharing.
Hi Diego. No, the transformer is electrically-isolated from the chassis. The vibrations in the trafo laminations where imparting a 150Hz hum onto the power rails. As for master volume, no the hum was constant, which is why I initially thought it was a problem with the phase inverter stage, which comes directly after the master volume pot.
how frustrating , thanks for the information. you should rcord a demo of it now it works , it is the lead version with the diodes ?
Wow would of never guessed.
Thanks for the video. I got a Randall with a similar issue...will definitely try this out. Just curious to know if the hum get louder with the volume up? On mine theres no difference in the hum with the volume up or down...with or without the guitar.
Have you changed the power tubes yet? If so, have you biased them?
The hum on my amp only happens with the volume off. As soon as I turn volume up a little, the hum goes off completely.
All the screws on my amp were slightly loose including the speaker screws. The screws needed less than a 1/4 turn to tighten them up. The loud hum has disappeared.
I'd like to ask a question please.... where does the hum go to when it disappears??
having sim issue on s sound city 50 plus
Did any of the transformer mounting bolts have a ground attached? This would have been my first guess.
Interesting point. I don’t believe in magic, so it appears that tightening the bolts may improve metal-to-metal contact between tranny and enclosure, resulting in a better ground connection?
So, are you saying that tightening that bolt eliminated the hum noise itself, but not the vibration? Obviously, the problem was the audible hum, which you got rid of, but I'm wondering if the vibration itself is still present?
Transformers naturally vibrate it is inherent to their design. It's wire wrapped around iron with electricity flowing through the wire it will always vibrate even if you can't see hear or feel it. The plates "lamination) should never be loose, always as tight as possible. When they are losses they will chatter like a wood jointer plane lol. It is good practice to. Tighten snug up all the bolts in your amps from time to time. Usually whenever you service it.
Large power transformers in building substations have to be “set up”, there is a procedure where you adjust the frame out to minimize the vibration which is what causes the hum, so, you have a mini sub station. Lol
You cancelled out Vibration or more to it? Genuine question.
The laminations had become delaminated (the lacquer must have failed after 40 years of hot-cold cycles) and tightening the bolts fixed that.
wait wait, Vox120+? Holy shit, thats my amp im trying to troubleshoot today...how the hell I found this video?!
Hope it helped!
YT reads your mind.
May have been a grounding problem, the bolt you tightened pulled the two pieces of chassis together.
Definitely not a grounding issue. The hum's fundamental was 150Hz, you woud expect 50Hz if it was grounding. The hum would also have disappeared instantly upon making proper ground contact, if that were tha case. (As you can hear, the 'de-hum' 'effect' was variable.) The cause was that the transformer's laminations had spread apart and the 50Hz current that was passing through the transformer's windings was causing them to vibrate (due to changing magnetic fields pulling and pushing the steel laminations). Transformers are dipped in clear lacquer when manufactured, but that can fail over time. This amp is over 40 years old, so lots of hot-cold cycled. Tightening the bolts pulled the laminations back into tight contact.
why though? how. shouldnt have any effect on the hum
And yet... it does.
The reason is because the transformer's laminations had spread apart and the 50Hz current that was passing through the transformer's windings was causing them to vibrate (due to changing magnetic fields pulling and pushing the steel laminations). Transformers are dipped in clear lacquer when manufactured, but that can fail over time. Tightening the bolts pulled the laminations back into tight contact.