Tube guitar amp hum solution – $0.00!!!
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.
#Tube #guitar #amp #hum #solution
Originally posted by UCdjP4yiP3vJydH5FETKfvEw at https://www.youtube.com/watch?v=1DJFZjkoYzo
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The chassis frame of the amp needs to be tightly constructed otherwise the chassis grounding will be imperfect. Essentially by tightening one part of the frame you provided a whole frame earth rather than a part frame earth. This does occur with guitar amps a little bit as they are constantly being moved about for gigs and are therefore more vulnerable to loosening up.
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.
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
No Money!Just a lot of Time vested,to find out!Glad you figured it out!Cool 4 U!Take care,now!
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!
Metal wrench, using both hands, amp powered on. I can't think of a single thing that could go wrong.
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
Wow would of never guessed.
Did any of the transformer mounting bolts have a ground attached? This would have been my first guess.
May have been a grounding problem, the bolt you tightened pulled the two pieces of chassis together.
Good Man!! …doing this fixed the hum issue I was having with my Marshall vs100, thanks a lot for posting this 'one weird trick!'!
wait wait, Vox120+? Holy shit, thats my amp im trying to troubleshoot today…how the hell I found this video?!
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?
Lol! Congrats, love this vid.
why though? how. shouldnt have any effect on the hum
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.
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!!
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.
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!
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
Awesome! I have one doing the same thing and suspect the transformer. I’ll give it a go!
how frustrating , thanks for the information. you should rcord a demo of it now it works , it is the lead version with the diodes ?
having sim issue on s sound city 50 plus