Managing Expectations on Tube Amp Hum

[JimmyEJames]

I'm not an engineer but even the engineers of the 50's & 60's stereo amps designed them not to have any buzz or hum. I have lots of friends who own Scott, Fisher, Marantz, Magnavox, Motorola console amps and none have hum as long as they are kept up. I think I heard one stock Magnavox with no capacitor refurb. NO HUM!

Now, pretend you're invited to a friends house to listen to an old console his dad left him. It sounds remarkably good but with a hint of hum coming through the speakers between tracks. I do know that that hum is not supposed to be there. It would be annoying to the music!

Now if you are talking about hobby amps built from the ground up or completely rewired, then yeah sure, you will have to chase down hum from bad wiring, bad grounding, power transformer not bolted down tight enough, EMF waves on the chassis...etc,etc,etc.

EDIT: In Lootheer's other thread, I also own one of those Motorola 3 channel amps (6AQ5 version) and it makes no noises. You can't even tell that it is on. Only the can capacitor has been replaced as a few years back it started humming very loudly!

Since you expert and mock me then why not give lootheer answer he need to fix his noise?
JJ

 

[JimmyEJames]

Now if you are talking about hobby amps built from the ground up or completely rewired, then yeah sure, you will have to chase down hum from bad wiring, bad grounding, power transformer not bolted down tight enough, EMF waves on the chassis...etc,etc,etc.

That not even make consistent sense? ; - (
So Mr. dcgillespie build amp from scratch and better chance for hum but old mass produce console amp no so much?
You really say ugly things if some one not agree with you 100% all the time
Have fun guys ; - (
JJ

 

[century tek]

OMG! , Me not know who is this guy that do not know I also grow up in 50's & 60's and do repair tube amp 40 years now!

All of them that I have ever repaired, audio & instrument amps, did not ever hum naturally.

 

[century tek]

Since you expert and mock me then why not give lootheer answer he need to fix his noise?
JJ

Me not hear his amp in person. Would have it fixed already if on my bench. Sorry, but even instruments amplifiers ARE NOT SUPPOSED TO HUM. Even your table radios growing up with ARE NOT SUPPOSRD TO HUM.

 

[petehall347]

a recording of the hum may help ..
in the meantime if you could possibly isolate the mains power transformer from the chassis it would rule something out . unbolt it and slide card under it or plastic .

 

[cademan]

Lol. don't know where this J is from but even I know that all the tube amps I ever heard growing up never hummed. In fact when I was 9 or 10, I would point out to neighbors and friends that their radio is humming and it should not. This would usually be a simple fix such as moving it to another location or maybe had fluorescent lamps hovering overhead.

In high school, I built an AA5 kit radio, and it was quiet as a church mouse at the very first power up. Also, while growing up, none of my parents tube radios or stereos ever hummed or I would have fixed them.

This Motorola story certainly sounds like someone else tried to do some repair on it and probably didn't quite have a first clue at what it was and was not supposed to do.

Music covering up hum doesn't sound like that is a unit I want to be listening to.

Instrument amps usually only hum when a cord is plugged into them and the volume turned up and whatever the pick-ups were picking up. No cord, no volume, no hum!

The only one humming here is me! Hmmmmmmmm.

 

[cademan]

A lot of that hum and buzz is on purpose! It is "The Sound".

 

[gadget73]

Instrument amps and audio amps are not the same critter at all. We are talking about an audio amplifier, which is not supposed to add or detract anything from the sound of the music you're listening to. This ain't Jimi's Marshall.

 

[Audiovet]

It would appear that many contributors did not notice that the OP experiences hum without any tubes inserted. All electronic arguments are thus moot.

We have two similar threads running - please see my post on the other thread.

MODS: Is it possible to combine these threads? They seem to be about the same subject.

 

[JimmyEJames]

Instrument amps and audio amps are not the same critter at all. We are talking about an audio amplifier, which is not supposed to add or detract anything from the sound of the music you're listening to. This ain't Jimi's Marshall.

Exactly understand that but that not what was proclaimed like universal truth I respond to this

Instrument amps usually only hum when a cord is plugged into them and the volume turned up and whatever the pick-ups were picking up. No cord, no volume, no hum!

Well what good is instrument amplifier if nothing plugged in no cord and no volume?
And then he say USUALLY?
Make up mind
And part about pick-ups not always true either listen to audio recordings I share with you it is good example of my point
Head noise is steady state

Me not hear his amp in person. Would have it fixed already if on my bench. Sorry, but even instruments amplifiers ARE NOT SUPPOSED TO HUM. Even your table radios growing up with ARE NOT SUPPOSRD TO HUM.

Guess you never play with Fender head or Marshall
What can I say to expert who know every circuit ever built!
And move radio away from fluorescent light is radio receiver front end pick up hum from ballast and transformer nothing to do with amplifier
Steady state noise is part of beast with many many many mass produce cheap console amps and radio amps
AND guitar amps and heads from good days
Just the way it is (was)
Think what you want I can not argue with experts who know what every tube machine ever built sounds like!
World not black or white friend just because you say so
JJ

 

[JimmyEJames]

Hum is caused by the alternating magnetic fields created by transformers and power supplies inside electrical equipment using alternating current. While playing a guitar without humbuckers, a musician would hear a hum through the pickups during quiet sections of music. Sources of studio and stage hum include high-power amps, processors, mixers, motors, power lines, and other equipment. Compared to unshielded single coil pickups, humbuckers dramatically reduce hum.

From this
https://en.wikipedia.org/wiki/Humbucker

I get you more if you want to argue at wikipedia article probably some other dummy making things up write this too!
JJ

 

[petehall347]

if the hum is indeed from the speaker just look at ways it can be coupling from power supply to speaker .. if its chassis hum that is another story .

 

[JimmyEJames]

if the hum is indeed from the speaker just look at ways it can be coupling from power supply to speaker .. if its chassis hum that is another story .

We don't even know what noise sounds like and still some experts suggesting how to fix it
If lootheer serious he would record noise and post
Every post he make since May is same question! ; - (
JJ

 

[cademan]

Well what good is instrument amplifier if nothing plugged in no cord and no volume?

I believe that this means with the amps powered up but with no input or volume turned up. Maybe getting a little off topic here so I am sitting back now.

Also, Wikipedia Is not always right as anyone can contribute to their content. I also know about all of the things that can cause hum but in general, They are not supposed to. We all know that. What's so hard about it to you JJ?

 

[inperson]

Some people who claim they hear no hum or noise from their speakers they themselves have bad hearing or their speakers aren't very sensitive.

 

[trainbuftony]

Humming without power tubes, doesn't seem likely with Permanent magnet speakers.
Maybe this was said in error.
One thing Which can cause a prominent hum, is if the Global feedback network goes open.

What are the chances that a previous owner decided to make a fashion statement by removing the feedback?

All we can do is guess.

 

[gadget73]

Its possible to hum with no power tubes. If the power transformer and the output transformer are positioned in such a way that they can magnetically couple, the hum field from the PT is induced in the output trafo and it shows up at the speaker. Thats mostly just bad design / layout if that happens but if the power trafo is replaced with an un-shielded one it might create a problem that was never there originally.

also 4 year old thread, so its all guesses at this point. A well designed amp won't be particularly noisy. A poorly designed one might be. One with dysfunctional parts, bad modifications, or any number of other introduced problems is anyone's guess. I've put together stuff that somehow despite all efforts had hum issues, and I've had other things that looked like the parts bin vomited into a chassis and it was perfectly quiet.

 

[Mr Boochie]

With push-pull fixed bias amps, use a bias supply with both BIAS and BALANCE controls. You can get pretty close to hum-free, provided the wire dressing is neat and consistent.

Hum pots on heater lines help, too.

 

[trinhsman]

The only time my amp hums is when it doesn't know the words.
As to the OP, I'm sorry, but I can't help you. If it is a ground loop, you could try a cheater plug. IMHO