power amp hummmmmmmmmmm

[greyhound]

it must be the time of year. my amp is also humming.
it must be the trafo because when i push on the top the sound decreases.
my question is (i guess) is it normal for a big amp to humm a little bit.
its a bose 1801 power amp. 2 x 240watts in 8 ohm load.
if done the polarity check.
there are no problems in the hifi chain
i was thinking about tightening the screws of the trafo and maybe put some big nails between the windings ore some sticks (wood) to put more pressure on it.

but is it allowed to humm. i can hear it only when my heads close to the amp.

the bose is great but infamous for blowing op your speakers , so there is a little worry there.

[yggdrasil]

A mechanical hum in the transformer is normal.

When you have a transformer with hum there isn't much to do, except keep the amplifier out of hearing distance.

Next step is to get an amp with higher quality transformer.

[Allanvh5150]

you could tighten up the screws a bit but dont push anything into the windings.

[doodlebug]

A couple of thoughts:

* Did you plug some things into the house that aren't normally used - like Christmas light systems? Do any of these have electronic controllers on them? The issue here is that that _might_ be throwing DC back onto the AC lines. This will cause some humming from the power transformer.

* How sure are you that this amp doen't need some attention? This thing will be on the order of 30 years old. Those big filter caps (I sold Bose back when they came out) I'd suspect of becoming leaky. Does the transformer get warmer than you remember? If so, it could be humming due to increased load due to higher than normal current flow.

Lastly, do you have speaker fuses in line on this amp. It was notorious for "going DC" and taking out speakers. While it was fixed with later revisions of the driver boards, I'd not take the risk.

Cheers,

David

[greyhound]

a few people have been through this amp and all told me it was okay.
it is just last week yhat i discovered the hummm. i have to hold my head close to the amp. in february a forum member from the dutch forum im on will check it out.
he knows this amp and will meassure everything there's to meassure inc. possible distortioncoming from the house.
but trying to fix it yourself is always bettre if its simple and you know what youre doing.

in this case im not sure what im doing so i'll wait until the new year.
there are to many reasons for the humm and maybe its normal and i just didnt notice it before.
when music is on you cant hear it even if you tried.:)

[Gary L]

I had a Luxman amp that also had a tranny hum. Had it checked and the tech told me he could tear it down and revarnish the plates if it really bugged me alkot or got to loud.
He did check all the other readings and found nothing out of spec so I just kept on useing it.

The fuses might be a good idea on an amp that has a reputation of going DC.

Gary

[JBL 4645]

I have similar issues with transformer humming. I think the best option is to place all amplification in a separate room away from the listening room to minimize this issue once and for all! Re-cut new cables to, travel to the listening room along with new cables to send the audio signals to the amplifiers.

[greyhound]

i guess houses in holland are a little bit smaller:D
no option for me

there are fuses in there but i always tought a fuse would be to slow to protect speakers. by the time it melts the damage is done.

im thinking of a relais. (dont know how to call it in english).

ore a condensator (same here) "the three legged fuse":)

[spwal]

My concern was, and maybe it is just in my mind, that the transformer slight humming came at the same time as a very audiable extra ammount of hiss from my speakers. Then again, maybe the transformer hum was there longer and i didnt notice it. I really think it is a new thing, i would have noticed something like that. maybe it was jsut the thanksgiving weekend, with everyone cooking at the same time.

can an audio tech give this a "check-up" without knowing too much about the unit itself? can a quick 30 min check up let me know if i need new parts?

the preamp is really a pretty simple looking piece of work.

thanks

[opimax]

I had a 1801 for a short time, could barely pick it up. It hummed everywhere, out the speakers(and it was just fixed for that) and the unit hummed mechanically, When the speakers started humming w/the unit i had to give it back.

I know there is one in Northern VA I am sure he would sell...you fix :applaud:

Mark

[JBL 4645]

Also adding to this I have a few but one, Marantz 1050 that hums due to the way its placed I guess, only the transformer, as well as the Kenwood KRF-X9050D THX select and most other audio electronics. The only time the room is silent is when most of the big stuff is turned off.

Now if I had a warm enough large separate room that I could place all the audio amplifiers into I would gladly do to eliminate this humming issue once and for all.

One other thing when I worked in the cinema in the past, thou I can’t ever remember hearing the amplifiers ever humming, not when there’s a projector running in the background, but I’m sure there would be some form of humming from the transformer. But you’d never hear this in the auditorium, thou you can just make out a faint sound of the (intermittent sprocket) buzzing away behind the port window, now then.

[opimax]

I would add that i do have an unfinished basement. Last week I put my 3 (4th being repaired) power amps there, drilled in the floor, ran power, pre and speaker level wires, etc. I was also able to rehook up the fans on the 2 that have them, those 2 older Perreauxs, both had physical hum, 1 more than the other (loud one helped get them downstairs!) might be officially "too loud". I am haveing both amps tuned up at some point and will mention at the time.
I don't remember the Adcom being loud but I think if you were near enough say a few inches, you could tell it was on but that is minimal.


Mark

[greyhound]

I had a 1801 for a short time, could barely pick it up. It hummed everywhere, out the speakers(and it was just fixed for that) and the unit hummed mechanically, When the speakers started humming w/the unit i had to give it back.

I know there is one in Northern VA I am sure he would sell...you fix :applaud:

Mark


so are you saying that if the noise doesnt bother me its no problem?

because i could live with the fact that there's a slight hum but do to its infamous character i keep a close eye on this amp.

Is still like it a lot. great looking impossible to move due to the ribs that try to penetrate your skin when you lift it.
what do you think about this amp.
http://audioheritage.org/vbulletin/http://img2.putfile.com/thumb/11/33104464657.jpg (http://www.putfile.com/pic.php?img=7181300)

[opimax]

What I meant to say my 1 run in with a 1801 was not a positive because of the condition of the amp. I couldn't deal with hum generated through the speakers but it was almost as loud as the music when played. by the end of the week it would hum with amp on, connectedly to speakers and no input connected but varied with the level controls but not in a linear way. The hum was loudest in the middle range and not equal to l and r. I tried to use iit on sub but still could here the hum

Mark

[JBL 4645]

so are you saying that if the noise doesnt bother me its no problem?

because i could live with the fact that there's a slight hum but do to its infamous character i keep a close eye on this amp.

Is still like it a lot. great looking impossible to move due to the ribs that try to penetrate your skin when you lift it.
what do you think about this amp.
http://audioheritage.org/vbulletin/http://img2.putfile.com/thumb/11/33104464657.jpg (http://www.putfile.com/pic.php?img=7181300)

greyhound

It’s called the (heat-sink) I bet that is hefty to lumber around the room a good (trolley truck) would be able to transport that beast around.:)

Not sure if the (Behringer Microhd HD400) hum and noise filter would remove the issues being disgust here. You can get more feedback for the Beheringer website link. And when searching for the best price use "Google product" its fast at finding the lowest prices. I'm thinking about buying of several of these to tackle the humming that is induced into the loudspeakers or rather its source could be between the amplifiers.
http://www.behringer.com/HD400/HD400_medium.jpg


http://www.behringer.com/HD400/ (http://www.behringer.com/HD400/)

[greyhound]

over here we have like this big sticky tape with lead on it (very heavy tape thats used to reduce vibration in cars and such. (you can also use it on a leak roof:D)
(lead bitume)
ive put some under the trafo and under the lid(lit) , tighten the screws and everything else i could see. humming is less now.

its now on a level wich doesnt atract my attention.
you have to get realy close now to hear it.
downside is that the pressure on the trafo will adapt to normal levels and the humming will come back some day.

maybe dip the whole thing in wax

[JBL 4645]

over here we have like this big sticky tape with lead on it (very heavy tape thats used to reduce vibration in cars and such. (you can also use it on a leak roof:D)
(lead bitume)
ive put some under the trafo and under the lid(lit) , tighten the screws and everything else i could see. humming is less now.

its now on a level wich doesnt atract my attention.
you have to get realy close now to hear it.
downside is that the pressure on the trafo will adapt to normal levels and the humming will come back some day.

maybe dip the whole thing in wax

Then how about (Blutack) thou it might not be very affective because it will compress down with the weight on top of it but in some cases it’s a very useful item to reduce certain vibrations.:)

http://www.blackboxcamera.com/STV5730A/images/blutack5.jpg

[greyhound]

hmmm whats that made of.
is it a isolation matarial can current flow through it?