How Quiet Should An Amp Be?

Tony Palmer · Post by **Tony Palmer** » 7 Feb 2015 6:39 am

I sat in on a stage with a big PA system and the tech plugged an XLR line out from the back of my Nash112 and said give me your max volume.
When I did, there was a loud hum that went through the sound system, to the point that I ended up not using my amp and had to settle for a stage amp someone pulled out at last minute

Sooo...I troubleshoot everything the next day and can't find anything wrong except when I turned the reverb up I got the hum. Then, to eliminate anything in the chain, I unplugged everything and turned the reverb up and got the same exact hum with nothing plugged in.
This is a used amp, never noticed any hum before but I went ahaead and ordered a brand new one.
The new one did the exact same thing! Moderately loud hum with reverb turned up to 10 and moderate volume.
Ok this would be the end of the story if I didn't then try the same thing with my Roland Cube30 which was DEAD SILENT with everything maxed out and nothing plugged in...totally quiet amp.

OK, I'm not starting a thread about diagnosing the Nash112 (although I hope that will come up) but more to the point, how quiet should we expect our amps to be?
Given that most of us use solid state amps, I would think pretty quiet.
So, is this a problem for all Peavey amps? Or just Nashville 112's?
Or all amps in general? All spring reverbs?
Basically I never noticed it before and, no, of course I never use much reverb anyway and the hum does decrease at lower levels.
Thoughts?

Bob Lawrence · Post by **Bob Lawrence** » 7 Feb 2015 7:07 am

Does your amp have a ground polarity switch ?

Bob Lawrence · Post by **Bob Lawrence** » 7 Feb 2015 7:09 am

Sounds like a ground loop problem .

Tony Palmer · Post by **Tony Palmer** » 7 Feb 2015 7:16 am

Bob, no ground switch.
Also tried this in two locations in my house, plugged into different outlets on two different breaker circuits.
Plus the stage makes three.

Bob Lawrence · Post by **Bob Lawrence** » 7 Feb 2015 7:22 am

When you are testing the amp at home do you have anything plugged into the input of the amp ? Are you just plugging it in and turning up the volume?

Stephen Cowell · Post by **Stephen Cowell** » 7 Feb 2015 7:35 am

Spring reverb hum usually comes from the transducers inside the pan... either there is a ground loop in that circuit or the transducers are picking up the hum.

Reverb transducers are 'single-coil'... although low impedance, they still have no true humbucking attributes. Placement of the pan can make the effect less... a fully shielded pan (for some reason these don't exist) would help.

You can troubleshoot the hum by disconnecting the pan and shorting the connection to the reverb recovery ('output'). You would expect this to kill any pan-induced hum, whether ground-loop or induced. This is the wire that hums when you touch the tip.

You can test for a loop by disconnecting the pan drive ('input')... if this fixes the problem then you have ground loop issues in the pan circuit. The ground should only connect to the pan case at one place, usually the output... if the pan cables' shields connect to the amp chassis and the pan chassis at all four points this creates the 'loop' of a ground loop.

The pan should be far from any transformers, this may be the underlying problem, since it's hard to do in a small amp. You can pull the pan out and move it around (leave it connected) and see what helps. Sometimes just swapping the pan end-for-end helps a lot.

Pete Burak · Post by **Pete Burak** » 7 Feb 2015 8:11 am

I also know from past experience with Peavey amp heads, that if you move the reverb tank farther away from the speaker (remove it from the cabinet and get it as far away as the cord will allow), this will reduce reverb tank based noise is some cases.
'Never tried this with a Nashville 112.
I'm thinking if the guy would have just mic'd the speaker, it probably would have never been an issue, I mean you would never run the reverb anywhere near 10 under normal gig conditions.
fwiw, I am not aware of any Peavey amp that has a dead silent spring reverb tank circuit.
Does your Roland have a spring tank, or digital reverb?

Tony Palmer · Post by **Tony Palmer** » 7 Feb 2015 10:15 am

OOPS!!!!

I was WAY OFF on my report about turning up the reverb...sorry.

It was the Pre Gain.
Turning up the pre gain anywhere PAST 5 with the master gain around 5 as well produces an unacceptable hum WITH NOTHING PLUGGED IN the input jack.
So, yes I would like help/opinions on this of course, but it lead me to my original post question: Are the majority of (solid state) amps noisy to some degree? My Roland Cube 30, which I use for a practice amp is totally quiet.

Mike Kowalik · Post by **Mike Kowalik** » 7 Feb 2015 10:46 am

Turn the Master Gain as high as you want but never have the Pre Gain higher than the Master.

Larry Carlson · Post by **Larry Carlson** » 7 Feb 2015 11:19 am

Threads like this one are the reason I hang out in here.
I have learned so much just by reading posts.
I don't say a whole lot in here, mainly because I don't know much, but I sure appreciate the knowledge I am picking up.

Now if I could just retain it.

Steven Finley · Post by **Steven Finley** » 7 Feb 2015 11:30 am

Tony,I have had the same problem with Nashville 112,I have had three over the years, all of mine did the same thing, however now instead I own two roland cube 80xl amps both 100 percent quiet,no problems.

Henry Matthews · Post by **Henry Matthews** » 8 Feb 2015 10:12 am

My Quilter Steeaire is quietest amp I have ever owned. Can't even tell its on. My Peaveys and Evans all have that little 60 cycle hum and I've tried everything but still there, some less than others.

Darrell Birtcher · Post by **Darrell Birtcher** » 8 Feb 2015 10:30 am

Your Roland Cube very likely has a noise gate built into it's firmware. You can't see it or touch it but it's there. It keep things quiet when there is no signal. I've yet to see a modeling processor without one.

You could accomplish the same thing with your NV112 by plugging a noise gate pedal in to the final loop of the amp. Take your time in setting the gate's controls and it will pass the sound man test and still sound okay.

When you are playing, the signal will cover up the noise enough to make the hum not noticeable. Good luck.

Jerry Roller · Post by **Jerry Roller** » 8 Feb 2015 10:57 am

Tony, I carry a Hum-X with me at all times. For about $50.00 you can pretty much solve hum problems. My 112s have a hum in some buildings. It has something to do with the electrical system in the building.
Jerry

Len Amaral · Post by **Len Amaral** » 8 Feb 2015 12:32 pm

Hi Tony,

Thumbs up on the Hum X as it eliminates ground loops. The Roland amp has digital reverb so you won't have problems as with spring reverb.

The Florida keys are very nice. Cool....!

Tony Palmer · Post by **Tony Palmer** » 8 Feb 2015 6:57 pm

I guess the Hum-x is a no brainer.
I'm ordering one now.
So is this no-load hum limited to the 112?

Jerry Roller · Post by **Jerry Roller** » 8 Feb 2015 7:15 pm

We recently hooked up a PA system and hum was bad enough to threaten our show. I told the "bossman" to try my Hum-x and it eliminated the hum. Just plug it into the receptacle and plug you amp into it, and most times it will stop the hum.
Jerry

Tony Palmer · Post by **Tony Palmer** » 15 Feb 2015 8:19 pm

Well I received the Hum-X thing and it made no difference at all.
I'm thinking I just never noticed it before and I just have to keep the pregain down

Brad Sarno · Post by **Brad Sarno** » 15 Feb 2015 8:35 pm

Turning the pre-gain down isn't really a fix. It's an indicator that there's hum in the system for some reason.

Can you describe the ENTIRE rig, all the components, and also; are all the pieces of gear plugged into the very same power strip?

Brad

Jerry Roller · Post by **Jerry Roller** » 16 Feb 2015 1:31 pm

Move the Hum-X to each AC plug in the chain and perhaps you will find where it needs to be.
Jerry

Stephen Cowell · Post by **Stephen Cowell** » 16 Feb 2015 4:57 pm

Jerry Roller wrote:Move the Hum-X to each AC plug in the chain and perhaps you will find where it needs to be.
Jerry

It hums with nothing plugged in.

Brad Sarno · Post by **Brad Sarno** » 17 Feb 2015 8:07 am

As I look back to the initial posting, I read this:

"...I troubleshoot everything the next day and can't find anything wrong except when I turned the reverb up I got the hum."

Doesn't this simply point to the hum in the spring reverb?

Spring reverbs often do pick up hum. If the hum goes away when the reverb is turned down, then that sounds like the culprit... Am I missing something else?

Brad

Michael Butler · Post by **Michael Butler** » 18 Feb 2015 6:33 pm

Brad Sarno wrote:As I look back to the initial posting, I read this:

"...I troubleshoot everything the next day and can't find anything wrong except when I turned the reverb up I got the hum."

Doesn't this simply point to the hum in the spring reverb?

Spring reverbs often do pick up hum. If the hum goes away when the reverb is turned down, then that sounds like the culprit... Am I missing something else?

Brad

brad: later, he said that it was the pregain and not the reverb, i believe. it did get rather confusing, and, you have already addressed the pregain.

play music!

Jerry Roller · Post by **Jerry Roller** » 18 Feb 2015 10:42 pm

I must say that I have two 112's and they are noiser than my other Peavey amps. I have always felt they should have had a ground reversing switch but I don't know if that would help or not. Most of my Sessions 400's and Vegas 400's are absolutely quiet. My Nashville 400 has a little hum but the Hum-X pretty well eliminates the hum in it.
Jerry

Tony Palmer · Post by **Tony Palmer** » 19 Feb 2015 8:53 am

Yeah, I apologize for the initial confusion in the post, but to recap:
My existing 112 has a hum with NOTHING plugged in the input.
It becomes noticeable and objectionable as the pre gain is turned up.
I bought a Hum X and it had no effect at all.
I then bought a brand new 112 and it does EXACTLY the same thing.
The reason I made the post was I wondered if a lot of other amps do this as well.
I didn't expect a fix for this and have resigned myself to putting up with the hum.