Noise/Hum

NJPOLKER

I'll do my best to explain.
Here is what I have in my system now - Arcam CD72 cdp - Anthem PRE2L pre-amp - Belles 350a amp - Ben's IC's - Audioquest Mammoth speaker cables. In the pre-amp I have four 6922 tubes w/Herbie dampers and have used Phillips RCA's Amperex with similar performance/problem/concern. They are not great tubes or expensive tubes and the problem may be with them. The unit has also been upgraded with two Dynamicaps and Dynamat.
Tubes used 6922's Amperex Holland manufactured - RCA which are German made Siemens and Phillips

Here is my problem. I can hear a low humming noise coming from my tweeters and can hear it when system is at idle or volume turned all the way down and hum does not change when adjusting the volume. It is more pronounced when I hook up the SDA2a than when the SRSII's are hooked up.

I contacted Chris Johnson at Parts Connexion to discuss further upgrades and resolving my concern with the hum. Chris is a treat to work with and very knowledgeable. I got him the spec's on the Belles and sensitivity of my speakers upon his request.

Chris,
Here is what I found on the Belles 350a amp
Frequency response -0.2 to 100,000 Hz
Distortion-Less than 0.1 at rated power
Damping factor- Over 2,000 wow
Peak Current- Over 64 amperes
Input sensitivity-1.98 volts for rated power
Input Impedance-50,000 ohms
Hum and noise >100db
Gain 21 voltage ratio or 2.44db
Power rating 120vac 10.0a fuse
Power at 8 ohms is 250 watts and at 4 ohms 500 watts and 1,000 watts in mono-block configuration.

Speaker sensitivity around 92/93

From Chris
Well, with a high efficiency speaker like that, and such a powerful amp, you need a very LOW GAIN preamp (we could reduce the 8dB even further, if we modded the unit here at pcX)......and if it's a tube preamp, you need to ensure you have very quiet tubes.

So, could it be I have poor performing tubes and need to use higher performing tubes or quiet tube as Chris suggested? Do you think its the noise tubes have and I just hear it more with sensitive speakers and loud tubes. I think the noise/hum that comes from tubes is called "rush" if I remember correctly. Every set of four tubes has the same hum as far as I can tell. Could it be a cable issue or connection? Could it have to do with the quality of power/current coming into my system?

Any suggestions are appreciated. So many areas to check into and probably more than I know, I need more guidance. Hopefully its a simple resolution.
Thanks in advance for your support.
Drew

Jed Leland

Hello Drew,
Am I correct that if you disconnected the preamp from the power amp you would still hear the noise? In other words, if you just had the speakers connected to the amplifier would the noise be the same? If so, is the noise the same in both channels? Is this noise only heard if you place your ear very close to the tweeter?
Cheers, Ken

george daniel

Do you have CATV in the mix?

NJPOLKER

Jed, I will disconnect the pre-amp and get back to you. Same noise both channels. I can hear the noise when sitting in the sweet spot with no problem when I have the SDA2a's hooked up but not as much wehn the SRSII's are hooked up but can still hear a faint humming with the II's.

George, No CATV just the 2 channel system and that's the way it will always be.

NJPOLKER

OK,
when I unplug the IC's from the pre-amp to the amp the noise is eliminated.

george daniel

try another pair,, and swapp outlets/isolate the pre.

Jed Leland

Hello,
Well, that tells us the problem is "up-stream" from the amplifier. You indicated that the preamplifier's volume control didn't effect the level of the noise, correct? That would mean the source of the noise is after the volume control in the preamplifier. If the preamplifier uses each tube for both the right and left channel then a noisy tube would effect both channels. If the preamplifier uses separate tubes for the left and right channels and since the noise is the same in both channels, you could have two tubes with noise. This would be in the line level section of the preamplifier, after the volume control.
Ken

tonyb

Most hum problems are usually a ground issue. Too many grounds plugged into one device. Try a different set of IC's or try plugging some gear into a different outlet.Hum issues are a pain,but you have to do some detective work to find the culprit.

NJPOLKER

I am starting to feel better about this.

I don't have extra IC's to swap out so I will figure something out for that.

I'll try the power cord/grounding issue now.

NJPOLKER

tonyb wrote: »

Most hum problems are usually a ground issue. Too many grounds plugged into one device. Try a different set of IC's or try plugging some gear into a different outlet.Hum issues are a pain,but you have to do some detective work to find the culprit.

I guess I should look at all components PC's/ground plugs being sure they are properly grounded.

CoolJazz

You've mentioned tube rush and hummm. They are two different things and it's helpful to differentiate.

Tube rush is more a hiss and would be from a upper mid frequency mostly. A hum is more in a low frequency direction. You can really further break down hum from a buzzy kind of sound too, which can help lead to what the problem is.

And you could have some of both, from two different problems. You should expect a small amount of tube rush from a fairly efficient speaker but not usually audible from the listening position. Pulling power from two different outlets or getting a seperate ground from a cable fed component are good reasons for buzz problems. A rounder, softer hum can often lead to audio cabling being to close to AC cables or audio cable in a strong magnetic field.

CoolJazz

george daniel

NJPOLKER wrote: »

I guess I should look at all components PC's/ground plugs being sure they are properly grounded.

Just try runniny the pre off of another outlet/circuit,, try using a drop cord to the pre to see if it goes away.

ben62670

When I have a get together here I run an extension cord from the dining room to my system to my audio. My living room outlet have too much bs in the way.

NJPOLKER

Here is what I have done now.
I took the Anthem pre out of play and put my Cambridge Audio integrated amp in play using the pre outs. Everything being the same except the CA replacing the Anthem and guess what............................... the noise is still present no change whats so ever.
I am surprised. DAMN

george daniel

try running off another circuit/outlet,,IE,, use a drop cord to see if the hum goes away when using another circuit that is not not shared with the rest of your gear.

NJPOLKER

Will do in a few minutes. I should use a heavy duty extension cord and run it from like hhmmmmmmm upstairs or my garage, does it matter?

tonyb

Preferably an outlet without juice sucking stuff on it like a fridge,furnace etc. I don't think it's the gear bro,rather than what you have everything plugged into. I'd still swap out the ic's too.

NJPOLKER

How about cheating out or removing the ground pin.

tonyb

NJPOLKER wrote: »

How about cheating out or removing the ground pin.

Don't remove the ground pin,just buy a 2 buck cheater plug,3 prong into 2. Whats everything connected into anyway?

NJPOLKER

The amp is into a simple two plug outlet and its the only plug into that outlet,
The CDP, PRE-AMP, TV, cable box are plugged into a simple power strip.

NJPOLKER

Update
First off Thanks George, Tony, Ken, Cooljazz and Ben the chicken man
It is amazing the things we learn. I unplugged everything then only plugged in my stereo components and the noise was reduced to a faint buzz. I plugged in the TV and cable box and noise returned. So I plugged the TV and cable box into one outlet and plugged the amp and power strip into the other outlet and the buzz/hum was reduced but not as much as when the TV and cable box are unplugged. I guess I was and am getting some interference from the TV set up. I feel a lot better knowing what was going on and now I know how to correct the hum/buzz.
When they say **** in **** out, well, thats needs to be a high priority when setting up a system. It really does start at the breaker box if not before. I wish Russ/Lightman lived closer.
I'll report back later when I have a chance to listen again but I noticed something really interesting. I play Steely Dan Aja for comparison purposes and I easily hit 12 o'clock on the pre-amp. I played Aja for a minute and pulled the Anthem pre-amp to check the two gain switches inside to see if the db's were still set at 8db, they were. This pre-amp has a selectable gain of 8db 16db or 24db. It seems I have a ton more power. I was at maybe 9-10 o'clock and it was LOUD and beautiful.
I can't wait to get some extra cash to buy three PS Audio Statement power cords and have the electrician install a separate circuit and outlets for my system.
I am thrilled it's not the pre-amp/tubes or cables.
Thanks again guys
Drew

tonyb

Could be the power strip is bad,happened to me many moons ago. You can also try installing a new outlet like a hospital grade one from Home Depot or an audiophile one from PS. Just my .02 but glad your getting down to solving it.

NJPOLKER

Hey Tony, you know, your alright Thanks a lot for your advice.

Jed Leland

Hello Drew,
You're welcome, glad to be of help. It is possible you have a ground loop between the cable box and the rest of your system. You might benefit from a ground loop isolator, most recommend the one from Jensen Transformers. Make sure the isolator has sufficient bandwidth for your particular cable converter box.
Take care, Ken

george daniel

Man,, I had to work late,,DREW,, because of the time I took on the phone with you today. JK,, glad you have discovered the source of your ills,,I have the little Jenzen jobbie in my rig--works just great too.:)

NJPOLKER

I just got finished cranking tunes for an hour or so and I gotta say my system has never sounded this great. The sound is clearer and better volume response than ever. The only thing I did was change things around to have a little better power/current coming into my system. Does that make sense? All this because I was trying to do away with the annoying hum. Now I am going to make my wife hummmmmmmmmmmmm.
Even my son walked down stairs when Jeff Beck was cranked way up and said that does sound incredible.
The midrange and bass are so very strong and clean it just blows me away. The Belles has a dampening factor of greater than 2,000 so I guess that really helps control the drivers in my SRSII's. I can only imagine how much better things will get once I buy good power cords, high quality outlets and a dedicated circuit.

NJPOLKER

george daniel wrote: »

Man,, I had to work late,,DREW,, because of the time I took on the phone with you today. JK,, glad you have discovered the source of your ills,,I have the little Jenzen jobbie in my rig--works just great too.:)

The reason I kept you on the phone so long is because I love the way you talk

tonyb

You may not know this,but George used to do phone sex to put himself through college.
Lucky you !

NJPOLKER

tonyb wrote: »

You may not know this,but George used to do phone sex to put himself through college.
Lucky you !

Did you have to let everyone else know that? We should have kept that between the three of us