Help trouble shooting an intermittent buzz

yep, 100% volume and input has no impact when it strikes.

Different Turntables, different everything really. The tough thing is really the infrequency of the occurrence, it's not uncommon for me to get 20 to 30 hours of run time without issue. It would seem there is no configuration that will make it happen and no chance that will make it go away when it shows up. Other than turning everything off for a couple hours.

 

Try a CDP, DVD, or tuner, connected to a Line input on the BAT.
If you do not have a CDP or DVD player use the Tuner on the Denon A/V receiver. Use the Tape Out RCA jacks.

Leave off and disconnected all TT and outboard phono preamp ICs from the BAT preamp.

 

I think I may have had a breakthrough.

On the back of the the power amp there is a button that will select between the RCA and balanced inputs. When I switched from balanced to RCA I did not hit that button to select RCA. Instead of receiving no signal as one might expect if the wrong inputs selected it just took away 30 to 40% of the gain.

So realizing it was set wrong, I hit the button and the stereo came alive and the Buzz was immediate. I hit the button again selecting the the wrong input and the buzz went away immediately.

 

Great news! Well, not great, but at least a breakthrough!!!!!!!

 

The push button switch when in the "out" position is in the closed contact position and connects pin 2 and pin 3 of the XRL connector together for single ended mode RCA cables. That is the correct switch position for RCA ICs.

If the amp now buzzes constantly you now have a good constant place to start from.

1) Unplug the left and right ICs from the preamp. Take some tin foil and stuff some in between the center pin and the outer shell of each RCA plug. Make sure the tin foil shorts out each center pin to outer shell of each RCA plug. This will short out the left and right channel inputs.

2) Turn on/power up the amp. If the amp is ok there will not be any buzz.

If no buzz next turn off the amp and remove the tin foil from the IC's RCA plugs.

3) connect the ICs to the outputs of the BAT preamp. DO NOT connect anything to any of the inputs on the BAT preamp. Turn volume control all the way down.

4) Turn on the BAT preamp. After preamp stabilizes turn on/power up the power amp. set the input to a line level input. an input other than the phono input.

If everything is ok there should not be any buzz. If there is a buzz is it coming from both the left and right speakers?
MUTE the preamp. Does that stop the buzz?

Instead of a buzz is it now a 60Hz hum? Hum heard through both the left and right channel speakers?
No buzz? Un-mute the preamp and turn the volume control up slowly listing for any buzzing sound. DO NOT go above 1/3 way.

IF there is not any buzz or hum with both the preamp and power amp turned on go to the next level.

5) Connect the TT directly to the RCA phono inputs of the BAT preamp.
Check for buzz or hum.

Post back your results thus far.

 

It is unfortunately not constant. I have been running it correctly for the life of the amp, I just didn't hit it the last time I switched cables.

I just spent all day waiting for it to buzz and it wouldn't presumably because of that switching error. Thanks for the suggestions, I'll make another run at it tomorrow.

 

My above post has been recently edited.....

 

In the last twelve days I installed a new hospital grade outlet and set up all my equipment as it was. I have run the system a lot and have been clean, I was nearly ready to call it cased closed.

I was out of town for four days, came home, put on a record and it hit within two minutes of operation. I hit the input selector buttons on the amp and it reduced the buzz (along with everything else) but it was still there for just a bit and then went away. Since then I have had nothing but clean operation and the amp was switched back to the appropriate input. So no solution but not present enough to really slow me down in about two weeks.

Something interesting just happened. Working from home today, I'm in my office playing a record to get things going. The office system is a Fisher 400, Musical Fidelity M1 phono, Debut Carbon and Dahlquist speakers. The intermittent buzz just happened in here. It's not nearly as loud as this system is not nearly as detailed and revealing but unmistakably the same noise. Just a couple seconds of static and then gone.

So this is the first time it has happened on a completely different system, in a different room but on the the same electrical circuit. The thing that is different about the office system is that I have added the phono stage rather than the internal on the Fisher. I'm not thinking it is the source of the problem but I do think it adds more gain or becomes "resolving" that whatever the issue is, it becomes audible.

 

Nothing was connected to the ground rod. The ground wire was buried in the dirt which might explain why it was intermittent and not constant. I am hopeful this is the solution, it certainly makes sense.

 

The plot thickens....if nothing else...good detective work there!

 

Swing and a miss. I've got an electrician coming next week.

 

and the saga continues. My electrician had to cancel the scheduled appointment this past Saturday, he was/is going to run a dedicated line.


I don't think the dedicated line is going to fix it (but I am still going to get it). I am thinking that there is some electronic device that is to blame. My first suspects are the dimmer switch, florescent light bulbs and a refrigerator. It was just happening with some frequency so I went to the breaker box and turned off the circuits that have a dimmer switch. The Buzz was not reduced or eliminated. Would this mean that the potential interference is NOT the dimmer switch? I would find it hard to believe that a dimmer switch that had no power going to it could do anything.

The buzz does sound similar to when a ballast is going out on a florescent light. The only florescent light I have are the compact ones that go into regular light sockets. Much like the dimmer switch, if they are not turned on, I would think this could be a suspect.

 

I've got a beer fridge in the garage that is about 15 years old. I just unplugged it, time to wait and see. I don't know how long I can go before my beer get warm.

 

Fingers crossed the dedicated line fixes it. If it doesn't, I'm wondering how dedicated a dedicated line is.

 

I was talking to a guy that repairs equipment and I played him my sound sample. His thought was something is interfering from inside the house. It doesn't corrupt the electric so to speak but it's transmitting a Morse code like signal that equipment can pick up. Sounds wacky to me but I'm in no position to pass judgments on new ideas at this point.

The garage fridge does have about 15 years of service on it and it operates in a challenging environment to say the least. It does keep beer pretty cold. I may be willing to give up drinking to resolve the issue, or just switch to bourbon full time.

 

Ah, that does make sense I suppose - almost like radio interference or something at that point.

Listen, as you're guzzling all the beer in your fridge before it has a chance to get cold, don't lose sight of the fact you didn't ask to have this problem.

 

If I drink that much beer I might have several problems I didn't ask for.

 

That ground wire outside your house that you put up a picture of is worrisome. I had cable TV that wasn't grounded (thanks, Comcast!), and when lightning struck nearby, my TV, receiver and anything else connected in some way to that TV cable line died. Luckily, I had renter's insurance.
Anyway, do you live near anything that would put out a lot of RF signal intermittently? An airport, or something like that? It could be something coming in from outside your home. Otherwise, I suspect the wiring in your house. It's amazing how many places I've rented that were botched electrically. All it takes is one idiot installing electrical outlets, or a breaker box to mess everything up.

 

There is a very small "airport" close by but it is for charter and privet planes. It is less than ten miles away but I do have a small radio station that is about a mile or less from my house. That and satellite surveillance from the government is all I can think o and I don't think I can get any of those guys to stop.

I was really optimistic about that ground wire being the issue and pretty bummed that fixing it didn't make any improvement. Well, the sonic quality of the buzz might be a little improved but that would be it.

Since I've had the fridge unplugged I haven't had any problems. If it goes another two hours with nothing, I'll plug it back in and see if that makes it return.

 

Sounds like a good plan!

 

I "think" I am at case closed on this issue.

In the 11 days since my last post I can say that the buzz has not presented while the refrigerator was unplugged. On Saturday when it occurred, before unplugging the fridge I opened the door to listen to inside and there was a similar noise that was coming from the mechanical parts behind the thermostat control. It was a much different sound, kind of more of a hiss but it had the same tempo or cadence of the buzz in they system.

What is happening or why is far beyond my understanding. I think it is less likely that the fridge is "broadcasting" a signal that is being received by the preamp as much as it is throwing some kind of disruption through the electrical system.

Also for the greater good, it would seem that this would argue against the case for a dedicated circuit for equipment. If you have jacked up stuff on any circuit, it finds it's way though the entire electrical system.

 

Maybe, maybe not.

IF the problem has been the fridge all along, and from what you are describing from the sound you hear from the area of the stat of the fridge, it may very well be the sound of arcing across contacts in the AC circuit. The arcing will not only send noise through the AC wiring it can/will be radiated through the air.

Factors that must be considered.
Is the branch circuit wiring that feeds the fridge run close, parallel for any distance, next to the branch circuit wiring that feeds your audio equipment? IF so the noise can/will be induced from the fridge's branch circuit wiring onto the branch circuit wiring your audio system is fed from. How long is the total length of the branch circuit wiring that feeds your audio equipment? Up down and all around?

Next, where in the electrical panel is the breaker that feeds the fridge located and where is the breaker that feeds the branch circuit that feeds your audio equipment located? Are they next to one another? Are they fed from the same Line, leg, of the hot buses of the electrical panel? Both on L1 or Both on L2?

I have found if a dedicated branch circuit is properly installed it will indeed help prevent/minimize noise caused by other devices, equipment, or appliances, fed from other branch circuits in the home. The wiring method used is just as important as the branch circuit wiring used.

 

For a variety of reasons I installed a new breaker and line in my garage. The only thing on this new circuit is the refrigerator and the buzz still made it to the stereo.

I will run another circuit just for the audio equipment at some point but I don't think that was the solution for this issue.

It's all far beyond my abilities to talk about with any certainty.

 

Here is a video for you to watch. Disregard what the Guy is trying to sell.


After watching the video I did my own experimenting and verified what the guy on the video had shown.

Things I also found.
Any other branch wiring is close proximity of the infected load side of the dimmer branch circuit wiring was also infected.

The further I got away from the line side of the dimmer the noise diminished, though not totally. I could still pick it up, slightly, at the breaker in the electrical panel feeding the branch circuit that feeds the light dimmer. Breakers in the panel immediately around the breaker I could also pick up the noise. The further I got away from the breaker on the panel to other breaker the fainter the noise.

For the final test I went to the two wall duplex receptacles that are installed on the end of the two dedicated branch circuits for my audio equipment. Clean, no hint of the noise.

 

This is an interesting video. From the conversation that I had with my electrician this weekend he said that the knob dimmers work differently that the fader switch I have on my dimmer. Apparently the the knob variety are quite problematic as illustrated in your video. Before I tracked the noise down to the refrigerator I was focused on the dimmers. Rather than removing them I went to the circuit box and shut off the power to the circuits that had dimmers. The noise persisted so I just just kept turning off circuits until the the noise went away.