Buzz around 60hz from subwoofer

A

AVT

Supreme [H]ardness
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So I've recently obtained the following setup for my desk, since my previous one was too big:

  • Vanatoo Transparent One Speakers
  • HSU STF-1 Subwoofer

The Vanatoos are brand new. The HSU STF-1 I scored on eBay for $125, it was manufactured circa 2007.

I'm getting a buzz centered around 60hz from the subwoofer, with the following characteristics:
  • starts off quiet, gets louder over time
  • produces a pop sound and quiets down if I play music
  • occurs whether or not the speakers are on, and whether or not they are plugged in
  • does not occur if the RCA cable is not plugged into the sub

I'm not sure what I can try here. Is there a problem with the sub? With the speakers?
 
you have a Ground Loop

try plugging your source and amplifier devices into the same AC outlet.
 
bloodypulp said:
you have a Ground Loop

try plugging your source and amplifier devices into the same AC outlet.
Click to expand...

Both the sub and speakers use two-prong plugs, and are plugged in next to each other in the same power strip, which is plugged into the same outlet. This should make a ground loop impossible, but I'm in an apartment and the electrical here is very old, so who knows. Is there anything I can test to further determine whether this is indeed the underlying issue?
 
Speakers are plugged into PC via optical (TOSLINK).
 
Have you tried ferrite chokes? From your description, one on the RCA cable should kill it.
 
Grebuloner said:
Have you tried ferrite chokes? From your description, one on the RCA cable should kill it.
Click to expand...

I don't have any. However, it I move the speakers and sub off of my desk and away from other electronics, the problem persists. I'm using a Rockford Fosgate twisted pair (unshielded) cable that used to be in car stereo setup. Is there any way to determine whether a ferrite choke will help?
 
And what about the source as noted above by bloodypulp?

As it only occurs when the RCA cable is attached, whatever is connected to the other end of that cable is what is being referred to as the source. You need source and speakers on the same circuit, or isolated by a good UPS.
 
If your sub has rca in, try that.

(guys, he said he is using optical above)
 
Krispy Kritter said:
And what about the source as noted above by bloodypulp?

As it only occurs when the RCA cable is attached, whatever is connected to the other end of that cable is what is being referred to as the source. You need source and speakers on the same circuit, or isolated by a good UPS.
Click to expand...

Here's a diagram:

PC --[TOSLINK optical]--> Vanatoo Speakers --[RCA]--> Sub

All three are plugged into the same power strip. Note that these are active speakers with a DAC and a sub out built in. There is no receiver, external amp, or anything else.

I'm at a loss as to how a ground loop can occur in such a dead-simple setup given that the PC is plugged in via optical, and given that the buzz is still there if I turn the speakers off and unplug them from the wall. If this is indeed going on, just about the only way I could think to get rid of it would be to get a ground loop isolator.

The RCA cable should be good as it's the exact same one in my car stereo setup and sounds good there, but I'm going to borrow a different one from a family member who used to buy Monster Cable products so I can rule that out.

Any ideas are appreciated since I can't seem to figure out what's going on here, or what sort of further testing I can do to try and diagnose the problem.
 
Last edited:
AVT said:
Here's a diagram:

PC --[TOSLINK optical]--> Vanatoo Speakers --[RCA]--> Sub

All three are plugged into the same power strip. Note that these are active speakers with a DAC and a sub out built in. There is no receiver, external amp, or anything else.
Click to expand...
Ah, you are using an rca lead to the sub.

I'm at a loss as to how a ground loop can occur in such a dead-simple setup given that the PC is plugged in via optical, and given that the buzz is still there if I turn the speakers off and unplug them from the wall. If this is indeed going on, just about the only way I could think to get rid of it would be to get a ground loop isolator.
Click to expand...
Buzz can be caused by many things.
ie a bad gnd or shielding in the rca lead can allow noise onto the signal path.

The RCA cable should be good as it's the exact same one in my car stereo setup and sounds good there, but I'm going to borrow a different one from a family member who used to buy Monster Cable products so I can rule that out.
Click to expand...
This is what I would try next.
 
Nenu said:
Ah, you are using an rca lead to the sub.


Buzz can be caused by many things.
ie a bad gnd or shielding in the rca lead can allow noise onto the signal path.


This is what I would try next.
Click to expand...

Just unplugged the RCA cable from the speakers while leaving it plugged into the sub, shorted it, and the buzz disappeared, so does not appear to be coming from the cable, but who knows, will try another cable anyway first chance I get to borrow it.
 
AVT said:
Just unplugged the RCA cable from the speakers while leaving it plugged into the sub, shorted it, and the buzz disappeared, so does not appear to be coming from the cable, but who knows, will try another cable anyway first chance I get to borrow it.
Click to expand...

Sounds like you have a grounding problem. A 60hz buzz is usually caused by ground loop or bad capacitors in your power supply.

Does your system contain both grounded and ungrounded devices? Are your houses wall sockets 100% certainly grounded?
 
B00nie said:
Sounds like you have a grounding problem. A 60hz buzz is usually caused by ground loop or bad capacitors in your power supply.

Does your system contain both grounded and ungrounded devices? Are your houses wall sockets 100% certainly grounded?
Click to expand...

I'm in a pretty old apartment building, but the electrical outlets here are all 3-prong. How good the ground is, I've no idea.

Both the speakers and sub are 2-prong devices, and are plugged into the same power strip. Is there something I can test to determine whether this is indeed a ground loop issue?
 
AVT said:
I'm in a pretty old apartment building, but the electrical outlets here are all 3-prong. How good the ground is, I've no idea.

Both the speakers and sub are 2-prong devices, and are plugged into the same power strip. Is there something I can test to determine whether this is indeed a ground loop issue?
Click to expand...

One way to make sure would be to pull a cable from device to device so that metal touches metal. If the hum disappears when you touch the chassis of the other device then you have a ground loop. If you have a computer in the mix the hum probably comes from your power supply.

Two more rare causes may be a broken RCA cable or bad capacitors in your amp. The ground loop or computer PSU current leak are the cause in at least 90% of cases.
 
This should solve the problem. Ground loops are a pain and an isolation transformer can do the trick in many cases.
 
Sycraft said:
This should solve the problem. Ground loops are a pain and an isolation transformer can do the trick in many cases.
Click to expand...

I blew up an amp once using an isolator just like that. I still don't know what happened but it died instantly when I plugged the isolator to replace the simple RCA cable.

Just a word of caution, especially if you connect a computer, test with a cheap amp first :D
 
So far I've never had a problem with one but good to know. I generally avoid them since they can mess with high frequencies, but for a sub, they can be a good cheap solution.
 
AVT said:
So I've recently obtained the following setup for my desk, since my previous one was too big:

  • Vanatoo Transparent One Speakers
  • HSU STF-1 Subwoofer

The Vanatoos are brand new. The HSU STF-1 I scored on eBay for $125, it was manufactured circa 2007.

I'm getting a buzz centered around 60hz from the subwoofer, with the following characteristics:

  • [*]starts off quiet, gets louder over time
    [*]produces a pop sound and quiets down if I play music
    [*]occurs whether or not the speakers are on, and whether or not they are plugged in
    [*]does not occur if the RCA cable is not plugged into the sub

I'm not sure what I can try here. Is there a problem with the sub? With the speakers?
Click to expand...

For what it's worth your list screams *Bad filter cap* in the subwoofer and it's leaking AC into the system which would indeed sound and act like a ground loop.

If you take a multimeter and set it to AC Volts and put one lead on the ground part of the RCA cable connector at the SUB and the other lead to any known ground I'm willing to bet you will get a voltage reading. That would be a bad thing. Do the same thing to your speakers just to be sure there is no AC leak there either.

Keep in mind that sub is ~8 years old~ and cap failures are not uncommon.

Also keep in mind that is a "BASH" AMP design (digital) and as such would be very sensitive to ground problems.

HSU Link

Owners manual link

The AMP in the SUB only carried a 2 year warranty but if you test as I mentioned and have voltage at your grounds I'd give HSU a call and see what they might charge for a referb AMP.

What ever you do DON'T try grounding the unit to your computer because if you do find an AC leak it might create a really big argument between your computer PSU and the SUB PSU...

I uses to sell Klipsch Subs that ate themselves alive on a regular basis. In fact the problem is so common replacement "Plate Amps" for subs are a big selling item.

OH, another quick check...Plug the RCA in only part way allowing only the center pin but not the grounds to touch, see if that stops the noise.

Luck man.
 
Sycraft said:
This should solve the problem. Ground loops are a pain and an isolation transformer can do the trick in many cases.
Click to expand...

B00nie said:
One way to make sure would be to pull a cable from device to device so that metal touches metal. If the hum disappears when you touch the chassis of the other device then you have a ground loop. If you have a computer in the mix the hum probably comes from your power supply.

Two more rare causes may be a broken RCA cable or bad capacitors in your amp. The ground loop or computer PSU current leak are the cause in at least 90% of cases.
Click to expand...

BillR said:
For what it's worth your list screams *Bad filter cap* in the subwoofer and it's leaking AC into the system which would indeed sound and act like a ground loop.

If you take a multimeter and set it to AC Volts and put one lead on the ground part of the RCA cable connector at the SUB and the other lead to any known ground I'm willing to bet you will get a voltage reading. That would be a bad thing. Do the same thing to your speakers just to be sure there is no AC leak there either.

Keep in mind that sub is ~8 years old~ and cap failures are not uncommon.

Also keep in mind that is a "BASH" AMP design (digital) and as such would be very sensitive to ground problems.

HSU Link

Owners manual link

The AMP in the SUB only carried a 2 year warranty but if you test as I mentioned and have voltage at your grounds I'd give HSU a call and see what they might charge for a referb AMP.

What ever you do DON'T try grounding the unit to your computer because if you do find an AC leak it might create a really big argument between your computer PSU and the SUB PSU...

I uses to sell Klipsch Subs that ate themselves alive on a regular basis. In fact the problem is so common replacement "Plate Amps" for subs are a big selling item.

OH, another quick check...Plug the RCA in only part way allowing only the center pin but not the grounds to touch, see if that stops the noise.

Luck man.
Click to expand...

Firstly, big thank you to everybody for the posts! Appreciate the help in figuring out what is going on here.

I've swapped out the RCA cable to a family member's Monster Cable product (ugh), and it has fixed part of the problem. I have now ordered a replacement shielded coaxial subwoofer cable on Amazon.

  • The annoying audible 60hz buzz is gone
  • The sub is still picking up some sort of noise spread broadly along its frequencies. This is nowhere near as loud as the previous 60hz buzz and inaudible unless I have my ear up to the sub or the port. Noise gets louder if I disable the crossover, and disappears if I unplug the RCA cable.
  • It still produces a pop sound if I pause my music for 10mins and then play it

I'd like to get rid of that pop noise if possible. Could this be caused by an old capacitor in the subwoofer's amp or something else that I can easily replace? I can probably acquire a multimeter and do further testing if it's helpful.
 
AVT said:
Firstly, big thank you to everybody for the posts! Appreciate the help in figuring out what is going on here.

I've swapped out the RCA cable to a family member's Monster Cable product (ugh), and it has fixed part of the problem. I have now ordered a replacement shielded coaxial subwoofer cable on Amazon.

  • The annoying audible 60hz buzz is gone
  • The sub is still picking up some sort of noise spread broadly along its frequencies. This is nowhere near as loud as the previous 60hz buzz and inaudible unless I have my ear up to the sub or the port. Noise gets louder if I disable the crossover, and disappears if I unplug the RCA cable.
  • It still produces a pop sound if I pause my music for 10mins and then play it

I'd like to get rid of that pop noise if possible. Could this be caused by an old capacitor in the subwoofer's amp or something else that I can easily replace? I can probably acquire a multimeter and do further testing if it's helpful.
Click to expand...

The RCA's plug into your speakers or an outboard crossover? The pop could be a momentary DC surge from one of those sources. You can test that with a meter as well. This time you set the meter to DC and the leads to the RCA cable that plugs into the SUB. Turn on each component separately and see which one gives you a momentary jump on the meter to test this part.

As to the noise...are we talking hiss?
 
BillR said:
The RCA's plug into your speakers or an outboard crossover?
Click to expand...

Setup looks like this: PC --[TOSLINK optical]--> Vanatoo Speakers --[RCA]--> HSU Sub

The HSU STF-1 has a switch that allows me to disable the crossover, that is the one I am talking about. There's no equipment other than the above.

The pop could be a momentary DC surge from one of those sources. You can test that with a meter as well. This time you set the meter to DC and the leads to the RCA cable that plugs into the SUB. Turn on each component separately and see which one gives you a momentary jump on the meter to test this part.
Click to expand...

The pop doesn't seem to be happening when I turn the speakers on or off. Only when I pause my music for a bit and play it again. Although I know the speakers go into standby after 15mins, and sub goes into standby after 30mins, so I'll have to do some testing to see if it only happens when going out of standby mode.

As to the noise...are we talking hiss?
Click to expand...

Sounds more like wind blowing. It's pretty much inaudible and is probably normal, the same as when tweeters emit a slight hiss, but I figured it was worth mentioning given the pop.
 
Glad the change of RCA cable helped.

AVT said:
The pop doesn't seem to be happening when I turn the speakers on or off. Only when I pause my music for a bit and play it again. Although I know the speakers go into standby after 15mins, and sub goes into standby after 30mins, so I'll have to do some testing to see if it only happens when going out of standby mode.
Click to expand...
Try a different audio player to see if it makes a difference.
But if its caused by the sub auto powering down when not in use, it cant help that.

Sounds more like wind blowing. It's pretty much inaudible and is probably normal, the same as when tweeters emit a slight hiss, but I figured it was worth mentioning given the pop.
Click to expand...

If you cant hear it from anywhere you sit, it doesnt matter.
 
I'd like to make a point that is probably relevant.

Audio, especially high definition, is prone to external electro magnetic noise.
Systems that are not earthed generally use plastics to shield the user from the live circuits.
Earthed circuits quite often use metal surrounds.

The earthing helps migrate EM fields to ground and metallic surrounds not only shield EM radiation but provide further routes to ground.


Your equipment doesnt make use of the Earth connection so you can expect a small amount of EM noise to be picked up unless special care has been taken to eliminate it.
fyi
 
It sounds a lot like somethings gone haywire in the subs amp. 'wind noise' or hissing is a typical sign of dried out caps and the popping noise is probably related, due to missing filtering.
 
The above is possible too.
Old equipment has consequences,
 
Did some more testing.

The pop happens every single time the speakers are turned off/on. It also happens every time they go out of standby mode (which they normally go into after about 10mins of inactivity). It also happens with a different sub that I own, so unless both are faulty, it cannot be an issue with Hsu's amp. Going to contact Vanatoo's customer service to see if there might be something wrong with the speakers.
 
Some amps do that if they don't have protection circuits. When the power rushes in, you get a pop. Better amps will disconnect their outputs for a bit to make sure that doesn't happen, but that is more expensive so not all do it.
 
The pop is not the main question here though, the 60hz buzz is. The buzz can be caused by multiple things starting from your RCA cables being routed too close to the power cables.

For example one time I connected my active monitors using a heavy duty RCA cable which was originally intended for car use so it had an extra lead for amp trigger. I used that cable to build an RCA-XLR conversion cable since I no longer had any need for car audio (my Mercedes has Bose audio pack which is good enough for me). After using the set for some time I noticed that it started to do a 50hz buzz sound (I'm in Europe, it was not low rumble but higher buzz). After some problem hunting (turned lights off and on, including my aquarium lighting and pumps, floor heating, a/c etc) I saw that the trigger cable was touching the power cable of the other monitor. I was sceptical but decided to wind that cable around the RCA cable anyway to be sure.

Lo and behold the buzz was gone. So that small external trigger cable was able to generate an audible buzz to both channels just because the right channel monitors power cable was in close proximity to the other end of the lead. That lead to the cable inducting voltage from the power line and spreading the disturbance all the way to the speaker inputs.
 
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