Hello all.
I'm new here and hoping for some help.
Our church is currently using a Wharfedale PMX 700 amp/mixer for popup events.
I am running an RCA/3.5mm audio lead from the audio outs of the amp to a 3.5mm to USB adapter into our laptop in order to record the audio.
As you can hear by the short mp3 sample here: sample of buzzing.mp3 - Google Drive
there is a very noticeable buzz coming through the recording.
This is NOT coming through the FOH speakers and is still there even if I unplug the laptop power supply.
What could be causing this and how can I stop it???
Thanks in advance
Tracy
Auckland
New Zealand
I'm new here and hoping for some help.
Our church is currently using a Wharfedale PMX 700 amp/mixer for popup events.
I am running an RCA/3.5mm audio lead from the audio outs of the amp to a 3.5mm to USB adapter into our laptop in order to record the audio.
As you can hear by the short mp3 sample here: sample of buzzing.mp3 - Google Drive
there is a very noticeable buzz coming through the recording.
This is NOT coming through the FOH speakers and is still there even if I unplug the laptop power supply.
What could be causing this and how can I stop it???
Thanks in advance
Tracy
Auckland
New Zealand
How long is the cable?
I'm getting a little inevitable hum on my four meter RCA cables from mixer to amp. Buying an organ separated the speakers from the turntable, and the mixer has to be near the turntable, max 2 m, due to low drive of mm phono cartridges. 2 m cables preamp or mixer to power amp never hummed. These are 100 ohm coax cables. This RA88a mixer is a $15 bargain and has RCA jack mains out.
Pro mixer setups use twisted pair from the mixer to stage amp. They also have differential drive on the mixer out end and a differential input op amp on the PA amp end. Of course, your lap top won't have a differential op amp input. In a classic PA setup, a 100' "snake" runs twisted pair from mikes to mixer out in the audience, and 4 twisted pairs run back to the stage where the amps are. The laptop would be under 4' from the mixer in that setup.
One tipoff to differential setup is TRS ("stereo") phone plugs for mixer output and amp input, although the $50 PV8 mixer I just bought I was just informed has the TRS plugs but not the two op amps to drive the mains differentially. The $1000 new CS800s amp I bought used does have the differential inputs.
If the cable is short, proximity to mains transformers, or bad grounding in the mains electrical panel, can cause undue hum. In a dry environment, the whole water pipe or copper coated rod mains "earth" connection can be missing actual connection to the water table in the ground.
I'm getting a little inevitable hum on my four meter RCA cables from mixer to amp. Buying an organ separated the speakers from the turntable, and the mixer has to be near the turntable, max 2 m, due to low drive of mm phono cartridges. 2 m cables preamp or mixer to power amp never hummed. These are 100 ohm coax cables. This RA88a mixer is a $15 bargain and has RCA jack mains out.
Pro mixer setups use twisted pair from the mixer to stage amp. They also have differential drive on the mixer out end and a differential input op amp on the PA amp end. Of course, your lap top won't have a differential op amp input. In a classic PA setup, a 100' "snake" runs twisted pair from mikes to mixer out in the audience, and 4 twisted pairs run back to the stage where the amps are. The laptop would be under 4' from the mixer in that setup.
One tipoff to differential setup is TRS ("stereo") phone plugs for mixer output and amp input, although the $50 PV8 mixer I just bought I was just informed has the TRS plugs but not the two op amps to drive the mains differentially. The $1000 new CS800s amp I bought used does have the differential inputs.
If the cable is short, proximity to mains transformers, or bad grounding in the mains electrical panel, can cause undue hum. In a dry environment, the whole water pipe or copper coated rod mains "earth" connection can be missing actual connection to the water table in the ground.
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That's very common on Laptops. I believe it's caused by a ground loop.
You even hear the mouse moving and HD spinning.
Connect the laptop to a non-earthed outlet, or use a non-grounded PSU. (Try a cheater plug). Don't tell me about safety and FCC regulations. All mobile DJ's I know do it.
You even hear the mouse moving and HD spinning.
Connect the laptop to a non-earthed outlet, or use a non-grounded PSU. (Try a cheater plug). Don't tell me about safety and FCC regulations. All mobile DJ's I know do it.
well it seems the OP tried that already, as mentioned in his first post (unplugged as in running off battery)
i would try an isolation transformer (repeat coil)
i would try an isolation transformer (repeat coil)
hello my buzzing friend 🙂 when you say the “audio outputs” where are you connecting from to record ? Tape output? Booth output? etc It sounds like 50hz mains hum ..like the signal ground is not connected
can you give me more info as will will try to help
have you tried a different USB adaptor or laptop , will be a processes of elimination
can you give me more info as will will try to help
have you tried a different USB adaptor or laptop , will be a processes of elimination
Maaco mentioned hearing noise when a mouse is moved or high frequency whining when hard drive's spin up, would that not be a sign of a bad laptop power supply i.e. leaky/weak filter cap's in the supply? i've run into an instance that a bad laptop battery was the cause of noise, the thing that was confusing was assuming that running of battery would eliminate a "ground loop noise" when in fact the faulty battery was behaving like a bad filter cap and allowing high frequency noise to modulate the audio, replacing the faulty battery solved the noise issue in that case.
would there be a way of uploading the mp 3 clip to this web sight rather then having it hosted elsewhere?
(i fell sad for all the threads that have pictures that have vanished to the ether because of external hosting)
(i fell sad for all the threads that have pictures that have vanished to the ether because of external hosting)
Hi all 🙂
Thanks for the great input so far 🙂
I will certainly try removing the battery next week.
I did insert a ground-loop-isolator which DID make a significant difference but as you can hear there is still a buzz.
No isolator - Buzz with no isolator.mp3 - Google Drive
With isolator - with isolator.mp3 - Google Drive
I will also take another laptop along and try that so see if it is something in the actual laptop.
The outputs I am using from the PMX are the RCA stereo outputs
amp record outputs.jpg - Google Drive
Thanks for the great input so far 🙂
I will certainly try removing the battery next week.
I did insert a ground-loop-isolator which DID make a significant difference but as you can hear there is still a buzz.
No isolator - Buzz with no isolator.mp3 - Google Drive
With isolator - with isolator.mp3 - Google Drive
I will also take another laptop along and try that so see if it is something in the actual laptop.
The outputs I am using from the PMX are the RCA stereo outputs
amp record outputs.jpg - Google Drive
Can you not get to the mp3 clips? it is supposed to be a public link?
The isolator was one of these: Surplustronics - Ground Loop Noise Isolator (Stereo) 3.5mm
The isolator was one of these: Surplustronics - Ground Loop Noise Isolator (Stereo) 3.5mm
I Believe Your source is producing the buzz.
Try connecting a non-balanced cable from the mixer to the speakers.
Are they buzzing ?
Batteries have circuits to control charging, and I they can produce noise on the ground if they are bad.
Try connecting a non-balanced cable from the mixer to the speakers.
Are they buzzing ?
Batteries have circuits to control charging, and I they can produce noise on the ground if they are bad.
The FOH speakers are already running unbalanced leads and the buzz doesn't come from them, only through the recording. ALso I have tried the laptop without the power supply, no change
sorry no subscription to Google Drive.
took a quick look at the isolator you linked to and it says nothing about what's inside. can you confirm with a multimeter that the input output grounds are indeed isolated?
whether your laptop is running off ac or the battery does not eliminate the possibility that the "buzz" in the recording isn't originating within the laptop things like voltage multipliers in the supply and video circuits can be nasty sources of noise.
if you have recorded other sources without issue then we are back to square one...
can you confirm the PMX 700 is connected to a grounded AC outlet? we may be looking for a "loop" while ignoring the possibility that we don't have a proper ground!
took a quick look at the isolator you linked to and it says nothing about what's inside. can you confirm with a multimeter that the input output grounds are indeed isolated?
whether your laptop is running off ac or the battery does not eliminate the possibility that the "buzz" in the recording isn't originating within the laptop things like voltage multipliers in the supply and video circuits can be nasty sources of noise.
if you have recorded other sources without issue then we are back to square one...
can you confirm the PMX 700 is connected to a grounded AC outlet? we may be looking for a "loop" while ignoring the possibility that we don't have a proper ground!
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The PMX is grounded as the New Zealand mains plug is a three-pin with the lower centre being earth.
we have the same standard here in Canada.(although primary is 120 Vac)
after a few decades of location PA and system installs i've lost count of the number of instances where assuming that things are as they are supposed to be has been the source of trouble.
broken or defeated ground pins on extension cords, improperly wired outlets and bad power bars are a reality.
verifying actual conditions is important.
what sort of test gear do own? do you have a multimeter?
after a few decades of location PA and system installs i've lost count of the number of instances where assuming that things are as they are supposed to be has been the source of trouble.
broken or defeated ground pins on extension cords, improperly wired outlets and bad power bars are a reality.
verifying actual conditions is important.
what sort of test gear do own? do you have a multimeter?
What type of USB adapter are you using , the ones I have seen only have a mono microphone input with power for an electret microphone .
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