Dirty power wrecking the sound...

Lisa Lane-Collins

Lisa Lane-Collins

Sophomore
Dec 9, 2012
270
0
16
Adelaide, Australia
I have zone control and amps in one room, and in another, a DJ set up, and the speakers that are powered by aforementioned amps. And a small patch point on the wall, 2 xlrs sending signal off to the amps and one speakon sending signal back for a sub.

Problems are 2 fold, well, 2 and a half

Presumably the DJ mixer is running off of a different circuit to the zone control/amp and there is heaps of hum, which can be neutralised with a DI, but even when it is gone there is buzz and just general machine noise. The other problem is that the signal coming back to the zone control is no where near hot enough. I tried to fix this by adding a mixing desk to the equation. When run off the same circuit as the zone4 this is viable, off the same circuit as the DJ mixer, EVEN MORE HUM. It would be incredibly handy to include a mixer in the signal chain at the DJ mixer end but everything I plug in introduces way too much noise.

The other problem (probably less easy to fix) is that every time I try and connect the DJ mixer to the amps via xlr or rca outs (at the DJ end or the amp end), I get zapped. It hurts!



And tangental to the primary question but I may as well chuck it in. Being that hum is my number one issue in this place, and the zone4 only accepts rca in (whyyyyyyy :-( ) what's the best way to get from xlr to rca?
 
Re: Dirty power wrecking the sound...

If you're getting a shock, that is an indication that something is seriously wrong and needs to be addressed immediately. It's not dirty power, it's mis-wired power. It could be a hot and neutral wire are reversed, or it could be that the ground points between the two circuits have a different voltage potential between them. If all of the grounds are not at the same point, you would also get the symptoms you describe.

Get it checked out immediately before killing anyone.
 
Re: Dirty power wrecking the sound...

Lisa Lane-Collins said:
Presumably the DJ mixer is running off of a different circuit to the zone control/amp and there is heaps of hum, which can be neutralised with a DI, but even when it is gone there is buzz and just general machine noise. The other problem is that the signal coming back to the zone control is no where near hot enough. I tried to fix this by adding a mixing desk to the equation. When run off the same circuit as the zone4 this is viable, off the same circuit as the DJ mixer, EVEN MORE HUM. It would be incredibly handy to include a mixer in the signal chain at the DJ mixer end but everything I plug in introduces way too much noise.
Click to expand...

If you're trying to use a regular DI, it's doing to drop the level to mic levels which won't be enough to drive line level inputs. You need line level isolation transformers, not a DI. Something like Whirlwind ISO1/ISO2 or the good Jensens. I believe the level drop is no more than 6dB.

Lisa Lane-Collins said:
The other problem (probably less easy to fix) is that every time I try and connect the DJ mixer to the amps via xlr or rca outs (at the DJ end or the amp end), I get zapped. It hurts!
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Sounds dangerous and potentially deadly. Get a qualified electrician in there ASAP to figure out the mess. Could be what JR said, a hot - ground swap or some other crazy stuff. It will also create huge noise problems as well as possible death. There might be other problems as well like ground neutral swaps or appliances on the circuit leaking current into the ground.


Lisa Lane-Collins said:
And tangental to the primary question but I may as well chuck it in. Being that hum is my number one issue in this place, and the zone4 only accepts rca in (whyyyyyyy :-( ) what's the best way to get from xlr to rca?
Click to expand...

Again, an isolation transformer that is able to go from balanced to unbalanced would be the best way to isolate ground loops, maintain correct impedances and keep the XLR signal balanced. The ISO1 can work as a balanced to unbalanced box as well as a line balancer.

ISO 1 - Catalog - Whirlwind
 
Re: Dirty power wrecking the sound...

Could it be that the hum is actually coming FROM the mixer? ie a bad filter cap?

I highly doubt it is "dirty power"-although people just LOVE to blame it on the power.

It could be a grounding issue (pin 1 or similar) on some piece(s) of gear.

Unbalanced connections can be a real pain-you have to unplug (signal wise-not power) EVERYTHING-and then start to hook it up and see when the hum returns.

THEN start to narrow it down. It could be coming from the "transmitting end" or by hooking up the "antenna" (signal cable) to the "receiver".

Adding a mixer is simply going to amplify the noise-not reduce it. Once it is in the system-anything that has gain is going to make it worse.

Is there any other audio gear in the place that does not have the noise? If so-then it is not the power.

To be honest-I don't think I have ever seen a situation in which the power was actually the problem-but was always blamed.

So I suspect internal device issues or input/output grounding issues.
 
Re: Dirty power wrecking the sound...

Ivan Beaver said:
To be honest-I don't think I have ever seen a situation in which the power was actually the problem-but was always blamed.

So I suspect internal device issues or input/output grounding issues.
Click to expand...

She's actually getting a pretty powerful shock interconnecting devices. I suspect there are real wiring problems in this venue.
 
Re: Dirty power wrecking the sound...

Well I think I found the reason for the zap zappy.... *glowers* .... the DJM800 takes an IEC .... there's no ground pin!!!!!!!!!

What in the hell do I do to fix that?!
 
Re: Dirty power wrecking the sound...

Lisa Lane-Collins said:
Well I think I found the reason for the zap zappy.... *glowers* .... the DJM800 takes an IEC .... there's no ground pin!!!!!!!!!

What in the hell do I do to fix that?!
Click to expand...

First off, replace the broken cable. Second, the removed ground pin is probably a symptom of something else wrong - it was probably removed in an attempt to eliminate hum.
 
Re: Dirty power wrecking the sound...

Rob Timmerman said:
t was probably removed in an attempt to eliminate hum.
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Did Not Work.

It's not the cord that's dodge, it's the mixer itself, assuming they are meant to be grounded, and the other one's I have all have a third pin at the power point end.

Harking back the the 'this rig aint loud enough' problem (haven't systematically tackled the hum yet, just set up my sound source in the same room as the amps trying to trouble shoot the volume drop). If I plug the xlrs from the DJ mixer straight into the back of the amp it's Beautiful. More volume in that room through those untuned speakers than anyone could possibly ever want. As soon as I adapt to rca (I have to to interface with the zone4), bam, volume gone, like maybe a good 3 quarters drop. This happens with or without the Zone 4 in the signal chain. I bought a Samson transformer isolator to make the adaptation from xlr to rca (and knock out any hum/buzz still hanging around) and even with it's in built attenuator cranked up, it's still not loud enough.

What in the world is the proper way to make the transition from xlr to rca for this kind of thing?!!!!!!
 
Re: Dirty power wrecking the sound...

Lisa Lane-Collins said:
Did Not Work.

It's not the cord that's dodge, it's the mixer itself, assuming they are meant to be grounded, and the other one's I have all have a third pin at the power point end.
Click to expand...
The DJM800 product information shows the three prong grounded IEC connection for the power, are you saying this one does not have that?

Lisa Lane-Collins said:
Harking back the the 'this rig aint loud enough' problem (haven't systematically tackled the hum yet, just set up my sound source in the same room as the amps trying to trouble shoot the volume drop). If I plug the xlrs from the DJ mixer straight into the back of the amp it's Beautiful. More volume in that room through those untuned speakers than anyone could possibly ever want. As soon as I adapt to rca (I have to to interface with the zone4), bam, volume gone, like maybe a good 3 quarters drop. This happens with or without the Zone 4 in the signal chain. I bought a Samson transformer isolator to make the adaptation from xlr to rca (and knock out any hum/buzz still hanging around) and even with it's in built attenuator cranked up, it's still not loud enough.

What in the world is the proper way to make the transition from xlr to rca for this kind of thing?!!!!!!
Click to expand...
If you are trying to adapt the XLR outputs on the mixer to RCA inputs then note that the DJM800 manual states "When using a cord with RCA-type plug, users are recommended to connect the plug directly to the MASTER 2 connectors without using an XLR/RCA converter plug." So are you comparing the 'Master 1' XLR output level to the 'Master 2' RCA output level? According to the DJM800 specs both outputs are the same nominal +2dBu output level, although the maximum level is +22dBu for the XLR 'Master 1' out and +20dBu for the RCA 'Master 2' out, so there should be no difference between those.

If you are using the Samson S-Convert to try to covert the XLR outputs to RCA note that it is also intended to convert nominal +4dBu balanced signals to -10dBV unbalanced signals, about a -11.8dB difference. And apparently even with the gain at maximum there is a 6dB loss between the XLR inputs and RCA outputs.
 
Re: Dirty power wrecking the sound...

Greg Cameron said:
She's actually getting a pretty powerful shock interconnecting devices. I suspect there are real wiring problems in this venue.
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Unless a piece of gear is defective-causing the issue.

Or it could be that in one (it only takes one) piece of gear has a problem with ITS AC supply-transferring the voltage "down the line".

There is a difference between "dirty power" and AC wired up wrong. TOTALLY different issues-and solutions.
 
Re: Dirty power wrecking the sound...

Kevin Graf said:
Getting zapped when setting up interconnects means that the building has an AC power wiring problem.
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Not necessarily. If for some reason there is no safety ground between a device and the receptacle then either someone touching the device or a signal ground connection to a properly grounded device could become the safety ground path. And if the chassis or any other relevant parts of the faulty device were 'hot' for any reason you then get current flow through that alternative safety ground path. In that case it is the device power wiring at fault rather than the building power wiring.
 
Re: Dirty power wrecking the sound...

Brad Weber said:
Not necessarily. If for some reason there is no safety ground between a device and the receptacle then either someone touching the device or a signal ground connection to a properly grounded device could become the safety ground path. And if the chassis or any other relevant parts of the faulty device were 'hot' for any reason you then get current flow through that alternative safety ground path. In that case it is the device power wiring at fault rather than the building power wiring.
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Yet again-a clear case of "divide and conquer".

MEASURE the power on all the outlets in the building-every leg to every leg and every leg to ground. Either fix any issues or stop blaming the power.

People just LOVE to guess all day. The way to figure out a problem is to MEASURE- and go from there.

Once you can show the problem via MEASUREMENT-THEN you can start to find the solution.

But if you don't know what is wrong-how can you go about fixing it?
 
Re: Dirty power wrecking the sound...

Why yes, that's exactly what it has. Does kinda look like it left the factory that way. Of course, now I am puzzled how it is meant to ground. Tried plugging in a different mixer and that was fine, no shocks. Then the 800 again and that was Also fine. By this point in time I'd been messing around with the patching at the amp end a bit though so maybe the problem came from there. Whatever was causing me to become the ground, it isn't anymore :-D.

The signal flow that Worked in the end. DJ mixer - balanced out - adapted to rca using a specifically made cable that summed black and ground (instead of black and red as I now suspect the adaptor was doing) - zone control - amps. The difference between using the tailored cable and the store bought adaptor (or even the Isolation box - gah waste of cash!) is night and day!!!! Another thing discovered, the DJ mixer has a master attenuation control at the back of it, wound that up and got quite a bit more volume that way.

So, not the power that wrecked the sound in the end at all but quiet source signals, unbalanced outs and unsuitable rca to xlr adaptors. Feeling quite proud now :-D (and my prize - not having to set up a second PA in that room for salsa dancing, an Excellent prize!)
 
Re: Dirty power wrecking the sound...

Lisa Lane-Collins said:
Why yes, that's exactly what it has. Does kinda look like it left the factory that way. Of course, now I am puzzled how it is meant to ground. Tried plugging in a different mixer and that was fine, no shocks. Then the 800 again and that was Also fine. By this point in time I'd been messing around with the patching at the amp end a bit though so maybe the problem came from there. Whatever was causing me to become the ground, it isn't anymore :-D.

The signal flow that Worked in the end. DJ mixer - balanced out - adapted to rca using a specifically made cable that summed black and ground (instead of black and red as I now suspect the adaptor was doing) - zone control - amps. The difference between using the tailored cable and the store bought adaptor (or even the Isolation box - gah waste of cash!) is night and day!!!! Another thing discovered, the DJ mixer has a master attenuation control at the back of it, wound that up and got quite a bit more volume that way.

So, not the power that wrecked the sound in the end at all but quiet source signals, unbalanced outs and unsuitable rca to xlr adaptors. Feeling quite proud now :-D (and my prize - not having to set up a second PA in that room for salsa dancing, an Excellent prize!)
Click to expand...
Glad you found the problem.

And the "dirty power" is once again proven to not be at fault---------------------------------------
 
Re: Dirty power wrecking the sound...

On a tangent, so are some venues wired a bit worse than others and can it introduce noise? The venue that comes to mind is a metal venue where everyone's guitar amps buzz. Not noticeable when they are playing but very obvious in between. I do live recordings of some of these bands in various venues around town and only notice the heightened noise floor in this one.
 
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Re: Dirty power wrecking the sound...

Lisa Lane-Collins said:
On a tangent, so are some venues wired a bit worse than others and can it introduce noise? The venue that comes to mind is a metal venue where everyone's guitar amps buzz. Not noticeable when they are playing but very obvious in between. I do live recordings of some of these bands in various venues around town and only notice the heightened noise floor in this one.
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It is not the way they are wired. Assuming they are up to local code.

But there are all sorts of "things" that can cause noise in the systems. Things such as fridges-HVAC units even old fashioned cash registers can cause all sorts of "hash". But poor quality light dimmers are often a major problem-putting "hash" back on the line.

This has nothing to do with "bad wiring" and everything to do with poor quality devices hooked up to the power in the building.

However it could be the path of the actual ground in the outlets and the actual resistance. This could be measured and verified one way or the other.

Again-divide an conquer. It is amazing how things can be narrowed down with a little basic work and not guessing based on very limited information.
 
Re: Dirty power wrecking the sound...

Ivan Beaver said:
It is not the way they are wired. Assuming they are up to local code.

But there are all sorts of "things" that can cause noise in the systems. Things such as fridges-HVAC units even old fashioned cash registers can cause all sorts of "hash". But poor quality light dimmers are often a major problem-putting "hash" back on the line.

This has nothing to do with "bad wiring" and everything to do with poor quality devices hooked up to the power in the building.

However it could be the path of the actual ground in the outlets and the actual resistance. This could be measured and verified one way or the other.

Again-divide an conquer. It is amazing how things can be narrowed down with a little basic work and not guessing based on very limited information.
Click to expand...

Any noise on line or neutral (harmonic content) isn't going to make it past the power supply in the unit. Noise on the ground wire could make its way into an audio path if a piece of equipment ties safety ground (protective earth) to signal (audio) ground. Equipment that dumps significant current onto a protective earth conductor is either poorly designed or failed (failed MOVs in power strips are a pretty standard cause). A GFCI is a good way to check for excessive ground leakage, as is getting shocked.

And this is all referring to conducted issues, not magnetically coupled issues such as you might get from adjacent cables.
 
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