Hi,

Simplify this and just run MiniDSP -> Crown and use the MIniDSP as a USB DAC in REW and sweep it without the AVR.

Also, if you do a slow sweep and show the water fall, let's see if your waterfall shows this ringing hum around 60hz. Then you'll have a good data point on how to address it, if it's that.

Very best,

 

So .... Opening the mini dsp software and disabling inputs to all subs.... Still noise.

I then muted the signal source to the mini dsp, still noise.

Even switched from analog to usb signal input .. noise still present

Unplugging the signal source rca from the mini dsp causes the noise to lessen but definitely still there very much



Only unplugging the rca from the amp to the minidsp does the noise stop.

Just tried a different rca... Same issue

 

Ground loops occur when you have a potential difference of voltage between your devices, and the path to ground, or to sink the additional voltage, usually at a frequency of 60hz, travels down the audio chain of connections.

Need to confirm the Denon s760h is plugged into a grounded plug. The hot lead that this plug is connected from the Service Panel, let's call LEAD RED.
We need to determine if the crown xls 2502 is plugged into LEAD RED, or if its connected to the other lead , lets call that one LEAD BLACK
Additionally, determine if the minidsp is connected to LEAD RED, or LEAD BLACK.

The key to ground loops is to ensure that the equipment is on the same GROUND PLANE.

Since most equipment is double isolated, such as your Denon, which will only have 2 connectors in the power plug, you can using bonding to connect all devices together, say with a 14awg green wire and lugs. This is a method to at least test with.


The other thing I ran into with Klipsch subwoofers quite some time ago, that I posted about, could be an issue that is feeding back into your system.
Check out this link.

https://www.avsforum.com/threads/klipsch-r-112sw-hum-identified.2994588/?post_id=56595976#post-56595976

 

All the equipment is on the same circuit. When i bought the house, it had all new wiring, outlets and panel installed but the panel had no grounding rod and the panel itself was not bonded to ground which I had to do.

But yes... Its on a grounded circuit. Not sure what you mean in regards to the live lead being red or black

Edit..... Ran some other tests...

It seems its the amp but not sure if I need to return it or get an art clean box.

Tried disabling inputs on mini dsp.... Noise remains.


Tried swapping rca cables .. noise remains.

Tried plugging crown amp into 3 outlets all on different circuits.... Noise remains.

Tried switching from high to normal input sensitivity.... Noise remains but quieter.

Tried bypassing mini dsp and connecting avr straight to crown and with all other subs disconnected.... Noise remains.

 

What marty said.

Ground-related noise (non-60 Hz, harmonic-related, which is technically more than a ground loop, but close enough for our discussion) is an emergent property due to ground references differences between equipment. Factors include not just the reference ground voltage in a static sense, but the voltage difference can be dynamic due to equipment dumping voltage into ground, and ground path impedance.

It's a real hassle.

As general practice, I find it easiest to disconnect everything, and then start connecting things from the speakers backwards. You're obviously not going to get any noise possible until you connect the speakers to the amplifier, because if the noise is upstream, but you have no speakers connected, you cannot know.

From there connect the MiniDSP to the Crown. If you have issues, you know where you need to resolve it. It may be resolved with an additional ground cable wired chassis to chassis, an isolation transformer, whatever. Once that is resolved, or deemed not a problem, move to the connection to the Denon AVR. Same Deal. Repeat, and be aware that it can be interactive.

An interface device like a Cleanbox Pro offers gain adjustment as well as balanced/unbalanced conversion. It might fix your noise problem, or it may not.

Balanced connectors are just doubled up outputs with one side inverted, and are also called differential, because the input signal is the amplitude of the difference in voltage between the + and - polarity signal connectors, as opposed to a single conductor referencing ground. As such, balanced connections are typically much more tolerant of ground-related noise, and will 'reject' common mode noise referenced to ground, because that noise is the same on both sides, not different, and as such, cancelled. Most of the time anyway. Lots of variables. I guarantee nothing

A good high quality isolation transformer is nice to have handy, just because. If you can resolve it without resorting to extra boxes, Mo' betta, usually, but in the end Mo'betta is the ultimate Mo'betta, and it comes in all sorts of configurations.

 

Calm yourself first.

Is it fine when the PC is powered up and not connected to the rest of the system other than through the power lines?

 

Sorry, i been on 12 day straight runs at work and been at this project for months, finally had a day off and wanted to get things buttoned up but expected a roadblock.... I just hate roadblocks I cant solve.

Nope.... When pc is on there is extreme hum that changes as I do stuff on the pc.

Pc audio passes through tv to the avr. Ive tried unplugging everything from the pc but hum still remains.

Connecting ground wires from chassis to chassis of components didnt help.

The PC is a pretty big part of my home theater room. Really there are no other outlets close enough to the tv to plug it in to. It has a 1000w psu so wouldnt want to use an extension cord other than to test.

What has me baffled is that neither of my klipsche plate amps had a hum, nor the 12sub I had behind the couch, nor the amp on my shakers.... None of them ever had an issue with hum from the pc.

I bought the crown xls 2502 new/open box from pro audiostar in aug so its probably too late to even return it if its the issue

 

Ground lift adapters are good diagnostics tools, maybe, but I wouldn't recommend using them as a fix.

It is possible that a jensen isolation transformer, or a balanced line driver (cleanbox is in this category, but you can also pick up AudioControl units cheap on Ebay), could remove the problem. If you have return privileges, it's free to try. If you have a 24 VAC power supply laying around, I could send you a spare balanced line driver. I have a small collection of doodads

 

I had this problem too, I could hear all sorts of PC activity through the speakers and subs. My easy solution was to just move the PC to a different outlet further away..