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Discussion Starter #41
Try grounding the AVR and amp chassis together with a separate wire
Tried it yesterday but it did not work unless i was doing something wrong. Not sure if I am supposed to remove paint from the chassis to make correct ground but I did not want to do that in case I have to return the Crown amp. Any other way to do so?
 

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Tried it yesterday but it did not work unless i was doing something wrong. Not sure if I am supposed to remove paint from the chassis to make correct ground but I did not want to do that in case I have to return the Crown amp. Any other way to do so?
In my experience 90% of ground loops are from the CATV ( cable tv/ cable internet ). as a diagnostic, have your equipment on listing to the hum, grab some stripped speaker wire. wrap one end around the metal catv connector ( NOT the pin just the external connecter screwed on to tv/cablebox/modem ).

While listing to the hum, put the other end into the ground terminal on the outlet or powerstrip and see if it goes away.

Also Im not sure how the attenuation knobs are wired internally and if its not required for bridge mode, but to be on the safe side, put both knobs to max.

The yamaha might be setting its sub trim based on the 10" which probably has more gain on the amp meaning more sensitive to incoming signal. try turning the 10" down on the rear of its amp and rerun ypao.
 

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Discussion Starter #43 (Edited)
In my experience 90% of ground loops are from the CATV ( cable tv/ cable internet ). as a diagnostic, have your equipment on listing to the hum, grab some stripped speaker wire. wrap one end around the metal catv connector ( NOT the pin just the external connecter screwed on to tv/cablebox/modem ).

While listing to the hum, put the other end into the ground terminal on the outlet or powerstrip and see if it goes away.

Also Im not sure how the attenuation knobs are wired internally and if its not required for bridge mode, but to be on the safe side, put both knobs to max.

The yamaha might be setting its sub trim based on the 10" which probably has more gain on the amp meaning more sensitive to incoming signal. try turning the 10" down on the rear of its amp and rerun ypao.
Interesting thing is that I do not have a cable box in the rack. I only have a

1) Yamaha RX A2000 AVR
2) PS3
3) Panasonic Bluray player
4) Crown XLS 2502

Even with the Yamaha unplugged from the wall outlet, if I connect the RCA from Crown to Yamaha, hum starts. If I disconnect RCA from Yamaha but let one end plugged into Crown, hum stops. I am wondering how can it be a ground loop if the Yamaha is not even plugged into an outlet. Can ground loop happen even if the Yamaha is unplugged?

When you say "plug wire into outlet, do you mean that I connect speaker wire to Yamaha chassis screw at one end and plug in the other end of the speaker wire into the ground prong on the electrical outlet? Is it safe to do so?

I have so far disconnected Mirage sub and only have the devastator connected. I did rerun YPAO after I removed Mirage sub from the equation.
 

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if you haven't got the devastator working yet and are sure that it is well constructed, you may wish to try a few things:

1. turn off all dsp in the crown amp for now (from what you are describing, you may have mixed up the high pass with the low pass and are filtering out all your bass)
2. set input sensitivity on the amp to 0.775v.
3. if using bridge mode, carefully inspect your connectors to ensure that +1 on your speakon ultimately goes to positive on your driver and +2 goes to the negative
4. make sure you are connected into channel 1 on your crown
5. make sure the gain on channel 1 is turned all the up (clockwise)

6. turn off YPAO and any other bass eq
7. set mains to small and crossover point to 80hz or 100hz
8. set subwoofer trim to +0 (make sure your speaker trims are also close to zero)

play some music that has some bass in it. turn the volume on your AVR up and the bass should knock your house down.

the recommendation to get a minidsp is good so you can put a protective high pass at 20Hz or so. it will also help with EQ if your AVR doesn't have full EQ capability.

hope that helps!
 

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Discussion Starter #45
if you haven't got the devastator working yet and are sure that it is well constructed, you may wish to try a few things:

1. turn off all dsp in the crown amp for now (from what you are describing, you may have mixed up the high pass with the low pass and are filtering out all your bass)
2. set input sensitivity on the amp to 0.775v.
3. if using bridge mode, carefully inspect your connectors to ensure that +1 on your speakon ultimately goes to positive on your driver and +2 goes to the negative
4. make sure you are connected into channel 1 on your crown
5. make sure the gain on channel 1 is turned all the up (clockwise)

6. turn off YPAO and any other bass eq
7. set mains to small and crossover point to 80hz or 100hz
8. set subwoofer trim to +0 (make sure your speaker trims are also close to zero)

play some music that has some bass in it. turn the volume on your AVR up and the bass should knock your house down.

the recommendation to get a minidsp is good so you can put a protective high pass at 20Hz or so. it will also help with EQ if your AVR doesn't have full EQ capability.

hope that helps!
Thanks LTD02 for the steps outlined.

1) I will do that first thing tomorrow. Kids sleeping and I don't want my better half to be questioning my existence at this late hour of the night :)
2) Yep, I have done that.
3) Checked the wire and it is per recommendation from Crown and as you explained.
4) Yep,connected to channel one
5) I have gain set at 3 o'clock position but will try with max tomorrow.
6) YPAO from what I know does not do any bass management but will check again tomorrow and report back on what sub settings are in speaker setup
7) Yep, I have all speakers set to small with LCR set at 80hz and surrounds and back LR set at 100hz
8) I am not sure how to set sub and speaker trim. Can you please advise on how to do that?

I do want the sub to produce that kind of output hence the reason I choose good equipment and a great cabinet design. I am sure I am missing on something and need your help in figuring this out. I have also ordered a minidsp and should have it by Monday. Wish amazon was as fast as it was prior to the corona age. Thanks again, I will update the thread tomorrow. Please do advise on how to set trim level at the AVR end.
 

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Is there an HDMI device connected to the Yamaha when it is unplugged from the wall and still humming? HDMI has a ground and can cause loops if the HDMI device is also grounded. Unplug all the HDMI devices to see if the hum stops. If it does stop reintroduce HDMI devices one at a time. You can get optical HDMI cables if it is an HDMI device causing the issue, but they are not the most cost effective solution.

I have around 5 devices in my current setup, any of which can cause a ground loop. Pay attention to things that use three prong outlets. Current can flow between those devices, usually that is not a problem until you introduce a grounded power amp.
 

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Discussion Starter #47
Is there an HDMI device connected to the Yamaha when it is unplugged from the wall and still humming? HDMI has a ground and can cause loops if the HDMI device is also grounded. Unplug all the HDMI devices to see if the hum stops. If it does stop reintroduce HDMI devices one at a time. You can get optical HDMI cables if it is an HDMI device causing the issue, but they are not the most cost effective solution.

I have around 5 devices in my current setup, any of which can cause a ground loop. Pay attention to things that use three prong outlets. Current can flow between those devices, usually that is not a problem until you introduce a grounded power amp.
Great point John. I will unplug everything tomorrow and try plugging in one source at a time with Yamaha AVR unplugged to see if the humming is still there or not. Will report back. Cheers!
 

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I have the MiniDSP 2x4 balanced, so I cannot test to see if the non balanced version would break a ground loop. If the power supply on the 2x4/2x4HD is two pronged it could very well break the ground loop from the AVR to the XLS. That would save a lot of headache and you could set a BW 2nd order 18Hz HPF or a BW 3rd order 16HZ HPF filter and let the NSW take the full power of the amp without worry.
 

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I had a ground loop hum from my denon receiver and had to run a ground from the chassis to a grounding adapter plugged into my power strip.
 

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I agree with removing the HPF and setting gain max for testing. The chances of you damaging that woofer are pretty slim, and you would have to probably ignore a ton of distortion. Though long term a proper HPF is probably a good idea.

Turn off any sub equalization for testing.

The receiver could also simply be not putting out enough preout voltage for the amp. Most plate amps, like I assume the Mirage has, will output max wattage on a pretty low voltage input level, like 0.2 or 0.3v. Sometimes the manufacturers take that into account and have preout voltages in the 0.3-0.5v range. Most pro audio equipment is 1.4v, with some having a option to go down to 0.775v (like the Crown XLS) at the expense of S/N ratio. 0.775v is still relativity high for home audio standards. If that is the case you may have to get something like a Cleanbox that can boost the signal to pro audio levels. It may also help with your hum problem, though I agree it is probably being transferred via HDMI like Red Five mentioned above.

If you are only lighting up the -20 light on the Crown you are probably only putting out something like 20W to the Sub.
 

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Discussion Starter #54
I have the MiniDSP 2x4 balanced, so I cannot test to see if the non balanced version would break a ground loop. If the power supply on the 2x4/2x4HD is two pronged it could very well break the ground loop from the AVR to the XLS. That would save a lot of headache and you could set a BW 2nd order 18Hz HPF or a BW 3rd order 16HZ HPF filter and let the NSW take the full power of the amp without worry.
Ordered minidsp and amazon will deliver on June 1st. Lets see which version I get. Will keep you posted.
 

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Discussion Starter #55
I had a ground loop hum from my denon receiver and had to run a ground from the chassis to a grounding adapter plugged into my power strip.
Can you share link to the adapter please? or any details how you did it will be very helpful. Thanks.
 

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Can you share link to the adapter please? or any details how you did it will be very helpful. Thanks.

seems I used an old power cable from a refrigerator or appliance and just wired the ground to the chassis of the receiver. I did scuff the paint a tiny bit to get to bare metal. Then I plugged it into the power strip I was using for everything and viola no more hum for me. I think I pulled one or both of the spades on the plug so I had no power going through it.
 

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Discussion Starter #57
I agree with removing the HPF and setting gain max for testing. The chances of you damaging that woofer are pretty slim, and you would have to probably ignore a ton of distortion. Though long term a proper HPF is probably a good idea.

Turn off any sub equalization for testing.

The receiver could also simply be not putting out enough preout voltage for the amp. Most plate amps, like I assume the Mirage has, will output max wattage on a pretty low voltage input level, like 0.2 or 0.3v. Sometimes the manufacturers take that into account and have preout voltages in the 0.3-0.5v range. Most pro audio equipment is 1.4v, with some having a option to go down to 0.775v (like the Crown XLS) at the expense of S/N ratio. 0.775v is still relativity high for home audio standards. If that is the case you may have to get something like a Cleanbox that can boost the signal to pro audio levels. It may also help with your hum problem, though I agree it is probably being transferred via HDMI like Red Five mentioned above.

If you are only lighting up the -20 light on the Crown you are probably only putting out something like 20W to the Sub.
Thanks. Will check that out and report back. I did read through an older thread which stated that power from the pre out should be sufficient. Take a look at post #17 on this thread https://www.avsforum.com/forum/155-diy-speakers-subs/1443652-minidsp-require-signal-boost-pro-amps.html
 

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Ordered minidsp and amazon will deliver on June 1st. Lets see which version I get. Will keep you posted.
Which MiniDSP did you order? IMHO, the only one you should be ordering at this point is the 2x4HD. It is obvious to me (though people will argue til they could be part of the Blue Man Group), that you do not have enough voltage from your Yamaha sub out RCA. Many people have experienced this, myself included. Pro gear runs at +4dBV, and consumer gear runs at -10dBm. These are two different scales and cannot be equated directly, which is what I feel some people misunderstand.

The Crown 0.775V setting does make a difference, but it is DEFINITELY not adequate for the lack of voltage output from your Yamaha. You will also notice that the hum is louder on the 0.775V setting than the 1.4V. I run an XLS 1502, and for awhile it was my subwoofer amplifier. I needed an ART Cleanbox Pro to get my input signal high enough to drive the Crown into the clipping zone. I ran my sub trim all the way up on my Marantz (without the CB Pro) and barely saw the first light on the Crown. I was not running a high pass filter though, so I would not recommend the CB Pro for your situation. Going back to the hum - I initially set the Crown on the 0.775V and there was noticeable hum. Setting it to 1.4V and turning up the Cleanbox to compensate did not produce the same level of hum, and I was hitting the clip indicator at the same volume level on the AVR while playing the same demo scenes. I can't tell you why on that one - compensation with the CB Pro should return the same hum level, but it didn't. In order to get approximately the same hum, the CB Pro needed to be up quite a bit more, and I hit the clip light at a much lower AVR volume level. Just my experience.

I do not have experience with the standard MiniDSP 2x4, but I have dealt with the Balanced and 2x4HD. The Balanced output voltage is 'probably' adequate for driving the Crown. I say 'probably' because I still feel you may need more to drive the Crown to 'tickling' the clip indicator. The 2x4HD however, has voltage output in spades. When I switched from the Crown XLS 1502 to a QSC PLX 3002, I still needed the Cleanbox in the signal chain. I now have a 2x4HD. I had to bump the gain up on the HD to get the same output as the CB Pro (4.5dB on the input, 4.5dB on the output. +9dB total), but there is PLENTY left in the tank if I needed more voltage to the sub amp.

I feel I must also add that I usually run my amp attenuation knobs (usually labeled 'gain', a misnomer) at about 25% from full (at 75%). This is because I like to have some knob control when listening to music. If I feel a particular track could use some reinforcement, I use the amp knobs to adjust to taste. It's my listening session, I don't really care how the 'mixing professional' wanted it to sound - I know how I want it to sound and what makes me happy.


Edit: Had to clarify where I run my amp knobs at - I run them at 75% (at about the 3'oclock position).
 

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Another thing to try - grab a headphone jack to RCA cable and plug your phone/laptop directly into the Crown amp and play something. When I was diagnosing a signal issue with my amp, I did this to remove the receiver from the equation. Turned out that I had my speakon connectors wired incorrectly (after checking a billion times). I'd recommend manually wiring the sub as well (run a wire from the binding posts on the amp to the binding post on the sub directly).
 

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Thanks. Will check that out and report back. I did read through an older thread which stated that power from the pre out should be sufficient. Take a look at post [URL=https://www.avsforum.com/forum/usertag.php?do=list&action=hash&hash=17]#17 [/URL] on this thread https://www.avsforum.com/forum/155-diy-speakers-subs/1443652-minidsp-require-signal-boost-pro-amps.html
Read post #17 . Ricci's post just talks about not using a boost box if you have adequate preout voltage, which I agree with. Not sure what it has to do with the preout voltage on your specific receiver. It's easy to test if you have a multi-meter. If you are only lighting up the -20 light of the Crown at full volume then you definitely are not feeding it enough voltage to get full output, let alone drive the amplifier to clip.
 
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