I was using the cheater plug. As I said, I've been doing this for years, as a matter of course. I don't care to A/B this stuff. I just hated the loose fit of the cheater plug and the cheap metals involved.
Lifting ground on Spectral amp
- Thread starter dan31
- Start date
or death!
I have been the least path of resistance to ground before and I am fortunately here to tell you it does not feel good.
This can have deadly consequences, dying in the name of better sound is not in the cards for me,except for the occasional subwoofer in a big wooden box.
Definitely not steel boxes in steel racks.
I know that in my environment I must lift the grounds for my mono blocks. I've yet to pin down just where in my wiring the feedback loop is occurring. I'm not confident enough that I have a clear methodology to uncover the source. I'm happy to entertain any ideas anyone might have in pursuing this.
What sort of "feedback"? Ground loop? How's everything connected electrically when that happens?
You are correct we should not play with safety. However there are proper ways of interrupting or minimizing the currents due to ground loops at audio frequencies, keeping the safety. But IMHO they should not be carried by amateurs. Since long I have used a custom power strip fitted with special diodes and capacitors to separately float the ground of each plug keeping safety, but just for test purposes.
For increased electrical safety we must have differential breakers of 30 mA type. Than you can feel safer when trying these non recommended practices.
Many people are horrified with audiophile practices and do not even test regularly their differential breakers or know the details about their safety ground system. There are more electrical risks in their kitchens or bathrooms than in audiophile systems ...
As far as I can tell it is a ground loop. What I have today is the following electrically:
4 separate circuits:
1) 20 amp with a Spectral 400 mono block and Spectral preamp
2) 20 amp with a Spectral 400 mono block and Berkeley Ref. 2 DAC
3) 15 amp with Shunyata DPC-6 (all digital gear plugged in here, including Mac Mini, WD hard drive, Eero WiFi access point, Synergistic Research Transporter, Sonore Signature LPS, Berkeley Alpha USB)
4) 15 amp with Synergistic grounding block and Synergistic FEQ
I've tested out isolating the preamp (no connections at all to inputs) while keeping interconnects to the mono blocks in play. Whether the preamp is powered on or not the amps exhibit a low level hum when the mono blocks are not floated. I've also tried floating the preamp while not doing so for the amps and still get hum. There are slight variations in the degree of hum if I reorient things. By putting both amps in a single 20 amp circuit and the preamp in the other. And using this same setup adding a cheater to the preamp lowered hum a tad more. I'm beginning to believe that I'm getting a loop from somewhere in the overall building wiring that will be rather hard to troubleshoot. But I may be quite wrong.
I know that the amps are very sensitive. Even placing the preamp within a foot of the amps degrades sound appreciably.
You could try floating everything but the preamp. That was my experiment. Perhaps both mono's ground lifted to one duplex. Then the Dpc-6 grounded to the wall with your source ground lifted and the preamp grounded.
The only ground would be through the preamp. You can then add grounding to a single piece in addition to the preamp and judge each piece as the grounds are returned.
Obviously you are the boss so don't do this if your unsure in any aspect of the exercise.
The only ground would be through the preamp. You can then add grounding to a single piece in addition to the preamp and judge each piece as the grounds are returned.
Obviously you are the boss so don't do this if your unsure in any aspect of the exercise.
My objective is to ground as much as possible while avoiding ground loops. I've already demonstrated that simply focusing on just the preamp and amps (without connecting anything else to the system) I get a ground loop unless I float the amps. Doing what you suggest just muddies the water without getting to the source of the problem. The only thing I've yet to try would be to, say ground one amp while floating the preamp and other amp. And doing so would still get me no closer to understanding the source of the loop.
Only way for me to get rid of nasty hum with spectral amps was lifting ground using cheater plugs. Only had this issue with Spectral. If this is such a pervasive issue, not sure why they can't address it. Does not do the brand any good.
If you have ground loops, the equipment will reveal it; Pass and others are the same way. So best to fix the ground loops. Steve, in this case, may be falling into the "dedicated" line trap, with different length power lines and primarily ground wires. Dedicated lines must have the exact same length wires (including ground) from the distribution box, of the exact same gauge and metal purity - read: entirely, 100% identical, or there will be ground impedance issues; consequently, the power cords must also be identical (including in length), as well as any conditioners, etc. If necessary, just "tie" the grounds between the power lines. If using sub-panels, are the the ground and neutral bonded together... etc. There are electronic tools at places like Home Depot to solve all these problems.
See also http://www.whatsbestforum.com/showthread.php?19492-Shunyata-DENALI&p=414903&viewfull=1#post414903
See also http://www.whatsbestforum.com/showthread.php?19492-Shunyata-DENALI&p=414903&viewfull=1#post414903
My guess it could be 3), try moving that if you can to another spot...a foot away. Or if that fails try 4). Whenever you have multiple PC's plugged into a single source,that could do it. I had the same thing drove me crazy. It just takes persistence,good luck.
Thanks for your feedback. I know the two circuits intimately. I watched the electrician run the same gauge cable of equal lengths from the breaker to the 4 outlet receptacle. And the three Zcords from MIT are all the same length. As I've noted, I can induce the hum with only the three Spectral devices connected into the two 20 amp circuits - and even with the preamp powered off. I'm not aware of how breakers operate. If the circuits are separated and the only common connection is from the breaker to ground, then it's well beyond what I can ascertain.
I plan on bringing in a Shunyata D6000/T next week for testing. My plan is to plug this into one of the two 20 amp circuits via a single Sigma HC power cord. The two amps will get connected into the 2 HC outlets of the D6000 and the remaining 4 outlets will serve the preamp, DAC, USB to S/PDIF converter, and Sonore LPC. That should begin to tell me more, I hope.
I plan on bringing in a Shunyata D6000/T next week for testing. My plan is to plug this into one of the two 20 amp circuits via a single Sigma HC power cord. The two amps will get connected into the 2 HC outlets of the D6000 and the remaining 4 outlets will serve the preamp, DAC, USB to S/PDIF converter, and Sonore LPC. That should begin to tell me more, I hope.
It seems to me the easiest test is to "tie" the grounds - run a ground wire from one outlet of one circuit to an outlet on the other circuit - I suspect this will get rid of the hum
If what you're suggesting is true, and I use only one of the circuits for the Shunyata D6000/T next week, and avoid the other altogether, will I still potentially still have a ground loop? At present the only other thing to test to confirm what you're suggesting is to use a single circuit for the amps and plug the preamp into another receptacle on yet another circuit. Am I right about that?
No, not exactly. Everything must be plugged into the same circuit, as a starter, using a power distributor - that gives you star-grounding. Then, you can move the amps into a separate circuit, and I am almost certain the hum will return, to one degree or another. All of these will simply confirm you have ground potential, and the dedicated lines are not identical. What you are doing right now by lifting the ground on the amps is to star-ground at the preamp's inputs through the interconnects; that's fine, I do that too, but I do it for sonic reasons, even though I plug everything into one distributor (which kills hum to start with); this configuration just stands the chance to offer ever so slightly better sonics; but your primary goal here is to kill hum, then worry about ultimate sonics.
Use an ohmeter and test the IC's that run between preamp and amp. There's a good chance one has a bad ground. It can show up in both channels.
There is leakage current to the chassis inside your electronics which causes ground currents/hum with no contributions at all from your electrical wiring. The solution to this is to use balanced interconnects. I see that your power amps have this. Are you able to connect them this way?
So, even if I plug both the Shunyata D6000 and the DPC-6 into the same 20amp circuit, via the two receptacles connected to that circuit, I'll still get the ground loop I've experienced?
If that's the case I could plug the DPC-6 into the D6000 so that I've one single plug into one circuit.
By the way, I have been using a Synergistic Research Grounding Block which incorporates star ground for their product set along with other elements of my system. These include the DAC and preamp via spare inputs. I'll disengage this for testing.
Unnecessary if everything is working correctly. That's why I'm suggesting to check continuity on each IC. A reversed hot/ground in an IC can cause this as well. The only place to suspect SE are going to cause a hum problem is phono that's unshielded, if nothing is broken/miswired or a **** poor design.
Better questions besides just checking this... Has the equipment always had the issue? If not, what changed when you heard it?
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