Dedicated 20 amp lines/should i use a sub panel

Hello Indranilsen,

The first thing I would do before deciding how to proceed would be obtain a multimeter, if you don't already have one, and measure the AC line voltage at various times of the day and night over the course of several days.

If you find that there is a correlation between the variations in sound quality and changes in line voltage, a power regenerator, such as one of those made by PS Audio, might be a solution. A regenerator is likely to also be helpful if noise or distortion on the AC line is contributing to the problem. On the other hand, though, some people have reported here over the years that in their systems some regenerators have resulted in compromised dynamics.

Also, in a thread several months ago you indicated that you were considering upgrading your Parasound Halo A-21 amplifier. If you haven't yet done that, I would suggest that you re-assess the situation after purchasing the new amplifier before deciding how to proceed. It's possible that a different (and presumably better) amplifier may be less sensitive to the power line anomalies at your location than the present amplifier.

Good luck. Regards,
-- Al
 

Noromance, sounds like a plan! FYI, though, the manuals I’ve seen for various REL subs recommend that when a single sub is used in conjunction with monoblock amps, and is connected at speaker-level, the black wire should preferably be connected to a ground point on the preamp. That may be worth trying when you get a chance, as you **might** find that sonics are improved at least slightly.

Jea48 1-5-2018
For proper operation the cap should be connected to the neutral conductor. Problem with the way it is now the neutral is fused....
At any rate if possible I would want the fuse on the Hot mains conductor and the cap connected to the mains neutral conductor to chassis ground.

Jim, the photo in Noromance’s system description of the underside of his amp, which as he mentioned has been modified, shows a somewhat different circuit configuration than the schematic Imhififan provided. It appears to show the fuseholder (and also the power switch) in series with the black (hot) AC wire. And although it’s hard to tell for sure, I think the cap is connected between the white (neutral) AC wire and chassis. So if that is correct, and assuming both amps are wired the same, what you are indicating should be done has been done.

Also, I wouldn’t be surprised if the modifier replaced the original power cord with a two-wire cord having a polarized plug, and in the process checked for optimal polarization. But as we’ve both said it might be worthwhile to try to verify that. The experiment I suggested in my previous post would provide some confidence that plug polarity is correct. A more conclusive way would be to disconnect the interconnect cables from the amps, turn them on, and use a multimeter to determine which plug orientation results in the lowest AC voltage between the chassis and the screw on the wallplate of the outlet. A cheater plug would be used for purposes of the experiment if that is necessary to reverse the orientation of the plug. To be sure those results are meaningful, though, it might be necessary to disconnect the electrostatic speakers from the amp as well as the interconnects. It should be safe to run the amp unloaded, given that it won’t be processing a signal, but personally my preference would be to connect load resistors in place of the speakers rather than running a tube amp unloaded even with no signal going into it.

Best regards,
-- Al

Thanks for your thoughts and questions, Jim.  Generally speaking a direct connection between AC safety ground and signal/circuit ground is an invitation to ground loop issues (both hum and high frequency buzz).  In good modern designs the two grounds are often connected to each other through a resistor having a resistance in the area of 10 to 100 ohms, which would probably be impractical to do in this case since chassis is used as signal/circuit ground in many places.  It would also stand a good chance of being sonically undesirable, due to the small impedances it might create between grounds at different circuit points within the amp.  So I would recommend that Noromance leave well enough alone, and if he chooses to upgrade the power cords on the amps that he **not** connect AC safety ground within them.

Also, regarding the "death cap" (and thanks to Imhififan for providing the good reference), it's worth noting in the photo of the underside of Nomance's amp that the cap has been replaced with a modern one.  So presumably leakage within that cap is not an issue.

But it doesn’t [hum] when I add my REL sub.

Noromance, what model is the sub, and if you are using the high-level Speakon connection what is the black wire connected to?

Also, if you want to pursue the hum issue further what you might try would be connecting each amp to its own dedicated line, with the two lines on the same AC leg, and then trying all four combinations of the orientations of their AC plugs. If the plugs are polarized or are 3-prong types, even though the safety ground is not used within the amps, for experimental purposes you could try that using cheater plugs.

Regards,
-- Al

Thank you, Larry (lak). Jim (Jea48) is the expert when it comes to electrician-type matters, and hopefully he’ll chime in. But FWIW I agree with all of the comments by Dill. I doubt that adding a sub-panel would provide any benefit, and as Dill indicated inserting additional contacts into the path won’t be helpful.

Unless, that is, the sub-panel is something like those made by Equi=Tech which incorporate a high quality transformer and would provide balanced power to the system. However their models cost in the vicinity of $10K or more, and weigh upwards of 300 pounds.

Good luck. Regards,
-- Al