Dedicated Line Noise Filter?

Thanks for the nice words, Lowrider.

Given that when only the preamp and power amp are connected there is a loud hum when a cheater plug is not used and a lower but still significant hum when a cheater plug is used, it sounds like two problems are present. One being a ground loop between preamp and power amp, and the other probably being due to something internal to the preamp, such as some of the possibilities Davehrab mentioned.

I say "probably" because it is also conceivable that what you are hearing when only the preamp and power amp are connected is the result of having the preamp’s high impedance inputs left unconnected and essentially "floating." Unconnected high impedance inputs often tend to be susceptible to pickup of hum and noise, that may even be coupled into them from elsewhere within the same component. Which would have no relevance to what would occur when a powered up source component having reasonably low output impedance is connected. And if you also hear a low level hum when a powered up source component is connected, perhaps that is due to a ground loop between source component and preamp. (Although if I recall correctly you may have sorted out that possibility some time ago with a Jensen transformer and/or a cheater plug).

But to assure that assessments that are performed with unconnected inputs are meaningful it would be desirable to purchase some RCA shorting plugs. A search for "RCA shorting plugs" at eBay will return many sellers offering those at low prices.

Finally, regarding the possibility of an internal problem in the preamp, the next time you are in contact with Ralph (I recall that you’ve discussed this issue with him) you might ask if the UV-1 uses AC or DC on its tube filaments. While I suspect the answer will be DC, if perchance AC is being used I would speculate that a tube problem may be contributing, unless you've eliminated that possibility via tube substitutions.

Good luck. Best regards,
-- Al

@almarg ... Thanks, Al. Can always count on you. I thought about using shorting plugs a while back, but now I can't remember if they can be used on the UV-1. I'll reach out to Ralph next.

What if Lowrider57 has lost a power supply cap or has a cracked solder joint in one of his component's

Yes, it's possible that there is an internal problem.
I did use a Jensen, following your recommendation, on the preamp output and the sonics were so terrible I quickly removed it. Ralph has stated many times how adding a transformer inline with an OTL component can have a negative effect, and wow, he was not kidding. So I can't remember if it corrected the ground loop.

The Jensen did perform well on the source which was involved in the ground-loop in my system. If you recall, my Sunfire amp was designed with the signal and the safety ground tied together, which threw a wrench into the entire system. I now have a tube amp, properly grounded, so there should be no ground-loop. I can't confirm that, of course, until the electrician verifies that his wiring is correct.
Many thanks to you and Jea48,
Jim

lowrider57

... In Philadelphia, a permit is not required for an electrical addition or upgrade in a residence.
The law states that an inspection is required at the time a house is being sold.

Sorry, but you’re mistaken.

" Electrical permits are required for the installation, alteration, replacement or repair of electrical and communications wiring and equipment within or on any structure and for the alteration of an existing installation. "

see: https://business.phila.gov/electrical-permit/

That your contractor didn't know this - and didn't insist on applying for the required electrical construction permit - raises questions about his competency, and whether he's even licensed to perform this work.

I agree, almarg and jea48 are a wealth of knowledge and willing to share.
Thanks guys...

Cleeds, that's interesting. The company that I use has about 20 electricians on staff. They come to the house to give a free estimate, then return about a week later to do the work. Perhaps they get the necessary permit before starting the job. Maybe someone in their office does this.
This the third time they have done work for me; an upgrade with new breakers, lines and receptacles, then my first dedicated line after I entered this hobby, and the latest work 2 weeks ago.