Jolida JD-100 New unit with bad HUM.....hum


I am in the process of breaking in a Jolida JD-100 C. Johnson’s mod #1. I received the cdp last night and have played on repeat for 15 or so hours. Out of the box listening was a little rough but improving every few hours. I like rock and roll and a bit Loud (so I’m told). I’m very concerned of a distinct hum that I am hearing at moderately high listening levels especially when I pause the cd. I have checked the power on both a house supplies and through a 5kva isolation transformer the I installed for my components. Tried grounding the JD-100 case from the ground terminal provided on the unit but no help. I have changed interconnects still the hum is there. I have change inputs to my pre and still get the hum. The CJ mod has upgraded output (RCA’s) so I tried the original and still the hum. This is the first experience with tubes I have had since the 70’s and I don’t know if it is just the normal tube hum or if I have a defective unit. Anyone’s advice would be greatly appreciated. Thanks T. J.
tjtrout20

Showing 3 responses by tjtrout20

Thanks guys for the response,
I do think this is a defective unit after a long listening session last night. I tried classical (piano solo’s) and some chamber stuff and unfortunately it was a lesson in frustration. Completely unlistenable. Spinning some rock and r & b stuff was much better as it veiled the hum and gave me a glimpse of the sonic qualities of this unit. My first instinct was an AC problem. The hum is audible at just over ½” power (200watt per side adcom amp) at my listening chair almost 10’ away even with the Jolida powered off. Turning the amp up from ½” power and it gets exponentially worst. Hum disappears as soon as I unplug the cdp's power at IEC. I’m reasonable confident that is not an isolation problem as the Jolida sits on the top TT shelf of an Atlantis Reference 5 rack with a basement slab floor under it. Speakers are 130lb NHT 3.3 again with spikes on slab. Regarding the hiss ??? maybe there……under the hum somewhere???? I guess when it rains..........the reverse on this unit is very jumpy also. Looks like I will be talking with Wally from Underwood hifi first thing in the am. Thanks so much for the help. T. J.

P.S. Last nights listen to John Hiatt’s mofi Bring the Family with Ry Cooder’s slide work on Lipstick Sunset made me forget about all bad vibrations in the world………for a little while.
Thanks again Distortion
I do have video running as I'm using a HTR as my pre amp. I'll go try the disconnect and see what happens. I’ll let ya know. I do believe that daisy chaining the grounds on each case is correct method as it would give all the same ground reference but still the nasty hum!!
Great day for Chile here in Colorado with a mild snowstorm here in the foothills and major up on the passes (2’ or more). I made a batch 3 Sundays ago that had to amount to about 12 to 15 lbs. I think I’ll pull some out of the freezer!!! Do you think a Chile recipe thread would get us booted????
Thanks Mijknarf,
My old cdp is indeed a 2-pronged plug (Yamaha carousel). Although I am not positive that the hum is not a problem of the supply power on my end and not an internal problem with the unit I don’t think it’s on my end. I have tried both standard utility power (110v) and a power system that incorporatea a 5 kva copper wound isolation transformer 230v primary and 110v secondary witch feeds a 125amp sub panel. The center tap of the transformer derives the neutral and ground and does not have a physical tie to the utility company, rather a grounding electrode system made of (4) 3/8” 8’ driven ground rods and develops the ground reference from that (no grounding or grounded tie no utility “noise”) 4 separate dedicated 20amp circuits serve my components each with #10 grounding conductor using #10 stranded wire from sub panel, terminated with sta-con spades connectors to Leviton hospital grade 20amp receptacles. The transformer is active and pulls almost 8 amps at idle so I installed a contactor ahead of the transformer with a 120-volt coil wired to a single pole switch to turn the system off when not in use. Although this system is not NEC compliant (don’t try this at home) is has worked wonders in terms of power quality and got rid of a nasty ground loop I had on my turntable for years. Nonetheless the Jolida when powered by the utility company or the transformer hums like…. er……. well it hums. Any problems with the reverse on your unit??? I did try removing the video connections to my HTR with no success. Thanks again!! T. J.