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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
mijknarf
266 posts
 
Can't help you beyond the fact that mine is mummless at any volume. Dosen't sound normal for this unit.
distortion
571 posts
 
Mine is dead quiet. Except for a slight tube hiss when I have the volume very exaggerated. e.g. to hear the tube hiss!

If you power down the CDP (with the switch on the front panel) do you still get a hum? Try unplugging the power from the back of the CDP, do you still get a hum?

Hum is usually associated with ground or AC issues. It could be an an internal issue with the CDP.

Hiss, just like tape only much much lower in volume, is typical with tubes. Usually hiss is not an issue, very faint to inaudible at normal listening levels.

Macrophonics, or tube ringing, can be an issue. It can also be a hum (usually not though). Macrophonics occurs when your tubes are being vibrated, either by an outside force or even by your speakers themselves. Isolation feet, boards, slabs, devices, cones, and spikes can all help. I use Vibrapods under my CDP. Place the CDP on a nice sturdy shelf all to themselves. This is better than stacking. Nearby speakers, magnets, or power supplies may have a negative effect on tubes too (although I am not sure of this, other A'goners probably will).
tjtrout20 OP
16 posts
 
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.
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