[fishydan]

Hello-

OK, first let me say I'm loving my Cornet.  RCA Cleartop and a pair of Telefunken 12AX7.  I'm using it with my Joule LA100 MKIII, and it's a very nice combo, but I've noticed something unusual.  When I switch to stereo on either the Cornet or the Joule, the hum goes up.  This is at a normal listening level, about 12 o'clock on the gain knob on the Joule.  If I go to mono, the hum level drops dramatically.  Now, the hum isn't overwhelming when present, but it's there.  Any ideas on why the hum would be different between mono and stereo?

Thanks,
Dan

[hagtech]

Could be a magnetic field getting picked up by the cartridge.  The mono mode might offer a cancellation (as coils 90 deg apart).  Does noise change depending on where the tonearm is?

What happens if you unplug one of the inputs?

jh

[fishydan]

Hello Jim-

By "going mono", I mean flipping the switch to mono from stereo on either the Cornet or the Joule pre amp.  I will try unplugging an input to see what happens.

thanks,
Dan

[fishydan]

Hello Jim-

The position of the tonearm doesn't have an effect.  Removing one input at the Cornet does diminish the effect somewhat, but stereo still has more hum than mono.

Thanks,
Dan

[hagtech]

Hummm, the mono switch on the Cornet2 shorts together the two inputs, effectively putting 24k ohm loading on the cart.  This could possibly reduce hum.

I'm thinking it is perhaps then a shielding issue.  Electric field shielding of the tonearm wires.  Are you using coax?  Do the shields of the RCA jacks on Cornet2 connect to chassis?

jh

[fishydan]

Hello Jim-

The tonearm cable is shielded coax, and the shields on the rca jacks do not connect to the chassis.

Just to clarify- the hum is really not objectionable, and is only really noticeable when my room is extremely quiet.

I will look at the path the tonearm cables are taking, to make sure they are not in close proximity to any AC cords.

Thanks,
Dan

[hagtech]

What happens when you turn the Cornet off?  You get about two seconds of continued useful operation.  During that time, does the hum go away?

jh

[fishydan]

Hello Jim-

Yes, the hum goes away if I power down the Cornet 2.

Thanks,
Dan

[hagtech]

Aha!  Then if it is a hum, the source is the power transformer.  If a buzz, then heater circuit.

Does the level of hum change with position or orientation of the Cornet chassis?  Does it change when you move interconnect positions?  

jh

[fishydan]

Hello Jim-

I tried moving the interconnects, but it didn't effect the hum.  The way my system is set up now, I can't really change the orientation of the Cornet.  I'll try to figure out a way to do it and report back.

Thanks,
Dan

[Eric H]

Hi Dan,

Have you tried other tubes, including (especially) the rectifier?  If you haven't tried swapping tubes this would be the first thing I'd do.  Even "good" tubes sometimes don't seem to work very well in particular places sometimes...  good luck!

Eric