[pretzel_logic]

I am still getting hum from my Cornet II which I finished some time ago. Initially it was very loud so as Tubes recommended I added a longer transformer ground and also fixed the problem with my RCA's touching the case. That cured the main problem but I still have a low hum, that changes with volume. It's barely audible at low volumes but certainly audible at higher listening levels during very low passages or between songs. Before the above fixes it was very loud all the time.

One other thing I had to do was eliminate the ground plug on both my Canary CA 900 preamp and the Cornet as I was getting a buzz through the CA 306 amp via the preamp. Not so sure how safe that is but my house ground was generating the buzz, initially through the preamp but I had to get it out of the chain so also the Cornet. So I've eliminated the buzz completely but still have a hum generated by the Cornet, any suggestions?

Thanks,

Brian

[hagtech]

You will need some Earth grounding somewhere in the chain.  Otherwise nearby sources (lamps, wiring) will induce hum into the TT.  You might hear the level of hum change just by touching things, like the tonearm or input jacks.  Best not to float a system.

jh

[pretzel_logic]

Yes, I am going to look into isolating the outlets I'm using and hopefully that will help. I do still have the amp grounded but to get rid of the buzz that was very audible I used a couple of the groundless adapters for the phono and linestage. At this point I get a very soft tick when touching the tonearm and a louder one when turning on a light.

I do still have the phono hum I'd like to eliminate but maybe it's also coming from the main power as well, who knows.

Brian

[PatOMalley]

touch the top of the front tube and the chassis. if that calms some of the hum it might be induced.

a way to tell is to play music and then turn the phono pre off by the power switch and leave all else play. If hum diminishes immediately it might be the transformer. If it lingers it may be induced. Figure that one out and there are fixes for the transformer.

If it is induced, good luck. I have still a tine wee small amount of hum after using a few tricks but I live on the top of a town in the middle of two antenna farms.

[Bill Epstein]

My Cornet is silent but using the Cinemags on the intended shelf in the pic is anything but.

Empty shelf.



I wish the ICs were 6" longer; the position and wire dress you see knocks the hum back to nearly inaudible. RF is like RE, location, location, location

[PatOMalley]

Bill Epstein,

It migt hum bucause it is above that transformer. Try moving that Cornet to the top shelf and move the SUT to the self underneath. OR make the shelf longer and place the sut alongsde the cornet. OR put the SUT on the shelf with the table.

[Bill Epstein]

Try moving that Cornet to the top shelf under the SUT to the self underneath

Boy, I'm sure glad I thought of that

Thanks O'Malley. It might even work!

[pretzel_logic]

Pat, I had the system on and get nothing when touching any of the tubes other than a couple warm fingers. When I turn off the Cornet the hum disappears immediately. Any suggestions on that or the transformer? As I stated originally I ran the trannie ground wire directly the the star ground per Tubes advice.

Brian

[PatOMalley]

I got the suggestion about power off from the web and the word on it is that if you power off and the hum immediately disappears while music is still playing then it is the transformers wiring or ground that is at fault.

Did you braid the transformers wires going to the board?

[pretzel_logic]

Hi Pat, braid as in twist I assume you mean, no I did not. Actually I didn't have music playing though either, but then I wouldn't have been able to hear the hum as it's not audible during play but there none the less between tracks and very audible then.

Not sure there is all that much wire to braid, I cut as JH suggested in the instructions so there isn't a lot of extra wire floating around.

Also, JH would probably feel good knowing that I have everything grounded again as I moved all my power cords to a different outlet and the amp and linestage buzz is gone.

Brian

[PatOMalley]

-twist- is what I meant.

A grounding problem can be fixed. Just like you did. But an induced hum? You gotta sacrifice a cheetah out on the front lawn and pray to the gods.

I wish there was a product like a lightening rod that would catch all the EMI and run it somewhere safe.

[pretzel_logic]

As far as the amp and line stage are concerned, moving the mains to a different outlet/power strip, on the same side as where the mains exit the units helped a lot. I had a mish mash of power cords touching all the IC's and moving the power cords helped a lot with buzzing and what not. The amp was always dead quiet with no inputs attached, but as soon as I plugged the linestage into the wall with the IC's connected I had a buzz in my left speaker even with the linestage off, that buzz is now gone but I still fear a transformer problem in that unit, I can hear a slight hum when the unit is on. Obviously I'm working on that and will have to talk to the manufacturer again, it's still under warranty.

As far as the Cornet II goes I'll still play with a couple things. The hum from that is coming from somewhere, and it increases as I turn up the volume and it's very audible between tracks, something I really want to eliminate.

Last night I realized something else with the Cornet, or remembered. I never cleaned off the boards with alcohol after assembly. I didn't have any in the house and now wonder if that's causing the hum. I guess that should be the first thing I do but at least I've solved a couple other problems in this whole process.

Brian

[hagtech]

The hum is coming from the power transformer.  It is not the tranny wires.  It is the magnetic field getting coupled (indiced) into the input section, perhaps wires.  Or a nearby step-up tranny.

jh

[PatOMalley]

In that case would ferrite on the + wire on the inside RCA be any benefit?
And/or would a physical shield around the inputs help?

[Speedskater]

Ferrites work at much higher frequencies.
Here are some of Jim Browns papers on ferrites and his papers on hum.

http://www.audiosystemsgroup.com/publish.htm

[PatOMalley]

So shielded input wires may work.

[hagtech]

Shielded wires protect against electric fields.  Not magnetic.  Twisted pairs do better for this.  You need to track down exactly where it is getting in.  Probably getting into the primary of the step-ups or phono cables.

jh

[PatOMalley]

i used very very short input wires not twisted more than once, two best, because of their short length. I thought going short was the best idea. So maybe I will pull them and use some longer Teflon coated 6n copper, twisted more than enough. it's something to do.

the hum on my machine is nothing to really complain about any more. it is minimal. annoying to a neurotic but still minimal.

One thing I am wondering is do people who use the stock solder-to-pcb connectors experience hum issues or is it just the wire connected RCAs?

[WGH]

One thing I am wondering is do people who use the stock solder-to-pcb connectors experience hum issues or is it just the wire connected RCAs?

Absolutely no hum here using the stock solder-to-pcb connectors.