[ecir38]

I powered up my Cornet2 this week and unfortunately I have a hum. The first thing I did to determine that the hum was coming from the Cornet2 was to disconnect the Piccolo and the turntable from the input. With just the output from the Cornet going to the Clarinet I have a hum that is noticeable in the 12 o’clock position on the Clarinet volume and gets louder if it is raised. The left channel is louder than the right. (edit: except when in mono it is the same)

I have read all search results for hum with the Cornet and to no prevail I still have the hum. Here are the things I tried so far. First I tried the obvious by swapping the interconnects and tubes. I moved the Cornet well over a foot away from all other electronics. I disassembled and made sure that the transformer and chassis ground have good connections to the chassis. One other thing I tried is turning the Cornet off to see what happened for the 2 seconds it takes to turn off. The result of this was hum was still present but reduced slightly and sounded more like a hiss.

Additional info:
The rca’s are not grounded to the chassis and have adequate room for interconnects. I did not use any heat sinks around the rca’s. The reason for this was from a past post stating that they weren’t really needed. I am now wondering if they possibly create a shield for the rca’s. I did not use them in the Clarinet and it is very quite with a CDP. Pic’s can be provided if needed.           

If ya’ll have any recommendations on where else I should be checking it would greatly appreciated. Is there a way I can check things out with a DVM? Another thing is I am not fully sure whether I am experiencing a buzz or a hum, don’t really know the difference. 

Thanks

[BobM]

The usual source of hum is some kind of ground loop. Try plugging the Coronet into the same outlet as your preamp. If that doesn't work then try lifting the ground on the Coronet with a cheater plug.

Those might work as an interim solution, but if you have that much hum then I think there may be something wrong inside the unit. You may want to check your assembly and connections to see if you have a lifted trace somewhere or a bad solder join.

Good luck,
Bob

[ecir38]

Bob, tried the clarinet plug on the cornet with no luck. I tried cheater plug with no luck. I performed visual inspection of joints and think they look great. Here are a couple of not so great pics.

[hagtech]

A buzz is that "zzzzzz" sound.  It means noise from rectifiers, likely a missing geound connection.  A hum is either 60Hz or 120Hz.  If 60, then it could be a missing ground connection (something floating) or a cable loop picking up ac mains.  If 120Hz, then likely a magnetic coupling from power transformer or some other power supply component (or machine), usually caused by too many ground connections.

jh

[ohenry]

I wouldn't rush out and buy another transformer, but I thought I'd pass along my experience...

I've had the Cornet for two years and always experienced a noticeable hum (I think it was the 120Hz variety).  I tried internal shielding, different cables, different tubes, different equipment positions, making sure the transformer mounting bolts were contacting the aluminum chassis, etc., and nothing seemed to help.  Recently, I noticed a fellow AC member selling the same model Hammond transformer and I bought it.  The new transformer was the only thing that reduced the hum.

The symptom that made me think the transformer could be the issue was that I noticed a slight change in the hum when I touched one of the transformer housing bolts.

The hum, while noticeable, wasn't a deal-breaker as evidenced by me happily living with it for quite a while.  I like my Cornet even more now.

[ecir38]

Herny, I was thinking that this may be the case too. I am going to swap the clarinet and the cornet transformer tomorrow and see what happens. I am not sure of where else to look. Thanks. 

[ecir38]

I went ahead and swapped the transformers and the same problems are still there so the tranny can be ruled out .

Looks like I will be living with this until more research points me into a better direction. Everything you read says hum issue can be a real pita, I will just have to keep trying differant things out. Might switch to better input and outputs next. The odd thing is that it is louder on one channel than the other.     

[freo]

I had a hum between my bottlehead pre and my power amp, a bought a hum and noise eliminating coupler from altronics in australia for $15 and the buzzzzzzz, hum went away, go to the bottlehead forum type in, hum and noise eliminating coupler, and see what you think
Regards Roger

[ecir38]

I'll go there and check that out. I've seen them before but thought this would  not be best to do thinking it may cause an audible degration. 

[WGH]

A visual inspection of the solder joints may not be enough. I had an intermittent noise problem that was finally tracked down to a perfect looking solder joint. Look closely at both sides of the board and touch up all the ground points.

Maybe putting in the heat sinks you left out would help.

Wayne 

[freo]

I was also worried about the loss of sonics, but I thought for $15 I would give it a go There is a small change in the sound, but I would not say it has deteriorated at all, just changed.
Regards Roger

[tubesforever]

Ground loops are a bugger.  If you have a true ground loop hum it should be exactly the same volume from both channels.  Since yours is louder in one channel than in another it may be a bad solder joint but everything looks great in your photos.

Could you have an issue with the turntable, tonearm, or cartridge grounding?  Try running separate ground wires to the tonearm and to the turntable.  If you disconnect one does the sound go quiet?

On my unit I made sure the wires were twisted on all my tranny leads.  so if I had a 120+ and a 120- these two got twisted as a pair. 

On my unit I ran the earth ground from the IEC plug to the earth ground lug on the Cornet 2 and then grounded this back to the PCB.  That way everything is star grounded.

This got my unit completely silent.

I do get a little hum when going from ss amps to tube amps but these are issues with the amp and not with the Cornet2.

Also, if using a cheater on the Cornet2 does not change a thing, try it on the preamp or the amp until you find which item is creating the loop.

Hope some of this helps. 

[stereohifi]

Hi everyone, i had a hum when i first used my Cornet2. This is a problem with grounding scheme.
1- Make sure that all your AC wiring is twisted.
2- Make sure that all your grounding is at the same center (star ground), that is , RCA inputs, third ground IEC Ac connector, PC board ground, chassis ground (metal top plate.)
3- Make sure that the transformer is grounded too! That actually resolved my problem.
My power transformer is a Hammond. In the schematics, it shows that there is a static ground wire, but that wire supposed to be gray colored, is not there!?
So you use one of the fixing bolts or your chassis for grounding the transformer .
Good luck!
This Cornet2 is so quiet, now that i can hear tube rushing noise on max volume, so i need a better Low noise 12AX7.....
Ah yeah, i forgot to mention that all of your HIFI as to be on the same grounded AC plug.
That's were mini power stations and filtrations devices comes handy.....

[hagtech]

but that wire supposed to be gray colored, is not there!?

That gray wire is hidden inside of the tranny.  Remove the bells and you can see it.  I probably need to work on better instructions for this area.

jh

[ecir38]

Just wanted to say thanks to all who responded, I got about 80% of the hum out. I can live with this for now and enjoy some music .

Here are the couple of other things I tried out.

I went ahead and bought a cheap ground loop isolator, I figured it would be nice to have for trouble shooting purposes. Installing this did not make a difference which to me meant I wasn't dealing with a ground loop.   

I decided to twist the tranny leads next. You have to take caution here not to just twist all of the wires together which could cause more problems. Here is what I did. On the primary I twisted blue and brown, black and white. On the secondary I twisted red and red, yellow and yellow, green and green. I think I did this right. This did not fix anything so probably is unnecessary.   

 

I had some foil tape and decided to use a makeshift shield where the heat sinks go that I didn't use. What-ta you know, this knocked the hum down considerably to an acceptable level. The hum is now only audible above playback levels. Looks like I will be buying some heat sinks or maybe making a custom shield in there place. Lessoned leaned, DO NOT leave the heat sinks out if you decide to build the cornet.

I installed the tuntable and piccolo back up, hum is still the same and everthing sounded great. I have to assume the piccolo is pretty quite the way I built it. I am hoping installing the shields and replacing to better RCA's will knock the hum out, I'll keep y'all updated. Now I just have to put some hours on the Cornet, might buy one of those iRAA filters.

[WGH]

Great news, now the fun begins.
The terminal blocks for the R223 resistor looks like a good idea too.

Wayne