[PT]

After three long months of waiting for parts and time to assemble, I now have my Cornet2 up and running.

It sounds great at low levels!

However, at higher gain I have a hum .  At normal listening (~80db) I can barely hear it with tonearm up.  At high gain (OK - when I want to rock) it hums significantly.   Disconnected input  and hum lowers, but faint buzz appears.  Probably what you expect from an open phono input, but I could be wrong.

Tried the cheater plug - a little worse and buzz comes up above noise floor.  Moved the cables around and reoriented the Cornet2 in relation to turntable - no joy.

Rega P3 has an odd grounding scheme in that there is no separate turntable ground wire.  Could this be it?

Any suggestions?

Thanks, Steve

[machine]

Is the transformer grounded to the case?

There should be 4 bolts that connect it, make sure at least one has good contact with the case.

Worked to clear up a major hum with mine.

[Rocket]

Hi Steve,

I had a problem with hum with my vinyl system for 2 years.  Turns out it was the denon dl103 cartridge.  I replaced it with the entry level benz micro mc20e2 high output mc and there is no hum present.

I tried everything to fix the hum in my system and only discovered this because I damaged the denon cartridge.

Good luck.

Regards

Rod

[bluesky]

One more suggestion for the Rega is to simply connect a small wire, possibly by an alligator clip to ground the tonearm to the chassis ground in your Cornet. 

If the hum disappears at least you know what the problem is and can then rig something better looking up to do justice to you're good looking components!

Rocket, hum through the cartridge?  I would never have thought to look there, that's a new one for me!

Ian

[Wayner]

I have the Rega P-3 as well. The chassis ground you are referring to is built on to the RCA shield of the right channel connector. This is a pratice used by several table manufacturers. Further grounding will only cause harm.

The one possibility is an internal tonearm ground loop. To prove this you need 2 alligator clips. Short out the + and - of the left and right channels (independently). This takes the cartridge out of the picture. Now try the volume control. If the hum decreased, the problem is with the cartridge, if not, it's the internal wiring in the tonearm.

If it ends up being the tonearm wiring, remove the alligator clips and connect the 2 - (commons) together and see if this improves the hum situation. You may find that this actually helps.

If that is the case, connect a short piece of wire between the grounds. Of course, don't ever solder on the cartridge pins. Remove the clips and solder on the back side of the clip. If you get solder inside the clip, it will be ruined, too. You will have to recalibrate your tracking weight, as you have added wire and solder.

You may also find that the hum is being influenced by a nearby power or pre-amp, especially tube ones. Another source of hum is fluorescent lamps and stuff like that. Remember it is either stray EMF or ground loop. Also remember that even the finest table/cartridge/pre-amp set-up has a noise floor. It's the nature of the beast. The trick is to get the noise floor as low as possible.

Good luck.

Wayner 

[amandarae]

I have the Rega P-3 as well. The chassis ground you are referring to is built on to the RCA shield of the right channel connector. This is a pratice used by several table manufacturers. Further grounding will only cause harm.

The one possibility is an internal tonearm ground loop. To prove this you need 2 alligator clips. Short out the + and - of the left and right channels (independently). This takes the cartridge out of the picture. Now try the volume control. If the hum decreased, the problem is with the cartridge, if not, it's the internal wiring in the tonearm.

If it ends up being the tonearm wiring, remove the alligator clips and connect the 2 - (commons) together and see if this improves the hum situation. You may find that this actually helps.

If that is the case, connect a short piece of wire between the grounds. Of course, don't ever solder on the cartridge pins. Remove the clips and solder on the back side of the clip. If you get solder inside the clip, it will be ruined, too. You will have to recalibrate your tracking weight, as you have added wire and solder.

You may also find that the hum is being influenced by a nearby power or pre-amp, especially tube ones. Another source of hum is fluorescent lamps and stuff like that. Remember it is either stray EMF or ground loop. Also remember that even the finest table/cartridge/pre-amp set-up has a noise floor. It's the nature of the beast. The trick is to get the noise floor as low as possible.

Good luck.

Wayner 

Great post!  It should be noted that the Rega tonearm wiring employs 2 channels (L+ and R+) and one common ground. That is the minimum requirement you need to generate "Stereo".

If you are using MC cartridge with a step up transformer (SUT), the grounding can be change at the SUT inputs.  Just disconnect one ground, L or R your choice, from the input going to the negative phase of the SUT, and connect that to the other ground of the RCA pair, and you should be good to go.  If you are using MM, then there should be a provision to lift the ground of one of the inputs inside the Cornet, to be connected to the other channel ground, so that it does not create a loop on the tonearm side.

regards,

Abe

[Wayner]

Great post!  It should be noted that the Rega tonearm wiring employs 2 channels (L+ and R+) and one common ground. That is the minimum requirement you need to generate "Stereo".

Thanks for making that clear, Abe

Wayner 

[PT]

Ok....thanks a bunch for all the suggestions which I tried over the course of the week, but no luck.  The hum which is in one channel moves to opposite channels when I switch the inputs from the TT.  So I don't think I have an issue with wiring or cold solder joint in the cornet2.  I moved the TT 3 feet away horizontally to minimize EMF - no change.  Picked up the TT and moved it around in relation to Cornet2 - no change.  My power amps are on the other side of the entertainment center six feet away so that's not a factor.  Just as reference, my previous phono preamp (32 year old Leach homebuilt) was dead quiet with the Rega.

By removing one input (didn't matter which one) the hum reduced.  So I says let me try a ground lift for one channel which I created by soldering a very short length of wire between a male and female RCA plug.  No change, hum came back with same intensity when I tried ground lift on either channel.

So I says in desperation let me change the cartridge from the Rega to an old Sonus Blue just to take the cartridge out of the picture.  (I had previously tried shorting the cartridge leads in all combinations - hum got worse).   While swapping out the cartridge, the pins for the Exacta are smaller than the Sonus....so while my ham fisted hands tried to open them a little...I broke one.

So in shame I've shut it down and waiting on replacement clips.  Unless I have an epiphany the only other thing I can think of is separating the tonearm ground in the Rega from the left channel signal ground or trying a different cartridge.

[hagtech]

Do you have hum with no cart connected?  Are the RCA jacks isolated from chassis?

jh

[PT]

Jim,

I used the AES phono jacks suggested.  They are isolated from the chassis.  The L/R ground lugs of the  input and output jacks are tied together and connected to their respective ground pads on the board.

With the cartridge leads removed, there is more hum.  Again with no input, some faint hiss and faint (negligible) hum.

Thanks, Steve

[PT]

This AM after I slept another night on it, I tried it again with no cartridge attached...definition of insanity right?   By accident when I placed a finger on the plastic REGA input connectors - more hum! Finger on each - even more!  Tried a pair of monster cables (metal rca plugs) - some background hum a little higher than no input since they were open air on the other end, but no change when I touched the metal phono plugs.   I think I'm on to something.  Jim I noticed you have a Rega...do you have the same symptom?

Thanks, Steve

[hagtech]

Maybe you have a broken shield in the cable?  I am running a P3 with a Dyna 20XL into a PICCOLO / CORNET.  Zero hum.  Very little noise.  I can add hum by routing cabling next to power transformers, though.  I also re-wired my P3.  I took the two ground wires off of the signal cable.  Now I run two ground wires (I think one is for suspension, the other for arm tube?) and two coaxial signal cables.  All of the grounds and shields connect at PICCOLO. 

jh

[PT]

Jim and all - I think I've pretty much closed the books on this.  In my holy grail quest, I replaced the original  Rega plastic RCA plugs with metal plugs which lowered hum.  At least I ddin't get a lot of hum when I touched the plastic connectors.  I split open the plastic connectors and boy are they cheap.  No continuous shield.  Next I opened up the tonearm base and separated the tonearm ground from the left channel ground http://www.aqvox.de/REGA%20250%20300%20Tonearm%20mod%20humm-free%20remove%20signal%20groundrega_mod.html

That helped a lot.  I was about to rewire the tonearm using guidance from http://www.hi-fi.com/diy/rega/index.html, but I was tempted by the prefabricated harness from Incognito sold by Galen Audio http://www.gcaudio.com/cgi-bin/store/showProduct.cgi?id=83.  After my wife - can you believe it - urged me not to be a cheapskate and get the incognito harness....which I did.  It was everything advertised to be.  Good instructions and high-quality.  This article http://www.tnt-audio.com/sorgenti/analogue_bits_e.html helped me to disassemble the arm.

So after all that...if I hook up the separate tonearm ground to the Cornet2, I get a lot of hum.  Without it I can't hear it a normal listening levels - high gain yes, but it's not that bad in relation to the S/N so it's trivial.  Most of the hum is in the right channel and very little in the left.  Remove the right tonearm input and it disappears so I fairly sure it's not the Cornet2.  So now I have given in for the time being to let go and enjoy the music.   So that's what I'm doing now with my wife waking up to Pat Matheny with some nice hot fresh coffee and beautiful Sunday morning. 

Thanks everyone!  Steve