[ncdrawl]

ok, the longhorn is an amazing mod. i love it. got it set up , tracking weight, etc.. only problem is now I am getting the dreaded grado/rega hum issue that gets worse as the stylus moves towards the end of the record..

how do i fix this?? surely with as old a problem as this, people have developed workarounds by now>>???????

[BikeWNC]

You might think I'm crazy, but I've had success getting rid of the hum by making sure none of the mounting nuts or bolt heads touch the cartridge body.  Take a look at the way the cartridge is mounted and if one of those touches the body turn it so it doesn't.  See if that helps. 

[Wayner]

The cartridge mounting is made of plastic.

Wayner

[BikeWNC]

On my Grado Gold cartridge there is both a metal side plate and then plastic in front of that.  It is possible when the cartridge is mounted to have the bolts touch the metal side plating (at least it is in my headshell)  I've found in my system if those bolts touch the metal on the cartridge the hum is enhanced. 

[Wayner]

I have run my VOM thru the mounting screws and thru the metal shield and get no reading. I believe the aluminum part of the cartridge is anodized, which is very resistant to current flow (and what also keeps aluminum from oxidizing).

I'll let you onto a little secret. The largest cause of hum in a Grado is proximity of cartridge to power amplifier. All power amplifiers or receivers have large core and coil or toroidal transformers that have a rather large magnetic field. Even toroidal transformers that are shielded (and they aren't really) have a powerful field.

To prove to yourself that this is the problem, the steps are easy, but you need to have a pair of headphones. First, turn your system on except the turntable. Do you have hum with the volume at high levels? Now, if you have a seperate amp and preamp, plug your headphones in and turn the power amp off. Did the hum go away, or get greatly reduced? Then the answer is to further remote your power amplifier from the table, like at least 42 to 48 inches minimum.

If you have no hum with the system on (including amplifier) and when you turn your turntable on, and hum begins, then the source of hum is your table. Very difficult to deal with.

I have used my Grado Longhorn on both of my Technics DD tables and there is simply no hum, not at turn on (of the table) or turn off. My amplifiers are at least 4 feet away.

Try this experiment and you may be able to turn that frown upside down.

Wayner  aa

[BikeWNC]

That could very well have been the issue in my system when I was tracking down hum with the Grado Gold.  I eventually moved the amp and preamp away.  Anything under the table caused some hum on the SL1200 with the Grado.  I also moved the mounting bolts at the same time because I had read about that too being a possible source of hum.  So the result of all that was no hum but the actual cause was probably as you say, the amp being too close. 

[Wayner]

Thanks for the confirmation! I can't say it's the cause in every system, but I'll bet for many, it could be as simple as moving the amp further away.

Wayner 

[Tom Alverson]

ok, the longhorn is an amazing mod. i love it. got it set up , tracking weight, etc.. only problem is now I am getting the dreaded grado/rega hum issue that gets worse as the stylus moves towards the end of the record..

how do i fix this?? surely with as old a problem as this, people have developed workarounds by now>>???????

Unplug the power to the Rega while it is playing and see if the hum goes away.  It the hum is still there then look for nearby transformers in amps/receivers etc.  If the hum goes away and the Rega has an AC motor there is not a whole lot you can do.  Some turntables have DC motors and can still get hum from a built in transformer that could possibly be relocated.

Tom

[Zheeeem]

ok, the longhorn is an amazing mod. i love it. got it set up , tracking weight, etc.. only problem is now I am getting the dreaded grado/rega hum issue that gets worse as the stylus moves towards the end of the record..

how do i fix this?? surely with as old a problem as this, people have developed workarounds by now>>???????

If you want to keep the same combination, the only solution would be to disassemble your TT and build/install a RF shield for the motor.

I can, to a limited extent, understand why a company might build an unshielded cartridge.  I cannot understand why a company would use an unshielded motor in a TT. 

[Wayner]

If you want to keep the same combination, the only solution would be to disassemble your TT and build/install a RF shield for the motor.

I can, to a limited extent, understand why a company might build an unshielded cartridge.  I cannot understand why a company would use an unshielded motor in a TT.

This is very difficult to do, if not impossible. Shielding a magnetic field is quite a 4H project. I'd like to know if even one person has had any success attempting this. You probably would need some Mu-metal to start with,,,,,,

Wayner

[Zheeeem]

This is very difficult to do, if not impossible. Shielding a magnetic field is quite a 4H project. I'd like to know if even one person has had any success attempting this. You probably would need some Mu-metal to start with,,,,,,

Wayner

Well, I'd agree with you except it's done all the time.  It is not so difficult or expensive, though there are challenges for a home hobbyist retrofit.

http://www.lessemf.com/emf-shie.html

[Wayner]

Well, the company's name is "LessEMF", not "NoEMF". Frank and I have talked about motor shielding from time to time. Somestimes the shaft of the motor is not of the right material and will emit. Pretty hard to stop, easy to say. I will say that if you have this problem with your table and a Grado, you'd be much happier finding a new table or in the case of Frank's HK, moving the source of the field to a different location, which in that case was a stepdown transformer/power supply.

Wayner

[Zheeeem]

Well, the company's name is "LessEMF", not "NoEMF". Frank and I have talked about motor shielding from time to time. Somestimes the shaft of the motor is not of the right material and will emit. Pretty hard to stop, easy to say. I will say that if you have this problem with your table and a Grado, you'd be much happier finding a new table or in the case of Frank's HK, moving the source of the field to a different location, which in that case was a stepdown transformer/power supply.

Wayner

I think the OP asked how to keep his current Rega/Grado combination but lose the hum.  Really, I cannot think of any possible way but to try to build an EMF sheild of some sort.

FWIW, you don't actually have to block all of the EMF.  Just enough so that it's not audibly picked up through the cartridge.  Given the amount of EMF trash in a typical home environment, trying to "eliminate" it would be a fools errand.  But there are a lot of things that can be done to reduce sources below the levels where it get picked up by audio systems.