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Hum with adc tonearm and adc xlm

Posted: 30 Jan 2006 22:59
by ger56
hello

I have hum at medium level on my thorens td 160 with adc tonearm and adc xlm .
The arm is grounded but it is not enough to make hum disappear .

When I touch the arm body it's ok but , when I touch the headshell I got hum and much more when I touch the cartridge body .

Any help and solution ?

Ger56

Posted: 31 Jan 2006 18:22
by audioorigami
hi

has any other cartridge worked ok in this arm/deck combo

it would help solve your problem faster

best wishes
j7

Posted: 01 Feb 2006 10:45
by ger56
Hello

I have to mount an other cartridge and come back to you .
In fact it seems the headshell is not grounded ! only the arm body .



Regards

Ger56

Posted: 01 Feb 2006 12:08
by Guest
Hi,

The turntable should have a seperate ground connected to the post at the
amplifiers cartridge input. This wire should ground the turntable, arm and
headshell, and crucially not be connected to the cartridge ground (L+R) at
any point. The only connection to cartridge ground should be at the input
of the amplifier.

Guaranteed pretty much no hum.


Posted: 03 Feb 2006 15:08
by HotHondr98
There are two possible causes I can think of for your hum.

1. If the headshell is a metal headshell, and is earthed via the tonearm earth, then you may have an earth loop. I’m not familiar with your ADC cartridge, but know that many cartridge manufacturers, such as Stanton, earth the metal body of their cartridges to one of the cartridge earth pins. This will cause an earth loop if the headshell is earthed, in which case Stanton recommend removing the earthing strap from the cartridge earth pin to the body – it just lifts off, after removing the cartridge connecting wire from that pin.

2. Alternatively, if you have a plastic headshell, or one made from another insulating material, you may need to earth the cartridge body – see if there is a metal earth strap near one of the cartridge earth pins, and connect it if it isn’t already! See figure 2 in the user manual for the Stanton 681EEE if you don’t know what I mean – the manual is available in the library here.

Note that earthing can get quite complex, and has fooled many professionals in audio fields, particularly when it comes to earth loops, when more than one earth is too many! I think that situation 2 is probably more likely to be your problem, as an earth loop would cause a hum all the time, which probably wouldn’t vary when you touch the cartridge. It sounds more like a shielding problem, which would be fixed by earthing the cartridge body, if it can be.

Posted: 05 Feb 2006 08:52
by ger56
Thank you all.

1. I change cartridge with a stanton 681 EEE with the metal strap and it did not change anything (even worse ) .

2. To Solve the platic headsehll problem , I just put 3 thin copper wire in the opeing of the headshell and arm body and it works , no more hum when i touch the headshell .

3. I change the earth wire and connect directly to the ground ( ac line ) it is much better but not perfect at high volume .

I am looking for a solution to avoid compeltely this hum but I understand many factors are together against .

Other idea are welcome .

ger56

Posted: 06 Feb 2006 14:30
by HotHondr98
Glad that you managed to fix some of it up – hum can be very annoying. I’ll just go over a few things that haven’t been covered, but that you may not know.

The first is to make sure that your turntable is well away from other components in your hi-fi system. Magnetic cartridges are very sensitive to hum pick up, and because other hi-fi components have transformers, which have an electro-magnetic field surrounding them, it’s easy to get hum induced into a cartridge. In particular, make sure that the turntable is as far away from your amplifier as you can move it, as (power) amplifiers have large transformers in them, that have a large magnetic field. Sitting a turntable on top of an amplifier, or next to it, is a certainty to cause hum. If possible, have your turntable a foot (30cm) or more away from an integrated amplifier, or a power amplifier. It should also be as far away from any other powered equipment as possible, although they generally don’t have such large transformers as occur in power amplifiers, so would cause less hum.

Is the hum there with other components, like CD players or cassette players? Remember, vinyl playback equipment will ALWAYS have more hum than things like CD players, tape players, or DVD players. The reason for that is that CD players put out a nominal 2 volt output, and most other things like tape players put out 1.2V. However, the Stanton 681EEE, for instance, only puts out 2.5mV, according to Stanton. That means it needs to be amplified by 480 times to reach line level (1.2V). In reality, to allow other, higher output cartridges to be used, the amplifier designer would reduce that down to maybe 200 times. But that will also cause the hum to be amplified by 200, so it will always be much louder than the hum which you are used to from a CD. That doesn’t mean it will sound 200 times louder, due to the logarithmic way our ears hear, but it will be quite a bit louder. It shouldn’t be noticeable at normal listening levels, or even quite loud listening levels. However, if you have turned the system up to levels at which you would never listen, then you may get hum, and it will always be more than with line level components. Is the hum still noticeable at the level at which you would normally listen? If not, then it may not be worth worrying about.

Posted: 06 Feb 2006 15:05
by ger56
HotHondr98

Thank you for your post .
My turntable is 1 meter from amplifier as I use 2 monoblocks tube I better do it ....

Hum is acceptable at medium level but higher it is noticeable ; but i suspect the preamp not to be perfect also , I will try an other one ....

Ger56

Posted: 06 Feb 2006 17:22
by bauzace50
Perhaps another angle, in this problem:
1- Is the cable from the preamp to the tonearm detachable? If so, can you see if the five male/female pins are all soldered to their corresponding wires...(on both plugs, male and female)?... My SME 309 had this problem, and it was traced to one of the five wires...the ground...unsoldered from its pin on its male connector... the plug is mercifully able to be opened by removal of one screw.
When mentioning five wires, this means the four cartridge leads, plus the ground wire, of course.
2- Have you tried a short piece of wire, touching the tonearm, at the same time as touching the other end to: (a)the cartridge body, or (b) the blue /or/ green cartridge wires?
3- If your XLM is the same as mine, the order of connecting the wires are, from top to bottom: Green (at the top) Blue, Red, White (at the bottom). Are these four wires well connected to the Headshell? Are these four wires connected to the headshell *in the correct order*?
4- Are the tonearm's internal wires soldered onto each pin? This is best verified by checking the CONTINUITY of each of the four leads, with an ohm meter, can you do this...maybe the green, or blue tonearm wire is unsoldered internally? Maybe the ground wire is disconnected internally?
Good luck! I hope this is not a case for a witch doctor.

wire connections

Posted: 06 Feb 2006 17:48
by bauzace50
Oops! in the above post, my meaning about soldered tonearm wires means on the correctly corresponding pins...*NOT ON the cartridge pins!*
Reference to soldered wires refers only to the corresponding pins in the tonearm and in the tonearm cable to the preamp. Only on the spots where soldering is pertinent. NOT where connection is made by pressure contact, such as the cartridge pins!

Posted: 07 Feb 2006 08:32
by Guest
ger56 wrote: 3. I change the earth wire and connect directly to the ground ( ac line ) it is much better but not perfect at high volume .
ger56
Huh ?

In reference to my earlier post, the turntable should not be grounded.

All earthing of the turntable should be earthed via the MM input ground.

If your turntable has a mains earth remove it. With a multimeter check
all metal parts of your turntable are earthed. Also check the earthing
of the turntable does not form loop(s), all parts earthed via a star point.

:)/srten.