Phono II HUM

[LSfarzo]

Hi all,

I hope that all you guys did spend a joyful xistmas.
I write you as I'm having some "hum" troubles with my phono II after having put in it a couple of Sowter 9570f in order to step-up the signal coming from my Benz ACE.

Before I used an MM (a sumiko pearl) and the HUM I heard was only between a track and another of an LP and only when I put the volume to a very high level.

I mounted the 5 cables of every tx following the instructions on the sowter site: "The cartridge should be connected to the White and Yellow leads. The amplifier should be connected to the Pink and Mauve leads. The Black (ground) lead is normally connected to the signal ground of the amplifier. You may need to experiment with different ground connection points to minimize hum.".
And so I did: i soldered the yellow cable to the inner spigot of the rca female jack and the white cable to the ground of the rca female jack. The black cable I soldered to the hearth post (the Tab 4 or Tab 1); the mauve cable was soldered to the I/P Tab (6 or 3) and the pink cable was soldered to the GND Tab (the RC Phono input earth tag, Tab 5 or 2). (I put two figures in the post that explain this).

When I power on the pre and the kat the hum starts to be audible just as I begin to raise the volume.
I tried to move the PSU at half a meter from the preII and the Phono II but I had no result.
I switched off all the other electronics apparel in the room and .. in the house but the result was the hum !

I build a little cable connecting the various earth plug that sits on the rear of all the WAD elements and then I put on of its end to the wall in order to put to earth everythin but nothing changes!!!

Please do you have some suggestions about this problem? Have you got some other nice idea about the some other ground configurations I could try?


I have to say that, if it was not for the hum, he sound is really astonishing ... an incredible step toward the MM configuration though there's too say that this is a really more expensive configfuration, too! I'm starting to listen to sounds and music and I did not even know that my LPs had..


Best regards,
Luca

[NickG]

Try both the black and the pink to the GND on the PCB, the external earth connection isn't the signal ground.

Try a wire from input socket (-) to the (-) on the pcb one wire for right and one for left.

[LSfarzo]

Hi,

I tried yhe NickG's solution and soldered together the pink and the black cable on the GND.
The hum has lowered but it is still really audible even at low volume expecially on the very low parts of the executions and between the tracks...

Some other suggestions?
Anyway I will experiment thw Will solution, too.. and see what happens.

I'll let you know but if in the meanwhile you have some other solution, please be so kind to tell me.

Bye
Luca

[NickG]

Does the hum change if you

1. unplug the input to the phono stage
2. unplug one of the connections to the preamp
3. move the phono further away from the preamp/poweramp
4. connect/disconnect the earth connection on the tonearm

[LSfarzo]

Hi Nick,

if I use another preamp input the story remains the same (the same hum).

If I unplug the tonearm earth connection that is plugged on the phono II earth the hum turns to be a really GREAT hum!
ACH!


Thanks Luca

[NickG]

How about 1, 2, and 3 :-)

2 involved removing ONE of the connections to the amp, to see if there was a earth loop.

[LSfarzo]

Hi Nick,

sorry for having been not quite precise.
The result is:
1)Unplug one or both input for the phono stage (the cables coming from the TT) the HUM disappears in both cases.
2) Unplugged one connection from the amp. The HUM still remains on the other channel.
2 bis) Unplugged the same channel from the phono input and from the preamp (i.e. the left channel has been unplugged for the cable coming from the arm and for the cable connecting the phono to the preamp) and the HUM stll remains.
3) Moved the phono stage further away (1 meters) from the TT and the PSU/Pre and the hum is the same.
4) Unplugged the hearth connection from the tonearm and the HUM rises up significantly.

So I could fear the problem lies in the arm earthing... I have a Benz ACE with a SME 3009 I just rewired with a VDH MCS 150 and for the arm-prephono connection I have a VDH MCD 501.
When I used the MM cart (with the arm already re-wired) I had no such HUM.


Bye
Luca

[NickG]

Ok, it sounds like you make have a earth loop between the arm and phono stage. Did you try Will's suggestion?

[LSfarzo]

Originally Posted by NickG

Ok, it sounds like you make have a earth loop between the arm and phono stage. Did you try Will's suggestion?

Hi,

I'll try Will's suggestion as soon as I can and I'll let know what happens.

Anyway thank you very much and I hope a great end of this year and a great 2007 for you .

Hi
Luca