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Old 26th February 2012, 10:59 AM   #11
Desmo is offline Desmo  Denmark
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Join Date: Jan 2007
Location: Aarhus
Hi Thorsten,

Thanks for getting into this thread Please see my posts above, there are plenty of pictures of the inside of the phono stage. All wires are routed exactly as shown in the build manual.

Yes, I have grounded shields on the tubes (mu-metal over thick copper). Also, I have tried two different set's of tubes. The noise is not tube related.

Yes, I have shielded all wires to/from the MC transformers. The wires are shielded from a few mm from enterering/exititing the transformers and to the ends of the wires where they are going to the RCA's and switches. The shields are connected to the chassis ground post as illustrated in the build manual.

Yes, I have measured the resistance between all ''loose metal parts'' of the chassis and shields (transformer box to chassis. Lid of transformer box to transformer box etc etc). Resistance is zero...

Last edited by Desmo; 26th February 2012 at 11:08 AM.
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Old 26th February 2012, 11:16 AM   #12
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Desmo View Post
Thanks for getting into this thread Please see my posts above, there are plenty of pictures of the inside of the phono stage. All wires are routed exactly as shown in the build manual.

...

Yes, I have shielded all wires to/from the MC transformers. The wires are shielded from a few mm from enterering/exititing the transformers and to the ends of the wires where they are going to the RCA's and switches. The shields are connected to the chassis ground post as illustrated in the build manual.
The MC transformers output wires have a fair bit of unshielded length.

Can you try shorting the input directly at the UTS Input and see what the noise ends up like?

Ciao T
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Old 26th February 2012, 11:21 AM   #13
Desmo is offline Desmo  Denmark
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Join Date: Jan 2007
Location: Aarhus
Quote:
Originally Posted by ThorstenL View Post
Hi,



The MC transformers output wires have a fair bit of unshielded length.

Can you try shorting the input directly at the UTS Input and see what the noise ends up like?

Ciao T
The unshielded length of wire is around 1 cm... Please see this picture again. (There is also a braided shield under the black heat shrink)

I have measured the noise when the mute switch is activated. It's around 1,5 mV at the output of the phonostage.

Click the image to open in full size.

Last edited by Desmo; 26th February 2012 at 11:25 AM.
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Old 26th February 2012, 11:35 AM   #14
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Desmo View Post
I have measured the noise when the mute switch is activated. It's around 1,5 mV at the output of the phonostage.
The Mute is a straight short across the output (output side of cap to ground), if you are still measuring 1.5mV across a dead short something is seriously out of whack. Can you confirm that mute shorts the outputs?

Ciao T
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Old 26th February 2012, 12:15 PM   #15
Desmo is offline Desmo  Denmark
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Join Date: Jan 2007
Location: Aarhus
Hi again Thorsten,

OK, did some measurements. Also to check my noise floor in the set-up...

YES, the mute does short the output. I must remember wrong about the measurement on the output with mute on - sorry...

Here are measurements with the inputs shorted by a small piece of wire soldered directly on the input and measurements made directly on the output. Please see pics below


Click the image to open in full size.

Click the image to open in full size.

Same as above, but lifting the probe so it's not touching the output. Ground wire on probe still connected to output ground on the UTS module... I can't think of reasons why the noise is higher when the probe is on the output than when it's ''open'' in the air?

Click the image to open in full size.

Last edited by Desmo; 26th February 2012 at 12:21 PM.
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Old 26th February 2012, 12:32 PM   #16
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Desmo View Post
Here are measurements with the inputs shorted by a small piece of wire soldered directly on the input and measurements made directly on the output. Please see pics below
Can you set the timebase so we can see waveform of the noise? 500mS seems very long.

Maybe 10-50mS?

Ciao T
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Old 26th February 2012, 01:27 PM   #17
Desmo is offline Desmo  Denmark
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Join Date: Jan 2007
Location: Aarhus
Hmmm... This is getting more and more strange...

As you indicate the noise I measure is of a high freq nature. So what I did for a quick ''real life reference'' was to put the phono stage back in my system.

This measurement was taken with the turntable connected to the MC input, and the tonearm ground connected to the ground post on the phono stage. Measurement is taken on the output of one channel. As you can see there is a bit over 100mV of 50 hz hum, and this is what I hear when I turn up the volume on my Tram II = loud mains related hum.

Click the image to open in full size.

I then did the same measurement with the input shorted, and the hum is gone on the output. This indicates a problem between the cartridge and the input of the phono stage.

However, when I use any other phono stage instead of The Vinyl Song there is no hum what so ever, indicating that there is nothing wrong before the phono stage.

I'm confused?

My analog system comprises the following:

Scheu Premier II turntable, digitally controlled motor.
Origin Live - Conqueror MK II tonearm, including the original fixed and shielded tonearm cable with silver bullet plugs.
Ortofon MC 70 Anniversary or Sumiko Celebration II pearwood cartridge

Click the image to open in full size.

Last edited by Desmo; 26th February 2012 at 01:43 PM.
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Old 26th February 2012, 01:33 PM   #18
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Desmo View Post
This measurement was taken with the turntable connected to the MC input, and the tonearm ground connected to the ground post on the phono stage. Measurement is taken on the output of one channel. As you can see there is a bit over 100mV of 50 hz hum, and this is what I hear when I turn up the volume on my Tram II = loud mains related hum.

Click the image to open in full size.

I then did the same measurement with the input shorted, and the hum is gone on the output. This indicates a problem between the cartridge and the input of the phono stage.
Seems a ground or earth loop somewhere.

If the Vinyl Song is basically quiet with shorted input on MM and MC inputs, connected to the system, then the problem exists between turntable and Phonostage, but not the VS itself.

Could there be a missing ground somewhere? Or an earth too much?

Can you give more information on the turntable, arm, arm cable and cartridge?

Ciao T
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Old 26th February 2012, 01:38 PM   #19
Desmo is offline Desmo  Denmark
diyAudio Member
 
Join Date: Jan 2007
Location: Aarhus
I just updated my previous post with my analog system...

The strange thing is, that when using the Whest Audio, with the exact same turntable, there is no hum. So when I connected The Vinyl Song, and there was loud hum it was a logical assumption that the problem is The Vinyl Song... I fully agree, that the measurement indicate a problem before The Vinyl Song, but on the other hand: The problem is only there with The Vinyl Song..!?

Click the image to open in full size.

Last edited by Desmo; 26th February 2012 at 01:40 PM.
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Old 26th February 2012, 01:43 PM   #20
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Desmo View Post
I just updated my previous post with my analog system...
Seems you only use the MC input.

Have a look if the MC inputs float or are grounded (100R//100nF will usually do this nicely).

Ciao T
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