4mx noise when 2 x ...
 
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4mx noise when 2 x phono connected

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Topic starter

hi,  ive recently tried to add 2 x record decks to my 4mx setup (both omnitronic dd-2250s).

if there is just one deck connected - then it works fine - but if i have two connected - then i get a lot of background / signal noise on souce 2...  i get the same effect if i swap the decks around so i dont think that it is caused by the deck itsef.

if i use a pre-amp and lower the source 2 input to line - then it seems to fix the problem but that means i need to use a pre-amp so that is not a great solution - id prefer to know if anyone has encountered this issue and how you resolved it?

edit - am using virtual dj 7

 thanks,

dan 

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Hello DJTayla,

1) I don't know DD-2250, but in the manual of close DD models, I see a phono/line switch. If you have a phono/line switch on your DD-2250 units, please let me know if setting both DD-2250 in line level, and 4-Mx audio inputs in line level, you still get this noise on source 2?

2) Can you check if both turntables are powered on the same power outlet?
If they have 2 different power supply, can you check if you still hear the same noise when powering both on the same power outlet as the computer?
I wonder if you hear a ground loop when connecting both grounds, with both turntables generating a different ground level.

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Topic starter

Thanks Maxdjack...

1) No pre-amp in the DD-2250s so  no phono/line switch..   IF I use a seperate Pre-amp and select Line level on Inputs 3/4 then the Noise goes away  (but this means I need to carry a pre-amp with me as well)

2) Yes both Turntables were plugged ibnto same 4-way - and I've tried isolating them and using a third (very different) turntable deck and no joy - still get te noise. In my opinion it is not a Ground hum (thats a warm noise(hum) whereas what I am getting is a very harsh white noise type interference - almost like to sound of machinery... ). The computer I am using is a laptop and I've tried with the Power source connected and disconnected - but same noise...   

If I connect just one deck into 3/4 (and have nothing in 1/2) then the noise is not there..   but when TWO decks are connected and set at Phono - then the noise is there on Source 2 - (inputs 3/4).

It seems to me that there is a problem with the amplification circuit for inputs 3/4...   I am not sure if that is something that can be fixed - or if I have to accept my 4mx is partially broken ?

 

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Hello DJTayla,

Please confirm
a) on DJ Console 4-Mx control panel that the input channel on both inputs (1-2 and 3-4) is set on Phono.
b) on DJ Console 4-Mx rear panel that the ground cables of both turntables are connected between 4-Mx ground screw and the turntables.

It does not look like an amplification issue, but as if the 2 turntables have no ground  (or do not share the same ground, which may occur with floating grounds).

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Topic starter

Hi..

a) yes - both inputs are set to Phono
b) yes both decks are connected to the Ground screw.

If I remove from ground screw - then I get the familiar ground hum.. reconnecting and this goes away and left with the white noise/interference on Source 2...

grr !!

 

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Hello DJTayla,

I suspect the issue comes from a ground difference of potential between both turntables.
To check if the issue comes from the ground can you try to the following process
1) connect the ground cable on 1 of the 2 turntables to another ground:
a- either with an ESD grounding plug, as this type of plug
  
b-  or to a metal pipe for water, going to a basin or to a heater (as water pipes are grounded),
c- or to a convector heater (as electric covector heaters are ground).

2) and check the audio quality of hearing both devices in the 4-Mx once 1 turntable is grounded to the 4-Mx ground screw and the other is grounded to an external ground.

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Topic starter

Hi - so been away from the internet over Christmas - but have tried to use my 4MX a number of times....  Keep on getting the Noise even with different setups at different locations.. 

Am trying to source a proper Grounding Plug - will keep this thread updated.

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Topic starter

DJTAYLA,

     Just a thought, are you using a surge protector or are you using a power conditioner?

TheSpinDoctor...

"If Music Be The Food Of Gods, Play On"

-Billy Shakespear

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Topic starter

Hi Sorry - been offline for a while...

No - not using a Surge protector or conditioner..   (were you suggesting this might Cause - or fix the issue ?)

So this was a Second hand device...  I am tending to think now that the original owner might have connected a Line level device whilst configured as Phono ? might a surge have caused damage ? 

 

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Hello,

1) Phono pre-amps are not that fragile: playing a line level signal in a phono input is a highly common mistake, so of course it makes a bad sound while playing at the wrong level, but it does not damage anything.
Moreover, if anything was damaged, the audio would be bad whether you connect 1 or 2 sources.

2) Have you tried adding a USB hub with a power adapter between your computer and your 4-Mx?
I think the issue may come from a noise in your computer power supply.

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Topic starter

Thanks for the response.. I'll see if I can get hold of a Powered USB Hub....

I've also posted another issue here http://www.herculesdjmixroom.com/en-gb/forum/en-hardware/028064/  with the Phono inputs... not sure if they are connected at all or not...

If I can get a hub - I'll give it a try and let you know,

ta.
 

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Hello,

Any News?

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Topic starter

not managed to get a powered hub from anyone...  and dont want to buy one as I am not convinced this is the issue..