Author Topic: qsxm3  (Read 20878 times)

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Offline yiancar

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qsxm3
« on: October 13, 2013, 10:20:27 PM »
hey guys, i notices hum in the preamp and desperate to find the fault i made the observations below.

connecting only the right channel everything is ok. once i connect both right and left channel hum appears in both channels.
also reversed the inputs to check if its the cardage but it seems to be related with the left channel of the preamp

any help with that ?

Offline peranders

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Re: qsxm3
« Reply #1 on: October 13, 2013, 11:03:30 PM »
Do you use shielded wires to the cartridge? Do you have a separate ground wire from the tone arm?
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Offline yiancar

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Re: qsxm3
« Reply #2 on: October 14, 2013, 04:09:00 AM »
yes i thing its shielded. there is a ground wire even i see no difference with it connected or not

Offline peranders

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Re: qsxm3
« Reply #3 on: October 14, 2013, 06:20:18 AM »
Are the shields tied together in the turntable end?
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Offline yiancar

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Re: qsxm3
« Reply #4 on: October 16, 2013, 03:13:34 PM »
i think so yes, any way i can check that for sure

Offline peranders

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Re: qsxm3
« Reply #5 on: October 16, 2013, 07:23:41 PM »
They should not be connected in both ends. It would be good to know if the turntable is humming with an another phono amp.
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Offline yiancar

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Re: qsxm3
« Reply #6 on: October 16, 2013, 07:45:02 PM »
the channel grounds are connected together, the cable shield/phono earth runs seperated

Offline yiancar

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Re: qsxm3
« Reply #7 on: October 16, 2013, 07:59:47 PM »
i find it very confusing when both channel of the preamp have ground there is hum everywere. you thinking that the cable picks the hum?

Offline peranders

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Re: qsxm3
« Reply #8 on: October 16, 2013, 08:53:39 PM »
From my amp you should have a straight connection to the cartridge four connections and a separate ground wire from the tone arm.
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Offline yiancar

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Re: qsxm3
« Reply #9 on: October 16, 2013, 08:58:14 PM »
any chance to modify that so to have a common channel ground?

Offline peranders

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Re: qsxm3
« Reply #10 on: October 16, 2013, 09:06:02 PM »
I recommend that you take a look at your turntable's wiring first.
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Offline yiancar

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Re: qsxm3
« Reply #11 on: October 16, 2013, 09:09:15 PM »
this also means that i should use isolated rca plugs so the grounds do not touch the chassis?
i mean what i dont get is that the 2 "ground" wires from the cartage will be in parallel as they are now right?
« Last Edit: October 16, 2013, 09:31:34 PM by yiancar »

Offline peranders

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Re: qsxm3
« Reply #12 on: October 16, 2013, 09:40:27 PM »
Isolated contacts is a must.
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Offline yiancar

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Re: qsxm3
« Reply #13 on: October 16, 2013, 10:07:33 PM »
this is how my turntable is wired

u recommend separating the grounds from pin number 2.

any good isolated rca to recommend?

Offline peranders

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Re: qsxm3
« Reply #14 on: October 16, 2013, 10:12:14 PM »
Wow, it's an old thing with DIN connector. Do you have some sort of adapter DIN-RCA? You have one signal ground from the cartridge and one ground for the chassis/tone arm.
/Per-Anders Sjöström, owner of this forum

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