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Old 12th January 2005, 09:23 PM   #11
Stabist is offline Stabist  Slovenia
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Default Grounding - pleas help

Hi!

This MC preamp is mine first tube-based project - so I wonder - how to ground it properly to the chassis??
I mean - I put one conector at the back plate for arm and TT's ground - I guess I have to connect it to ground from 230V outlet .. But what else should I connect to that connector?? Maybe also the ground from RCA plugs - but via resistor?? Or???

Thanks!
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Old 12th January 2005, 10:18 PM   #12
Stabist is offline Stabist  Slovenia
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This is how the interior looks (it's still in experimental phase so wire lenghts are not "optimazed" yet) - on the right there will be tube preamp, on the left allready is PSU. In between an Al plate will come (altough I wonder - does Al plate represents any improvement??
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Old 13th January 2005, 12:01 AM   #13
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Hi,

Quote:
I put one conector at the back plate for arm and TT's ground
If you're using a MC cartridge you probably won't have to ground the arm, in fact I don't have to ground the TT either in my system.
Nonetheless you should experiment with whatever gives you no audible hum.

Quote:
I guess I have to connect it to ground from 230V outlet ..
I never do that for preamps and similar devices; our local mains outlets aren't grounded anyway except for a few in the kitchen area and places where heavy machines are put.
May be different for you though....

Quote:
Maybe also the ground from RCA plugs - but via resistor?? Or???
Use circuit ground for that...
Try to find a point with lowest noise by using a scope if you can.
I normally don't elevate the ground by means of resistors in a preamp.
If it doesn't have any groundloops there should be no need for it.

Cheers,
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Old 10th February 2005, 11:20 PM   #14
Stabist is offline Stabist  Slovenia
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Finished

Playing

No bigger hum - except the specific "hisssss" that all tube-based stuff I've owned had ...
I just have to find the reason for this - when somewhere near my room some stuff goes "on" (I suspect the refrigerator)- it can "pop" in speakers??
And also when turning preamp down - it's better to turn the volume down - othervise it pops very loudable ...
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Old 10th February 2005, 11:23 PM   #15
Stabist is offline Stabist  Slovenia
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Wood sides still need to be finished ...

Otherwise almost everything is finished ...
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Old 10th February 2005, 11:24 PM   #16
SY is offline SY  United States
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Is that copper foil wrapped around the tubes? If so, do you have something inside it to prevent reflection of the plate IR emission back into the tube?
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Old 10th February 2005, 11:31 PM   #17
Stabist is offline Stabist  Slovenia
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And this is the TT setup I use ...
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Old 10th February 2005, 11:33 PM   #18
Stabist is offline Stabist  Slovenia
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Quote:
Originally posted by SY
Is that copper foil wrapped around the tubes? If so, do you have something inside it to prevent reflection of the plate IR emission back into the tube?

Yep it's copper ... What kind of reflection?? The copper shield is used because without they were to sensitive to hum - I just aproached to around 10-15cm from tubes - and the hum became to heavy ... I didn't know there can be some negative effects??
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Old 10th February 2005, 11:36 PM   #19
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Yes, there can be. Tube anodes are hot; being encased in a vacuum, the primary way they transfer heat away is by radiation of IR. You've just wrapped them in a mirror, relatively speaking. What you want is something black and heat conductive between the copper and the tube, and if possible, fins on the copper.
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Old 10th February 2005, 11:41 PM   #20
Stabist is offline Stabist  Slovenia
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Aha - now I see what you mean - well I'll intend to test them without cooper shield - but during "tests" and whithout cartridge load on the input they just begin to hum ...
But if there will be the need to leave the copper shield in place I'll try to fix the problem you mentioned!!! THANKS!

But then again - I must say that they are pretty cool - comparing with my ex-Unison Research SE amp - it had a pair EL34 and ECC82 - OK I understand for power ones they were HOT - but also ECC's were much hotter than this one here ...
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