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Old 9th May 2011, 11:25 PM   #211
Salas is offline Salas  Greece
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Quote:
Originally Posted by taniknight View Post
Just to clear something up, from Salas' advise on bar grounding, I thought that the bar should only see chassis ground at the input end and power ground at the output end.

However, Fran's sketch shows chassis ground at the PSU grounded end. Naturally, Fran, if it sounds good, it is good. I just thought I'd make sure I hadn't missed something.

Regards,
Tani.
From the linked article: ''You only want your buss to connect to chassis ground at one point, either at the power supply first filter cap or at the other end of the buss at the input jack. If you connect the buss to ground at the power supply, you will need to use an isolated input jack (run the shield connection over to the ground point of the cathode components of the first stage). Then you will need to add a 0.01uF capacitor (ceramic disk caps are good for this) from the shield terminal of the input jack directly to the chassis with the shortest possible wires. This will keep radio frequencies from getting into the amp.''

So it can work both ways depending on input sensitivity and PSU nodes distribution. I usually go to chassis input side. I use the small capacitors (MKT for me) from RCA rings to nearest chassis spot in phonos if I ground at the PSU end. I don't necessarily take the plastic spacers out if I ground input side, I chassis ground the bar on a screw and nut near the inputs and link them RCA rings there too. By ''only'' I mean chassis link at one point.
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Old 9th May 2011, 11:43 PM   #212
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Great, that cleared it up, as reading the full article would have.

Thanks Salas, and well done Fran.

I'm still a fair way off starting mine. So many other things to do.... but the more I learn before I solder, the better.
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Old 9th May 2011, 11:56 PM   #213
Salas is offline Salas  Greece
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Use shielded coax for inputs and outputs as well. Pushes hum lowest.
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Old 10th May 2011, 12:24 AM   #214
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Quote:
Originally Posted by Salas View Post
Use shielded coax for inputs and outputs as well. Pushes hum lowest.
On that note, is it best practice to use 2-wire plus shield, with the wires carrying signal and ground, and the shield grounded only at the input end. Or should I use single wire shielded cable, similar to standard RCA interconnects, with the shield carrying the signal ground? Or...?

In an op-amp phono pre, I once used 2-wire plus shield to carry left and right signals, with the shield carrying a common ground. I knew full well that it wasn't likely to be the best configuration, but I thought I'd try. I suspected that cross talk would suffer, but it seems OK when listening... I get an indication of cross talk by disconnecting left input and right speaker output and play music... whatever makes it to the speaker has crossed over from the other channel, correct? Of course it doesn't tell you where the cross talk is coming from...

Tani.
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Old 10th May 2011, 12:27 AM   #215
Salas is offline Salas  Greece
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I use individual single coax. I use double and shield for each channel If I want to pseudo balance outputs to XLR.
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Old 10th May 2011, 08:03 PM   #216
RCruz is offline RCruz  Switzerland
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Hi Fran

I finally got to mod my riaa setup and now I have 15.33n instead of 15.72nF.

Much better overall.... Bass is more delineated and the highs are clearer. Must wait 48 hours before I can really apreciate it but it is a keeper.
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Old 10th May 2011, 08:55 PM   #217
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Things just got quieter round here.....

I went back and rewired the inputs and outputs and input 6n2 cathodes to ground with shielded cabke. Like in the articke, I then took a 0.01uf cap from each input jack plus the shields to the chassis right at the input jacks. Interestingly, I first tried running a short piece of wire from the 3 caps to the ground point, this was about 50mm long. Result was buzz, at low level but still there. Cutting the wire short and tying to the chassis closer made all the difference.

So now that done its dead quiet. Listening now for a little while and then try the k42y coupling caps.


Fran
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Old 10th May 2011, 09:44 PM   #218
Salas is offline Salas  Greece
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Quote:
Originally Posted by woodturner-fran View Post

So now that done its dead quiet.


Fran
Sounds like a proper Itch.
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Old 10th May 2011, 09:58 PM   #219
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Salas ... I'm scratching all over...
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Old 10th May 2011, 11:04 PM   #220
Salas is offline Salas  Greece
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Made you to a hoochie man!
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