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Old 20th November 2004, 09:27 PM   #1
GeirW is offline GeirW  Norway
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Default Propper grounding.

Gday.

How would you ground your amp. propperly.?
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Old 20th November 2004, 10:16 PM   #2
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Default Thread to read

Check here:
earthing!!!!!!!!!!
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Old 21st November 2004, 10:13 AM   #3
GeirW is offline GeirW  Norway
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Gday.

Good read, i think you can conclude with:
common earthing and off-axis alignment of the
trann`s. (the latter is kinda self exsplaining me think.)
When it regards common earth,
old amp`s (depends on designer i guess.) use a light-weight
metal (copper) bar, across the amp/innside the chassis, where everything is connected.
Me thinking common grounding to chassis/top would be
depending on choice of metal.?
In my case, the chassis/base is wood, and the top-plate
is copper/brass. (haven`t fully made upp my mind yet,
maybe i go all wood.)
In case, wouldnt a "bar", be a good choice.?
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Old 21st November 2004, 08:19 PM   #4
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Bar ain't necessary. Nothing more than an ampere peak in most tube amps, can use 24 gauge wire. It's a poor excuse for something which can very easily be finessed.

The Number ONE reason for any ground loop is going to be grounding the first stage to something other than the signal source. I don't care about any more of your grounding, as long as you do that. And bypass cathodes as they are supposed to be.

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Old 21st November 2004, 08:45 PM   #5
GeirW is offline GeirW  Norway
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Gday.

TnX. for the reply Sch3mat1c.
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Old 22nd November 2004, 07:33 AM   #6
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Default "Star" grounding is the way to go

Ensure that all ground connections, such as the grid resistor, cathode resistor and HT decoupling capacitor from each individual stage are grounded together. This is to prevent ground currents from circulating between different stages and causing noise by interfering with each other. This is much better than using a bus-bar, IMHO. As mentioned by Sch3mat1c, the first stage is the most critical but it may not necessarily be the only stage that matters.

It is important to avoid currents from flowing through the chassis, so the chassis should be grounded at only one point, preferably at or near the signal input socket.

Heaters are best grounded at a center-tap; if your heater winding doesn't have a CT, you can create the same effect by using a voltage divider of two 220 ohm resistors connected in series across the heater winding, with their mid-point grounded. Grounding here means AC grounding; the DC voltage will depend on the cathode-heater voltage limits of the tubes you're using and at what potential the cathodes are sitting. It is generally considered a good idea to have a low voltage, of about 25v or so, between the heaters and the cathodes (with the heaters more positive). This is supposed to minimize hum being picked up capacitively by the cathodes from the heaters. Use a voltage divider across HT to get the required heater potential. End-to-end resistance of this voltage divider should be high, e.g. 1M. Make sure there is a good AC connection from the heater center-tap to ground, using a 10uF capacitor.
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