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Old 22nd June 2010, 06:54 PM   #231
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Quote:
Originally Posted by westers151 View Post
If I have my power supply in a seperate enclosure then I would be wanting to rectify this at the transformer and only send DC across the power umbilical.

How would I connect that to the board as the board assumes the rectification is done by a bridge onboard?
Nothing happens by delivering AC current through an umbilical cord, but you could rectificate before if you want to. Don't mount the rectifiers on the board, assemble the bridge on a piece of veroboard in the transformer enclosure. Then connect the umbilical cord + and - to the holes of + and - tracks. And the center tapped out of the trafo to ground.
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Old 22nd June 2010, 07:20 PM   #232
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Originally Posted by billo44 View Post
I have built a ground (loop) breaker Like the one Regi suggested from the ISP site Earthing (Grounding) Your Hi-Fi - Tricks and Techniques .

1) I don't understand how this device works or how I can test that it is working correctly?

2) I read that I should have used crimped connectors rather than solder, I understand the thinking here, but is it really necessary?

3) I should use one for each channel?

Can someone kindly point me towards a method to test this device and perhaps a little reading which might help me understand the principle of how this works? I have two decent DMM's, a dc bench supply to 32 volts, a variac, (and isolation transformer), and a bulb tester.

I don't understand how the amp works either but I can test that with my ears...this is a safety issue! I want to be sure my grounding is secure.

Thanks
Bill
1- If you measure impedance with your DMM, you should get 10r. The only way it will conduct without an applied voltage is through the 10r resistor. If you apply more than aprox 1,5v or 2v, it will conduct current without almost any resistance. The paralleled capacitor will allow current to flow in high frecuencies (to allow the chassis acting as a more effective shield)

2- Not necessary to crimp, but it will be safer in case of HIGH currents flow. No worries because you have a high current bridge and fuses (or you should).

3- If you use one for both channels, you will have to join grounds from each amp board. Less channel separation. I am going to use 2, so they will join at the Safety Earth ground, where all my equipment (not only audio) is meeting.

Regards,
Regi
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Old 22nd June 2010, 07:28 PM   #233
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I forgot to quote the most relevant points from the article:
Quote:
-Don't earth the internal electronics, or use a simple 'loop breaker' circuit to allow the case to act as a shield for radio frequency interference, but no solid connection is made (this is a common approach). This provides protection should there be a failure from the incoming mains to chassis

-The loop breaker works by adding a resistance in the earth return circuit. This reduces circulating loop currents to a very small value, and thus breaks the loop. The capacitor in parallel ensures that the electronics are connected to the chassis for radio frequency signals, and helps to prevent radio frequency interference. Finally, the diode bridge provides the path for fault currents. The use of a large chassis mounting (35A) type is suggested, since this will be able to handle the possibly very high fault currents that may occur without becoming open circuit. Note the way the bridge is wired, with the two AC terminals shorted, and the two DC terminals shorted. Other connection possibilities are dangerous, and must be avoided.
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Old 22nd June 2010, 08:29 PM   #234
udailey is offline udailey  United States
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I think I would rectify in the amp enclosure.
1: The boards rectify for you if you put in the MUR820's included in the kit
2: You will need heavier cable to carry the higher current to the amps
3: If the AC picks up some noise on the way to the amps case you can destroy most of it with the rectifiers. With DC what will you do to destroy the noise besides push it through the caps?
Uriah
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Old 22nd June 2010, 10:12 PM   #235
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Thanks all - I'd read elsewhere about doing rectification at the traffo side of things and then having only DC on the umbilical.

I guess I could use IEC sockets to transfer the AC - Neutral and Live conductors could be for AC1 and AC2 and the earth socket for PG. I'm planning on running a seperate safety earth between the boxes that will be bolted to the casing at either end, so that would be all bases covered.

Cable could be mains 13A stuff - unlikely to need such a high rating, but it adds to the safety, plus I can get 10A or 16A rated IEC male and female plugs/sockets.
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Old 22nd June 2010, 10:21 PM   #236
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Quote:
Originally Posted by westers151 View Post
Thanks all - I'd read elsewhere about doing rectification at the traffo side of things and then having only DC on the umbilical.

I guess I could use IEC sockets to transfer the AC - Neutral and Live conductors could be for AC1 and AC2 and the earth socket for PG. I'm planning on running a seperate safety earth between the boxes that will be bolted to the casing at either end, so that would be all bases covered.

Cable could be mains 13A stuff - unlikely to need such a high rating, but it adds to the safety, plus I can get 10A or 16A rated IEC male and female plugs/sockets.
Not suggested to us mains type connectors for secondary voltages. To much chance of a wrong cable being plugged in.

I "suggest" you use the Neutrik power connectors or mic jacks...
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Old 23rd June 2010, 12:32 AM   #237
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Originally Posted by Lazarus500 View Post
C4 and C5 came supplied with 10 mm lead spacing and the circuit board has 7.5 mm spacing. How are you dealing with that?

TIA,

rick
I am guessing everyone is in the same boat with C4 and C5. Are you just bending the leads to fit the 7.5mm spacing? If so, do you bend both leads 90 degrees against the bottom of the cap and another 90 degrees to point down again? Just leave one straight and bend the other? What is best?
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Old 23rd June 2010, 12:57 AM   #238
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Originally Posted by troystg View Post
Not suggested to us mains type connectors for secondary voltages. To much chance of a wrong cable being plugged in.

I "suggest" you use the Neutrik power connectors or mic jacks...
Nice tip.

But, if you are the only one to use it, and rely on yourself, you can be safe.
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Old 23rd June 2010, 12:58 AM   #239
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Originally Posted by udailey View Post
3: If the AC picks up some noise on the way to the amps case you can destroy most of it with the rectifiers. With DC what will you do to destroy the noise besides push it through the caps?
Uriah
This is the first time I've heard such a thing

Regards,
Regi
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Old 23rd June 2010, 02:03 AM   #240
troystg is offline troystg  United States
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All else being equal, AC transport is much more immune to noise pickup than DC because of the extra components before the final use at the amp circuits.

With that said, usually all things are not equal and doing a CRC circuit is what is typically used.


Quote:
Originally Posted by regiregi22 View Post
This is the first time I've heard such a thing

Regards,
Regi
A LOOOOONG time ago Mr. Erath and Mr. Gerald taught me that just because I hadn't seen or heard of it doesn't mean they hadn't done it before I was even born. I am SURE that applies around the world.
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