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Old 16th December 2008, 01:04 PM   #2201
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OK, I'll go bigger.....


Thanks for the help, I know its a question thats asked loads.... probably because we are all looking for the cheapest way out of the heatsink problem. Many thanks......



Fran
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Old 16th December 2008, 02:26 PM   #2202
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Quote:
Originally posted by jameshillj
Yeah, Phresh,

Now, if you take this a step further, you seperate the power rails (supply) and amp speaker wires (output) - this is just better power distribution and returns - obvious, really.

This results in the 3 seperate and distinct groups/types of earth wiring, okay?

When you have a seperate p/supply case, add another one that keeps both cases tied directly to the mains earth connection, not the "star"earth on the supply, with everything else.

The same thing applies with preamps, Xovers, etc, even tho there isn't large currents - the "ground plane" needs to be much cleaner.

The idea of using balanced line level signals can be quite useful but also produces it's own problems and even more connections!
Thanks, I knocked up a couple of diagrams to try and show the schemes i'm working on.

The first is fairly standard with audio grounds tied in he amp and the power supply grounds tied in the power supply. These are then connected through the power cable. The chassis grounds are connected through an external banana plug so that they are both 'behind' the disconnecting network.

EDIT: Deleted second image due to it being completely wrong!


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Old 16th December 2008, 03:11 PM   #2203
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Nichoh46: thanks for the suggestion - I had looked at RS, but they didn't come up in the search. I looked at farnell, but as it turns out now RS are cheaper for the transformer too so now I will build a dual mono one with 2 x 160VA transformers and bigger heatsinks for the same $$.


Thanks,

Fran
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Old 16th December 2008, 03:38 PM   #2204
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The power supply is the place for your "Star Earth" and is okay, but the second star earth in the amp case combines all the speaker return currents with the amp 0volt reference points plus adding noise to the input shields - this (IMO!) is where it's better to run them seperately back to the p/ supply star earth [the chassis earth is okay].
Mind you, many amps do exactly as you have drawn and it works just fine - in fact, the original F3 (for example) has a very similar setup to your schematic but all in the one case and there's no problems at all.

Suggest you just assemble both cases and if there's problems, split the earth returns then. If you want to do the multi wire method, there are some excellent mutlipin plugs but none of them are cheap!
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Old 16th December 2008, 03:59 PM   #2205
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I have thought that this way is also acceptable.

Seasons Greetings,

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Old 16th December 2008, 04:44 PM   #2206
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http://uk.rs-online.com/web/search/s...-7034&x=23&y=9


there is 300x300 too
http://uk.rs-online.com/web/search/s...duct&R=4907040
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Old 16th December 2008, 05:29 PM   #2207
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Yeah, I bought the 300x300 type. Its a reasonable price for them....



Fran
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Old 16th December 2008, 08:56 PM   #2208
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hello
i planning to build a 10 channel amp, and i was wondering if i could stuff 5 F5 boards in to single case (how big the transformer would have to be?) or should i do 5 dual mono blocks?
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Old 16th December 2008, 09:32 PM   #2209
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Ground loops are one of the problems that you will tend to enjoy with
10 channels. I recommend 10 little transformers making 10 isolated supplies
that share a common chassis earth ground through resistors. This way
you can make it pretty quiet without special effort.

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Old 16th December 2008, 09:45 PM   #2210
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Thanks for the replay, and what should be their wattage?
Could i go for 5 with dual secondaries?
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