amb
Member of the Trade: AMB Laboratories
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Simple twisted pairs are good for less than just a few inches. If you go longer than that (such as with crossfeed), then I suggest using shielded cables. I don't really believe in fancy silver wiring inside the case, especially when the distances are so short. Copper is fine.
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It is not necessary to twist the output wires, but if you want to, you can just twist the three together.
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You don't need to shield any of the output wiring. For the inputs, if you shield it, just use two shielded cables, one for each channel, and connect the shields together for the signal ground.
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Aluminum does not shield against magnetic interference from the power transformer. A ferrous metal may work better, but only if you completely enclose the PSU in a box. There is really no substitute for sheer distance. Assuming you use a low-leakage toroidal transformer, you should still allow at least 4 inches of space between the transformer and the amp board if you want a quiet noise floor. I can't emphasize this enough: It doesn't make sense to build a "maxxed" amp with fancy boutique parts, only to spoil it with hum and noise induced from the transformer. The best solution is to put the PSU in a separate case than the amp and use an umbilical DC power cord, or put it in the same case with a lot of space between the two.
Originally Posted by GregVDS Is a simple twisted pair coming from RCA connectors on the backside to the front switch - crossfeed is sufficient (+- 1 foot, 30cm), or should I better opt for the shield-braided cable (like a microphone cable). Is here silver wire interesting, or normal copper is ok? |
Simple twisted pairs are good for less than just a few inches. If you go longer than that (such as with crossfeed), then I suggest using shielded cables. I don't really believe in fancy silver wiring inside the case, especially when the distances are so short. Copper is fine.
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Again, form the output R, L and G, should I use two wires from ground to output R and L in order to have twisted pairs from pcb to neutrik jack? |
It is not necessary to twist the output wires, but if you want to, you can just twist the three together.
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And also, the output ground is ok for shielding? the input ground is ok for shielding too (since they are not the same)? |
You don't need to shield any of the output wiring. For the inputs, if you shield it, just use two shielded cables, one for each channel, and connect the shields together for the signal ground.
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And last, Is there a minimal thickness for internal separation between M³ and PSU pcbs, in terms of aluminium foil I mean. I plan to build a very tight enclosure, to be able to have it with me at work, and come back home with. Hence, the psu and M³ will be very close. I was planning to separate them by an aluminium plyed foil (0.8mm thick), shielding the psu. The outer box will be in aluminium Alodined internally. |
Aluminum does not shield against magnetic interference from the power transformer. A ferrous metal may work better, but only if you completely enclose the PSU in a box. There is really no substitute for sheer distance. Assuming you use a low-leakage toroidal transformer, you should still allow at least 4 inches of space between the transformer and the amp board if you want a quiet noise floor. I can't emphasize this enough: It doesn't make sense to build a "maxxed" amp with fancy boutique parts, only to spoil it with hum and noise induced from the transformer. The best solution is to put the PSU in a separate case than the amp and use an umbilical DC power cord, or put it in the same case with a lot of space between the two.