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Old 24th August 2015, 04:26 AM   #221
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by a.wayne View Post
Only if you increase the amt of class-a bias ....
Do you prefer more devices at lower current than fewer devices at higher current?
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Old 8th December 2015, 03:09 PM   #222
mbrennwa is offline mbrennwa  Switzerland
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Default Max wire length (FE --> power boards)

What's the max length of the wires from the front end board to the power board?

Here's why I am asking: I am planning to build a F5T monoblock with four power boards, one board on each side/front/rear (yes, heatsinks on all four sides). Since the transformer will be somewhere in the center of the chassis, I'd think it would be better to keep the front end (FE) board away from the center. I thought of mounting the FE board to the rear heatsink, and then have wires going from there to the four power boards. The wires from FE on the rear to the power board on the front will end up being 40 or 50 cm long or so.

What do you guys think?
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Old 8th December 2015, 03:29 PM   #223
AndrewT is offline AndrewT  Scotland
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Each output device needs a 3wire connection. I have asked, but got no answer to how we run these wires.

Twisting all three together seems wrong to me, but might be the best way.
Twisting the two high current wires together could be better and leaving the low current alongside, or spaced apart?
Or all three spaced apart?

I don't know.

Once that is answered maybe we could work out what it is that could cause an instability problem and then define the maximum distance in terms of parasitics/inch.
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Old 8th December 2015, 08:21 PM   #224
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by AndrewT View Post
Each output device needs a 3wire connection. I have asked, but got no answer to how we run these wires.

Twisting all three together seems wrong to me, but might be the best way.
Twisting the two high current wires together could be better and leaving the low current alongside, or spaced apart?
Or all three spaced apart?

I don't know.

Once that is answered maybe we could work out what it is that could cause an instability problem and then define the maximum distance in terms of parasitics/inch.
I think that twisted wires will minimize the pickup of hum, because the loop area between the wires will be small. Or is the resistance/impedance seen by the wires (on the FE board or the power boards) too small for efficient hum pickup?

Twisted pairs (or wires that are close to each other) may also add some inductance and capacitance. According to some online calculator tool, the capacitance of a 50cm long twisted pair would be in the range of 30 pF, and the inductance in the range of 200 nH or so (see attached screenshot; depends a lot on the thickness, distance and insulation of the wires).

(How) Would that affect the performance of the circuit?
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File Type: png Screen Shot 2015-12-08 at 21.16.58.png (55.7 KB, 524 views)
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Last edited by mbrennwa; 8th December 2015 at 08:24 PM.
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Old 9th December 2015, 12:23 AM   #225
AudioSan is online now AudioSan  Norway
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twisting the 2 high current wires and run them strait to the PSU. they don't need to run through the FE board.
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Old 9th December 2015, 07:20 AM   #226
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by AudioSan View Post
twisting the 2 high current wires and run them strait to the PSU. they don't need to run through the FE board.
Thanks for this. What about the third wire? Plain? Shielded? Twisted with a grounded wire?

What's a reasonable max length for all these wires?

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Old 14th January 2017, 10:13 PM   #227
joesch1999 is offline joesch1999
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when doing the v3 will two 4u's be good or will I have to get 2 5u
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Old 15th January 2017, 12:39 AM   #228
6L6 is offline 6L6  United States
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Building an F5 Turbo v2 (in-Progress)
5U
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Old 9th August 2017, 09:03 AM   #229
Erlend Sæterdal is offline Erlend Sæterdal  Denmark
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Building an F5 Turbo v2 (in-Progress)
Default Heatsink all to small?

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