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Old 21st December 2012, 06:20 PM   #711
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Quote:
Originally Posted by Marra View Post
Thanks for confirming what I was thinking.Do I stick with two pairs of outputs and bias high or try four and bias lower.I guess its try both and see which I prefer.
Try v2. Stepping is no problem, but will require bigger PSU and toroid. More pairs means more total Yfs and DF. Also lower bandwidth. Really unnecessary unless you need the power. Main reason I am building up stereo versionis to see if Wayne is right and more equals better sound.
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Old 21st December 2012, 07:35 PM   #712
a.wayne is offline a.wayne  United States
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8 pair? that is just insane i hope there is dual input pairs too
Whatever it takes , thinking of seperate supplies ala XA -series, even dutchie would be impressed ....

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Old 21st December 2012, 07:45 PM   #713
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aha. a X-ed turbo V3. then there will be dual input fets
but it's stil insane
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Old 21st December 2012, 07:49 PM   #714
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Definitely got to go balanced at that point.
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Old 21st December 2012, 08:05 PM   #715
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yes
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Old 21st December 2012, 10:57 PM   #716
BigE is offline BigE  Canada
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OK, I'm *very* confused.

I can't understand a whole bunch of AndrewT's post. So, I go back to the F5 manual, and try to turn all the pairs into a single pair.

When I look at the F5 manual, I can see where the 62 watt dissipation per channel comes from:

One pair of devices, Rails are +/-24 volts, the Ib = 1.3 per device.

That's either (2 x 1.3A) x 24 or (1.3 X 48) = 62 watts

Two channels gives you 124 VAbias. Sizing the transfomer for twice that gives you 248 VA. A 300 VA is more than enough transformer.

Output power I^2 * R = 2.6 * 2.6 * 8 = 54 Wpeak = 27 Wrms.

-------------------------------------------------------------------
Let's change the bias a little.

One pair of devices, Rails are +/-24 volts, the Ib = 1.5 per device. 3 amp total.

That's either (2 x 1.5A) x 24 or (1.5 X 48) = 72

Two channels gives you 144 VAbias. Sizing the transfomer for twice that gives you 288 VA. A 300 VA is still enough transformer.

Class A Output power I^2 * R = 3 * 3 * 8 = 72 Wpeak = 36 Wrms.

-----------------------------------------------------------

Try 2 pairs of devices, 3 Amp total and 50 volt rails. Ib = 0.75 A per device.

If this was one pair, it would be 1.5 amp each device.

Class A Output power: ( 3 * 3 * 8) = 72 Wpeak = 36 Wrms.

NOTICE THAT THE CLASS A OUTPUT POWER DOES NOT CHANGE, since it is biased to the same current.

Sizing the transformer: That's either (2 x 1.5 A) x 50 or (1.5 X 100) = 150 VA. Double that for 300 VA. Two channels is 600 va.

---------------------------------------------------------------------

4 pairs ( 8 devices ) 6 amp total ( 0.75 amps/device). If it was one pair, it would be 3 amps/device.

Class A output power: ( 6 * 6 * 8 ) = 288 Wpeak = 144 Wrms.

Sizing the transformer: That's either (2 x 3 A) x 50 = 3 x 100 = 300 VA. Double that for 600 VA. Two channels is 1.2 Kva.

-------------------------------------------------------------

Are these numbers reasonable?
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Old 21st December 2012, 11:20 PM   #717
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A toroid that is 3 to 5 times the dissipation amount is the best way to calculate things. Bigger is almost always better in this case. For exact theory, look on ESP site.
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Old 21st December 2012, 11:23 PM   #718
6L6 is offline 6L6  United States
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Quote:
Originally Posted by BigE
A 300 VA is more than enough transformer.
For a standard F5? Yes, certainly. It's what Nelson uses in the factory built ones.
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Old 22nd December 2012, 03:37 AM   #719
a.wayne is offline a.wayne  United States
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Definitely got to go balanced at that point.
Not where I'm going......
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Old 22nd December 2012, 04:00 AM   #720
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bigE those numbers are correct. exept for the last one. the rail voltage is to low to reach 144W at 8ohm. same for number 2 and as buzzbord said. transformer rating of 3times dissipation is a good way to go. 2 times is minimum. i like 3 times. that gives you more headroom and lower temp in the transformer. but when a transformer reach a certain size, then bigger is not allways better
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