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Old 17th February 2012, 11:39 AM   #221
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This in case no diodes are used.
As diodes minimize losses.
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Old 17th February 2012, 11:47 AM   #222
AndrewT is offline AndrewT  Scotland
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I would expect the diodes to have at most a marginal effect on current contribution while the amp is operating in ClassA mode.

The diodes would in my opinion only provide significant increases in available current when output current is significantly more than the Max ClassA output.

If the diodes were already passing significant current in ClassA mode then I think you will find that they over-rule the stabilising effect of the source resistor.
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Old 17th February 2012, 11:55 AM   #223
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Quote:
Originally Posted by MASantos View Post
Hw did you decide on the value of K and what does it represent?
Hiraga mentions a formula (le classe A)
Pmax = 2Vcc*a)^2
8*Rl

and uses a = 0,85 for bipolars, being the 'collector loss'; with FETS there is also inefficiency in driving, first of all a voltage component (not so much resistance) and there are source resiatances that dominate...
For his amp at 18V+/- he gets 15 watts; his formula at 33 volts this gives 50 watts too! I assume that this K is a similar 'drivability'.
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Old 17th February 2012, 12:01 PM   #224
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At 3.5A, loss is 1.65v into source resistor let alone .
Diodes should keep about 0.65 volts across that resistor at the same current.
Which is 1volt less.

Last edited by bobodioulasso; 17th February 2012 at 12:03 PM.
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Old 17th February 2012, 01:23 PM   #225
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Quote:
Originally Posted by AndrewT View Post
I too get lost with the introduction of k.

Prior to that K, everything is correct.

...

ClassA output current.

I have assumed the power factor of the linear power supply at the range of 0.6~0.8
Shouldn't it be calculate in this way? If its wrong, please point me out
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Old 17th February 2012, 01:50 PM   #226
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peak output voltage level + voltage loss across the drain resistor + voltage to open up the output devices.

(and a little extra )
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Old 17th February 2012, 03:38 PM   #227
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where can i buy the f5 turbo PCB s from ?
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Old 17th February 2012, 04:28 PM   #228
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Quote:
Originally Posted by biju55 View Post
where can i buy the f5 turbo PCB s from ?
Just about now, people are discussing few layouts. They are not available to buy from anywhere. You can probably make your own PCB following the layouts discussed here.
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Old 17th February 2012, 04:40 PM   #229
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If you are in a hurry, you might use Cviller F5 V2 boards from diyaudio store.
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Old 17th February 2012, 06:17 PM   #230
Variac is offline Variac  United States
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Or the F-5c V2 boards from the store

But they would both need some reworking..

Last edited by Variac; 17th February 2012 at 06:20 PM.
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