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Old 8th February 2012, 04:45 PM   #681
EUVL is offline EUVL  Europe
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> I second that! You can put me on the GB list now.

I thought you wanted a F5X Preamp first ?


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Old 8th February 2012, 04:50 PM   #682
Horio is offline Horio  United States
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Quote:
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> I thought you wanted a F5X Preamp first ?
Yea...That too!
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Old 8th February 2012, 04:55 PM   #683
EUVL is offline EUVL  Europe
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One at a time. First finish the F5X.




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Old 8th February 2012, 05:23 PM   #684
EUVL is offline EUVL  Europe
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A discussion about output device choice can be found here :

F5 Turbo is posted
Further details published :

F5 Turbo is posted


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Old 12th February 2012, 02:57 PM   #685
EUVL is offline EUVL  Europe
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There are some discussions about the level of Vgs match between P type & N type output devices at the GB thread :

Potential EUVL F5X designed case user distribution check

While the discussion over there is whether the supplier has delivered what he promised, most of you would be interested in how well the P-N matching has to be. After all, perfectly P-N match is an absolutely rarity.

Potential EUVL F5X designed case user distribution check

The consequence of a slight mismatch between P & N devices is an increase in second harmonics. While this is more important for the single ended F5 ( and hence Nelson's modified version to include a trimpot across the two feedback shunt resistors), it is much less important for the F5X, as even harmonics will cancel out between the left and the right halves, provided they behaves identically. And the latter can be achieved through good N-N and P-P match, which is much easier to obtain. I consider a 20dB cancellation between left & right halves to be achievable.

Further fine tuning of the even harmonic contents of each (L or R) half is still possible, either by trimming the feedback shunt resistor, as Nelson proposed, or by trimming the output MOSFET source resistor, as he did earlier with his First Watt F5's using Fairchild devices. Note than the Fairchild devices has no P-N match at all. The Vgs at 1.3A (for single ended F5) differs by more than 1V !!

All these issue would be dealt with once fitzfish finds time to start the Build thread.
Right now he does not have enough time to sleep.
One should not forget that this is hobby, and we all have a living to make in the first place.


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Old 12th February 2012, 03:03 PM   #686
EUVL is offline EUVL  Europe
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For more info on P-N match we published in 2008, see :
F5 power amplifier

followed by the same info for Fairchild MOSFETs as used by Nelson :
F5 power amplifier


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Last edited by EUVL; 12th February 2012 at 03:08 PM.
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Old 12th February 2012, 05:32 PM   #687
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Quote:
Originally Posted by EUVL View Post
For more info on P-N match we published in 2008, see :
F5 power amplifier

followed by the same info for Fairchild MOSFETs as used by Nelson :
F5 power amplifier


Patrick
Patrick.... I appreciate you taking the time to "dig out" the relevant info, and for posting the links. It really helps us who are still attempting to come up to speed on F5 and F5X topologies. These "mega-threads" have a wealth of good info in them--digging them out can be a real chore, so my thanks for doing that legwork. I know you're busy--I appreciate you taking the time.
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Old 12th February 2012, 05:57 PM   #688
EUVL is offline EUVL  Europe
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Old 26th February 2012, 03:56 PM   #689
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EUVL:

Is there any consensus about the X topology vs. balanced as shown in Nelson's F5 Turbo Balanced Template? How would one introduce the P3 adjustment into the X?
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Old 26th February 2012, 04:07 PM   #690
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There is no consensus. This is how I would build a balanced F5.
As said in post#1, only one of the many ways to skin a cat.

And as already mentioned, in simulations and measurements, the floating and grounded X behave similarly.
But the floating X is capable of taking single ended input. The grounded X needs balanced input signals.

With proper matching between left and right halves, all even harmonics will cancel out in the F5X.
There is no need to introduce the P3 adjustment. In particular not with Toshiba Mosfets.


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