F5X -- the EUVL Approach - Page 79 - diyAudio
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Old 13th September 2012, 07:24 PM   #781
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Do someone have an order number or reference number for the little transformer from Toroidy ? The name of the person that order maybe would make.

Thanks,

Davide
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Old 14th September 2012, 07:16 AM   #782
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Hi Davide,

These are the links with the information:

Specifications: F5X Transformers

Toroidy address:
F5X Transformers
The reference at the trafo label is TS15VA.

Antonio
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Old 20th October 2012, 04:54 AM   #783
EUVL is offline EUVL  Europe
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A while ago, we promised to test deliberate mismatch between N & P devices in the F5X.
We keep our promise, as always.

Here the measurement results.

The N FETs has Vgs of about 2.7V, the P FET 2.2V. So there is a huge mismatch.
NN & PP are matched to within 10mV, basically to the measurement repeatability.

Firstly one should look at the single ended F5.
This can be tested by grounding the X and measure only one (L or R) half of the balanced amplifier.

As you can see, there is a significant increase in second harmonics due to the mismatch Fig on the right), as expected.

We are currently testing a method to restore that balance (to lower 2nd harmonics). To be published later.


Patrick
Attached Images
File Type: jpg FX5_GNDX_L.JPG (94.3 KB, 701 views)
File Type: jpg FX5_GNDX_Lmismatch.JPG (99.2 KB, 688 views)
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Old 20th October 2012, 05:00 AM   #784
EUVL is offline EUVL  Europe
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As we have always maintained, if the left and the right halves of the amplifier is identical,
the X configuration will cancel any residual even harmonics in balanced mode.

This you can see this even harmonics clearly in the figures below, showing THD measured in balanced mode.
Again the one on the right has the said mismatch.
Note that this is only the case if you are using a balanced input signal.

So while perfect NNPP match is still the ideal, a slight mismatch between NN & PP does not lead to disaster.
That is, if you are building the fully differential F5X.



More to come.


Patrick
Attached Images
File Type: jpg F5XTHD.JPG (93.6 KB, 684 views)
File Type: jpg F5XTHD_mismatchFET.JPG (93.3 KB, 675 views)
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Old 20th October 2012, 09:42 AM   #785
AndrewT is offline AndrewT  Scotland
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Hi,
Wahab slated the F5 as a very high IMD amplifier.
Can you do an IMD test to his procedure to show if he is right or wrong?
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Old 20th October 2012, 09:57 AM   #786
EUVL is offline EUVL  Europe
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He who makes the accusation should provide the proof ??
Do you trust simulated results, or was there measurement backup ?

The F5X is not the F5, different devices, bias points, ......
So if you wish to verify the F5, you should ask those who have one, e.g. Nelson.

We'll eventually do a test on the F5X, out of curiosity.
But that would be after all the other stuff that we have to do that has higher priority.


Regards,
Patrick
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Old 20th October 2012, 06:09 PM   #787
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Quote:
Originally Posted by EUVL View Post
So if you wish to verify the F5, you should ask those who have one, e.g. Nelson.
The F5 was designed for low distortion at 1 watt, which is about .0015%.
As the distortion vs bandwidth figures are quite good, I would not expect to
see any IMD test that showed high distortion at reasonable levels.

On the other hand, I only care about the sound.

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Old 22nd October 2012, 01:12 AM   #788
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Patrick
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Old 27th November 2012, 10:24 AM   #789
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Further to the discussion in post #783, we have done more work on the compensation method and are ready to publish.

Attached from left to right are the single ended ouputs from an F5X :
on the left with properly matched devices,
in the middle with mismatched N-P devices (0.5V difference in Vgs),
and last but not least the same mismatched devices but with gain compensation by changing resistor values.

As you can see the compensation works, but not as perfect as I wanted it to.
So it still make sense to have properly matched devices, especially in singl ended mode.
The performance in balanced mode has already been discussed in post #784.

Thanks to dave for all the experimental work.


Patrick
Attached Images
File Type: jpg FX5_GNDX_L.JPG (94.3 KB, 334 views)
File Type: jpg FX5_GNDX_Lmismatch.JPG (99.2 KB, 81 views)
File Type: jpg FX5_GNDX_Lmismatch_R15sourceR.JPG (99.7 KB, 82 views)
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Old 27th November 2012, 12:13 PM   #790
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Does not seem to be a significant advantage to perfectly macthed devices over mismatched ones with gain correction. In fact, while the corrected graphs fets are slightly higher in distortion, their harmonic distribution looks better to me. what is your opinion on this EUVL. Is the lower overall distortion worth the higher harmonics. I know this applies only to SE input.
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