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Old 24th October 2012, 11:56 AM   #161
EUVL is offline EUVL  Europe
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> I have noticed in matching that some devices are more affected by changes in temperature than others.

That is precisely why I always insist, to the annoynace of some here, to match under operating conditions.
And of course I know why this is so. And I can give you a hint.
See if you can find any data at all on the Rthjc of Toshiba FETs.




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Old 24th October 2012, 12:27 PM   #162
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I don't doubt you at all, but your setup is advanced and it's development is a cost you absorb. While not excellent, like your results, Nikon's measurements were stool good to very good. I think it all becomes more important in your implementation of an X version of the F5. I am thoroughly impressed by both of your efforts.
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Old 24th October 2012, 12:48 PM   #163
NicMac is offline NicMac  Italy
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Quote:
Originally Posted by buzzforb View Post
I think it all becomes more important in your implementation of an X version of the F5.
I think it is the other way around. The X version, in contrast to the single ended F5, should be immune to NP-offset induced distortion because of its balanced topology.

I think patrick actually posted a practical demonstration of this a few days ago.

While you may think the nikon1975 set is "good to very good" this is not really the case. The Yfs of the N-devices are all over the place and perfect P-devices, or a balanced topology, will not fix this.
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Old 24th October 2012, 01:14 PM   #164
EUVL is offline EUVL  Europe
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Nic has shown you a good matched set from other suppliers.
I have seen much more terrible ones from his measurement data.

So while he is being polite and diplomatic to those offering matched sets here,
what you saw above is the pretty side of the story.


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Old 24th October 2012, 01:53 PM   #165
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Have you guys had the chance to test distortion specs using devices from different matching sources?
Most folks build amps here, listen and enjoy. Few go further and measure and tweak to get ultimate performance. While it makes perfect sense that others efforts are inferior to your own, what is the practical implications of the findings. What do they translate into in terms of performance. Clearly if I was trying to avoid the topic, I wouldn't post. The info ids great.

I think this introduces the beauty of P3 in Nelson's design. It does allow for some level of adjustment for less than stellar output devices.
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Last edited by buzzforb; 24th October 2012 at 01:58 PM.
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Old 24th October 2012, 02:59 PM   #166
NicMac is offline NicMac  Italy
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Here is the data on the NNNNPPPP set of heinz1
Attached Images
File Type: png heinz1.png (96.7 KB, 178 views)
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Old 24th October 2012, 04:21 PM   #167
EUVL is offline EUVL  Europe
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With the limited time that I have and the many task that I still want to do,
I rather spend my time on perfecting things, rather than finding out what I can get away with.
My personal choice.

It is perhaps better to post the question to Nelson.
He makes a living from this, so he needs to be practical.

All these will be less obvious for a circuit with global negative feedback.
It will be much more observable in circuits without.
Which is of course what I want to do next .....

You are of course welcome to obtain "bad" FETs from Nic and test them to prove matching is not critical.
At least that is as far as measurement goes.




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Old 24th October 2012, 05:03 PM   #168
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As I am building a large number of amplifiers for a HOA project I do not need full PPPPNNNN matches and instead PPNN PPNN matches would seem appropriate for most of them. Will limiting to single channel matching increase the matching pool?
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Old 24th October 2012, 05:20 PM   #169
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Quote:
Originally Posted by EUVL View Post
With the limited time that I have and the many task that I still want to do,
I rather spend my time on perfecting things, rather than finding out what I can get away with.
My personal choice.

It is perhaps better to post the question to Nelson.
He makes a living from this, so he needs to be practical.

All these will be less obvious for a circuit with global negative feedback.
It will be much more observable in circuits without.
Which is of course what I want to do next .....

You are of course welcome to obtain "bad" FETs from Nic and test them to prove matching is not critical.
At least that is as far as measurement goes.




Patrick
I applaud your effort in designing a high performance amp while having to take into consideration the ablilities of those assembling them. I am not trying to be difficult, but simply trying to ascertain just how much difference the ideal matching makes. Many have talked about how Nelson amps sound better. Perhaps htis is one fo the reason why. ONce again, I have nothing but respect for your effort. Just learning.
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Old 24th October 2012, 05:21 PM   #170
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To ashaw :

No. Not much.
You are much better of with NNNN PPPP match.
See my recent post in the original F5X thread.


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