F5X -- the EUVL Approach - The Build Thread - Page 34 - diyAudio
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Old 12th January 2013, 05:07 PM   #331
NicMac is offline NicMac  Italy
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>How equal are your currents, to mA ? Even 1mA x 8R load is 8mV.

On the outputs? The outputs are loaded with 4.7R dummy resistors. I have 3.5 mV and 0.6 mV offset so that would be 0.74mA and 0.13mA flowing here.

So the goal is to achieve zero output offset even if this results in slightly different bias currents?
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Old 12th January 2013, 05:09 PM   #332
NicMac is offline NicMac  Italy
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> Let us know how it sounds later on.

Is that important

Looooooong way to go. The F5X has a component density comparable to an iPhone and I still have to find out how to squeeze it all in there.
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Old 12th January 2013, 05:11 PM   #333
EUVL is offline EUVL  Europe
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Yes.

I assume you have grounded X.
After you float the X (or perhaps even you might use the H as published by NP in F5T and also discussed in F5XP article), you will need to readjust anyhow.
But the aim is indeed zero voltage offset at bias and temperature on both outputs relative to Gnd.


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Old 12th January 2013, 05:13 PM   #334
EUVL is offline EUVL  Europe
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> The F5X has a component density comparable to an iPhone and I still have to find out how to squeeze it all in there.

Compared to the iphone ?
Tones of space.




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Old 12th January 2013, 05:15 PM   #335
EUVL is offline EUVL  Europe
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BTW I suggest you use min. 1.5mm2 silicone flexible test leads for your power wiring.
Preferably 2.5mm2.
You pass constantly 4A through them after all.


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Old 13th January 2013, 04:25 PM   #336
NicMac is offline NicMac  Italy
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> After you float the X (or perhaps even you might use the H as published by NP in F5T and also discussed in F5XP article), you will need to readjust anyhow.

I have read NPs F5T and your F5XP articles, but it is not clear to me how the H configuration would be implemented on the F5X amp boards. Can this simply be done using jumpers?

I now have the amp (in grounded X configuration) dialed in to 2A bias with <1 mV dc offset on the outputs. The sink is 60˚C and I am considering to bias a bit lower (1.8A?) as live a place where 28˚C is a normal room temperature good part of the year.

I will float the amp later when the supplies and the rest is ready.

Nic
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Old 13th January 2013, 05:52 PM   #337
heinz1 is offline heinz1  Europe
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Quote:
Originally Posted by NicMac View Post
In the amp BOM the two P MOSFETs are designated Q1 and Q8. I think this should be Q1 and Q6. Q8 is a JFET and the PCB is correctly labeled.
I may have an old BOM and I did not check the schematics.
...
That should be already known to Dave.

F5X -- the EUVL Approach - The Build Thread

For this reason, I wrote "Q6(Q8)" in the spreadsheets accompanying the MOSFETs in the GB.
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Old 13th January 2013, 06:42 PM   #338
EUVL is offline EUVL  Europe
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H by jumpers.
No connection to Gnd, just the 4 corners linked together to an H.


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Old 13th January 2013, 08:06 PM   #339
NicMac is offline NicMac  Italy
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Simply like this?
Attached Images
File Type: jpg Hjumpers.001.jpg (54.4 KB, 295 views)
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Old 14th January 2013, 09:12 AM   #340
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Nic, what your rail voltage @ 2A ?

I may do some testing next week or so.

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