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Old 5th April 2013, 02:12 AM   #811
EUVL is offline EUVL  Europe
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One more comment I want to make about how to compensate for the difference between K170/J74 Yfs.

In my first build, I calculated the combined open loop gain of the first & second stages of the top & bottom halves respectively and balanced them by adjusting the value of the MOSFET source resistor as well as the feedback resistor network values.

I have in the public version changed that approach, not only because it is more complex to calculate and understand, but also for philosophical reason. The current design philosophy is that any "error" should be corrected for locally where they occur. And since the 2SK1530/2SJ201s are perfect complementaries, the correction is only done at the front end, namely the 5R extra degen for the 2SJ74s.

The same approach is used for the F5XP, for example. In this case, the first stage also has the 5R degen for the 2SJ74. So the gain of the first stage is balanced. The second stage also has an imbalance between the 2SK216 and 2SJ7 both in Yfs and in Vgs, and this is then compensated by adjusting the source resistor values.

The advantage of this more laborious approach is that if one day we find a perfect complementary pair of TO220 devices, we can take out the Renesas laterals and subsititute these in, but then with equal source resistor values.

i.e. if each stage is individually balanced, you can change one without affecting the other.

As said, it is a philosophical thing. There is no proof if one sounds better than another.
What I said in post #1 ?
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Last edited by EUVL; 5th April 2013 at 02:15 AM.
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Old 14th May 2013, 12:49 PM   #812
ramallo is offline ramallo  Europe
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Today I powered up one of my amp modules

Click the image to open in full size.

330mV after 2:30 hours, -20V/+19,98 supply

190mV offset on negative side 90mV on positive (to ground)

need I to do an adjustment like the regular F5 for get the lowest offset on each side?
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Old 14th May 2013, 02:25 PM   #813
EUVL is offline EUVL  Europe
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> 330mV after 2:30 hours, -20V/+19,98 supply

Measured after CRC ?
Sounds high; what is the bias current ?

> need I to do an adjustment like the regular F5 for get the lowest offset on each side?

Yes.
But perhaps better to post at the build thread and continue from there ....

F5X -- the EUVL Approach - The Build Thread


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Old 15th September 2013, 09:09 PM   #814
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Quote:
Originally Posted by EUVL View Post
As promised.


Patrick
From the diagram attached to post #706.

I see VE + and - for left speaker are connected to the same pole?
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Old 17th September 2013, 12:02 AM   #815
EUVL is offline EUVL  Europe
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I do not quite understand the question.

I checked the diagram and cannot spot any mistake around the left speaker.
The only thing is that Mark (who drew the schematics) was using 12V relays, so he wired the left & right protection relays in series.

Maybe you can explain further ?


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Old 17th September 2013, 02:24 AM   #816
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Thanks Patrick,

Attached is my query, Iíve highlighted the connection from the left speaker that runs back to left channel + and - amp board from only ONE speaker pole.

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File Type: jpg Screen shot 2013-09-17 at 12.17.33 PM.jpg (77.5 KB, 307 views)
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Old 17th September 2013, 05:04 AM   #817
EUVL is offline EUVL  Europe
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No John.
Close the relay contact on the left and draw the line from Amp VE+ in red.


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Old 17th September 2013, 06:11 AM   #818
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Thanks Patrick, of course, makes much more sense now, I couldn’t see it for the life of me.
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Old 28th September 2013, 01:42 AM   #819
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If I may ask, why place the relay on the +positive side?
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Old 28th September 2013, 05:46 AM   #820
EUVL is offline EUVL  Europe
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Why not ?
Any side will do. You can also use DPDT.


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