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Old 20th September 2011, 02:56 PM   #11
Zen Mod is offline Zen Mod  Serbia
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Originally Posted by JBL4435 View Post
Look at the inverted left part of the schematic.
They are already crossed

you got me there



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Originally Posted by JBL4435 View Post
1 "Kiste" Beer if you show me the input resistors in that schematic

naah .... there aren't any ;

but you know that you must have them
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Old 20th September 2011, 02:57 PM   #12
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.....
Output resistors?
what with them ?
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Old 20th September 2011, 03:02 PM   #13
JBL4435 is offline JBL4435  Germany
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what with them ?
Output to ground resistors 33 to 68 ohms to stabilize relative dc offset.
Are they helpful in this design?
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Old 20th September 2011, 03:10 PM   #14
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you already have them - look at feedback net

they have same function .
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Old 20th September 2011, 03:19 PM   #15
EUVL is offline EUVL  Europe
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> you already have them - look at feedback net

But not when you float the X, dear Choky.
I personally would put 220R 1W to Gnd at both outputs.
But feel free to experiment.

No need to challenge Heinz1 for eine Kiste Bier.
I did not put the input resistors on the schematics, not even on the main PCB.
They are the same as in Nelson's single ended F5.
So I only posted the parts that needed to be changed.
Thought it was trivial.


Patrick

.

Last edited by EUVL; 20th September 2011 at 03:21 PM.
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Old 20th September 2011, 03:23 PM   #16
EUVL is offline EUVL  Europe
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Oh, BTW, there is at least one very good reason why the proper F5X board is superior than 2x single ended F5 board for this build.
I let you think about it first.

It has to do with the power supply.


Patrick
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Old 20th September 2011, 03:29 PM   #17
JBL4435 is offline JBL4435  Germany
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I personally would put 220R 1W to Gnd at both outputs.
But feel free to experiment.
Thank you!

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So I only posted the parts that needed to be changed.
Thought it was trivial.
No!
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Old 19th October 2011, 09:22 PM   #18
JBL4435 is offline JBL4435  Germany
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Default Clipping Q1/Q2 ??

Is it possible to drive Q1/Q2 into clipping?

When testing the Boards with 2 output pairs into 4 ohms (not yet x-ed) I get clipping at 2.2 to 2.3V input. With this input I get around 50W into 4 ohms. No improvement over the version with 1 output pair.
This clipping appears independent of the values of the current limit circuit. I can even leave the circuit out.
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Old 20th October 2011, 04:34 AM   #19
EUVL is offline EUVL  Europe
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It is a voltage clip.

The circuit has a gain of 6. So output is at 13.8V with 16V rails.
As expected not enough headroom left for the MOSFETs.

Since you are using 2 output pairs, you can increase rail voltage and reduce bias current per FET while keeping dissipation per FET below 32W.

I would try 20V 1.6A per FET as a start.


Patrick
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Old 20th October 2011, 05:25 AM   #20
NYCOne is offline NYCOne  United States
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1 "Kiste" Beer if you show me the input resistors in that schematic
This is how I built one:

Building a World-Class Cascoded Balanced XF5 on a Budget

I used 1K and 100K as NP did in the original and have no problems.
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