F5X from diyAudio Boards P-F5c-2V20e

[Zen Mod]

Originally Posted by JBL4435

Look at the inverted left part of the schematic.
They are already crossed

you got me there

Originally Posted by JBL4435

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

[Zen Mod]

Originally Posted by JBL4435

.....
Output resistors?

what with them ?

[JBL4435]

Originally Posted by Zen Mod

what with them ?

Output to ground resistors 33 to 68 ohms to stabilize relative dc offset.
Are they helpful in this design?

[Zen Mod]

you already have them - look at feedback net

they have same function .

[EUVL]

> 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

.

[EUVL]

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

[JBL4435]

Originally Posted by EUVL

I personally would put 220R 1W to Gnd at both outputs.
But feel free to experiment.

Thank you!

Originally Posted by EUVL

So I only posted the parts that needed to be changed.
Thought it was trivial.

No!

[JBL4435]

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.

[EUVL]

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

[NYCOne]

Originally Posted by JBL4435

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.