F5 power amplifier

[Melon Head]

Originally Posted by EUVL

I consider this remark misinterpretation and perhaps somewhat misleading.

I was hoping it might provoke some discussion on the matter, which it did, so thanks.

Could you comment on whether there should be (or could be) another reference to ground around the feedback loop. This was not omitted on the Aleph JX, though it is a slightly different arrangement from the original.

[gaborbela]

Good question Thanh about the ground around the feedback loop !!!
If that help please take a look at the Aleph J and the AlephX J .
Also F5 the F5X .
Many differences between the AJ & F5 circuit .
But these question make me curious to .
I just try to get help here to , more people think on the same think we can get probably more idea .
Is not possible to run some simulator test?
Greets

[tinitus]

Sounds like the same issue regarding whether to connect cascode resistor directly to ground, or through base resistor, as I recall it
Masters answer was that there is no simple answer and that you have to try both to know which to prefer

My guess is that F5 ground scheme is exstremely simple, or so it seems
I would expect one should be very careful not to disturb this delicate balance
There are no coupling film caps either, which would be to ground
Im sure theres a good reason why not

[galop]

Hello ,i have problem with f5 power supply.I have transformer 18-0-18 ,2 rectifiers and capacitor bank.when i put the minus from first rectifier bridge to plus to second one ,become short cut.what to do?

[gaborbela]

Hello tinitus
The cascode story out of the table after I decided to go with the X wich would be powered by 24V rail .
For that reason I no longer need cascode .
Our question with Thanh the feedback loop ground .
If you take a look the regular F5 the four 100R resistors (R5, R6, R7, R8) is connected to the ground by the two 10R resistors (R1,R2)
Now at the X verizon R1 & R2 cross connected , X-ed .
My question if those resistors still have to be connected to the ground to ???
I think is very important these to be clear !!!

[gaborbela]

Sorry I forget to attach the schematic , that would make easier to understand our question .
If you look at the red box there is a ground connection .
Do I have to use that ground at the X verizon???
These is my last question , if I will know the answer I can go on to each the PC boards .
PLEASE IF SOMEONE KNOW THE RIGHT ANSWER LET US KNOW ,please help with these . Thank you very much !!

Greets

[tinitus]

A long way still
The way you show in drawing may work better with a single bridge

[gaborbela]

I have a heavy duty Semikron 100A bridge probably I will use that .
In my Aleph X works well . And the quality not bad either . Also your drawing is OK .
I did com paired these bridge with a couple another type bridge , I like these better .
My opinion about the ground question we not supposed to connect the X to the ground at least not that way how is connected in the reg.F5 . It would be shorted the X .
But I hope I get some answer from some expert guy . Because the feedback at the F5 is connected to the ground by the 2 10R resistors .

Greets

[tinitus]

I think it was answered before
Balanced input has a pos and neg AND a ground
You may say that the usual ground on a "single ended" is changed to a hot negative
Ground on a balanced is different from ground on a single ended
Probably not right either, but whatever

Also bare in mind that F5 is a ready to go design
And in its commercial form should work flawlessly anywhere in the world, with all sorts of strange gears connected
Could be its just a precaution against noise issues

Anyway, either of them are supposed to work as is
Just choose the one you like and build it

btw, I have just been told that my coming heatsinks weigh in at 25kg

[gaborbela]

That heatsink more than enough , specially for SE type F5 . You wrote if I remember well your max power supp. it will be around 26-28V rail.
I think I go on and I each the boards .
After I will found out what is the best solution about those questions I still have . I will use a low voltage transformer to power it up , to get some experience with the bias and offset .
Of course right now the X is my only plan .
Greets