F5 power amplifier

[bobodioulasso]

Originally Posted by arche13

good evening

What should be the maximum output voltage for the power transformer can be used f5 a voltage greater than 18VAC as drawing on original NP
I think using a voltage between 18 and 24vc before rectification and filtering what should be the bias?
thank you all

Using V2 boards, you can build a 50w F5 using 2 outputs and a cascode.
2x25v transformer. (2x33v DC) Bias about 0,85A each output leg.
See diyaudio store and Cviller's blog.

[Bksabath]

Originally Posted by arche13

good evening

What should be the maximum output voltage for the power transformer can be used f5 a voltage greater than 18VAC as drawing on original NP
I think using a voltage between 18 and 24vc before rectification and filtering what should be the bias?
thank you all

My 2 cents
As hi as your heat sinks alowd.

Papa said <I wold not push big ones (TO247) at more than 50 W each >
I had my F5 at 2.8 A (1.4 A each) and 35V or there about rails for a while with no problems.

Just make shure Junction temperature dont go over 75 C then is just heath sink size and how much time and money you invest in the thermal coupling

Red Kerafol heat spreaders clamping methode.

Papa also said that < at higher voltagge they sound better>

I have not made standard F5 to compare as with for 4 Homs speakers I went for big hammer first.

Just get speaker protection for peace of mind.

[triode_al]

Originally Posted by arche13

Good evening

Which has to be the maximal tension of exit(release) for the transformer of food(supply) of f5 can one use a tension superior(higher education) in 18vac such as on original plan.
I plan to use a tension enter 18 and 24vc before recovery and filtering what has to be the way?
Thanks to all

Bon soir. Not nearly as bad translation as chinglish! At least you give food for thought.

[arche13]

transformers 300VA delivers 21.6 vac piece can be used with f5 base?

[bobodioulasso]

What is writen on the transformer?
Did you measure 21,6 unloaded?
If so, the transformers are 20v ac.

It's Ok for an F5.
Just set the bias to about 1,2A instead of 1,3A to keep dissipation right.

[luvdunhill]

Originally Posted by jackinnj

Gain of the first stage is P1/[(1/gm)+Rs] and is nominally 10, so adding 50R is going to get a bit closer to 10X from the original. You don't have to add P3 -- you can parallel values against one or the other against R1/R2 (Refdes from the original schematic).

I experimented with this and it doesn't take much tweeking of P3 to lower the THD. I'll state again, however, that right out of the box the F5 THD% is 0.006% to 0.008% @1W into 8R

As there's still a bit of water in the workshop, I won't be able to demonstrate with a chart for a while!

So, at what point when increasing the feedback resistors, say from 2x100 to 2x200 do you have to start decreasing the 10 ohm degeneration resistors or moving up to V grade JFETs? How high of gain have people experimented with? I realize it will no longer be a F5, but I'd like to take this chance and learn a bit more about the inner workings of this circuit.

[Pistu]

best wishes for a speedy recovery! Merry Christmas and Happy New Year.😉
Massimo Bianchi🎅🎅🎅

[jacco vermeulen]

Significate che qualcuno è malato ?

[Zen Mod]

tutti qui sono ....... genere di

[Pistu]

I am sorry ... I did not read the date of the post of Nelson. Merry Christmas
Massimo