F4 power amplifier

[Nelson Pass]

Originally posted by bogdan_borko
As I can see, the bias current trough the resistors network for the mosfets gates is about 1.4mA. Some wold say that`s funny! You have to drive the gate`s capacitances (3*IRFP240).

Of course that is the DC value, but the JFETs are capable of
sourcing quite a bit more AC. How much do you think you need
here in order to sound good?

As to the matching thing, please note that the parallel devices
are matched - we have been referring to the (mis)match between
P and N types.

[Nelson Pass]

Originally posted by Jon Ver Halen
Nelson, with his greater experience, may be better able to describe all of these amps.

Not likely. I think I'm just going to quote you from now on.

[eLarson]

Like asking which kid is favorite, eh?

[bogdan_borko]

Sorry my mistake. Sometimes a man can`t see a tree even if it`s in from of him...

I`m working right now on my own design (voltage amplifier + current amplifier(follower) and I`m wondering wath is the best choise for voltage amplifier. I need 18V peak to peak and input impedance of follower is about 50K. I was experimenting in simulator with a one stage nfb single ended voltage amplifier with heavy local feedback working with +250V and results are very very good. I made it in practice and the sound is magnificent. The only "problem" is that is capacitor coupled.

I could post the schematic here if anyone interesed...


cheers!

[TJ]

Hi , i like to make some mod on this amp ,will anyone like to help me ? i have a lot of amplifier transformer ( Marantz ,Hk pioneer) most of them have ~ 45-0-45 vdc @ 4A , can i use on F4 ? and i like to reduce the bias to class AB and use only 1 or 2 pair output mosfet . possible ?



btw ,to be honest , i like all the diy amp design by Mr Pass , but that kind of amplifier not practical , waste too much . (u can build it but u cannot enjoy it ) !!! and how many people on earth can afford big horn speaker ? i rather stick with Class AB and not all in this Class are rubbish .Some are better than Class A .

[apassgear]

TJ,

You are an old member, and have learned that most all amps on this side of the forum are class A. What you are proposing is a completely different animal and IMO not recommended.

On the Solid State forum you will find hundreds of nice class AB amps with those rail voltages, if I were you I would stick to those. No offence intended.

[Babowana]

Originally posted by TJ


btw ,to be honest , i like all the diy amp design by Mr Pass , but that kind of amplifier not practical , waste too much . (u can build it but u cannot enjoy it ) !!! and how many people on earth can afford big horn speaker ? i rather stick with Class AB and not all in this Class are rubbish .Some are better than Class A .

There are many good speakers offering high efficiency.
Many music lovers like such speakers and want to drive them
with good amp.

Papa is offering us elegant amps free.

Why a devil should complain?

[Zen Mod]

Originally posted by Babowana




There are many good speakers offering high efficiency.
Many music lovers like such speakers and want to drive them
with good amp.

Papa is offering us elegant amps free.

Why a devil should complain?

you are (same as really You are) right with these..........
but I can't to not see that you are grumpy lately?

[Babowana]

Originally posted by Zen Mod


but I can't to not see that you are grumpy lately?

Thanks, Choky, for making me look back myself.
I agree that I have been grumpy recently here and there.
I apologize to all nice and friendly people here.

And, I hope this thread will be no more polluted after this.

[GRollins]

I thought it was my job to be the grump!

Grey