F5 power amplifier

[EUVL]

That is one way.

Another is to cascode like Borbely using JFETs, which is much simpler.
In this case, because of the 4mA or so bias, I would recommend using J111 / J174 as cascode devices (instead of 2SK246 / 2SJ103).
You should get a good 5V Vds on the Toshiba's then.

And yes, have done that many times in various circuits, including my AX-J 100W.


Patrick

 

[bobodioulasso]

Erno Borbely article:
http://www.borbelyaudio.com/adobe/ae599bor.pdf
http://www.borbelyaudio.com/adobe/ae699bor.pdf

 

[tinitus]

hi all
is the f5 scalable to higher power levels like the aleph series of amps

say more output devices and voltage with bigger sinks to match

if so would 100w into 4 or 8 ohm be doable

im currently using 2x f5 to biamp some esl and i love the sound at low volume but they do struggle at anything over half level

i know the f5 is not suitable to drive my esl but the sound is so nice id prefer to look at ways of getting more power than to build another amp

cheers

It wont be an F5 anymore, and the sound you like may be gone too
I fear the same even with just double output pairs
I suppose that just the slightest change, and it will sound different

Maybe you need a good 60-100watt, class AB and 1ohm stable
I will probably get shot for saying that

 

[bobodioulasso]

In my opinion, the best way to increase power is to use an electronic crossover and as many F5 as there are voices.

 

[tinitus]

Ehh, in some cases sure, but I would say that really depends

Anyway, that could be a lot of power consumption, and still 25watt

 

[bobodioulasso]

still 25watt

Not true, and there are many other advantages to go this way.
Though this is quite a long story...
http://sound.westhost.com/bi-amp.htm
See all the article and specially go to:
1.4 - Actual vs Effective Power

 

[pro]

My main system, with a 50W gainclone on the low (12" W 300 hz) and a trans 10W zenV4 on the high(5 1/4 full range) , active crossover and 92 db efficiency, sounds loader then 100W 90 db 2 way loudspeaker

 

[AndrewT]

Ehh, in some cases sure, but I would say that really depends

Anyway, that could be a lot of power consumption, and still 25watt

if music were a single frequency, then multiple amps and multiple speakers would be no louder than a single amp and speaker.

But we all know that music is not a single frequency.

 

[bobodioulasso]

I use a 3 way active crossover.
1 x F5 for highs from 2khz
1 x F5 for mids /low mids from 120hz to 2khz
2x150w class ab for closed subs under 120hz.
Average efficiency is 92db

I can -in my home- hardly reach the power limits.

...I was forgetting: that sounds fantastic!

 

[tinitus]

Not true, and there are many other advantages to go this way.

I know
And sounds like impressive setup
But you also admit to use 150watt AB on woofer, which was my point, sort of

Though. when I suggested paralel output transitors with slightly raised bias, it was turned down with " no more power and still 25watt"
Kind of same thing
As would be a more powerful power supply, mono amps etc.

Though I understood it was about having more power to drive ESL
And thats what I relate to
I asked for impedance specs, but no reply
I dont know if active crosssover and multiple amps is a possible option with ESL
We may misunderstand each other

I plan to do 2way, and use F5 to drive a compression driver/horn, and AB amp to drive 18" woofer
So we do agree, sort of

 

[bobodioulasso]

I must admit i forgot this was about ESL, sorry.
Can't you help me to find the right post?

 

[tinitus]

Dont worry
It was interesting
Must be because we dont have the 100% clean answer to it anyway

 

[tinitus]

Can't you help me to find the right post?

Starts from post 4366

ESL
Isnt the problem having very low to infinite impedance

 

[bobodioulasso]

Is'nt a current feedback amplifier better for ESLs ?

 

[pro]

I don't think so. A current feedback is good for an impedende as much flat is possible. With an infinite impedence, the voltage swing will clip at very low volume.

 

[bobodioulasso]

Such as a voltage feedback amp will give zero current into an infinite load.
Aren't Quad amplifiers current feedback?

 

[pro]

I don't know if we mean the same thing. If current feedback means transconductance or very high output impedence, then as the load goes up (at risonance for exemple) the current remains constant, while the voltage follows the impedence.
Or not

 

[bobodioulasso]

yes, output current is proportionnal to input voltage in a C.F. amp.

Some amplifier designs mix the two kinds of feedback.

http://pagesperso-orange.fr/jm.plantefeve/systeme.html

see: Voie "médium" à contre-réaction mixte

 

[Nelson Pass]

I don't think so. A current feedback is good for an impedende as much flat is possible. With an infinite impedence, the voltage swing will clip at very low volume.

If you read the article, you may discover "current feedback" is
misnamed, and really is more like low impedance voltage feedback.

 

[bobodioulasso]

Hi Nelson,
We were not saying that the F5 is a current feedback amp but discussing about the benefits of such an amp (CFB) driving ESL speakers.