F5 power amplifier

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steve jones

steve jones

Member
Joined 2002
An amp simple enough for even a tube guy?

Hopefully a few quick questions. I'm a Neanderthal with SS stuff (still learning to walk upright I guess).

Gathering parts to build a pair of F5s to use with my Altec Model Nineteens.

I've received 2 pair of 2SK170 and 2SJ74 BLs matched at 6.7mA Idss.

Nelson just mentioned 8mA. Do I need to juggle any resistor values on the schematic to use what I've got, or is the Idss value not that critical to its circuit requirements?

Also, for the 0.47 and 100 ohm resistors, are non-inductive required (if wirewounds are used)?

Thanks,
-Steve
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
Re: An amp simple enough for even a tube guy?

steve jones said:
.........
Nelson just mentioned 8mA. Do I need to juggle any resistor values on the schematic to use what I've got, or is the Idss value not that critical to its circuit requirements?

Also, for the 0.47 and 100 ohm resistors, are non-inductive required (if wirewounds are used)?

Thanks,
-Steve
Click to expand...


there is no need to alter values of resistors;

non inductive can't harm , but they aren't so critical ; at least in my book .....

use whatever you have now ; later you can go for fancy ones
 
Nelson Pass

Nelson Pass

The one and only
Joined 2001
Paid Member
Re: An amp simple enough for even a tube guy?

steve jones said:
I've received 2 pair of 2SK170 and 2SJ74 BLs matched at 6.7mA Idss.

Nelson just mentioned 8mA. Do I need to juggle any resistor values on the schematic to use what I've got, or is the Idss value not that critical to its circuit requirements?
Click to expand...

If by chance you find yourself short on bias, you can raise the
values of R3 and R4 (or even eliminate them) to develop enough
voltage to get the bias current you want.
 
Zen Mod

Zen Mod

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Joined 2003
zenmod.in.rs/
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steve jones said:
Thanks to both Zen Mod and Nelson for the help and advise.

:)
Click to expand...


who's Nelson ?
 

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bananaslug86

Member
Joined 2007
I went out and bought the May issue. I am translating the article into modern standard Neanderthal as we speak. So far I understand that water goes down the drain, through the gate(valve) and becomes the source of many fine sounds. The rest is still magic. But since I can barbeque on a rock, I feel competent to build this amp. :D

slug
 
myhrrhleine

myhrrhleine

Member
Joined 2006
bananaslug86 said:
I went out and bought the May issue. I am translating the article into modern standard Neanderthal as we speak. So far I understand that water goes down the drain, through the gate(valve) and becomes the source of many fine sounds. The rest is still magic. But since I can barbeque on a rock, I feel competent to build this amp. :D

slug
Click to expand...

Those little things are homes for magic genies
so long as they are kept inside, they work their magic.
But if one escapes (looks like smoke) then things stop working ;)
 
dfdye

dfdye

Member
Joined 2005
Re: F5 article

Nicola said:
Argh, the postman is putting his life at risk, i haven't received the April release of AXP yet. Would anybody accept to mail me a scan or when might it be available under FirstWatt ?
Click to expand...
Wow! I ordered a brand spanking new subscription and already got the May issue. I haven't had time to sit down and read it yet, but it is indeed sitting on my desk right now. :D

You definitely need to sit your postman down and have a little "chat".
 
D

darian

Member
Joined 2006
Hello everyone,

Sorry to be annoying but that's funny how no one did give a damn about the Profet schematic in it's time despite the rave reviews by audioXpress... So it's all by a well-known french designer named Plantefeve and he's got a nice website about amplifiers too. So, as he was somehow the first to introduce this design, I invite you to have a look at his page. Just to give him a little thumb up for that. And yes, he also has a low impedance feedback version of it...

Just my 2 cents

Thanx
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
zenmod.in.rs/
Paid Member
darian said:
Hello everyone,

Sorry to be annoying but that's funny how no one did give a damn about the Profet schematic in it's time despite the rave reviews by audioXpress... So it's all by a well-known french designer named Plantefeve and he's got a nice website about amplifiers too. So, as he was somehow the first to introduce this design, I invite you to have a look at his page. Just to give him a little thumb up for that. And yes, he also has a low impedance feedback version of it...

Just my 2 cents

Thanx
Click to expand...


that's how things works ;

anyway - for curious ones , Profet and Plantefewe's work is well known ;

you'll see (if you search) that his schematics are sorta often cited here

in any case - hat is certainly often off , regarding work of eccentric French constructeurs ....... ;)

not to mention that you have some of nicest loudspeakers in recent history ..... (meaning on Cabasse oldies, Triangle , Supravox, Fertin)
 
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