F4 power amplifier

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#2,803
WISH LIST

Nelson Pass said:


You have been exceptionally good this year, so for Xmas you get
a nice surprise.

A little bit of old and new to keep you warm through the winter.

:santa2:
Click to expand...


I for one on my wish list from Santa is a high power transcondutance AMP for Bass amp. Maybe an F100? bit of old and new!

Just any article that can help mitigate transitor addiction would be nice.
😀 😀
 
#2,805
> 600mV across 0r47 is double the current I'm now running. Am I correct?

If you are running 270mV then yes.
Maybe you should try this first before adding FETs.
You heatsink will certainly be no longer be 30 degC.
And your total current consumption per channel should then be about 4A, or 8A for stereo. I am assuming you run singled ended and not balanced.

😉


Patrick
 
#2,806
If I were you good boys and girls I would keep your eye on the Burning Amps thread:

http://www.diyaudio.com/forums/showthread.php?postid=1673891#post1673891

Seems like a likely place for some goodies to pop up.
It appears that there will be lots of opportunities for mixing and matching the various components and topographies

Nelson started calling the cases he gave away at the Burning Amp Festival "The Burning Amps" so I guess that's what they are! very 😎 : Burning Amp Mk 1, Burning Amp Mk 2,
 
#2,809
F4 and Aikido

I have moved this post from the Moskido thread:


Inspired by this Moskido thread I want to build a hybrid power amplifier with the Aikido and Nelson Pass F4.

In post 111 in this Moskido thread Kashmire suggest to remove the input FETs and biasing diodes and hook the Aikido up to the two coupling capasitors.

Doing this, how much gain (dBs) will be lost? I need to now, so I can calculate how much gain the Aikido have to replace.

Let me mention that I already have a Aikido stage ready with 6N6P i both position, and it is playing very well. B+ =200V.
Rk in first position=220 ohm in second 430 ohm. I assume a gain between 15-20??

How well will this suite into F4?



Regards

Eivind Stillingen, Norway
 
#2,810
Re: F4 and Aikido

Liliya said:
I have moved this post from the Moskido thread:


Inspired by this Moskido thread I want to build a hybrid power amplifier with the Aikido and Nelson Pass F4.

In post 111 in this Moskido thread Kashmire suggest to remove the input FETs and biasing diodes and hook the Aikido up to the two coupling capasitors.

Doing this, how much gain (dBs) will be lost? I need to now, so I can calculate how much gain the Aikido have to replace.

Let me mention that I already have a Aikido stage ready with 6N6P i both position, and it is playing very well. B+ =200V.
Rk in first position=220 ohm in second 430 ohm. I assume a gain between 15-20??

How well will this suite into F4?



Regards

Eivind Stillingen, Norway
Click to expand...
Not sure what you would accomplish other than simplifying the circuit path, which is always good. I use a dual 6cg7 Aikido into a "stock" F4 input stage with great results. About 19db voltage gain total, since the F4 does not add any gain itself.

Tom
 
#2,811
Aikido + F4

I too am running an Aikido into an F4. I am using octal 6sn7 in both positions. I have not modified the F4. The sound is very nice. My speakers are a set of Bipolar Fostex Fe127 in a Fonken design enclosure. I seem to have lots of gain with great wide band frequency. All is good.
 
#2,816
Didn't you get my email ? -- I don't believe that they have to match. I should take two very mismatched N and P channel devices and see if there is any noticeable effect.

WRT the F5 I found that by adjusting the gate resistors on the JFETs you could smooth out the response -- probably only important if your ear has the frequency response of a dog, however.
 
#2,817
jackinnj said:
Didn't you get my email ? -- I don't believe that they have to match. I should take two very mismatched N and P channel devices and see if there is any noticeable effect.

WRT the F5 I found that by adjusting the gate resistors on the JFETs you could smooth out the response -- probably only important if your ear has the frequency response of a dog, however.
Click to expand...


No I didn't. What a bummer.

So I will order one channel from you, and not worry about matching 170's between the channels.


Thanks!
I need to order quads of F5 stuff, trying to make a monoblock set for those as well. See if I can get F5 to drive F4...

Regarding Dog ears, no - I think I have tin ears, although I can hear test signals to 20k still.🙂
 
#2,819
Re: Re: F4 and Aikido

tms0425 said:

Not sure what you would accomplish other than simplifying the circuit path, which is always good. I use a dual 6cg7 Aikido into a "stock" F4 input stage with great results. About 19db voltage gain total, since the F4 does not add any gain itself.

Tom
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Hi all,

I am also intersted in a similar hybride-F4. Since I am a totally newbie to electronic, I do not understand if it is possible or not run the F4 into A/B class and gain precious power/ 8 ohm 😕

Thanks
Paolo
 
#2,820
Since I am a totally newbie to electronic, I do not understand if it is possible or not run the F4 into A/B class and gain precious power/ 8 ohm
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In order to convert a class a design to class AB, you need 3 things. Higher voltage power supply, lower bias, and more gain,
The 8 ohm power is set by the highest voltage that the power supply can provide, minus drops in the circuit at maximum power, usually just the output devices. Power = V(sq)/R Remember to convert to RMS.
Higher voltage power supply means more power dissipated across the transistors at idle. The choices are to increase heat sink, lower bias, or lower power supply voltage.
The issue with that is that class A sounds better, within its power limitations.
precious power
Click to expand...
To me, power is only precious if its quality. The world is awash in class ab amps that work OK. The F4 is about putting out a few clean watts without requiring supplemental cooling or reinforced floors.
Having said that, its possible to Bridge an F4 to get 100 watts from a balanced input into 8 ohms. If you need more than that, its probably time to look at either more efficient speakers or other amplifier technologies.

Hope this helps.

Doug
 
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