F5 power amplifier

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#4,442
bobodioulasso said:
:scratch: and :scratch: and :scratch:
So, how do you call the kind of feedback described by the second drawing?
Click to expand...
Depends on the amp being used. I guess you rather mean what the effect of the feedback is called as seen from the load's perspective, not the feeback itself:

a) is constant voltage (drive impedance = 0)

b) is constant current (infinite drive impedance)

@Andrew: yes, one also can make negative output impedance. The whole span of possible output impedance is possible, from -infinity through zero to +infinity. One of course has to take care of system stability, with negative output impedances espcially.

EDIT: Take a look at this article from Rod Elliott:
http://sound.westhost.com/project56.htm

- Klaus
 
#4,443
KSTR said:


... except that you chose to personally redefine the commonly accepted term in engineering that "current/voltage feedback" stands for. This only adds to confusion, especially for less experienced readers.

- Klaus

Click to expand...


I refer my info to "Malvino, Electronic Principles, 5th Edition, McGraw-Hill International Editions". I have not used any personal definitions at all.

If you can borrow this book from your library, go read the book from page 656 to page 691. It will help.

🙂
 
#4,444
Standard textbooks can also be wrong, or better said, define things differently.

The european standard, Tietze/Schenk "Halbleiterschaltungstechnik", as well as many online resources define the term in the way I use it.

Issue cannot be solved this way, it seems.

- Klaus
 
#4,446
Oh c'mon, how could I know that you have a textbook that defines things different to the "mainstream"? So it looked like you were defining things on you own, to me, at the point of when I made that statement. Nothing personal, anyway.

Can we leave it at that?

- Klaus
 
#4,449
Re: Re: Balanced F5

bobodioulasso said:


I am not shure what you precilely ask but it seems to me that you have to
-either use a balanced F5
-or to convert into an unsymetrical signal. Transfo or opamp.
Click to expand...

- or you can go for Michael Rothacher's Amazing Circlotron, an amp derived from F5 that has a balanced input only.

Nelson said it'a a cute design. 😉

http://www.audiohobby.com/
or
http://www.passdiy.com/default.html
 
#4,451
Hi all
I built one channel of the F5, and now it's under test.
I have some problems. I am running the bias at 350 mA, becouse I have not jet enough heatsink, but I think it should work well.
The problem is that the offset that is 0 mV at idle, rises at about two Volts at clipping, that is about at 18 V when I give a sin wave of 1 KHz. Rails are +/- 23.5 VDC. That without load.
If I connect the load (8 hom 100W resistor), the clipping arrives at 8/9 V and the offset rises at 10 V or so.
Could please anybody give me some advice on this problem?
Thank you

Some pictures of the device under test 😀

[
An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
#4,455
Thank you for answear.
Caps are just DC filtering, can that be a problem?
Yes Papa, the positive wave start to clip and more the volume goes up more the negative wawe decrease, without clipping, until DC is reached. But that just under load. Without load both clips at 18VDC and offset rises at about 2 VDC.
Where have you seen tweeters Bobo?
 
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