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OllBoll
diyAudio Member

Join Date: Nov 2010
Quote:
 Originally Posted by Lazybutt Everything is possible within reason... or rather ... within components specs. With such a simple circuit, you can play with U and I by just playing with components values. Just check Umax and Pmax of every components, and keep a safety margin. I is set by R16//R17 in the current source... if it's not obvious to you (it wasn't to me), read the Zen Amp series articles to understand how, but in essence, increase R16//R17 to reduce I

I've read the Zen articles which is what gave me the idea since Nelson experiments with lots of different voltages and the F2 is if I remember correctly based on the Zen. I'm no electronics expert though so I thought I'd also ask to be sure

So now another question if someone knows, is current linear in proportion to R16/R17 or is it some exponential whatnot such that I ideally need a pot to dial in amount of current?

cochleus
diyAudio Member

Join Date: Oct 2009
Location: S.E. Michigan
Quote:
 is current linear in proportion to R16/R17 or is it some exponential whatnot such that I ideally need a pot to dial in amount of current?
It is inversely proportional. That is; I=0.66/R or, R=0.66/I
Read first Zen article for describing this type of current source in better detail.
__________________
"It always comes down to the best guess..."

 13th July 2012, 06:19 PM #453 cochleus   diyAudio Member     Join Date: Oct 2009 Location: S.E. Michigan In other words it's just simply Ohm's Law. R16/R17 are current sensing resistors. The circuit is designed to keep the voltage drop across R16/R17 at 0.66V. __________________ "It always comes down to the best guess..."
 2nd December 2012, 02:42 PM #454 kingludd   diyAudio Member   Join Date: Dec 2012 F2J DIYer needs help Hi, I've been a 2A3 amp user a while but like to go SS with the F2J...... keep hearing about boards available from Daniel.. how do I get in touch with him ? And is Bias adjustments etc. requiring a lot of equipment ? Lot of Thanks, Mike
 2nd December 2012, 02:59 PM #455 flg   diyAudio Member     Join Date: Jul 2005 Location: North East Audio Sector - diyAudio Peter Daniel Or PM from the Forum __________________ "It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
 2nd January 2013, 03:44 PM #456 OllBoll   diyAudio Member   Join Date: Nov 2010 Hello there again, I'm considering adding an input transformer since I have a balanced source. If I've understood correctly the Jensen JT-11P-1 works well for this area. So now the question: The Jensen is 10k:10k, and the F2J has 10k input impedance so I should just hook up the trafo before the F2J without putting any extra resistors on either side? Thanks in advance, Olle
 2nd January 2013, 07:42 PM #457 Zen Mod   Official Court Jester diyAudio Member     Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain most probably don't be lazy - put link to datasheet , so we can check it together __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
 2nd January 2013, 08:17 PM #458 OllBoll   diyAudio Member   Join Date: Nov 2010 Forgot that =) http://www.jensen-transformers.com/datashts/11p1.pdf
 2nd January 2013, 08:41 PM #459 Zen Mod   Official Court Jester diyAudio Member     Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain just go with typical application pic , having R1+C1 combo across secondary __________________ my Papa is smarter than your Nelson ! clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa...© by Mighty ZM
 16th January 2013, 07:05 PM #460 OllBoll   diyAudio Member   Join Date: Nov 2010 Just powered up and measured my F2J with the input trafo and 48V rail voltages and halved current Max clean output @ 8 ohm is ~ 4 Vrms so 2W if I've understood correctly. Much more than 24V but still not a lot and hoped for more, I think it will be enough though since it will drive 300 and upwards with 94 db efficient drivers.

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