DIY F2 clone

[OllBoll]

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

Nice, thanks for answering =)

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]

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.

[cochleus]

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.

[kingludd]

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

[flg]

Audio Sector - diyAudio
Peter Daniel
Or PM from the Forum

[OllBoll]

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

[Zen Mod]

most probably

don't be lazy - put link to datasheet , so we can check it together

[OllBoll]

Forgot that =)
http://www.jensen-transformers.com/datashts/11p1.pdf

[Zen Mod]

just go with typical application pic , having R1+C1 combo across secondary

[OllBoll]

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.