First watt F2j with SJDP120R085

[e_fortier]

That doesn't really answer my question but thanks.

 

[Zen Mod]

sorry

yes , you can decrease Iq , simply because for 8R load , PSU voltage is limiting factor for power , not current

in fact - just build ACA (with later mod for slightly higher Iq ) and you're good

you have pcbs in store etc ....

you can take ACA as later, improved F2

 

[e_fortier]

Thanks ZM,

Not looking for much power, simply try to reduce dissipation if possible.

I have build an ACA already, the 19Vdc with 2k2 mod and the 24V version with no mod.

ACA (24V version) is roughly 30W dissipation. This is great for my needs.

For the F2, do you have any idea of the Iq I should be aiming for for a 8 ohm load and what components to change to get there. Sorry about all my questions.

BR,
Eric

 

[e_fortier]

Can anyone help answering last paragraph of above post (no.83) ?

I'd really like to go ahead with this amp unless it's dissipating 75w per channel at idle.

Thanks
Eric

 

[woody]

Yes it does idle at 75 w per channel. The 2 .47 ohm resistors set the current source at
about 3A. and that X the 24v power supply gives us ~ 75W.

 

[Zen Mod]

5W/8R demands voltage envelope of 17V9

remember that we are looking at things in peak to peak realm

current envelope is (from zero to) 17V9/8R=2A21

half of that is where Iq lies

so , Iq needs to be 1A1 , minimum

practically - same conditions as with ACA without Iq mod

anyway - that's how my brain is working today

I think it's time for second coffee today

 

[Zen Mod]

easiest way of changing things is - remove one 0R47 resistor on top ( either R16 or R17)

readjust with P1 to have plus side of C3 where it was (vs. GND)

that will halve Iq and dissipation

 

[e_fortier]

Thanks !!