Well, here's my latest F5 in operation -- I now have 8 F5's in operation including some for which I did the PCB's by hand -- this version has some stuff I've found necessary or helpful over the years -- I provisioned parallel surface mount JFETs -- pairs of mmbf5460/mmbf5457 which get you close to the J74/K170 and are very inexpensive -- P3 is there of course as well as mounting holes for paralleling in various source resistors.
I put some local capacitance on the board -- when testing these amplifier with long leads you invariably get some oscillation. The RFI mitigation cap and output zobel aren't strictly necessary until they become necessary.
I constrained the board dimensions so that it would fit in the chassis/cases which the DIYAUDIO store is offering, although I roll my own.
I put some local capacitance on the board -- when testing these amplifier with long leads you invariably get some oscillation. The RFI mitigation cap and output zobel aren't strictly necessary until they become necessary.
I constrained the board dimensions so that it would fit in the chassis/cases which the DIYAUDIO store is offering, although I roll my own.
An externally hosted image should be here but it was not working when we last tested it.
I wanted to add P3 to my project. I'm a little worrried about causing extra noise, oscillation etc. if the pot is too far from the input FETs.
Here's the schematic to go with the revised board:
An externally hosted image should be here but it was not working when we last tested it.
The changes to the F5 circuit are in the F5 tubo manual. I just figured they are the latest therefore they must make it better.
John,
I see you haven't included the provision for the small value gate stopper resistors (47R & 68R) and filter capacitors on the input jfets, as in your early design with the double sided board?
Did you find these additions to be counter productive?
Is it possible to line the power resistors up "sideways" to attach the Caddock style (TO220/247 packages) power resistors to a common heatsink thru the centre of the board?
And perhaps adding a Cmultiplier/simple zener regulator onto the ends of the board with room for 25mm power supply caps?
I see you haven't included the provision for the small value gate stopper resistors (47R & 68R) and filter capacitors on the input jfets, as in your early design with the double sided board?
Did you find these additions to be counter productive?
Is it possible to line the power resistors up "sideways" to attach the Caddock style (TO220/247 packages) power resistors to a common heatsink thru the centre of the board?
And perhaps adding a Cmultiplier/simple zener regulator onto the ends of the board with room for 25mm power supply caps?
Good idea. The way i have it setup is as a voltage divider for no useful reason! My bad.