First Watt F8

[EUVL]

Finished PCB on heatsink.


Patrick

.

 

[Dennis Hui]

Very nice. It's always good to see a sim matching up to reality.

Cheers,
Dennis

 

[EUVL]

That was a Canadian effort, not far from you.


Patrick

 

[marconi118]

why 2SK3497?
A simple IRFP240 will work?

 

[EUVL]

Already explained years ago in the J2 thread.
FirstWatt J2
FirstWatt J2


Patrick

 

[marconi118]

nearly impossible to find 2SK3497
any FQH44N 20S
FQA28N15 7S
could do the trick?
or even a irfp150?

 

[twitchie]

Thanks for postulating a DC variant and sharing it Patrick!!!

A simple IRFP240 version will work but the IRFP150 is even better (than the IRFP240).

Something in the back of my mind keeps asking me why would Papa go single rail and coupling caps for the F8 when it is a small change from the J2 to this? Did he leave the door open on purpose or are there undiscovered mysteries and a trail of clues left behind still?

 

[Zen Mod]

Papa's Ways, mysterious ones!

 

[EUVL]

To do the DC version properly, you need to change the feedback network resistor values to suit the JFET Idss.
OK for DIY, but not necessarily what you want to do in production.


Patrick

 

[twitchie]

Thank you Patrick!

 

[marconi118]

would it be possible to do a DC version "a la UDNESS" using a N Jfet (2sk209) and P mosfets at output FQA9P25?

 

[EUVL]

Yes.


Patrick

 

[twitchie]

That would be strange

 

[marconi118]

this would be great for all not having J74 and SJEP120 on hand

 

[Dennis Hui]

That would be strange

There are stranger things...

 

[EUVL]

The UDNeSS has the advantage that it has differential input.
So you can play with inverted input signal and reversed speaker polarity to get reversed H2 phase.
This you cannot do with a "F8" variant.


Patrick

 

[marconi118]

DC coupled "F8" has already the beloved negative H2 phase?

 

[jens r.]

would it be possible to do a DC version "a la UDNESS" using a N Jfet (2sk209) and P mosfets at output FQA9P25?

As a first step in Spice, I've been trying for a few days to simulate a version with readily available components from the work of Patrick. However, that is far from finished, maybe someone here would like and above all know more to develop this further?
Best wishes
Jens

 

[EUVL]

The challenge is dual rail, DC coupled.


Patrick

 

[jens r.]

I have great respect for your work and your philosophy, but I find the approach of an amplification of equal to one with DC voltage charming.