Mosfet amplifiers including Susan Parker Zeus amplifer

[nige2000]

whats the signal path then

buffered line level into 1:10 transformer into tk buffer into tweeter ?

[abraxalito]

For the 'turbo tweeter' amp it needs more volts into the step-up trafo than normal line level, it'd need 20V peak to peak. Then a step down tweeter trafo between amp and tweet.

[nige2000]

Ok with u now
Gain stage to get to 20v or use two trafo buffer combinations to get to 200v signal?

[abraxalito]

I was thinking that coming from a normal line level into your active XO there should be a step up so the XO is running 20V swing. Then for the step up to the 'turbo tweeter' amp the level is already OK. The bass/mid amp probably won't need more stepping up unless you're after higher power. If you do need more power then the XO could be built with 40V FETs, 40V swing should be enough for anyone!

[nige2000]

Is the gain stage in place of the stepup trafo going ahead ?

[abraxalito]

Yeah the gain stage is about 70% built just I've gotten distracted into optimizing the step-up transformer now...

Its running now - first thing to attend to is as level a playing field as I can manage, since the trafos provide isolation as well, not only gain. I'm noticing some sibilance which wasn't there with the trafos but that's reduced significantly by feeding I2S to my DAC from a media player (isolated) rather than my PC.

Not happy with the first pass SQ - compared to the transformers its flatter, less involving, a bit harsher on more complex material. A bit like the trafos when their outputs weren't buffered. I have some tweaking ideas to apply, firstly to the PSU then other minor adjustments - if those don't work then I shall experiment with a no GNFB design.

Much improved now - needed extreme decoupling on the supply (multiple paralleled ceramics) and a series inductor. Still going to go ahead with trying out the no-GNFB design though. Subjectively this transistor (FET and BJT) gain stage gives the amp a tad more bass 'heft' than the trafos do.

[nige2000]

Yeah the gain stage is about 70% built just I've gotten distracted into optimizing the step-up transformer now...

im hoping your gonna come back tell me i dont need to make transformers, leave the winder in the shed:)

[jkeny]

Yeah the gain stage is about 70% built just I've gotten distracted into optimizing the step-up transformer now...

im hoping your gonna come back tell me i dont need to make transformers, leave the winder in the shed:)

:)

[nige2000]

Any news?

[abraxalito]

I'm enjoying the sound now with the tranny gain stage. I'll send you the schematic after I've tarted it up to show the real component names (rather than LTspice models). Its using a fairly small MOSFET as the input (to get the input C down) - are you OK with soldering sub-SOT-23 packages?