4P1L PSE Amp Finished!

I’ve been travelling a lot lately so haven’t had the chance to update on this project. A couple of weeks ago I finished the 4P1L PSE Amp:

4P1L PSE Amp

The amp is outstanding, just like previous incarnations and tests I have conducted over the years.  The level of detail and tone is unique. This is what I always loved from the 4P1L. I’m running it very hot (70mA per pair) and the output transformer is Amorphous Core 3K2 (more detail to be shared soon). It’s a simple stage with filament bias, so no cathode capacitor. The filaments are wired in series to reduce the heat dissipation. Despite this adds a bit more on the output impedance, the bass is powerful. I’m very surprised with the bass, but the level of treble is amazing. It goes over 40-50kHz, I will still need to undertake the classic measurements but so far is great!

It’s absolutely dead quiet. No traces of hum. 

Some more pictures below:

Glowing 4P1L and filament resistor stack!

And the full system below: