Puppy Power 3
Puppy grows up

700mW single-ended power amplifier

2001 Jim de Kort


This is the last installment in my Puppy Power amplifier. The third version gets rid of some compromises that I made earlier in the power supply. The driver stage has been replaced with the KC3 which gives a lot more gain than the 31 did and also sounds a bit better. The 31 sounds more open and transparent, but a bit too fresh. The KC3 is very sweet sounding, a bit less in the highs. It's a matter of taste I think.

The battery B+ supply made way for the standard rectified supply since I am using the battery supply for my preamp. The Puppy Power 3 is making way for my new amps, Exodus, and will serve as back-up amps only from now on.

The filaments are all fed by rectified DC now, running on current regulators. The battery on the driver filament gave me some hassles after not using them for a period of time (I don't have built in chargers). As these amps will be on the shelf once my Exodus amps are complete I do not want to have a battery draining away in these amps. The 71A now also has a better filament supply than it had originaly. Plenty of room in voltage and current, less hum.

Due to the better power supplies I have extra voltage on the 71A. This allows for a higher voltage swing over the primary, thus giving more output power. Well... I doubt you will hear the difference though, it's only about 100mW extra :)))

I used a spare 4V winding for the KC3 filament supply. This required me to use a low drop regulator. Even still it is quite a squeeze, not much voltage headroom left.

The chassis will undergo a nice cleaning as well. The rush paint job that I threw on last year will be blasted off making room for the copper underneath. It will be "pearled" to give a very fine matt surface. A few layers of transparent lacquer should keep my fingerprints off of the copper.



Signal section, about 1Vrms input sensitivity.

 


The B+ supply

 


And the filament supplies



Filaments using batteries before the supply mods.


Close-up of the 71A and KC3.