Audio Note P1SE Amplifier

Grzegorz 'gsmok' Makarewicz (May 11, 2013)

A cool tube amplifier with a rather unusual mechanical design for our times – everything, including the charmingly glowing tubes, is carefully hidden inside a black chassis. Since there are so many photos of this amplifier in a closed case, I decided to use a disassembled, unretouched image as the cover photo (the dust covering the components is as authentic as possible).

Below is a photo gallery, in which I tried to capture as much detail as possible. The amplifier isn't completely "virgin," or as the jargon goes, "tangled inside." There are some minor signs of tampering here and there. This doesn't change the fact that for anyone seeking inspiration for the circuit and mechanical design, the photos shown may be helpful (at least I hope so).

The amplifier offers 10W of power and is part of the OTO SE amplifier circuit. Below are diagrams of the amplifier itself and a portion of the power supply. As you can see, the amplifier is a two-stage design, with an SRPP pre-stage using an ECC83 double triode and an output stage using parallel-connected EL84 tubes.

And now for the design details – nothing can be hidden. The electronics are housed on two printed circuit boards: a larger one housing the amplifier components (both channels on a single board), and a smaller one housing the power supply components (rectifier and filters). These are complemented by two robust output transformers and a mains transformer.

The top-down shot below clearly shows all the components mentioned above. The additional shield between the power supply and the amplifier board is also visible.

And here's the amplifier's printed circuit board itself. Solid, thick laminate and equally solid, thick signal traces.

Now it's time for the power supply section, with the mains transformer and the printed circuit board with the bridge rectifier and filter capacitors. The white ceramic resistor is like a "guest from another world." This resistor doesn't quite match the other components visually.

And here are the output transformers. This is an SE amplifier, so the transformers have so-called gaps (visible in the photo). These transformers are responsible for the amplifier's excellent sound. The manufacturer is renowned for the quality of its transformers. Their quality is matched by a price that is literally jaw-dropping.

The potentiometer, like the previously mentioned resistor on the power supply board, does not look original.

Unfortunately, this isn't a very successful modification. Perhaps the original potentiometer was damaged.

Finally, a few photos from the outside, but still with the housing cover removed.

I really like this amplifier. The design is quite old, so you can buy a used one, so-called second-hand. This can be a very good investment. Before buying, it's worth making sure the amplifier hasn't been modified. In my opinion, the less "tampered with," the better. And finding such an untampered example isn't easy, as these amplifiers are often subjected to various audiophile modifications. I think one reason is the easy access to the internals. I've seen units with coupling capacitors comparable in size to transformers. Fortunately, most of these modifications can be removed and the amplifier restored to its original condition. 

Author: Grzegorz 'gsmok' Makarewicz