For some time I wanted to build something using 6V6 tubes, so when I found a nice pair of NOS 6V6s at a flea market, I took the opportunity. I also wanted it to include a phono input for an MM turntable but remain simple to build. I therefore decided on a very straightforward single-ended design using a 12SL7 at the input (one triode per channel) and 6V6GT tubes strictly connected as pentodes in the output stage. The output transformer is the well-proven SE5K6-UNI. For the phono section, I built a small discrete solid-state preamplifier specifically for this project.

Let’s start with the phono module, designed exclusively for MM cartridges:

Here is the spectrum analysis of the standalone RIAA module:

The amplifier was assembled on a wooden frame — below you can see the build process:

And here’s how it looks from the outside:

The tonal character of this amplifier was intentionally made (by circuit design) less bright and rounder in the high range, as I wanted to use it with high-efficiency speakers (Klipschorn Heresy) with horn tweeters. The feedback ratio is minimal, since these speakers are known to be somewhat lacking in the low range.

Measurements
Power: 2.85 W RMS per channel @ 3 Vpp input
Damping factor (DF): 4.0
THD @ 1 W: 0.5%

Frequency response @ 1 W (line input)

Frequency response through the phono preamp (reverse RIAA applied, phase omitted as it is inverting)

Square wave @ 1 kHz and 10 kHz

Spectrum analysis @ 1 W (line input)

Spectrum analysis @ 1 W (phono input)

How does it sound? The bass is definitely there, and the volume is impressive — with just 3 watts, the room fills with powerful, pleasant music. Highs and lows are both well defined, voices are warm and present, and you start wondering why anyone needs more powerful amplifiers. I paired it with the USB Mini DAC and started with Beethoven’s Ninth Symphony — which honestly sounded awful (probably a poor CD), but then I tried Vivaldi’s Four Seasons and, together with my friends — including a professional orchestra musician — we all fell silent, amazed by the beauty of the sound. Then I played Pink Floyd and other bands, as well as modern singers — everything sounded rich and enjoyable. I brought the amp to some friends’ houses and tested it with various speakers, including JBL LX66, and it always sounded delightful — with the floors vibrating from the bass. In short, a project I’m truly proud of.