While analyzing the circuit and testing my first tube/hybrid headphone amp, I rekindled my love for tube based audio. Sure tubes distort more than transistors, but that's also the main reason they sound more natural and pleasing than transistors. Tube distortion is mainly of the even harmonics (for a 1kHz signal, 2kHz, 4kHz, etc.), transistors distort mainly the odd harmonics (3kHz, 5kHz, etc.). Even harmonics are musical intervals of the fundamental and of each other. Odd harmonics aren't musically related so they sound more harsh and unnatural. So transistor hi-fi has adopted the theory that they just need to apply tons of negative feedback to reduce all distortion to near unmeasurable levels. Ok, now you have a completely sterile amp which does it's main function of amplifying, but has no character of it's own. Fine for some listeners, but I really like the dynamic and organic sound of tubes, including a splash of second order distortion.
Once we had our headphone amps, both my friend and I both started thinking about how cool it would be to create a tube based hi-fi power amp. I started reading everything I could about tubes, tube theory and amp designs. I purchased some software to model the driver stage, the output stage and the power supply. Soon, I was obsessed with designing, prototyping and building my own.
I decided I "needed" a good amp of a similar design as a reference to know how my prototype compared. I found a great deal on a Cary SE-1. It can use either 2A3 power tubes or 300B. Both sound amazing yet have their own distinct character. The 2A3 is probably a better all around sound, very detailed and great imaging. The 300B has a darker, warmer feel. Now, I'm really hooked on tube audio and look forward to chance I get to go into my man cave and rediscover classic old albums.
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