This is a lovely Abraxas Audio 6EM7 SET speaker (8 ohm, OPT-coupled) and headphone amplifier. Built by Jeff Larson, who many of you may remember as the erudite EE who has built more diverse, high-quality custom amps than any other DIY-er, now (sadly) retired. He was driven to try new designs with the less-often used tubes. This is an example. This was not his first 6EM7 build, so it's not an 'experiment'. Check out the build. The high attention to circuit detail and symmetry, the quality of the build and exterior aesthetics of wood, aluminum and professionally-painted bell covers synergize into a piece that looks and sounds special. For a DIY build, this is a work of art. It sounds fabulous on all dynamic phones I have owned (HD 600/650/700, Beyer DT990-600 and T90, AKG 701/702 and Shure 1840). I would not use this for planars, because I have found they just sound better on SS head amps, because speaker amps have too high output impedance values (here 8 ohms), which requires higher impedance phones (ideally, 80 ohm and up). Furthermore, because of the low damping factor, tube amps do not do well with planar phones, unless the amp is over-powered (e.g., ~10 watts or more). I have well over 1,000 positive feedbacks in total, on all the usual sites, under this same name, and never any negative feedback. TERMS CON-USA only, Paypal only. I will not respond to unsubstantiated audiophiles, unless they provide their email or use-name on Audiogon (apology), or here on AA and have posts or feedback. It weighs around 7 pounds and is a very solid build. Will come with A-NOS RCA, GE and Sylvania 6EM7 tubes pairs (I believe in original boxes for all 3 pairs, and all test NOS). Thank you. More detail below. _____________________________________________
_____________________________________________ DISCLOSURE: It's my policy to give more-than-full-disclosure up front in any for sale ad. The 6EM7 tube has two dissimilar triodes in one envelope. The lower power side is like a 12AX7, while the higher power side of the 6EM7 has similar electrical properties as the 2A3, except indirectly heated. My experience with 2A3 amps on HE speakers is good; but with headphones is NOT GOOD, because of the problem of hum. Ever wonder why there are no 2A3 headphone amps out there? The reason is hum. Remarkably, with headphones, this 6EM7 amp is dead quiet on the left channel and almost-dead quiet on right channel. Remember, we are talking headphones that have up to 1W/103 dB sensitivity. The hum on the right is so low on high efficiency phones that you must have the source on pause, and be in a dead silent room, and not be near a computer, or near a street with traffic flow (if with open phones), and you have to concentrate to hear it. I have a lot of DC in my home, and that might be the cause. If you plan to use this for high eff. speakers, even in a small room, or in near field, it will be dead quiet--guaranteed--unless you put your ear up to the woofer or full-range driver, as if it were a headphone. If you plan to use this with dynamic phones, the hum will not be an issue, I guarantee it, unless the phones are very efficient and low impedance (e.g., IEMs). Pedantic Footnotes:
Zero-noise from transformer-coupled amps is rare with headphones--if it exists at all. MOTE: I am being maybe 'overly' honest. A retail outfit cannot be that way. A builder will place resistors in-line with the headphone jack to cover up noise, which is a terrible idea, especially with lower-impedance phones. Another common approach is to use SS in the power circuit--a hybrid approach. Personally, I would have use all SS or all tube in am amp. If I want 'tubiness' with SS, I'll sue a tube preamp, if I use a preamp at all. Another approach is DC heaters, which adds expense and size, as do chokes. Effective, but now you are looking at $3K and up in cost. Finally, some manufacturers will cheat and actually use a separate headphone circuit to achieve dead quiet--but they will not disclose this, that a separate HP amp is built within the main amp. That's just dishonest. Thank you again.
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