I don't intend to necromance, but I think there is a fundamental misunderstand of the nature of what "balanced" means in this context, and I would love to correct it for future understanding for anyone who reads this should Massdrop re-drop this. "Balanced" means that it is outputting two signals 180 degrees out of phase. Instead of just two pins on your headset per channel, there are instead 3, 2 voltages and a dedicated ground path (in a 4-pin XLR setup, there are +/- pins for each speaker and a shared ground path whereas a single-ended output has a + for each speaker, but the - is wired to the ground, which is itself wired to the cable's Faraday shielding.) At the speaker, the voltages are re-phased so that any noise collected along the way gets "diffed" out. That's ALL "balanced" means. Now there are SEVERAL ways you can produce a "balanced" signal and several places where you can generate the 180-degree phase shift before transmitting it to the output stage in an effort to eventually transmit the most noise-free signal possible. In it simplest implementation, an input signal will get processed and then sent through the amplification circuit, which will then be passed to an output-phaser for balancing. This prevents any noise from the CABLE up to the headphones, and is generally just so you can use ultra-long cables. In its most complex implementation, a phaser will pump discrete input signals to two signal decoders (XMOS chips in a USB situation,) which will then pump that to two DACs, which will then pump THAT to two amplifiers, which will then be attached to individual channels on the output, essentially treating each channel as a discrete DAC+Monoblock, the rationale being that any noise from the DAC and Amp circuit, not just the cable, will be diff'd out as well when they're re-phased. This requires EXTREMELY precise clocks to prevent jitter and is usually exclusive to extremely high-end products. For the TA-10, I would hazard that they are balancing at the output stage (hence the single tube.) The TA-20 appears to move that balancing back to BEFORE amplification, as it does not have a DAC integrated. If you look at a more high-end product like, say, the Schiit Jotunheim, they have a picture of their DAC circuit, which has 2 AKM4490EQ chips on it but only one CM633A USB decoder, meaning its phased before the DAC.
So Tl;dr: the TA-10 IS balanced, but at a different level of complexity.