Would love to know more about how this effects sonic differences - all for a commercial offering.
The "OG" DIY T2 (mine is a George Parris build) has a thickening & reinforcing effect in the lower range. There's more warmth and body in the midrange through bass, and bass seems more punchy & weighty as well. The effect is significant enough that it has a transformative effect specifically on the original 009. In fact, whereas you'd be pairing the 009 with a warm-as-you-can-get source on (say) KGSShv or Carbon amps, you'll now be seeking out more aggressively detailed and voiced sources with the 009 + OG T2. But as a whole, the 009 + OG T2 is magic - and it's my favorite. Note that I generally DON'T prefer dead neutral. I almost always voice my systems to tilt a bit towards warmth and body. You can see that with my preferences in amps, speakers (Tannoys), cartridges (Koetsus, Benzes), phono stages. It's actually weird that I love the 009 so much - not in my typical wheelhouse, but I bonded with it early on (actually first heard it on Purk's OG DIY T2).
The OG T2 isn't a good match for ES1a or L700 (imo), because these headphones become a bit congested in the lower midrange & bass. It's just a bit too much going on down there. I do remember the Sennheiser HE90 being spectacular on OG T2, probably because it also particularly benefits from the bass & body reinforcement. But it's been a while since I heard that combo.
I'm also going on memory here for the BHSE (sold mine circa 2018?), but Kerry's Nascent T2 (not quite the latest Eksonic but close) has a voicing which reminded me of BHSE with its performance "supercharged". It doesn't have the lower range "boost" of the OG T2. Treble is very similar on both T2's - really clean and detailed but very slightly relaxed. Compare either T2 to a Carbon KGSShv which will sear your eardrums off when paired with 009 or L700 lol. I would call the Nascent's voicing neutral-ish, with a slight warmth & sweetness affected from the tubes.
The Nascent sounds really great with 009, but doesn't quite bump them into the "magic" range. It was also a wonderful match with 007, ES1a, and L700. A bit overkill for the L700, but oh-so-good. Like the BHSE (but better), it's going to sound good with everything. It's a well-tempered voicing.
Unfortunately I don't have the X9000, SGL, CRBN, or whatever new 'stats are the rage these days. Those would be the more likely application for potential T2 buyers these days.
I've also heard Purk's OG DIY T2 - not a George P build, but sounds effectively the same (going on memory). The transistors and boards seem to be what gives each T2 its sound. The tube rolling effect on both T2's is relatively mild - this goes for both EL34 and 6922. You're not going to make one T2 sound like the other by rolling. I think the Russian Mullard EL34 are a great value for the money here. You don't really need to go beyond that, though of course I have some nice Holland brown-base EL34 in there now. For affordable 6922 I like the Matsushita 7DJ8, though Siemens E88CC are great if you need to spend a bit more.
The 009 / T2 / vinyl combination is absolutely wonderful, but you have to be careful not to end up with treble too recessed. I find this Herron phono stage a little too aggressive and sterile in my Tannoy rigs, but it's the prefect partner for an OG T2. The OG Yggy was also a great OG T2 source. My current DAC is a Phison PD2 that's a bit warmer (when using coax input via Audiophilleo) and I thought it would be stellar here but it's not quite. The Phison was better than Yggy on the Nascent T2.
