xDuoo TA-66 OTL Tube Headphone Amplifier: A Kind of Magic

I believe I got the Voshkod tube - there is a rocket logo on the tube.

I agree with this. TA66 is a good amp for 120-ohm+ impedance cans. I am catching myself listening to TA66 for far longer than I typically do sitting in front of my computer. Piano sounds realistic, as are vocals with accurate timbre - it has got the timbre reproduction down for midrange and treble. Bass tone and dynamics are generally good until you get into the sub-bass region or music that requires a broad bass tone (like the bass drum in a symphony) or electronic bass that's highly dynamic. These and other omissions are the kind I can absolutely live with for the price of the unit. Given its footprint and low cost, I think TA66 is the perfect 24/7 desktop amp.

 

It’s amazing for the asking price. I recently got a HD800S to build around this. The HD600 and 650 were good, but the HD800S really shines with this. Aside from the interconnects the amp is the least expensive thing in the chain. Purr1n is spot on to have the amp on the 800/S amp list.

I wonder if anybody has tried Beyers with this?

 

Any DACs for this amp and the HD800 OG that match the value/quality? I have a Modius E and Bifrost 2 OG. Do I have them already?

 

I fed the TA-66 from both BF2OG and Yggdrasil MIB with HD800S, and yes, the xDuoo does scale just fine, but its not some jaw dropping pants-on-fire revelation like mana from heaven using a "better" or MIB-level DAC. But this all kind of depends on where you are in your journey.

 

I don't know -why- I tried this (it doesn't seem like a good idea), and I can't decide whether it falls under "undocumented feature", "something that really should not work this way", or what, so I'm just going to mention it and maybe somebody can help make sense of it.

With the power off, I connected the output of a DAC to the AUX OUT of my TA-66. I plugged a headphone in, and I heard the DAC's output. The relay pot does not attentuate the volume at all. This also happens with the power on, mind. I don't seem to have damaged anything - the amp still works as normal with things plugged in correctly.

For a few reasons this seems odd - for one, because that's labeled as an output, so I don't see why it should function as an input; a Magni 3+ I checked at the same time does not do this through its preamp outs, for instance. It certainly seems like it could have something to do with the various complaints about this as a preamp.

What exactly is going on here, and why would it work like this?

 

I’ve been thinking about dipping my toes into the tubes world for a while, and Vali 3 seemed the logical choice. Now the TA-66 might be another option?

From what I read here, I think the Vali is probably the better choice because

• My main headphone is the HEDDphone Two, and the TA probably doesn’t have enough power for that. (Also output impedance, but that doesn’t necessarily have to be a problem due to the AMT drivers—that’s what I read, at least.)
• I don’t have an HD800.
• I have an HD650, but its mid bass hump is close to too much for my taste as it is already.
• My DAC (iFi Neo iDSD) leans towards the warmer side (though I could counter that at least a bit by choosing HQPlayer modulator and filter wisely).

Do you agree?

I’m a detail whore, though, which seems to point more towards the TA-66?

I’m not really in search of a cheap but good tube amp right now, but might try that out during the coming year or so.

What would you recommend?

 

I think the impedance on the Heddphone is (way) too low for the OTL TA-66. For tubes you're probably better off with something with an OPT or a hybrid.

 

I would recommend an SW51+, it's very detailed and not very bass heavy and works great with the HD650.

 

I didn’t care for the pairing with Modius E’s SE out…things were held back. Its XLR via transformers is something else. You’re looking at an extra $175 in parts and DIY for Cinemags, case and sockets.

 

I think you’re right based on what you listed. The Vali 3 is cheaper and smaller and slams. A bargain.

However, let me add that the TA-66 has that OTL goodness that I sprung for a HD800S and haven’t looked back.

 

I’ve been using the Xduoo TA66 with the NDH30 for a couple of weeks now, and they complement each other beautifully. I find myself listening to the TA66 much longer than usual while sitting at my computer. NDH30 sits between HD650 and HD800 in terms of general sound profile with angled drivers (potentially great soundstage if your HRTF is compatible). The piano and vocals sound realistic, with accurate timbre, particularly in the midrange and treble. The bass tone and dynamics are generally good, though sub-bass region or music that demands a broad bass tone, such as the bass drum in a symphony or highly dynamic electronic bass may leave some sub bass performance of NDH30 on the table (NDH30 has much stronger bass and sub bass performance than 800S with good slam and macro dynamics on the right amp such as CFA3). For general relaxed listening with some level of insight I prefer NDH30 over 800S. Dac used is emm labs dac2 with ET3 as CD transport.

 

Happens on Eufonikas too. If you'd open up the unit, you'd probably see that the AUX OUT and HP OUT are wired in parallel or daisy chained to the output stage. Simply said, you're going directly from AUX OUT into HP OUT with nothing else in the way.

 

This caught my interest. I pulled the trigger on a TA66 for a secondary room setup with the HD800S. Except now it my be my primary.

I found the stock tubes are really good, But I got curious after reading @atomicbob and @joch tube suggestions.

I found the Sovtek suggested by @atomicbob does make the bass a little fuller. At first I thought this was at the expense of the highs and resolution. But after a day or two the highs came back.

I tried Joch's suggested Svetlana-wing C and the higher spec'd voskhod's. These also needed a day or two, and first I only changed in the Svet. The svetlana brought slightly more low end heft and the highs were the most resolving of the three tubes. I can't tell for sure if the vosk's were really better, maybe a little more refinement, maybe, or could be expectation bias.

The differences weren't major and staying stock is fine, but not a fun as tube rolling.

I compared the HD800S on my Icon HP8 which I have had for ten years, I upgraded the caps and put some nos 70s sylvanias 6S7N. This has been a fantastic pairing. It slightly out resolves the TA 66, and the stage is very slightly wider. But the TA 66 counter punches with a meatier note weight, wetter presentation with mo better bass. I think it's a good trade.

Thanks for this thread!

 

IMO TA66 is a shoo-in for 2025 Golden Schlong Award.

@shabta @atomicbob
I got the Svetlana wing C and it made a pretty big difference in my system. Way better bass response with good sub bass quantity and bass detail. Midrange has also improved in terms of micro dynamics and resolution. The amp also became quite a bit more transparent with pretty good soundstage depth and width. This was on an Emm Labs DAC2. I think Emm Labs makes a good pairing with this amp. Now this sounds more like baby ZDS.

 

I know might sound like an odd thing to do, but I think I’m quite possibly going to be selling my Folvangr and replacing it with the TA-66. Obviously they’re not that similar - though both in the OTL family. And since I AliExpress’ed my xduoo the price difference is like 8x. But I’m guessing/vaguely hoping that my increased enjoyment will not be so incredibly huge enough to keep the FV around for the HD800, HD6xx, ZMF Verité Open, Beyer 1880 600’s. And there’s a part of me that always worries I’m going to start a house fire. Perhaps that’s my way of saying I really think I’m going to like this amp. Because man I love my FV. Anyone else done the side-by-side? TA-66 arrives in a week.

 

I would highly recommend waiting to make any decisions until after you have actually received the amp. Then you can compare them side by side and see which one you like listening to better. I would be interested in your thoughts once you've listened to them both for a few days.

 

hell yes I’m waiting. This is hope. Like I said, I love my FV. But thanks for the reminder to not get out over my skis.

 

@atomicbob Is Svetlana wing C the same as Sovtek 6AS7g? I often see these brands mentioned together.

 

For current production, both brands are owned by New Sensor Corp and are produced in Russia (which I believe also owns/reissues many of the old brand names/IP like TungSol, Mullard, Electro-Harmonix, etc).

For "old" stock, Svetlana and Sovtek were different companies. Svetlana around forever, Sovtek founded in the late 80's/early 90's out of the ashes of the former Reflektor company and plant. I believe all the New Sensor brands are now manufactured in that plant.

 

I guess I should clarify, the svetlana I am using is NOS. It's a different tube then the sovtek. Which is pretty obvious when you hear them.