xDuoo TA-20 Tube Balanced Headphone Amplifier Review

[cursive]

Thanks for the tips guys. I got a good deal on one with damaged packaging that should be here monday, so very excited to test it out. It's my first exposure to any sort of tube amp other than guitar amps.

Anxious to try with Hifiman Ananda, HE-560, and Dan Clark Ether CX.

I'm trying to be patient and wait until it gets here and just try it with the stock tubes, but the equipment lover in me is already making lists of tubes to try haha. A slippery slope indeed.

 

[cursive]

Just got the amp in today, loving it so far, sounds good with my old HE-560 which are my hardest to drive headphones.. Perhaps this is a silly question, but it appears one tube glows more than the other? Is this anything to worry about?

I'm honestly not even sure if it's one tube per channel, or how the circuitry is setup.

 

[bgtip]

Just got the amp in today, loving it so far, sounds good with my old HE-560 which are my hardest to drive headphones.. Perhaps this is a silly question, but it appears one tube glows more than the other? Is this anything to worry about?

I'm honestly not even sure if it's one tube per channel, or how the circuitry is setup.

As far as I remember it's not one tube per channel, the circuit passes through both. Swap the tubes L/R to determine if the tubes cause the different glow, or the slots. Google 'faulty tube'. TA-20 has circuit protection, so no worries if the tube is faulty. A pair of my tubes triggered the protection from the day one, but I persisted (stupidly) and after about 50 hours this pair triggers no more - I don't recommend this, I just didn't care at the time.

 

[cursive]

@bgtip thanks for your thoughts on that, swapping them L/R is a good idea to confirm if it's normal or not.

It sounds awesome to my ears, a nice alternative to my other SS only amps, sometimes it's nice to have a little distortion in the chain .

No protect lights or imbalance as far as I can tell, so just typical human nature to overthink something that's not a problem lol.

 

[cursive]

Update: After listening for a while at lower volumes I started turning up the volume and noticed an extra "sparkle" - not quite a crackle - on the edges of treble, and so I turned down the D90 MQA output from 0.00dB to -09.0dB output - D90 MQA in Pre mode and those breaking edges disappeared. Now the treble is crystal clear at low and high volume.

I've further reduced the output to -12dB to be "safe", as there is plenty of headroom on the volume dial. Instead of running the Aiva volume at 55 (0.00dB) I have it at 65 (-12dB), max TA-20 indicated volume is 95.

Xduoo doesn't list their input sensitivity for RCA / XLR so I figured I'd need to "play it by ear" and adjust the D90 MQA output. I have asked so many other questions of Xduoo that I am still waiting for the answers - I'll eventually get around to verifying what the TA-20 RCA/XLR max input should be.

I noticed this part of your experience hmscott, and it has me wondering. In amirs initial review he said "So the optimal input is about 0.1 volt. And the unit starts to clip at a little above 3 volts. So our dashboard at 4 volts input is showing more of a worst case situation than other input levels would indicate. But not much."

So I think you're on to something. I wasn't sure if what you described as hard edge might be clipping?

I'm using the ta-20 with the SMSL SU-9 which outputs 5.3 volts at full volume (99) over XLR. Unfortunately due to their volume numbering system I'm not sure how much I need to turn it down to achieve 3 volts, or what db of attenuation that is, but it makes me want to try it at 3 volts to make sure and avoid any clipping. Might have to measure with a multimeter or something.

 

[icsi85]

I noticed this part of your experience hmscott, and it has me wondering. In amirs initial review he said "So the optimal input is about 0.1 volt. And the unit starts to clip at a little above 3 volts. So our dashboard at 4 volts input is showing more of a worst case situation than other input levels would indicate. But not much."

So I think you're on to something. I wasn't sure if what you described as hard edge might be clipping?

I'm using the ta-20 with the SMSL SU-9 which outputs 5.3 volts at full volume (99) over XLR. Unfortunately due to their volume numbering system I'm not sure how much I need to turn it down to achieve 3 volts, or what db of attenuation that is, but it makes me want to try it at 3 volts to make sure and avoid any clipping. Might have to measure with a multimeter or something.

Set to 56 ( 2.998v)

 

[cursive]

Set to 56 ( 2.998v)

Wow, thank you! Saved me from having to measure this weekend. That's quite a bit lower on the volume than I would have guessed.

 

[muslhead]

Just got the amp in today, loving it so far, sounds good with my old HE-560 which are my hardest to drive headphones.. Perhaps this is a silly question, but it appears one tube glows more than the other? Is this anything to worry about?

I'm honestly not even sure if it's one tube per channel, or how the circuitry is setup.

I had this amp when it was first introduced and it struggled to fully power my HE 1k-v2. It ran out of gas and begin to really distort. You arent having that problem with the 560's?

 

[cursive]

I had this amp when it was first introduced and it struggled to fully power my HE 1k-v2. It ran out of gas and begin to really distort. You arent having that problem with the 560's?

Just did some listening tests, keep in mind all of this is with the 1/4 in output, not even balanced, so there should be a lot more power to be had if I went balanced. Also this is old he-560 with 2.5mm cup connections, and the wood trim.

Listening to my HE560 I have my DAC SMSL SU-9 at full volume, (99) 5.3v. I have to turn the TA-20 to 50-60 volume to get a comfortable listening level. By 75 it's uncomfortably loud, and I wouldn't listen that loud for more than a few seconds. It perhaps sounds a little distorted, but no major distortion or clipping that I can detect, just loud tube sound?

If I lower my DAC to 56 volume (3.0v) to make sure and avoid clipping as mentioned in the previous post, then I have the TA-20 at 75 to 85 for comfortable listening. If I turn the TA-20 all the way up at 95 volume, then I can listen there for a bit, but it is pretty darn loud.

That is strange, I just looked them up on the hifiman site, both are 90db sensitivity, 35ohm on the HE 1k-v2, and 45ohms on the HE-560.

If I had a balanced cable for the HE-560 there's no way I could ever even come close to running out of headroom on the amp. Were you using balanced with your HE 1k? Also do you know the output of the dac you were using at the time?

 

[icsi85]

Wow, thank you! Saved me from having to measure this weekend. That's quite a bit lower on the volume than I would have guessed.

Yeah, that sounds too low... thinking about this. Sorry, didn't save you time... :-(

 

[muslhead]

Just did some listening tests, keep in mind all of this is with the 1/4 in output, not even balanced, so there should be a lot more power to be had if I went balanced. Also this is old he-560 with 2.5mm cup connections, and the wood trim.

Listening to my HE560 I have my DAC SMSL SU-9 at full volume, (99) 5.3v. I have to turn the TA-20 to 50-60 volume to get a comfortable listening level. By 75 it's uncomfortably loud, and I wouldn't listen that loud for more than a few seconds. It perhaps sounds a little distorted, but no major distortion or clipping that I can detect, just loud tube sound?

If I lower my DAC to 56 volume (3.0v) to make sure and avoid clipping as mentioned in the previous post, then I have the TA-20 at 75 to 85 for comfortable listening. If I turn the TA-20 all the way up at 95 volume, then I can listen there for a bit, but it is pretty darn loud.

That is strange, I just looked them up on the hifiman site, both are 90db sensitivity, 35ohm on the HE 1k-v2, and 45ohms on the HE-560.

If I had a balanced cable for the HE-560 there's no way I could ever even come close to running out of headroom on the amp. Were you using balanced with your HE 1k? Also do you know the output of the dac you were using at the time?

Weird, i used balanced only.
The DAC was a chord qutest which I could not find the output specs for.

 

[cursive]

Weird, i used balanced only.
The DAC was a chord qutest which I could not find the output specs for.

The qutest isn't balanced, which I didn't realize, it's specs say 2.5v, but Amir actually measured the qutest at 3.0v at full volume. Either way the HE-1k v2 are awesome headphones, I have an Ananda, but love the look and build of the HE-1k in that stainless and brown. Hope you found a nice amp to enjoy them out of.

Yeah, that sounds too low... thinking about this. Sorry, didn't save you time... :-(

Thanks for your efforts man, your math was right on if the 99 steps were equal. But it appears the DAC definitely has a curve applied to the volume where it ramps up quicker at the end. Finally got a measurement this evening, not sure if it would help anyone else, but 99 volume on SU-9 is 5.3v, 95 volume for 4.0v, and 90 volume for 3.0v.

 

[muslhead]

The qutest isn't balanced, which I didn't realize, it's specs say 2.5v, but Amir actually measured the qutest at 3.0v at full volume. Either way the HE-1k v2 are awesome headphones, I have an Ananda, but love the look and build of the HE-1k in that stainless and brown. Hope you found a nice amp to enjoy them out of..

Schiit Magnius solved my problem

 

[hmscott]

@cursive - wow, that's great, looks like you've been having fun getting to know your TA-20

I posted the feedback from Xduoo as well, I guess you missed it, the TA-20 can take a maximum of 8v input.

I've been running the D90 MQA in DAC mode "flat out" maximum output since that feedback from Xduoo, no overdriven symptoms so far.

I went back and added another update to my post so as to not confuse others.

Also, some more feedback from Xduo:
"Xduoo reply below 8V is all no problem. if it is above 8v, it will cause distortion." - [email protected]

The D90 MQA XLR at most outputs 4Vrms @ 0dBFS, so it won't overdrive the TA-20.

Glad you are having fun with your TA-20

Just got the amp in today, loving it so far, sounds good with my old HE-560 which are my hardest to drive headphones.. Perhaps this is a silly question, but it appears one tube glows more than the other? Is this anything to worry about?

I'm honestly not even sure if it's one tube per channel, or how the circuitry is setup.

Nothing to worry about - tubes have unique physical aspects unto themselves, some tubes are reported to "flash" when starting up - I haven't experienced this on the TA-20, but thought I should mention it.

That is why when I order a pair of tubes for the TA-20 I find a place that does testing, gain measuring - matching internally and externally - between the two tubes, and check and cull for noise - this culling of tubes greatly increases the chance you will get a good sounding balanced noise free experience when plugging the tubes into the TA-20.

I've found tubedepot.com, audiotubes.com, vivatubes.com, have treated me very well. I'll add others later as I am ready.

I'll update more later - 4 pairs of tubes to test, I'll list details later.

Right now I'm taking a break from the TA-20 and I am using my Topping A90 with some new headphones - HD660s, Hifiman Ananda, Hifiman HE6SE V2 - spoiler - I prefer the sound from the TA-20 on those headphones, but the A90 sounds great too

 

[cursive]

@cursive - wow, that's great, looks like you've been having fun getting to know your TA-20

I posted the feedback from Xduoo as well, I guess you missed it, the TA-20 can take a maximum of 8v input.

I've been running the D90 MQA in DAC mode "flat out" maximum output since that feedback from Xduoo, no overdriven symptoms so far.

I went back and added another update to my post so as to not confuse others.

Also, some more feedback from Xduo:
"Xduoo reply below 8V is all no problem. if it is above 8v, it will cause distortion." - [email protected]

The D90 MQA XLR at most outputs 4Vrms @ 0dBFS, so it won't overdrive the TA-20.

Glad you are having fun with your TA-20

Thanks for clarifying, I must have missed that bit, I didn't realize you contacted them about it. Strange that Amir measured clipping at just 3v then? I must admit even at full volume on the SU-9 I definitely don't hear anything that seems unintended.

I did end up swapping my tubes left and right, and one of the tubes definitely glows more than the other, it didn't seem to be size dependent, but no idea what to think about that, it sounds good. I have some JJ ECC802s coming after all the positive feedback here, so dipping my toes in, but trying to just be content and avoid the money pit lol.

 

[hmscott]

Thanks for clarifying, I must have missed that bit, I didn't realize you contacted them about it. Strange that Amir measured clipping at just 3v then? I must admit even at full volume on the SU-9 I definitely don't hear anything that seems unintended.

I did end up swapping my tubes left and right, and one of the tubes definitely glows more than the other, it didn't seem to be size dependent, but no idea what to think about that, it sounds good. I have some JJ ECC802s coming after all the positive feedback here, so dipping my toes in, but trying to just be content and avoid the money pit lol.

The tubes are physical devices, quite often soldered by hand and assembled by hand, so there is variance between the tubes themselves.

Here are modern day nicely narrated videos of the Shuguang Tube Manufacturing Factory that was closed down in 2018 and is being moved - perhaps opening soon?:
Building the Shuguang EL34-B Vacuum Tube - Part 1
Building the Shuguang EL34-B Vacuum Tube - Part 2, Sealing the Bottle

Decades jumps backwards in tube manufacturing:
Tesla Tube Factory Visit—Czech Republic 1998
Vacuum Tubes/Valves by Mullard 1950s

If anyone has found a nice 12AU7 / ECC82 / ECC802s manufacturing video please post a link

And, you might want to read up on the thread for the Ananda / HE6SE V2 over on head-fi, I've been sharing listening to those headphones on the TA-20 there:
https://www.head-fi.org/threads/hifiman-ananda.879628/post-16155042
https://www.head-fi.org/threads/hifiman-he6-se.886229/post-16152217

I'll update here in a while about new tubes on the TA-20, I've got several pair yet to test.

 

[BubbaJay]

I believe the TA-20 has the same amount of power out of both single-ended and balanced, I think it's 2 watts @32ohms for both. More amps should do that but you'd still get the sonic benefits from going balanced it's just you'd have the same power single-ended.

 

[hmscott]

I believe the TA-20 has the same amount of power out of both single-ended and balanced, I think it's 2 watts @32ohms for both. More amps should do that but you'd still get the sonic benefits from going balanced it's just you'd have the same power single-ended.

Yup, and I've driven the HE6SE V2 out of both the 4-pin and 6.35mm ports - sounds equally awesome

 

[cursive]

I believe the TA-20 has the same amount of power out of both single-ended and balanced, I think it's 2 watts @32ohms for both. More amps should do that but you'd still get the sonic benefits from going balanced it's just you'd have the same power single-ended.

Hmmm... I might be mistaken but on checking Amirs post on the first page of this review, he seems to show the TA-20 having double the power using the balanced output. 1.6 watts out with the 1/4 in jack and 3.4 watts out with the XLR jack. This is measured at 50 ohms though, so could be a little different @ 32 ohms. The Xduoo specs definitely say equal power @ 32 ohms, so not sure what is correct. I'll have to test it and maybe see what volume number I'm at on SE vs BAL.

 

[hmscott]

I wrote a response to someone getting a ZMF Pendant SE over on head-fi, where I mention some of my recent Xduoo TA-20 NOS tube results:
https://www.head-fi.org/threads/fii...attery-64-gb-rom-1299-99.920276/post-16220968

Basically I've found that Life % measurements of lower than 95% indicate a good chance that tube will hiss with my more sensitive BA IEM's. But, all tubes testing above 85% sound great on all of my headphones. I haven't bought a lower testing tube yet... it might be that even lower testing tubes will sound fine with headphones.

It's weird really, the less well measuring tubes can still sound great with headphones, but not with sensitive BA IEM's.

Fortunately for me I prefer headphones for stationary use; I do enjoy IEM's for mobile, and my SS FiiO M15 / BTR5 / Hidizs S9 are noiseless with my sensitive IEM's.