Xduoo Amplifiers
Mar 26, 2022 at 5:52 PM Post #1,186 of 1,421

albertmuc

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Because of the now burned-in tubes (see photo), I once again express my enthusiasm for the inexpensive "xDuoo TA-20". Balanced connected to the decent-sounding "RME ADI-2 Dac", I prefer the "xDuoo TA-20" with its tube magic, which takes the edges out of the sound, makes voices livelier and everything more three-dimensional.
Actually, I wanted to invest in a “somehow better” tube amplifier, but it already sounds very good…
Don't be put off by the low price of the xDuoo!

95FFD3DB-8D7F-461E-AA17-ACBECA54A85E.jpeg
 
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Mar 26, 2022 at 6:52 PM Post #1,187 of 1,421

hmscott

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Because of the now burned-in tubes (see photo), I once again express my enthusiasm for the inexpensive "xDuoo TA-20". Balanced connected to the decent-sounding "RME ADI-2 Dac", I prefer the "xDuoo TA-20" with its tube magic, which takes the edges out of the sound, makes voices livelier and everything more three-dimensional.
Actually, I wanted to invest in a “somehow better” tube amplifier, but it already sounds very good…
Don't be put off by the low price of the xDuoo!
I think Xduoo was trying to help me find my tube Nirvana when they gave me the TA-26, it really is a big jump in Tubiness! :beerchug:

I was about to stop collecting tubes for the TA-20, but when I listened to the TA-26 with stock tubes; I'm all in again big time! And, the TA-26 is even less expensive than the TA-20! :ksc75smile:
 
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Mar 27, 2022 at 5:11 AM Post #1,188 of 1,421

ostewart

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Thanks for the next tip! I already thought about it, the rear tube will be drowned. Where can I get such a saver? Or under what "word" should I look for him?

https://www.ebay.co.uk/itm/281952845500

@hmscott personally I wasn't looking to "save" the tube socket as such, it was more of a height thing to bring the 6080 tube a litle higher so aesthetically it looks better - it could also help with thermals as the hot element is higher and not as close to the capacitors (fully outside of the amp now)
 
Mar 27, 2022 at 8:14 AM Post #1,189 of 1,421

muchacho

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https://www.ebay.co.uk/itm/281952845500

@hmscott personally I wasn't looking to "save" the tube socket as such, it was more of a height thing to bring the 6080 tube a litle higher so aesthetically it looks better - it could also help with thermals as the hot element is higher and not as close to the capacitors (fully outside of the amp now)
Thanks for the tip, this is exactly what I meant so that the 6080WC and 6SN7GA would not be drowned due to the heating inside the amplifier and that they would also be visible. I like to enjoy listening in the evening, when the pleasant warm glow of the tubes stands out and combines with the same pleasant sound ... In the end, I found and ordered this base pad: https://www.fruugo.cz/osmickova-pozlacena-trubkova-zakladna-pro-usporu-z-trubky/p-61951742-124933236
 
Mar 28, 2022 at 3:46 PM Post #1,190 of 1,421

roderickvd

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I received my TA-20 today and am listening to it as we speak. I am sorry to say that my initial impression is very disappointing. The sound is unpleasantly distorted, grainy, and the soundstage compressed. For reference, my previous amp I am comparing this to is a home-built AMB β22.

This is listening to my 250Ω Beyerdynamic Amiron Homes (XLR) and my home-built Soekris dam1121 (RCA) as source. Swapping the balanced headphone cable with an unbalanced cable did not make any discernible difference.

I changed the stock tubes to a NOS matched pair Sylvania 6189W's, also to no avail.

I should receive my Denafrips Ares II this week, which will provide XLR input to the TA-20. That together with some further burn-in will hopefully fix whatever I'm hearing, or I'll be selling this unit. Hopefully I won't need to?

Edit: man, I do hope it's those OPA's that are doing the RCA unbalanced to balanced conversion internally. Fingers crossed.
 
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Mar 28, 2022 at 9:24 PM Post #1,191 of 1,421

hmscott

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It is easy to give up quickly, I've seen others do that as well. I hope you stick with it and work out what tubes sound good in the TA-20. :)

Early on I found and posted this review comparing the Sylvania 6189 and the PSVANE 12AU7-TII:
https://www.audiosciencereview.com/...mp-money-can-buy-for-hd800s.18522/post-606270

"5.0 out of 5 stars - A surprisingly huge step up from Sylvania and other NOS tubes
Reviewed in the United States on May 19, 2020
Verified Purchase
Came in a beautiful presentation box with papers showing serial #s and measurements. Used them to roll from Sylvania NOS. 6189/12AU7. I was amazed at how much stronger these PS VANES were over the Sylvania NOS.
Truly impressive!
Update: I also have some RCA NOS, Mullard re-issues, and a few other matched NOS tubes of varying brands.
These PS VANE T2 tubes clearly outperformed them all in my XDUOO TA20 hybrid headphone amp.
I liked them so much that I ordered a 2nd pair, along with matching PS VANE T2 power tubes of another designation, to go into a Cayin HA1A MK2 headphone amp I recently ordered elsewhere.
The difference between this PS VANE T2 and others is immediately a huge noticeable improvement. The others I could tell differences, some more subtle than others. If you blind folded me and asked me to identify 1 of the other brands over the others, i might guess correctly half the time. Then there's these. They're unmistakable.
Its like going from a home theater in a box with a 50" 720 p monitor with Dolby Digital 5.1 (not bad) to a 140 inch UHD projector and a 7.2.4 Dolby Atmos system( WOW). There's no going back.
They probably would be wasted on a guitar amp where distortion might be preferable, but for hi fidelity music reproduction, these are really hard to beat."

And, while at the time I really enjoyed the PSVANE 12AU7-T II tubes in comparison to the "new reissue" 12AU7's I tried in the first weeks, I wouldn't say it was "up there" enough to recommend today. Which would put the Sylvania 6189W well down the list under the PSVANE 12AU7's as well. So I wouldn't feel bad if it doesn't sound good to you either.

We moved the TA-20 tube rolling discussions to the TA-20 review thread within a few posts in that thread above:
https://www.audiosciencereview.com/...-headphone-amplifier-review.10118/post-611207

I also made a bunch of posts on my early experience with TA-20 in that thread. If you want to speed through to the best tubes, I'd not buy those early trial 12AU7 tubes. At least wait until you find where I switched over to 12AT7 there and here, then found the E80CC and E180CC tubes, both Mullard NOS made in the Mullard Mitchum plant in Surrey England and the top sounding for me so far, the Amperex E180CC made in Heerlen, Netherlands.

Hopefully you can find local vintage tube sellers that can get you those same Amperex / Philips or rebranded tubes made in the Heerlen plant - it is right there in your "back yard"

There are a lot of tubes that sounded "flat" to me as well, but I didn't give up, I kept upping the "ante" buying more expensive tubes - but looking for the best price historically before blowing too much. I tried to keep it to $50/tube as for the ECC81/4024/8162 Mullard ala Mitcham Surrey England plant, but went as high as $80/tube for the "Pinched Waist" Heerlen E180CC pair.

You also need to burn-in the tubes for 50-100 hours before making "sound judgements" on what the tubes can do. New tubes - as in never used - need to burn off the cathode material for a while before the tube will "mellow" out and fly right. The TA-20 and the stock tubes need burn-in too, some have reported enjoying those stock tubes after 40-50 hours - I never burned them in myself, I started rolling new tubes first thing.

And, we really cannot A/B test tubes except side by side in the same set up's, as swapping tubes means cooling down and heating back up for hours before the best sound comes through.

So patience is the watch word, and let things age in first before making sound judgments :)
 
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Mar 29, 2022 at 2:08 AM Post #1,192 of 1,421

roderickvd

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Thanks for your extensive reply. As always, it seems!

Have you been running the amp from a balanced or unbalanced input? I really think — hope — that it’s that. Also because rolling the stock tubes made no discernible difference, I think it’s elsewhere in the chain.

I am fully aware that it takes a good number of hours of burn-in for tubes and caps to come to life. I did however have much higher expectations even on initial listening, based off of many reviews with positive first findings. On forums like this one as well as Zeos’ super positive review. My initial impressions are far from that.

As for the Sylvania’s, I will not argue that the Heerlen tubes are a another step up surely. Still, there are *many* who think the Sylvania’s make the top of the list just beneath that, having posted reviews counter to the one you quoted. Personal preference of course but I’m holding on to the thought that these are some good tubes which should not produce such unpleasant distortion by a far stretch.

Again, Zeos loved the TA-20 on first listen even with stock tubes.

I’ll continue listening on this unit and wait for my Ares to arrive, and postpone final judgement until I’ve hooked that up balanced.
 
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Mar 29, 2022 at 4:31 AM Post #1,193 of 1,421

-Darkstar-

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I received my TA-20 today and am listening to it as we speak. I am sorry to say that my initial impression is very disappointing. The sound is unpleasantly distorted, grainy, and the soundstage compressed. For reference, my previous amp I am comparing this to is a home-built AMB β22.

This is listening to my 250Ω Beyerdynamic Amiron Homes (XLR) and my home-built Soekris dam1121 (RCA) as source. Swapping the balanced headphone cable with an unbalanced cable did not make any discernible difference.

I changed the stock tubes to a NOS matched pair Sylvania 6189W's, also to no avail.

I should receive my Denafrips Ares II this week, which will provide XLR input to the TA-20. That together with some further burn-in will hopefully fix whatever I'm hearing, or I'll be selling this unit. Hopefully I won't need to?

Edit: man, I do hope it's those OPA's that are doing the RCA unbalanced to balanced conversion internally. Fingers crossed.
Even though it's a hybrid and not a full tube amp, I'd give it around 100 hours before making a final decision. My TA-30 sounded very closed in at first, also.
 
Mar 29, 2022 at 12:16 PM Post #1,194 of 1,421

hmscott

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Thanks for your extensive reply. As always, it seems!
...
I find if I answer in short without supporting info, worse conclusions can be jumped to due to inadequate information - and their inability to read my mind. :)

So I prefer to go into detail in my responses vs trying to repair a misunderstanding in many following posts. So far that works well, unless the person isn't interested or doesn't read well. And then in the long term my longer responses are helpful to others that come across them later.

I'm answering to help, and if I don't cover things well at first edit, I often come back and edit my post(s) to fill in words, details, and add links to firm up the specifics. And, I come back sometimes with "Updates".
Have you been running the amp from a balanced or unbalanced input? I really think — hope — that it’s that. Also because rolling the stock tubes made no discernible difference, I think it’s elsewhere in the chain.
I've run the TA-20 in both XLR and RCA, and I prefer XLR on the TA-20 but on the Topping A90 I prefer RCA...it isn't a big difference for either, it is a preference based on longer term listening, and I had to pick one or the other in order to drive both at the same time from my Topping D90 MQA DAC.

Right now I am driving the TA-20 via XLR from the Topping D90 XLR output, and the TA-26 via the RCA output of the Topping D90 - the D90 can be set to output to either RCA or XLR or both at the same time.

Again the difference between the XLR and RCA input of the TA-20 for me is much less than between good and great tubes, and between a broken in TA-20/tubes - and the sharp edged harshness of new unused tubes - harshness which can be extreme with some new tubes!
I am fully aware that it takes a good number of hours of burn-in for tubes and caps to come to life. I did however have much higher expectations even on initial listening, based off of many reviews with positive first findings. On forums like this one as well as Zeos’ super positive review. My initial impressions are far from that.
Well, not so much to come to life as to remove the rough edges of harshness from the new tubes/equipment. There are other dimensions to the changes, but you are reporting - in my estimation - the harshness of distorted edges from the new tubes and/or new TA-20, both not yet broken in.

I've experienced it many times with new tubes on the TA-20 and now on the TA-26. The tubes do at first have good qualities and bad qualities. Some/most tubes shed the bad sharp/harshness qualities over time and as I and many call it - mellow out. And, the sound stage can widen and the overall frequency balance can improve. Each tube is different in the changes over burn-in, but so far none have become worse sounding.

I also experience this burn-in harshness with IEMs/headphones - as with the Sendyaudio Aiva Zeos uses in the TA-20 review where he says you really need a Hybrid amp for Planars - which I have found isn't always the case - the TA-26 drives my Hifiman HE6SE V2 quite well - even though it is very inefficient and has low impedance.

I've A/B'd both the Hifiman HE6SE V2 and Hifiman Ananda between the TA-20 and TA-26, and with certain tubes in the TA-26 - specifically the 1976 Cetron 7236 power tube and the 1944 Kenrad VT-231 Black Beauty (Black Glass) the TA-26 sounds just as great as the TA-20 with Haltron E80CC (Heerlen made) or E180CC Heerlen made tubes.
As for the Sylvania’s, I will not argue that the Heerlen tubes are a another step up surely. Still, there are *many* who think the Sylvania’s make the top of the list just beneath that, having posted reviews counter to the one you quoted. Personal preference of course but I’m holding on to the thought that these are some good tubes which should not produce such unpleasant distortion by a far stretch.
In my experience my first tubes - as carefully researched and selected as I could make them - didn't hold up over time, and like the Sylvania 6189W your early tubes may similarly be near the bottom of your list, after you run through a lot more tubes, hunting for better and better tubes.

tubemazestore - a longtime tube seller on eBay that also has a tube review site with 5000+ reviews submitted as of August 7, 2020 - see top rated 12AU7 list below.

The Sylvania 6189W Triple Mica received 3.84 out of 5 - (32 votes, average: 3.84 out of 5) Is your 6189W a 3 Mica build?, one on the bottom of the stack and 2 with a short gap on top? Most 12AU7's (and other 12xx7's variants) are built with 2 Mica, one top and one bottom, but the best sounding are typically the 3 Mica variant also usually built with stronger posts and tie points to keep the tube rigid in the glass envelope - those more solid builds reduce the noise and microphonics.
https://tubemaze.info/sylvania-618912au7wa-gray-plates-triple-mica/

Here are the tubemaze.info site's top rated 12AU7 tubes as of August 7th, 2020:
https://tubemaze.info/the-best-12au7-tubes/

"Which 12au7/5814 tube won the right to be called the best and the worst?

Updated August 7th, 2020

Based on user ratings in the last 8 years and over 5000 ratings submitted, here is the list of winners and losers. The system is based on 5 stars. We will treat 5814, 7316 and 12au7 in the same category – since they are the same tubes, just different quality.

Old Stock 12au7
Winners

Amperex 7316 Long Plates Foil Getter (4.8)
Mullard 12au7 Long Plates []-getter (4.6)
Mazda 12au7 Gray Plates (4.57)
Mullard 12au7 10M Series (4.5)
Tung-sol 12au7 Black Glass (4.43)
No surprises here, all of them are crazy good tubes. Amperex 7316 with long plates still reigns supreme.

The 3-Mica Sylvania 6189 with 3.84 rating didn't make the top 5, and probably not the top 10...note below the PSVANE 12AU7-T Mk.1 received an average of 3.18!, the site search doesn't find the PSVANE 12AU7-T Mk II - too new?, but it did find the PSVANE 12AX7-T MK II which received a 3.38. So perhaps I would enjoy the Sylvania 3.85 more than the PSVANE 12AU7-T Mk II, but in any case I have a far more enjoyable 12AU7 in the Tung-Sol 12AU7 Black Glass 4.43 rating - which are my current best sounding 12AU7 tubes - I recommend to always get backup's of your favorite tubes - if possible :)

Losers

Sylvania 12au7 Short Black Plates (3.0)
Sylvania 12au7 Gray Plates (3.0)
Mullard M8136/12au7 Box plates England (3.28)
Now that is a surprise, based on 39 reviews submitted, Mullard M8136 took the third place from the bottom! The very unexpected outcome for this tube. Interestingly enough, Mullard CV4003/12au7 Box Plates earned a very respectable rating of 4.4

New Production 12au7
Winners

Well, there are really no winners in this category for new production tubes, all of them rated very poorly. - That is my experience as well, while "nice" they really don't do the TA-20 justice.

Losers

ShuGuang/Ruby 12au7 Gray Plates (2.0) - AFAIK these are the stock tubes provided with the TA-20.
Psvane 12au7-T (3.18)
- These are the predecessors to my PSVANE 12AU7-T Mk II's and PSVANE 12AU7-S Mk I's.
Electro-Harmonix 12au7 (3.22)
And again ShuGuang 12au7 takes the lead on being the worst of the worst – 2.0 is quite an achievement – again, too bad that a lot of manufacturers choose to ship their equipment with this tube. - IDK why Xduoo keeps using these as the stock tubes when the much better Chinese PSVANE tubes are available now...some Chinese amp makers offer a PSVANE tube upgrade option - perhaps Xduoo could add that as an option for the TA-20 / TA-26 / ?? models?

DISCLAIMER: This is not a definitive list of all best and worst 12au7. It’s purely based on over 5,000 ratings submitted by the users of this site."

My comments added to the article quoted above are in Italic Bold....
Again, Zeos loved the TA-20 on first listen even with stock tubes.
I’ll continue listening on this unit and wait for my Ares to arrive, and postpone final judgement until I’ve hooked that up balanced.
Zeos was comparing the difference between the TA-10 single-ended sound vs the TA-20 Balanced sound, and as far as the stock tubes Zeos says "I think if you swapped tubes you could have an "end game" "- and Zeos's comment wasn't that stock tubes sounded better, but that Balanced sounded better - more specifically the TA-20 sounded better with stock tubes than the TA-10 with burned-in swapped tubes.

But I don't think Zeos did a good job qualifying that comparison if you got out of it that the stock tubes were great sounding, or that they were responsible for what Zeos was praising - it wasn't the sound of the stock tubes it was the difference in sound presentation between the "single-ended" TA-10 and the "balanced" design of the TA-20.

As above the TA-20 stock tubes got a 2.0 rating and I agree that they are very harsh sounding on their own, and not at all enjoyable, that is why I didn't listen more than a short while (minutes) to them before rolling in tubes that sounded much better than the stock TA-20 tubes.

Zeos's comments as above start here: Xduoo TA-20 _(Z Reviews)_ Truly Balanced

The TA-20 Balanced sound sounds much different than the "Pulled to the Center" single-ended TA-26 sound...at least initially. Now that I've listened to the TA-26 for a few months that "sucked to the center sound" I had with the stock tubes and unburned in TA-26 is completely gone.

If you continue rolling tubes, and continue using the TA-20 all day long - keep it playing music even if you aren't listening to it to get it through full burn-in, you will find a much more musical and melodious sound from your TA-20 too :)
Even though it's a hybrid and not a full tube amp, I'd give it around 100 hours before making a final decision. My TA-30 sounded very closed in at first, also.
Totally agree, and for me the TA-20 sound kept improving all during the first couple of months of use, and that was about the time I found the Tung-Sol 12AU7 Black Glass tubes and stopped listening to the Topping A90 completely - except for specific comparisons to answer questions posed to me online. Now, the A90 is sitting unplugged under the TA-20...

I would expect the TA-30 to need as much burn-in time too.

For me the stock TA-26 was stuck on stock tubes for a couple of weeks until I could get new tubes plugged in, and I often went back to my TA-20 simply because I thought the TA-26 stock tubes as still new sounded too harsh - but, with the TA-26 wide sound stage and "airy tubiness" being much better than most TA-20 tubes sound, even while the harshness played out during burn-in.

@roderickvd - I also should mention that for both the TA-20 and TA-26 with new tubes I find it helps to reduce the XLR 4.0V drive output from the D90 DAC as it reduces the "edgy-ness" or harshness at listening volume with new tubes. With new tubes not yet burned in, on the Topping D90 I reduce the XLR 4.0V output by setting a -15dB or -20dB attenuation - with the PC source audio still set at 100% output to maintain analog Signal-to-Noise audio integrity, and that helps to reduce the harshness during burn-in. After the amp/tubes burn in I run the D90 DAC at 0.0dB output attenuation - like right now.

The DAC output attenuation, even as little as -3.0dB, -6.0dB or -9.0dB might be enough to help you reduce the harshness you are hearing during new TA-20 / new tubes burn-in. Trying playing around with the DAC attenuation starting at -3.0dB and increase attenuation until the harshness is reduced as well as possible. Of course, increase the volume on the TA-20 as needed to return the listening level to where you like it.

Nothing beats actual hours burn-in time, but I can make the harshness more tolerable during burn-in by reducing the DAC XLR 4.0V drive input to the amp.

Additional detail for reducing DAC output: This probably only applies to XLR output @4.0V or more as with the Topping D90/D90SE. If you are feeding the TA-20 / TA-26 via RCA 2.0V or less it won't make a difference.

Thanks to @roderickvd for his feedback, I've updated the info above to reflect his experience :)

Update:
tubemazestore was paused for a while, but it is back online again, not very much is currently listed, I hope he brings back more of his inventory online soon :)
 
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Mar 29, 2022 at 2:17 PM Post #1,195 of 1,421

roderickvd

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I find if I answer in short without supporting info, worse conclusions can be jumped to due to inadequate information - and their inability to read my mind. :)

So I prefer to go into detail in my responses vs trying to repair a misunderstanding in many following posts. So far that works well, unless the person isn't interested or doesn't read well. And then in the long term my longer responses are helpful to others that come across them later.
Well, much appreciated!
Well, not so much to come to life as to remove the rough edges of harshness from the new tubes/equipment. There are other dimensions to the changes, but you are reporting - in my estimation - the harshness of distorted edges from the new tubes and/or new TA-20, both not yet broken in.
Yes, you may be on to something there. Edit: I also find it lacking in authority and presence, is that something recognisable?

It's true that I'm new to this tube game. The scientist in my has long pulled me towards the "best amp is a wire with gain" kind of thinking. It's that thinking that also led me to build my AMB β22, which may be considered reference depending on which standard you hold it to, and pulls out every technical trick in the book. But I have come to realise that this is not truly what I'm after -- at the end of the chain, I prefer that warm, lush sound of my dad's 70s setup so to speak. And here I am getting into tubes.
The Sylvania 6189W Triple Mica received 3.84 out of 5 - (32 votes, average: 3.84 out of 5) Is your 6189W a 3 Mica build?, one on the bottom of the stack and 2 with a short gap on top? Most 12AU7's (and other 12xx7's variants) are built with 2 Mica, one top and one bottom, but the best sounding are typically the 3 Mica variant also usually built with stronger posts and tie points to keep the tube rigid in the glass envelope - those more solid builds reduce the noise and microphonics.
https://tubemaze.info/sylvania-618912au7wa-gray-plates-triple-mica/
Yes, those are the ones. The babies were once intended for use in guided missile systems aboard highly dynamic platforms like navy ships. Unsurprising then, that they have excellent linearity, low noise and low microphonics. Again I may have fallen into the trap of technical prowess when in fact something mellower would better suit my ears... it's like a constant source of conflict between the mind and the heart :smile_phones:

Then there's a bit tongue in cheek too -- I work in the defense sector so imagine the coffee talk at work where I'm ever so proud to announce that guided missile technology has now found its way into my hifi equipment :dt880smile:
New Production 12au7
Winners

Well, there are really no winners in this category for new production tubes, all of them rated very poorly. - That is my experience as well, while "nice" they really don't do the TA-20 justice.
Here's a question that might show my newness to this tube game: aren't all PSVANE's new production? If so I do not understand why they also appear on other lists, sometimes quite well rated (and sometimes not so).
If you continue rolling tubes, and continue using the TA-20 all day long - keep it playing music even if you aren't listening to it to get it through full burn-in, you will find a much more musical and melodious sound from your TA-20 too :)
Doing that now. Also realising that investing in a pair of top tubes later on should be on the list -- once this unit has proven its worth to me to do so.
Zeos was comparing the difference between the TA-10 single-ended sound vs the TA-20 Balanced sound, and as far as the stock tubes Zeos says "I think if you swapped tubes you could have an "end game" "- and Zeos's comment wasn't that stock tubes sounded better, but that Balanced sounded better - more specifically the TA-20 sounded better with stock tubes than the TA-10 with burned-in swapped tubes.
I couldn't find the timestamp of it, but if my memory serves me, then he also said that the TA-10 shone with some "special tube" but he would be perfectly happy with the TA-20 on stock tubes. Not at all denying those stock tubes are meager at best and immediate candidate for rolling, but more taken as a queue as to how initial listening would have some wow factor.
For me the stock TA-26 was stuck on stock tubes for a couple of weeks until I could get new tubes plugged in, and I often went back to my TA-20 simply because I thought the TA-26 stock tubes as still new sounded too harsh - but, much better than the TA-20 stock tubes sounded to me, and with the TA-26 wide sound stage and "airy tubiness" being much better than most TA-20 tubes sound.
That's insightful, thanks.
The DAC output attenuation, even as little as -3.0dB, -6.0dB or -9.0dB might be enough to help you reduce the harshness you are hearing during new TA-20 / new tubes burn-in. Trying playing around with the DAC attenuation starting at -3.0dB and increase attenuation until the harshness is reduced as well as possible. Of course, increase the volume on the TA-20 as needed to return the listening level to where you like it. Nothing beats actual hours burn-in time, but I can make the harshness more tolerable during burn-in by reducing the drive input to the amp.
My DAC runs at -9.0 dBFS by default. That also meant that I had to dial the volume know to around the 70's to get a decent volume. I thought that higher volumes from the amp would also incur more distortion from the amp -- a balancing game. So I changed my DAC to 0 dBFS and now volume around the 60's. No change.
 
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Mar 29, 2022 at 3:21 PM Post #1,196 of 1,421

hmscott

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Well, much appreciated!
NP, my pleasure :)
Yes, you may be on to something there. Edit: I also find it lacking in authority and presence, is that something recognizable?
Yup, no presence or authority, and no "slam" or "dynamics", it's "flat".

Those words don't mean much without experience with their opposites :)

Which takes running many tubes through your amp, taking the time for them to burn-in and take time to heat up to stable unchanging sound - several hours usually - with 70F ambient, longer or not at all in a heat losing ambient.
It's true that I'm new to this tube game. The scientist in my has long pulled me towards the "best amp is a wire with gain" kind of thinking. It's that thinking that also led me to build my AMB β22, which may be considered reference depending on which standard you hold it to, and pulls out every technical trick in the book. But I have come to realize that this is not truly what I'm after -- at the end of the chain, I prefer that warm, lush sound of my dad's 70s setup so to speak. And here I am getting into tubes.
Yup, the sterile sound can be boring. Comparing against tubes with flat sterile sound will show better resolution in the SS amp, but against tubes with dynamics and slam, with a wide sound stage and "airy tubiness" will make that sterile SS amp pale in comparison. My Topping A90 was always that way, sterile, but very accurate sounding, with my FiiO M15 in "Over Ear mode" - high current mode - would sound oh, so much more enjoyable than the A90, and now the TA-20 and TA-26 shine with even more edifying sound.

Truly, listening with the Heerlen Tubes in the TA-20, and more so on the TA-26 with the 7236+5692/Melz or 7236/Jan 6AS7G+Kenrad VT-231 is awe inspiring with music and video soundtracks I enjoy.

Remember the old adage, "Those who expect an outcome will find a way of making that outcome happen."

You can find tubes that will always make that SS amp sound "better", but you can also find plenty of tubes that will make you very happy to have tried the TA-20 and have started on the tube amp path.

And, that will hopefully lead to a nice all Tube amp like the TA-26 with equally excellent tubes like a Domino Plate 5998, or Tung-Sol/Cetron 7236, or Bendix 6080WB with Ceramic Spacers and Graphite plates - this is where the Slam/Dynamics solid support comes from in the TA-26, the power tube. Then the Preamp tube needs to be as you like it, a CBS-Hytron 5692 gives solid presentation + sparkling highs, VT-231 Tung-Sol Black Beauty (Black Glass) again with solid presentation + less sparkling highs, or a Melz 6N8S with super extended highs... lots of fun tuning and endless swapping - with a very wide sound stage and "airy tubiness" only found in a few tubes in the TA-20.
Yes, those are the ones. The babies were once intended for use in guided missile systems aboard highly dynamic platforms like navy ships. Unsurprising then, that they have excellent linearity, low noise and low microphonics. Again I may have fallen into the trap of technical prowess when in fact something mellower would better suit my ears... it's like a constant source of conflict between the mind and the heart :smile_phones:

Then there's a bit tongue in cheek too -- I work in the defense sector so imagine the coffee talk at work where I'm ever so proud to announce that guided missile technology has now found its way into my hifi equipment :dt880smile:
Yes, searching for the same attributes you admire in SS amplification with bring you right back to the sound of SS amplification - but that isn't all there is with Tube amps, if you find the right tubes. Once you find them and hear them, you will know what we are saying, and then you can help others to find that nirvana level of sound too :)
Here's a question that might show my newness to this tube game: aren't all PSVANE's new production? If so I do not understand why they also appear on other lists, sometimes quite well rated (and sometimes not so).
It is all done within the comparisons made available to them, to each of us, we are comparing our previous experience against our new experiences, it is all relative to something, it must be so to rate one above or below another experience - including our own personal favorite aspects of the sound as well, which might be very different than others experiences.

And, the same tubes may sound different in different tube amplifiers, especially when put into different applications, with different design parameters and as such we can only compare tubes using the same equipment we are using ourselves, which is why I try to find actual TA-20 and TA-26/DV 336e reviews of tubes, so that their opinions and comments can apply to our needs. That isn't always possible, so averaged ratings are sometimes all we have to reference.

As quoted in my previous post, under that top 12AU7 ratings list, they say:

"DISCLAIMER: This is not a definitive list of all best and worst 12au7. It’s purely based on over 5,000 ratings submitted by the users of this site."

Within their ratings, these tubes are rated accordingly. Other lists, sites, persons, may of course find other attributes more enjoyable for them, causing tubes to be rated in a different level and order within their respective lists.
Doing that now. Also realizing that investing in a pair of top tubes later on should be on the list -- once this unit has proven its worth to me to do so.
And, that is the tough part. I had enough faith from my short experience listening to better and better new reissue and cheap used NOS tubes to know I needed to "up the ante", but from more reading and searching on eBay over months of comparing what tubes I was looking for were selling, that I could find a good price if I wanted to wait, or a slightly more expensive cost if I didn't want to wait, it is that simple.

You don't need to spend hundreds or thousands for a pair of rare tubes - the scarcity of a tube doesn't necessarily indicate the quality of sound you will get out of the tubes - some people collect rare tubes simply to have rare tubes, and then there are the hoarders, and speculators that raise the price for profit, ruining access to those of us looking for "our sound" to listen to music.

All of these tubes cost under $10 new, some a little more, but none of the 12xx7 tubes cost more than $50 new - so that is where I put my target price for tubes for the TA-20, a max of $50 each, or $100/pair, $200/quad - remember to buy extras of the tubes you really enjoy - they aren't making them any more and they do wear out. Having a couple of pair for backups is cool, having hundreds of pairs may indicate you want to be a tube dealer or speculator, long term.

Unfortunately the TA-26 "top sought after tubes" will require a bit more "top end" flexibility. About $150/tube seems to cover the ones I realistically want, while others like the 7236 can be had for $35-$50 "New in Box".

YMMV... please come back and let us know how you enjoy those $1000-$2000 GEC tubes in your future TA-26 amp :)
I couldn't find the timestamp of it, but if my memory serves me, then he also said that the TA-10 shone with some "special tube" but he would be perfectly happy with the TA-20 on stock tubes. Not at all denying those stock tubes are meager at best and immediate candidate for rolling, but more taken as a queue as to how initial listening would have some wow factor.
I know, it's tough slowing down and listening carefully and critcally to what he is saying without jumping to already established conclusions, but please give it a try again at the link "time" above, or here again starting at 108 seconds in to the video.
That's insightful, thanks.
Thanks, then you will want to re-read my post as well as re-listen to Zeos's words starting at that 108s time stamp to get some more fun insights, among others:

Zeos says that even with the stock tubes that the "topography" of sound that the TA-20 provides over the single-ended TA-10 is apparent. Not that the TA-20 stock tubes sound good. In fact he follows that statement up immediately with "swapping stock tubes may provide an end-game of sorts", and later he says he will swap tubes before bringing it to the meetup/show where he wants to demonstrate the TA-20 dual tube sound vs the TA-10 single tube sound. Of course using 3 of the same tube would be a fairer comparison, and taking the time to make sure all of those tubes and TA-10/TA-20 are fully "burned in" before showing them off, would be most fairest.
My DAC runs at -9.0 dBFS by default. That also meant that I had to dial the volume know to around the 70's to get a decent volume. I thought that higher volumes from the amp would also incur more distortion from the amp -- a balancing game. So I changed my DAC to 0 dBFS and now volume around the 60's. No change.
Well, then with your set up you aren't overdriving the TA-20. Your single-ended output must be 2.0V or thereabouts, vs my Topping D90 MQA XLR output of 4.0V. For a single-ended RCA output from a DAC, 2.0V is the standard output, and not high enough to cause a distortion problem. Perhaps my tips will come in handy when you get that balanced output DAC... with similar 4.0V output.:)

Have fun :)
 
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Mar 29, 2022 at 3:47 PM Post #1,197 of 1,421

roderickvd

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Yup, no presence or authority, and no "slam" or "dynamics", it's "flat".

Those words don't mean much without experience with their opposites :)
Oh, fear not, I know :)
Unfortunately the TA-26 "top sought after tubes" will require a bit more "top end" flexibility. About $150/tube seems to cover the ones I realistically want, while others like the 7236 can be had for $35-$50 "New in Box".

YMMV... please come back and let us know how you enjoy those $1000-$2000 GEC tubes in your future TA-26 amp :)
I'm pretty sure *that's* never going to happen :k701smile: although a TA-26 indeed is on my list for later.

In a totally different class I am also interested in a Little Dot MKVIII SE. It's an attention-grabber for sure, and has four times the power of a TA-26, but the SNR of 96 dB leaves me unimpressed. Compare that to the 110 dB of the TA-26. Quite a feat for an OTL, I'd say.
Zeos says that even with the stock tubes that the "topography" of sound that the TA-20 provides over the single-ended TA-10 is apparent. Not that the TA-20 stock tubes sound good. In fact he follows that statement up immediately with "swapping stock tubes may provide an end-game of sorts", and later he says he will swap tubes before bringing it to the meetup/show where he wants to demonstrate the TA-20 dual tube sound vs the TA-10 single tube sound. Of course using 3 of the same tube would be a fairer comparison, and taking the time to make sure all of those tubes and TA-10/TA-20 are fully "burned in" before showing them off, would be most fairest.
Thanks for spelling that out for me, you're right. It's a pity there's no fair comparison of the TA-10, TA-20 and TA-26 there. Thought it was surprising for him to compare the TA-26 to the Darkvoice 336 but not even mentioning the other TA's.
Well, then with your set up you aren't overdriving the TA-20. Your single-ended output must be 2.0V or thereabouts, vs my Topping D90 MQA XLR output of 4.0V. For a single-ended RCA output from a DAC, 2.0V is the standard output, and not high enough to cause a distortion problem.
The single-ended output of a dam1121 is in fact as low as 1.4V RMS even at 0 dBFS.

I see the D90 has an output impedance as low as 100-300Ω. The dam1121's is 640Ω and I believe my upcoming Ares II to be 1250Ω or thereabouts for XLR. I haven't been able to find the input impedance of the xDuoo's, but if that's on the low end then that could also account for a lack of dynamics when paired with a high output impedance DAC.
 
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Mar 29, 2022 at 4:06 PM Post #1,198 of 1,421

hmscott

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Oh, fear not, I know :)

I'm pretty sure *that's* never going to happen :k701smile: although a TA-26 indeed is on my list for later.

In a totally different class I am also interested in a Little Dot MKVIII SE. It's an attention-grabber for sure, and has four times the power of a TA-26, but the SNR of 96 dB leaves me unimpressed. Compare that to the 110 dB of the TA-26. Quite a feat for an OTL, I'd say.

Thanks for spelling that out for me, you're right. It's a pity there's no fair comparison of the TA-10, TA-20 and TA-26 there. Thought it was surprising for him to compare the TA-26 to the Darkvoice 336 but not even mentioning the other TA's.

The single-ended output of a dam1121 is in fact as low as 1.4V RMS even at 0 dBFS.

I see the D90 has an output impedance as low as 100-300Ω. The dam1121's is 640Ω and I believe my upcoming Ares II to be 1250Ω or thereabouts for XLR. I haven't been able to find the input impedance of the xDuoo's, but if that's on the low end then that could also account for a lack of dynamics when paired with a high output impedance DAC.
The GEC tubes are in that rarity/cost range where you'd need to have "true dedication" to your "obsession". :wink:

Yup, at one time the Little Dot MKVIII SE was on my list too...I'm eyeing other steps up in Amps for later down the road, but for me the TA-20 and TA-26 have "outmoded" the Little Dot amps and the Dark Voice amps I was looking at. Those brands are nice though, and I know many enjoy them. :)

For a lower priced step up upgrade to the TA-26, I've "discovered" the dual mono La Figaro 339 - which uses the same tubes as the DV 336e/TA-26, but 2x the number! I'm now buying in pairs... sigh.
Xduoo? Are you there? How about a dual-mono upgrade to the TA-26? Something like a TA-52? :L3000:

Zeos doesn't want to be that kind of reviewer, but he tries to expose a wide range of equipment in an easy to take form for many to access. Zeos also had a "Tube Week" not that long ago, including the TA-26 and mentions of other Xduoo Tube amps, for those of you that have missed them you might enjoy them, if not, please keep it to yourself - we already know he's not the best reviewer - he says so himself all the time...but, everyone, please do post your favorite tube amp reviews, Xduoo especially On Topic here, but hey, what do you like??
Code:
Xduoo TA-26 _(Z Reviews)_ --Start of Tube Week--
https://www.youtube.com/watch?v=dYe0SxWvi8o
Code:
Miltra OTL PCL86 _(Z Reviews)_ Future Tubes from the Future
https://www.youtube.com/watch?v=YzCcw_qbq8M
Code:
McIntosh MHA200 _(Z Reviews)_ 💎U.S.A. Tubes💎
https://www.youtube.com/watch?v=ik0MMdgZiN4
I sent an email to Xduoo asking a few questions, but I used links back here to ask them, so I think I need to ask again explicitly in the email, I'll try again soon :)

One of those questions were the impedance of the outputs on the TA-20/TA-26. But, from usage, I think the headphone outputs are very low impedance - as I can listen to my low impedance IEM's, Planars, but not so for dynamic headphones as my 16 ohm DT-770's sound flat and weak on the TA-26, while the IEMs/Planars rock on the TA-26. The 16 ohm DT770 sounds great on the TA-20!:)
 
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Mar 29, 2022 at 4:30 PM Post #1,199 of 1,421

Silver Wolf

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Not looked at the TA-26 but the TA-20 output impedance is 4.5 ohms and TA-30 is just under 3 ohms (can't remember exactly but from memory was 2.7 or 2.9 ohms )
 
Mar 29, 2022 at 4:38 PM Post #1,200 of 1,421

roderickvd

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Yup, at one time the Little Dot MKVIII SE was on my list too...
What happened? Mitigating the risk of going off-topic, perhaps what drew you to the xDuoo's instead?
Zeos doesn't want to be that kind of reviewer, but he tries to expose a wide range of equipment in an easy to take form for many to access. Zeos also had a "Tube Week" not that long ago, including the TA-26 and mentions of other Xduoo Tube amps, for those of you that have missed them you might enjoy them, if not, please keep it to yourself - we already know he's not the best reviewer - he says so himself all the time...but, please do post your favorite tube amp reviews, Xduoo especially On Topic here
I know. I missed those tube reviews of his, will check them out. At the same time you're very right, when you start hunting for those popular tubes you see prices going up fast. Much more fun poking around the likes of eBay, seeing what's being offered and see what you stumble on. Of course, having a wish list to cross-reference them to.
I sent an email to Xduoo asking a few questions, but I used links back here to ask them, so I think I need to ask again explicitly in the email, I'll try again soon :)

One of those questions were the impedance of the outputs on the TA-20/TA-26. But, from usage, I think they are very low impedance - as I can listen to my low impedance IEM's, Planars, but not so for dynamic headphones as my 16 ohm DT-770's sound flat and weak on the TA-26, while the Planars rock :)
Oh, that'd be great. I'm particularly interested in the input impedance too but let's talk output impedance.

The output impedance of the TA-20 was measured on ASR as 4.5Ω. That's not great but not bad either. I like to leave a damping factor of 10x so you should be safe from 45Ω onwards. A ratio of 8x is good enough so you should be safe even with those modern 32Ω cans (well, almost...)

I haven't seen the TA-26 measured, but we can estimate it. Given a typical 6N5P transconductance of 4400 mΩ, you'd expect an OTL output impedance of 227Ω. Now with common damping factors that's rather tough to match. And also non-intuitive: if this were true, would all OTL designs not suffer from poor parings? The EE is explained here on ASR. Management summary: those damping factors are common wisdom for low impedance outputs, not when matching high impedance output with high impedance loads.

I forgot to ask: any experience with rolling the coupling caps in these amps? I saw one forum member having tried Mundorf MCap Classics, and not hearing any improvement immediately after. I don't find that surprising, first because the standard MCaps aren't better of perhaps worse than the stock ELNA SILMIC's -- already quite good! Second because such caps need burn-in very much.

Staying within the Mundorf brand I would look at the SUPREME EVO line (looking at the oil and silver/gold ones as money allows). Not only are they excellent caps by themselves, they are also half the size of what's normal, allowing for greater spacing between them. That means lower capacitive coupling and so lower crosstalk.

Then perhaps sprinkling in some small-package bypass caps.

Just rambling here. Again wondering if more of you have had any cap rolling experience?

Edit: @hmscott I also looked at the La Figaro 339. Initial thought: awesome! Two seconds after: wait, a dual mono setup with a single XLR-3 output? That's just silly. By having a shared ground you're throwing away the benefits that a true balanced amplifier give you (well, one major aspect anyway). Not saying balanced headphones are the holy grail, but here the entire thing might as well have been single-ended.
 
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