[albertmuc]

https://www.ebay.com/itm/265405072714?hash=item3dcb60054a:g:BVAAAOSwf7NhL8nv

Just ordered a pair. We'll see how these fares

I also ordered out of solidarity

 

[jonathan c]

Glad to hear it. Like i mentioned above i went for the foil getters rather than matched pair in this instance. I'm excited to see what the hype is about, as i really was determined to stick with my E180CC tubes for the foreseeable future. I find them just about perfect tbh, so it'll take something special to dislodge them from the sockets permanently

There is plenty of raving about the RFT foil getters in the Schiit Mjolnir II threads !

 

[hmscott]

Each of you with a TA-20 might want to try the 12AT7/ECC81 out for yourselves.

When plugging in the 12AT7/ECC81 and variants like the 6060, 8162, CV4024, E80CC, E180CC, I've found they all bring a very special sound that in comparison the 12AU7's sound "uninspiring", at least to me and the people that have posted their own thoughts on trying them in their TA-20's.

The 12AX7 has even more gain than the 12AT7, and it indeed sounds "hot" to me in the TA-20, so I've only tried a couple of pair of them, and then that was enough to convince me the magic is in the 12AT7 and variants in the TA-20.

The E180CC's I've plugged in to the TA-20 are really the pinnacle of the best tubey sound in the TA-20, but the Brimar 6060 Yellow T's, Tung-sol Black Glass 12AU7 come close

PHILIPS HOLLAND PINCHED WAIST D FOIL GETTER E180CC <= Latest, competed well with the TA-26, until the latest combination of tubes for the TA-26, see below
Matched Pair E180CC NOS Mullard Holland Valve Tubes
E180CC 5965 12AV7 NOS Mullard Holland Valve Tubes

The TA-26 with stock tubes right out of the box was far more tubey sounding to me than the best 12AT7 in the TA-20, and the TA-26 has only gotten better with 1940's/50's/60's tube changes. Earlier I posted my recent tubes for the TA-26, and right now these 2 pairings are really amazing, and only the newest E180CC Amperex Pinched Waist tubes come close, but not quite enough. These tube combinations on the TA-26 really are thrilling:

Jan RCA 6AS7G + KEN-RAD JAN CKR 6SN7 GT VT-231 1944 LEGENDARY BLACK BEAUTY CHROMED FOIL

And it really is a toss-up whether that KEN-RAD VT-231 or this CBS JAN CHY 5692 are "better", they both sound different with the JAN RCA 6AS7G, both thrilling and compelling, I was mesmerized with the JAN 5692+JAN 6AS7G.

Sorry about that, we were talking about the TA-20?

I've written a lot here on the TA-20 tubes and Xduoo interactions, and I will continue to post about new TA-20 tubes as I find gems like this one, which shows I haven't completely given up on the 12AU7 in the TA-20, these are supposed to be comparable to Telefunken Smooth Plate tubes. As I've tried to find affordable NIB Telefunken tubes and find them far too pricey, I am hoping these come close:

4 Strong Matched NOS IC Ei Yugoslavia Long SMOOTH Gray Plate 12AU7 / ECC82 Tubes

It has been very enjoyable slowly stepping through the 12AU7's until I found enough people recommending 12AT7 as sounding so much better in the TA-20, that I asked Xduoo if 12AT7/12AX7's were also supported in the TA-20:

Spoiler: Xduoo's short reply relayed through Hifigo

is it possible to substitute the 12AU7 with 12AT7 or 12AX7 : Xdoo reply yes no problem. <= for TA-20, and others have inquired Xduoo with same answer

And, I've been running nothing but 12AT7 variants for the better part of a year with no apparent problems. No smoke or any increase in heat output of the TA-20 or the running tubes.

Also, the difference in "gain" is handled / balanced by the Xduoo discrete transistor SS output stage. On the TA-20 a difference in "gain" between the 12AU7 and the 12AT7/12AX7 does not affect - increase- the TA-20 volume. The Volume Dial setting on the TA-20 remains the same for the same output no matter which 12xx7 tube is installed.

I have my eyes out for other desireable 12AU7 tubes, but for right now I am mostly focusing on the TA-26

 

[hmscott]

If you can, order a pair of RFT ECC82. These are fantastic 12AU7s (especially the ‘foil getter’ version). I have been using these in a Rogue RH-5.

+1 on the RFTs. I’ve been saying this for years.

https://www.ebay.com/itm/265405072714?hash=item3dcb60054a:g:BVAAAOSwf7NhL8nv
Just ordered a pair. We'll see how these fares

There is plenty of raving about the RFT foil getters in the Schiit Mjolnir II threads !

In this case; No. The reason for that was that a matched pair was simply unavailable with the foil getters, at least for a sane amount of money.
Also i have yet to have an audible issue regarding the matter (mached vs unmatched pair) tbh, meaning as long as the tubes are all good, of the same type and NIB+NOS i will not be able to hear anything out of sorts unless one ore both of the tubes are faulty.
If my equipment cost 10-20 times more i might care, but the differences in this case should be miniscule if any.

The only consideration I've found is that in general the tube dealers match the best measuring tubes and sell the odd ends as singles. I've requested many times of sellers to test and provide only 100%+/100%+ tubes, "NOS"/"NIB" included. Anything less than New is Used - with who knows how many hours on the tube(s). Recently I got lucky with that Jan RCA 6AS7G "NIB", as he couldn't do more than Emission tests with his tester, fortunately it turned out to be a great tube.

Starting out I was looking for inexpensive Used tubes with 85%/85% or greater Lifetime measurements for the TA-20, and most were fine tubes - already broken in - but when I finally branched out from headphones to IEM's I quickly found most of those tubes HISSED like crazy, oddly I didn't hear it in the HD598cs at the time.

For that RFT 12AU7 with Foil Getter, they will simply pull them as "unused open box" from a production case, so our result is random and untested, but "New in Box" for a great low price.

And, the RFT 12AU7 have always looked interesting, and I'm looking forward to trying the Ukraine RFT ECC82 12AU7 Tube on my next Tube buying hunt.

At $20/tube I'll probably get 4 of those RFT tubes, 2 pair, with tubes as backup, as a hedge against getting 1 bad one out of a single pair. It takes so long to get packages from Ukraine/Russia these days, 6-8 weeks or more, it would be sad if I ordered 1 tube/pair of anything, and a single tube ended up bad, so I'd have to order again and wait another 6-8 weeks for a replacement tube.

The Russian tubes I've bought so far - for the TA-26 - have only been from 2 sellers, but both sellers came back with the same response, they don't test tubes, they sell new tubes direct from manufacturers case, you get what they pull from the box, untested. 12-rocketman also has some Melz 1578 pairs for $350, very desireable variation, with sonic differences from the regular 6N8S, too expensive for me

6N13S / 6AS7G / ECC230 TUBE SVETLANA Double Triode NOS DATE 1960`s USSR Lot 1pc. - Estimated delivery Fri, Feb 18 - Mon, Mar 7
6N13S /6AS7G /ECC230 /6N5S TUBE SVETLANA TRIODE NOS IN BOX OTK lot 1pc. or more - Estimated delivery Fri, Feb 18 - Mon, Mar 7
6N5S / 6N13S / 6AS7G / ECC230 SVETLANA TUBE NOS OTK USSR RARE 1950`s lot 1pc. - Estimated delivery Fri, Feb 18 - Mon, Mar 7
6N13S / 6AS7G / ECC230 SVETLANA TUBE Double Triode NOS OTK USSR Lot 1pc. - Estimated delivery Fri, Feb 18 - Mon, Mar 7
1pc 6N8S / 6Н8С ~ 6CC10,6SN7,1578 Double triode NEW. OTK. MILITARY. METAL BASE - Estimated delivery Mon, Mar 7 - Fri, Apr 1

This is from a different seller purchased recently, hopefully they will arrive close to the estimate:
6N8S / 6SN7 / 1578 MELZ TUBE HOLE PLATE NOS METAL BASE DATE 1953 Lot 1pc. - Estimated delivery Wed, Mar 16 - Wed, Mar 30

With the prices so low I was able to order a spread of decades, and multiples of the 6AS7G variants, but none are tested or matched - for the TA-26 there are 2 different tubes, so there is no need for a "matched pair".

Once I got approval from Xduoo for using 12AT7/12AX7 tubes in the TA-20, those 4 Strong Matched NOS IC Ei Yugoslavia Long SMOOTH Gray Plate 12AU7 are the first 12AU7's I've invested in since. Also available from:

Spoiler: Also listed on Reverb from a different seller

https://reverb.com/item/619810-ei-y...te-preamp-tubes-built-on-telefunken-equipment
About This Listing
WE ARE OFFERING SINGLE VINTAGE 70'S EI YUGOSLAVIA BRANDED INTL SERVICEMASTER 12AU7A ECC 82 SMOOTH PLATE PREAMP TUBES. THESE WERE BUILT ON TELEFUNKEN MANUFACTURING EQUIPMENT IN THE 70'S. THEY HAVE SUPERB BUILD QUALITIES WITH HEAVY GLASS, LONG 17MM SMOOTH PLATES, HALO GETTERS AND PROVIDE THAT GREAT FLASH WHEN ENERGIZED. THE MUSICAL QUALITIES OF THESE TUBES ARE FAR SUPERIOR TO ANY CURRENT PRODUCTION TUBES AND RIVAL SOME OF THE BEST 12AU7 VARIANTS EVER MADE. PRICING IS PER SINGLE TUBE BUT WE CAN MATCH PAIRS OR QUADS AT NO ADDITIONAL CHARGE.

FYI, I haven't bought anything on Reverb, or from this seller...but I have purchased a dozen times from desireme1979 and every time I've felt well treated and she's a tough but fair bargainer that has come through for me so many times when I've requested her to find specific tubes she isn't currently listing on eBay, and again with these IC Ei 12AU7's. Costing a bit more from her, but given her excellent service, I don't mind paying a bit more than the lowest price

Those TA-26 tubes are about 2x-3x the cost per tube of the TA-20 options I've purchased, about $50/tube for the best sounding 12AT7 variants and more like $150+/tube on average for the 6SN7 and $70/tube for the 6AS7G, but it has been worth it for the thrilling sound. Those average prices can be a lot higher, there are a lot of overpriced tubes out there, the most sought after being the main targets for excess pricing.

The Russian 6AS7G and 6SN7 variants are so inexpensive, I'm hoping what I've heard about pairing a 6N13S/6N5S with the Shuguang Natural Sound Series CV181-T or 6N8S is claimed to be end game for some on the Darkvoice 336E, perhaps it will be the same on the TA-26 .

I really need to prioritize getting a Sennheiser HD600 and HD650 with 300 ohm impedance, starting with the HD600. My HD660s 150 ohm impedance headphone sounds awesome on the TA-26 and TA-20, but on the TA-26 it is possible that a 300 ohm impedance might sound better, like my Beyerdynamic DT990/DT880 600 ohm impedance does compared to the 16ohm and 250 ohm Beyerdynamic DT-770/DT880's. It is time for a new pair of 300 ohm headphones for the TA-26.

 

[jonathan c]

XDUOO TA-20: Is it fully balanced internally (i.e. between input and output) or does it only ‘feature’ balanced sockets? I cannot tell from the ‘xduoo.net’ description.

 

[hmscott]

XDUOO TA-20: Is it fully balanced internally (i.e. between input and output) or does it only ‘feature’ balanced sockets? I cannot tell from the ‘xduoo.net’ description.

Good question, fortunately Xduoo shared the signal architecture:

"Hi, Scott
1. U1, U2 is the OPA which convert the single-ended signal from RCA into a balanced signal. If it is a balanced input, the signal does not pass through U1 and U2.
The circuit architecture diagram is as follows:

Although the diagram doesn't show it, there are 2 AUX IN's, AUX1 and AUX2, all 3 positions are run through by pushing in the Volume control. There are 3 Blue indicator lights under the Balanced Headphone Socket on the bottom right that show which position the input switch is in right now.

I use both AUX IN's, with 1 coming in from a Docked Nintendo Switch, and one on a 2M long input cable I can use to plug in portable radio's and other devices with a 3.5mm Audio Line output. I've specified and ordered custom Worlds Best Cables using thinner Mogami 2893 Quad Shielded cable.

This all came about when I asked Xduoo about swapping in better OPA's, and once Xduoo explained the design it became clear there might not be better OPA's for this application, and the Balanaced Input doesn't pass through any OPA at all.

So yes, the TA-20 is a Fully Balanced design from input to output

 

[ostewart]

I've been spending some time with the TA-26 and really like it - https://www.head-fi.org/showcase/xduoo-ta-26.25647/reviews#review-27937

I've got some RCA (Hewlett Packard branded) 6AS7G tubes on the way, paired with a Sylvania 6SN7GT (Rogers branded) tube - really easy to tube roll and a lovely little OTL amp for the price.

 

[PetFju]

I had an interesting experience with my TA-26 (again). I hooked up my AKG K712 Pro's, which are quite nice on tube amps according to a lot of people. This resulted in an unfortunate experience. They basically sounded the same way as Sundaras on this amp; Flat, tinny, and bass-shy. And when turning up the volume there was quite audible distortion.
Now i have to say i didn't expect this, as the 712's are dynamic driver, 62 ohm headphones. And as such should be within the specs suited for this amp. That really sucked, i have to admit.
For now i am still stuck on my Atrox V2 for these cans, so maybe i should run the TA-26 as a pre for that to get some tube magic out of it (even though they sound excellent on the Atrox).
Anyways; anyone know if the pre out of the TA-26 is decoupled from the headphone jack out? Meaning; will the headphones have to be disconnected to use the pre out?

EDIT; BTW another question..I have in my budget for the next month to get either a Sennheiser HD 650 or a pair of HD 660S to use with the TA-26. Any experiences with any of these on the TA-26 out there?

 

[hmscott]

My eBay order for 4 Russian 6H13S (6N5P) 6AS7G Svetlana tubes + 1953 Melz 6N8S (+ 1 free 6H13S tube) have arrived, and it only took 10 days shipping from Russia to get to Northern California.
https://www.head-fi.org/threads/for-6as7g-tube-rollers-here.410326/post-16819953

I'll try them in my TA-26 in reverse age order paired with a 1957 RCA JAN 5962 Brown Base tube that I've been enjoying paired with a 1950 JAN RCA 6AS7G. Then I'll swap the 5962 with the 1953 Melz 6N8S.

 

[hmscott]

I had an interesting experience with my TA-26 (again). I hooked up my AKG K712 Pro's, which are quite nice on tube amps according to a lot of people. This resulted in an unfortunate experience. They basically sounded the same way as Sundaras on this amp; Flat, tinny, and bass-shy. And when turning up the volume there was quite audible distortion.
Now i have to say i didn't expect this, as the 712's are dynamic driver, 62 ohm headphones. And as such should be within the specs suited for this amp. That really sucked, i have to admit.
For now i am still stuck on my Atrox V2 for these cans, so maybe i should run the TA-26 as a pre for that to get some tube magic out of it (even though they sound excellent on the Atrox).
Anyways; anyone know if the pre out of the TA-26 is decoupled from the headphone jack out? Meaning; will the headphones have to be disconnected to use the pre out?

The AKG K712 Pro's should be well driven by the TA-26. Did you set your source at 100% drive?, and modulate the drive from your DAC into the TA-26?

I'm finding that while it is nice to set a -15dB to -20dB attenuation on the D90 DAC to allow for more volume dial range, the best sound is when I set the D90 to 100% output (or put it in DAC mode), but then I have a very narrow "notch" to use for Volume.

I get less punch in the HD660S if I use the -15dB to -20dB D90 Pre-mode attenuation, but I don't find it so affected that it outweighs the advantage of having 9 oclock to 1 oclock on the volume dial to "play with".

But if you have a bright headphone like the AKG 712 Pro, it might sound too thin - as you are reporting - to pre-attenuate using the DAC/source, so running the source chain at 100% and dealing with the "notch" for volume range, might provide the best sound right now. You could also try an iFi iEMatch+, see below, to allow more range on the volume dial of the TA-26.

Also, I've played with various metal combinations for IEM wires, and appled that when I bought headphone cables. I use OCC Copper Only for bright headphones, and OCC Copper coated with Silver for everything else.

You could try getting OCC Copper cable like this one:

GUCraftsman 6N OCC Copper For SENNHEISER IE300 IE900 AKG N30 N40 N5005 4.4MM Headphone Upgrade Cable
https://www.aliexpress.com/item/1005003286992781.html

IDK if that is the correct connector for the AKG 712 Pro, so be sure to ask them first before ordering. They were very helpful to me when I first ordered cables for my Hifiman Ananda, HE6SE, and HD660S.

I ordered all 4.4mm or 4-pin XLR ended GUCraftsman cables, nothing for 3.5mm or 6.35mm as needed by the TA-26, so I am using the stock cables from Sennheiser and Hifiman, and they all sound great to me on the TA-26. The HE6SE V2 sounds better on the TA-20, but the Ananda sounds good to me on both the TA-26 and TA-20.

Eventually I'll order GUCraftsman cables with 6.35mm/3.5mm ends or the TA-26, probably one each OCC Copper / Silver for the Hifiman headphones - so I can swap both with Silver/Copper to see how they sound on the TA-26, on a set of Copper/Silver for the HD660S/HD600/HD650.

Interestingly I found a discussion on diyAudio discussing what tube amp specifications would be well matched to the AKG 712 Pro:

Suggest me diy tube amp for my AKG K712 Pro
https://www.diyaudio.com/community/...e-amp-for-my-akg-k712-pro.324786/post-5484022 <= Detailed answer

There are also attenuation/filtration adapters you can try, here's a few from iFi for 3.5mm headphone matching with low impedance headphones to headphone amps:

iEMatch+ - 3.5mm The newest version...
https://ifi-audio.com/products/iematch-plus/

iEMatch - 3.5mm Previous version, I've still found it on sale...
https://ifi-audio.com/products/iematch/

iFi also has a 2.5mm/4.4mm versions for balanced connections.

And, iFi has a previous design they still sell called the "Ear Buddy", similar ideas, attenuate power to allow turning up the amp to gain bits of resolution:

Ear Buddy
https://ifi-audio.com/products/ear-buddy/

iFi also is starting to build these iEmatch+ design features into their amps, in addition to the normal Gain settings, to help low impedance/sensitive headphones "match" with the amplifier.

I haven't tried them yet, but others have reported them helping with various low impedance headphones/IEM's matching their headphone amp/DAP/dongle

EDIT; BTW another question..I have in my budget for the next month to get either a Sennheiser HD 650 or a pair of HD 660S to use with the TA-26. Any experiences with any of these on the TA-26 out there?

It is what I am going to work on in the next month or two, depending on headphone sales, an HD600 300 ohm and an HD650 300 ohm, both might sound even better than my HD660s 150 ohm, but IDK how, as this HD660S pairs so well with the TA-26 already.

I'm going to start with the HD600 first, I've been told that is really the one to get for tube amplifiers, but others say they enjoy the HD650 the best, so perhaps I'll buy whichever is on the best discounted sale first.

 

[alexeyi]

I had an interesting experience with my TA-26 (again). I hooked up my AKG K712 Pro's, which are quite nice on tube amps according to a lot of people. This resulted in an unfortunate experience. They basically sounded the same way as Sundaras on this amp; Flat, tinny, and bass-shy. And when turning up the volume there was quite audible distortion.
Now i have to say i didn't expect this, as the 712's are dynamic driver, 62 ohm headphones. And as such should be within the specs suited for this amp. That really sucked, i have to admit.
For now i am still stuck on my Atrox V2 for these cans, so maybe i should run the TA-26 as a pre for that to get some tube magic out of it (even though they sound excellent on the Atrox).
Anyways; anyone know if the pre out of the TA-26 is decoupled from the headphone jack out? Meaning; will the headphones have to be disconnected to use the pre out?

EDIT; BTW another question..I have in my budget for the next month to get either a Sennheiser HD 650 or a pair of HD 660S to use with the TA-26. Any experiences with any of these on the TA-26 out there?

I sometimes use my HD660S with the TA-26 and I find the pairing very good even with the stock 6.35 cable. In very few cases, on some of the old songs in my library it sounds a little bit muffled, but for the rest no problem.

 

[hmscott]

I sometimes use my HD660S with the TA-26 and I find the pairing very good even with the stock 6.35 cable. In very few cases, on some of the old songs in my library it sounds a little bit muffled, but for the rest no problem.

It might be the tube pairing currently, as I've had the same "muffled" sound reaction with some songs - resonating to the music, building up a "standing wave" which adds an unusual pressure in my ears - which interferes with the clear sound I usually hear.

So far only the JAN RCA 5692 has completely removed that "muffled" sound, very surprising actually. Even my "best" 6SN7GT VT-231 "Black Beauty" does it to a smaller degree, all of the VT-231's can produce that higher than normal "standing wave" pressure with some music.

I'm hoping to find other 6SN7 tubes that have less or none of that "resonance", so far the 6SN7GT has the most, 6SN7GTA has a bit less, and maybe the 6SN7GTB will improve the sound to the 5962 pristine clean sound level.

I think I'll try the 1953 Melz with the 1950 JAN RCA 6AS7G, and see if the Melz will do as well as the 5962 - or where it falls between the VT-231 and 5962

And, this might be a great example of what some call "lifting a veil" obscuring the sound, it was very apparent when I moved from one of the 6SN7 GTA SYLVANIA NOS SAME DATE CODE TALL GLASS PLATINUM MATCHED QUAD tubes to the JAN RCA 5692, the pressure was gone and the clarity was revealed and the delivery was more dynamic with more distinct Bass. And, when I went back to the KEN-RAD JAN CKR 6SN7 GT VT-231 1944 LEGENDARY BLACK BEAUTY CHROMED FOIL NIB MINT from the 5962, the pressure was back.

I'd like to add that for the most part I didn't notice that resonating pressure, it was only during certain tracks, and is a very small % of my music, video, etc. In fact the fast action dynamic movie sound is awesome with the VT-231 tubes, as is R&R, same for Hip-Hop and Rap, no problems. It is only some audio that does it.
I was trying to find a word to describe that resonating high pressure feeling, and "muffled" is a good one, thanks!

 

[alexeyi]

It might be the tube pairing currently, as I've had the same "muffled" sound reaction with some songs - resonating to the music, building up a "standing wave" which adds an unusual pressure in my ears - which interferes with the clear sound I usually hear.

So far only the JAN RCA 5692 has completely removed that "muffled" sound, very surprising actually. Even my "best" 6SN7GT VT-231 "Black Beauty" does it to a smaller degree, all of the VT-231's can produce that higher than normal "standing wave" pressure with some music.

I'm hoping to find other 6SN7 tubes that have less or none of that "resonance", so far the 6SN7GT has the most, 6SN7GTA has a bit less, and maybe the 6SN7GTB will improve the sound to the 5962 pristine clean sound level.

I think I'll try the 1953 Melz with the 1950 JAN RCA 6AS7G, and see if the Melz will do as well as the 5962 - or where it falls between the VT-231 and 5962

And, this might be a great example of what some call "lifting a veil" obscuring the sound, it was very apparent when I moved from the KEN-RAD JAN CKR 6SN7 GT VT-231 1944 LEGENDARY BLACK BEAUTY CHROMED FOIL to the JAN RCA 5692, the pressure was gone and the clarity was revealed.
I was trying to find a word to describe that high resonating high pressure feeling, and "muffled" is a good one, thanks!

At the moment, the IRL situation(work+personal life) does not allow me to spend my time studying and rolling tubes.
Hopefully, as we approach summer, I will have some spare time to get deeper into rolling tubes for TA-26. If I get the right combination or a specific tube that can fix the issue that seems to bother us a little, I'll post my finding here. Ultimately we are all about enjoying the music

 

[hmscott]

At the moment, the IRL situation(work+personal life) does not allow me to spend my time studying and rolling tubes.
Hopefully, as we approach summer, I will have some spare time to get deeper into rolling tubes for TA-26. If I get the right combination or a specific tube that can fix the issue that seems to bother us a little, I'll post my finding here. Ultimately we are all about enjoying the music

What tubes are you listening with on the TA-26?

 

[alexeyi]

What tubes are you listening with on the TA-26?

If I remember correctly, I have a Tung Sol 6SN7 and a SED wing 6AS7G. It has been a while since I switched the default Chinese tubes.
Sound is really clean and crisp with the combination, just what I am after. Hope it helps you.