[hmscott]

Great news, per Xduoo response below, the TA-26 can easily handle the 950mA heater current of the NOS Mullard ECC32/CV181. Normal 6SN7 tubes draw 600mA.

The modern Chinese CV181-? models are actually 6SN7 designs, and are not at all related to the original Mullard ECC32/CV181 design specifications. So the modern Chinese CV181-? tubes are also compatible with the TA-26.

I asked Hifigo.com / Xduoo.com (service@hifigo.com and service@xduoo.com ) specifically about the Mullard CV181 which draws 950mA heater current vs 600mA:
The question I sent through Hifigo: https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/post-16857775
Answer direct from Xduoo: https://www.head-fi.org/threads/the-reference-6sn7-thread.117677/post-16860831

From service@xduoo.com to service@hifigo.com, me - Mar 11, 2022, 10:20 PM (13 hours ago)

"Hi,
No problem, the TA-26 maximum heater current is 4A
Best Regards,"

Unfortunately, these power tubes draw 5A heater current, well over the TA-26 maximum of 4A:

6528 - equiv to 5998 but very high gain at 9, twice the current load. Make sure you amp can handle it
6336 - like 6528 but low gain at 2, still twice current load. Make sure you amp can handle it
https://www.head-fi.org/threads/for-6as7g-tube-rollers-here.410326/post-5441008

They are available on eBay, but are not compatible with the TA-26
6336: https://www.ebay.com/sch/i.html?_from=R40&_nkw=6336+tubes&_sacat=0&_sop=16
6528: https://www.ebay.com/sch/i.html?_fr...itleDesc=0&_odkw=6528+tubes&_osacat=0&_sop=16

Specifications Sheets: show their heater current requirement s 5A, too much for the 4A capability of the TA-26
6336A: https://frank.pocnet.net/sheets/127/6/6336A.pdf
6336B: https://frank.pocnet.net/sheets/077/6/6336B.pdf
6528: https://frank.pocnet.net/sheets/127/6/6528.pdf
6528A: https://frank.pocnet.net/sheets/077/6/6528A.pdf

 

[hmscott]

As an additional question to Xduoo, about the 6BL7/6BX7:

hmscott <hmscott@gmail.com> Dec 31, 2021, 2:57 PM to service@xduoo.com
"Hi, I didn't want to get too many things into that one email, so here is the 2nd part of what he asked, can the TA-26 support the 6BL7/6BX7, I am assuming pertinant to my question about the 6as7ga:
"Scott,Yes,I have,NOS or used?The best tubes that fits your 8BD socket if you have enough filament current is 6528 and you may try 6BL7/6BX7,THX"
What do you think?
Thank you!, Scott"

Here is Xduo's response:

service@xduoo.com Feb 28, 2022, 2:46 AM (12 days ago) to me
"Hi, Scott
Looking at the datasheet, it can be used, but we haven't tried it, and we can't buy this tube in China
Best Regards,"

Trying the 6BL7 / 6BX7 in the TA-26 would be experimental

6BL7 Information: https://tdsl.duncanamps.com/show.php?des=6BL7
6BX7 Information: https://tdsl.duncanamps.com/show.php?des=6BX7

 

[hmscott]

Hi Guys/Gals, found these interesting articles on tubes, not quite specific enough for any particular thread, but I thought as tube people you'd enough them

How worried are you tube amp owners?
"Tube amp owners, with this tube "crisis" how worried are you?"

As a IEEE article about tubes, I found it very informative:

THE COOL SOUND OF TUBES
One of the last remaining tube domains is in music applications, but there the devices flourish and even innovate

 

[hmscott]

I hadn't heard, but just found out that Hifigo is dealing with Shenzhen's shutdown for Covid:
https://hifigo.com/pages/hifigo-shipping-delay-during-shenzhen-covid-19-lockdown

HiFiGo Shipping Delay During Shenzhen Covid-19 Lockdown​

We are sorry to tell you that Shenzhen, our city, had locked down due to Covid-19 guidelines from Goverment untill March,20th.
Shipments have been and will be delayed. We are still able to ship out our orders while adhering to the guidelines, but the processing and shipping time would be longer than usual. Some orders may have already been shipped out but may take a while for the courier companies to update the tracking links.
Please be assured that our whole team is doing our best to handle the orders as quickly as possible. We will continue to keep you updated, should there any major changes again. We sincerely seek your understanding in this matter and our customer service team will be 24/7 for you still online. Thank you very much.
Cheers,
HiFiGo Team

Hopefully the lockdown ends when planned...

Update: Hifigo posted an additional update at that URL and via their front page header:

Updated 3/20/22
We are happy to tell you that HiFiGo shipment will be resumed since 3/21/22, we really appreciate your highly support and understanding during this week. Your order will be handled asap when we are back tomorrow.

 

[roderickvd]

I think I'm bit by this too. This weekend I placed an order with Shenzhen Audio through Amazon. On Monday the shipping label was printed and registered with DHL, but so far the package hasn't been received by DHL yet. I've seen the same happen with some AliExpress orders from around the same time.

 

[hmscott]

I think I'm bit by this too. This weekend I placed an order with Shenzhen Audio through Amazon. On Monday the shipping label was printed and registered with DHL, but so far the package hasn't been received by DHL yet. I've seen the same happen with some AliExpress orders from around the same time.

You could email them and ask
support@shenzhenaudio.com

I hadn't known of the lockdown, and I didn't check the Hifigo.com site before I sent an email asking for a custom cable to go with an IEM order, and this is the reply I received back:

"Hello Scott,
Owing to the covid-19, Shenzhen is in a lockdown and would last one week. And the workers in the factory don't work. So we would handle this thing next week.
Hope you could understand.
Best Regards, xx"

I wrote back:

"Thank you xx! Of course, I hope you all stay safe and healthy!
Good health and happiness to all of you
Scott"

"Hello Scott,
Thank you~
You too "

I'm sure the nice folk at Shenzhen Audio would also be happy to assist your inquiry about the state of shipping your item(s).

Long back, when Covid first hit, and China was having country wide shutdowns, I had an order that was waylaid for weeks, but as soon as they could go back to work (Hifigo.com) they shipped it right out. We exchanged many emails during that lockdown time, getting to know each other, discussing various subjects, and I think it helped both of us get through it all.

 

[roderickvd]

I can be patient. Other than to satisfy my curiosity I am sure that they will ship as soon as they can. DHL will alert me once they have. Hopefully the good folks in Shenzhen will be safe and healthy.

 

[Ufanco]

I been doing some tube rolling on the Xduoo t20 so thought I add my thoughts on tubes I tried. My setup is shanling m6 pro 21 as source into a Oriolus BA300S mkii as preamp then the Xduoo Ta20. Using the Mest mkii iem’s I wanted the amp and preamp to not add any hiss to the sound. This setup allowed me to reach this goal.
Tubes tried so far and ranking of each.
AMPEREX 12AU7/ECC82 so far the best sounding that I tried.
NORTHERN ELECTRIC 12au7 came with the used Xduoo surprised on sound since it’s a new tube.
RCA Cleartop 12au7 close to the northern electric feel each has it plus and minus.
WESTINGHOUSE CONN Long black plate D getter 12au7 nothing special sound wise.
stock tube well the music played that about all. Shame they included these tubes highly recommend replacing, even the inexpensive RCA cleartop is a big improvement over these tubes.

It’s a bit overwhelming since there so much choice on the 12au7 tube options. still i’m having a blast trying different tube since there’s definitely a difference in sound quality. Much more noticeable than a cable or even a tip change.

​

 

[roderickvd]

Shenzhen shipped this morning. Quarantine must have been lifted according to plan! Should arrive first week of April.

 

[Ufanco]

Shenzhen shipped this morning. Quarantine must have been lifted according to plan! Should arrive first week of April.

Awesome I would suggest looking for something to replace stock tubes well you wait. Even something like a rca cleartop sounds much better than stock. Can get some great deals on the ones marked conn. There made for organs and inexpensive.

 

[roderickvd]

I already have a matched pair of Sylvania 6189’s waiting to be installed!

 

[albertmuc]

„xDuoo TA20“: I currently use the XLR (balanced) input and the single-ended 6.5mm output for my headphones.
Would there be a sonic gain on the XLR (balanced) output…?

 

[roderickvd]

For sure. The single-ended output goes through an opamp, the balanced one doesn’t.

 

[hmscott]

„xDuoo TA20“: I currently use the XLR (balanced) input and the single-ended 6.5mm output for my headphones.
Would there be a sonic gain on the XLR (balanced) output…?

For sure. The single-ended output goes through an opamp, the balanced one doesn’t.

Well, we know that the 2 RCA single-ended inputs are converted to balanced signals internally via opamp's. The now balanced signal is pre-amplified by the tube stage, and then further amplified by the discrete Class-A transistor stage to drive the headphone outputs.

An opamp isn't needed, or possible, to convert the amplified balanced signal, it is split off to the XLR and SE outputs via the discrete output stage.

Both the XLR and SE outputs are supposed to be the same wattage output.

Here is what the Xduoo product page says for power output via the XLR and SE outputs:
Output power: Phone: 2,000 mW (32 ohms); XLR: 2,000 mW (32 ohms)

I do recommend using the Balanced output if only to hear the difference between the balanced output and the single-ended output, and on many amps/DAPs there is a power advantage given to their balanced output so for listening on headphone amps other than the TA-20 it is important to be equipped to connect with an XLR / 4.4mm / 2.5mm / 3.5mm balanced cable to connect to a balanced output to reap the power and potential tonal advantages.

On the TA-26 I do notice a tightening of the center image with the SE output as compared to the TA-20 SE and XLR balanced output - at least it is noticeable to me

 

[albertmuc]

Well, we know that the 2 RCA single-ended inputs are converted to balanced signals internally via opamp's. The now balanced signal is pre-amplified by the tube stage, and then further amplified by the discrete Class-A transistor stage to drive the headphone outputs.

An opamp isn't needed, or possible, to convert the amplified balanced signal, it is split off to the XLR and SE outputs via the discrete output stage.

Both the XLR and SE outputs are supposed to be the same wattage output.

Here is what the Xduoo product page says for power output via the XLR and SE outputs:
Output power: Phone: 2,000 mW (32 ohms); XLR: 2,000 mW (32 ohms)

I do recommend using the Balanced output if only to hear the difference between the balanced output and the single-ended output, and on many amps/DAPs there is a power advantage given to their balanced output so for listening on headphone amps other than the TA-20 it is important to be equipped ti connect with XLR/4.4mm/2.5mm balanced output to reap the power advantage.

On the TA-26 I do notice a tightening of the center image with the SE output as compared to the TA-20 SE and XLR balanced output - at least it is noticeable to me

@hmscott: Thank you for your experiences!


With "xDuoo TA-20" the use of balanced input is important, so I use it.

The tonal difference between the balanced output and the single-ended output seems to be not striking. If there are any further listening experiences regarding the tonal differences between the two outputs on the TA-20...

Would like to use the balanced output, as far as "really" advantageous, unfortunately I would have to buy a balanced cable first, hence my question…