[hmscott]

Does TA-20 rca Output tune signal with tubes or is it just passtrough?

Some users here say RCA doesn't pass through:

But users there say the reverse:
https://drop.com/buy/xduoo-ta-20-ba...k/2785712?utm_source=linkshare&referer=EM4X5H
https://drop.com/buy/xduoo-ta-20-ba...k/2627137?utm_source=linkshare&referer=EM4X5H

I am confused.

Xduoo Confirmed through Hifigo that the TA-20 RCA Output is a passthrough - without going through the Tube/SS stages.

Xduoo's TA-20 Manual has this to say:

Which says the TA-20 RCA Aux1/Aux2 ports output directly through the AUX Output port without passing through the Tubes or SS, a simple source passthrough.

The Xduoo TA-26 AUX Output (RCA) does go through the tubes. The TA-26 PDF Manual says:


Product details not mentioned in the marketing materials, are often mentioned in the product manuals

 

[hmscott]

Ok, so after a few hours on the GE 12AU7WE JAN and the RCA 12AU7 cleartops i am surprised to say the differences aren't glaringly obvious.
So far i do not get all the hype around the RCA tubes, but it might just be that they need more burn-in.

I think the RCA Cleartop 12AX7 in Guitar Amps has the "special edge", at least that is what I've heard. In the TA-20 the 12AU7 RCA Cleartop sounds nice, but nothing "special". Same goes for the JAN tubes I've heard - great but nothing special. Only the Tungsram Black Glass 12AU7 and Tungsram/Philips E80CC (12AU7) stands out for me so far, but the 12AT7's outshine all of the 12AU7s I've heard so far.

I did however recieve my "Royal Air Force" Mullard CV4024/12AT7's. And oh boy...They've only been in the TA-20 for less than 30 minutes, and as such one can say that they're not burned in, or even warmed up for that matter, but the sound..This is why i got a tube amp in the first place. Just airy and big, with taut bass, yet detailed and smooth highs. If this carries on, or gets even better with time, i honestly think these tubes are a golden pick for these amps.
I will update after some time has passed. Have a good week-end everyone!

That is awesome!, I'm happy for you, it's great to find a sweet sounding pair of tubes, it makes all the time hunting worthwhile.

That's pretty cool about the "Royal Air Force" branding; please post some photo's when you get a chance of the tube lettering on the sides, and if you find some more, please "share" a link.

The best 12AU7's I've heard don't have the airy sound of the '58/'68 Mullard M8162 CV4024 BVA Made in England - or 12AT7s in general - as compared to 12AU7s in the TA-20.

The E180CC NOS Mullard Holland Valve Tubes and E180CC 5965 12AV7 NOS Mullard Holland Valve Tubes are still in transit, the Royal Mail tracking peg hasn't moved for 10 days and probably won't till it makes land-fall, hopefully soon. USPS is now showing the tracking too, a good sign.

 

[hk29]

Quick impressions on the MT604 with the stock tubes using iBasso DX220 Max balanced line out to Meze Empyrean:

1) Takes of the sharp edges of sounds and rounds them out
2) Provides holographic image
3) Bass blooms nicely (Less detail, but pleasant)
4) "Darker"/ treble is rolled off slightly with less air -- I suspect this is due to the stock tubes.

Overall really nice and "musical" - vocals sound real. And I think the level of detail from the MT604 is "good enough" in the sense that its about the same as I would normally hear in real life talking to someone.

It's a nice complement to the iBasso sound which is more transparent, sharper image, more detailed, and slightly warm. They both sound forward and intimate.

Lastly, the dual volume control is a pleasure to use and very easy; You adjust one, and the other when the image snaps in the middle and it sounds balanced; it takes another 1-2 seconds to adjust it in. The volume knobs have a nice weight and are smooth. Of course if you're OCD (no offense intended), then maybe you'd feel a bit more hesitant, but then this $170 amp probably isn't for you to begin with ... point is don't let the dual volume knob sway you away from trying this amp.

And because I use 4.4mm from the iBasso, its great the MT604 uses 4.4mm as well.

Great little amp! This will do nicely when I just want a bit of tube sound but still maintain a transportable system...

 

[PetFju]

That is awesome!, I'm happy for you, it's great to find a sweet sounding pair of tubes, it makes all the time hunting worthwhile.

That's pretty cool about the "Royal Air Force" branding; please post some photo's when you get a chance of the tube lettering on the sides, and if you find some more, please "share" a link.

Here Is a picture of the tube. It also has some faint typings on the back, as you can see i picture 2. The boxes they came in are standard white with black lettering
[

 

[Silver Wolf]

If I'm reading codes correctly looks to be Mullard's own Mitcham factory, build week 3 of Jan 1972, but I get confused easily lol.

 

[PetFju]

If I'm reading codes correctly looks to be Mullard's own Mitcham factory, build week 3 of Jan 1972, but I get confused easily lol.

It might be me who's confused here. I Honestly don't know much about this other than what Google tells me..lol

 

[Silver Wolf]

My understanding is the bottom line of code on the back tells you factory and production date info.

 

[cirodts]

when I insert the valve on the right side of my TA-20 I hear a click what could it be?

 

[hmscott]

when I insert the valve on the right side of my TA-20 I hear a click what could it be?

With the power off, you hear a mechanical click? There could be a loose nut/bolt for that tube "riser" that holds the socket, perhaps? Mechanical stress can cause even tight couplings to "creak/click". If the TA-20 wasn't so tightly packed between the bottom plate and that assembly I'd suggest taking a look, but for now I wouldn't go that far, yet. Perhaps it won't further loosen, but over time it might. Keep an ear on it for now?

If I'm reading codes correctly looks to be Mullard's own Mitcham factory, build week 3 of Jan 1972, but I get confused easily lol.

It might be me who's confused here. I Honestly don't know much about this other than what Google tells me..lol

My understanding is the bottom line of code on the back tells you factory and production date info.

Here are some online listings of the codes and how to read them; you both sound like you've found them ok - these are a few of the useful links I've found that might help others too:
https://mullard.org/blogs/news/mullard-valve-etched-codes-how-to-interpret-them
https://www.audiotubes.com/mullcode.htm
Download or view the tube type code list.

That last link is "Brent Jessee's" and he lists and sells tubes too, even if the entry is out of stock much can be learned from his tube listings. These are his 12AU7 and 12AT7 listings, also the preamble of tube variants leading each for sale listing is very helpful when looking for new tube types:
http://www.audiotubes.com/12at7.htm
http://www.audiotubes.com/12au7.htm

 

[waveSounds]

Hey folks, I had an MT-602 turn up today - which I'm enjoying so far with a pair of Mullard CV4010 tubes I already had from a Little Dot MKII - but I have a question about its operation. What's the general consensus on when to plug in and unplug the headphones in regards to powering on and off? I know the amp waits for about ~20 seconds before it literally clicks into operation with a bit of the sound transmitting through the drivers, but if my cans are still plugged in when I turn it off it produces a pop much louder. Is this the norm with these amps?

Edit - searched the thread and found this from a member earlier on.

My 602 also has a nasty pop when you turn the unit off, I unplug my headphones every time I remember. I don't understand why this wasn't addressed by Xduoo during development/production of this amp. Long term affects of the pop and the extra unplugging and plugging of the headphones...

Unless anyone else has something else to add I guess I'll just follow this chaps advice and go with unplugging prior to turning the amp off.

 

[hmscott]

Hey folks, I had an MT-602 turn up today - which I'm enjoying so far with a pair of Mullard CV4010 tubes I already had from a Little Dot MKII - but I have a question about its operation. What's the general consensus on when to plug in and unplug the headphones in regards to powering on and off? I know the amp waits for about ~20 seconds before it literally clicks into operation with a bit of the sound transmitting through the drivers, but if my cans are still plugged in when I turn it off it produces a pop much louder. Is this the norm with these amps?

Edit - searched the thread and found this from a member earlier on.



Unless anyone else has something else to add I guess I'll just follow this chaps advice and go with unplugging prior to turning the amp off.

My 602 also has a nasty pop when you turn the unit off, I unplug my headphones every time I remember. I don't understand why this wasn't addressed by Xduoo during development/production of this amp. Long term affects of the pop and the extra unplugging and plugging of the headphones...

Xduoo should have designed in a function like at power on to switch out the headphone(s) when switching off the amp, to eliminate Pops when powering down:
https://xduoo.net/product/mt-602/

Perhaps Xduoo did intend that same circuit/relay design to also interrupt the signal to the headphones during power off?

I'll ask Xduoo, and you guys can also use the contact form at Xduoo, or email service@xduoo.com to report the problem. "The squeaky wheel gets the grease"

I've seen pop reducers for speakers, perhaps there are some that could be used for headphones, I'll update here if I find them...

Here are a few inline filters that also mention removing pops. Perhaps one of those will attenuate that shutdown pop enough that you can feel comfortable leaving your headphones connected at power off with one inline.

Perhaps @iFi audio knows which would be the best one to try for your Pop at shutdown issue?

"Annoyed by hisses and pops from your earphones?" - iFi Ear Buddy
https://ifi-audio.com/products/ear-buddy/

"Do your earphones suffer from pop and hiss? Sound quality just not quite ‘there’ at normal listening levels?
You need the iEMatch+"
https://ifi-audio.com/products/iematch-plus/

"Do your earphones suffer from irritating hiss and pop? Not getting the full impact of your music?"
iFi iEMatch(3.5), iEMatch4.4, iEMatch2.5,
https://ifi-audio.com/products/iematch/
https://ifi-audio.com/products/iematch4-4/
https://ifi-audio.com/products/iematch2-5/

You could also use a front end switch box - 6.35mm/3.5mm headphone outputs to single 3.5/6.35mm input, and before powering off switch to an empty headphone output position.

The "Nobsound Little Bear 4 Way Audio Switch" has a big Red Mute button that you could press before powering down the MT-602 to block that "Pop". A nice side benefit is you can connect 4 of your headphones at the same time, and switch between them.

Nobsound Little Bear 4 Way Audio Switch; 3.5mm Audio Switcher; Stereo AUX Audio Selector; Audio Splitter; 4(1)-in-1(4)-Out
https://www.amazon.com/Nobsound-Audio-Switcher-Selector-Splitter/dp/B07Q1W4484

 

[waveSounds]

Thanks for that, @hmscott. Really helpful stuff! I actually already have an IEMatch but hadn't thought about using it with this amp until you mentioned it. I've just plugged it in (set to ultra) so we'll see what happens when it's time to flip the power switch in a bit. At the very least, it has expanded my usable volume from just below 9 o'clock with a significant decrease in source volume to boot, to 12 o'clock and only a minor decrease in source volume. A small win, eh!

 

[Silver Wolf]

Just got the NOS Mullard m8162 factory matched pair I bought last week. Certainly in good/like new condition for age, just fitted them in to the TA-20 and am about to have a listen once they warm up.

 

[waveSounds]

Thanks for that, @hmscott. Really helpful stuff! I actually already have an IEMatch but hadn't thought about using it with this amp until you mentioned it. I've just plugged it in (set to ultra) so we'll see what happens when it's time to flip the power switch in a bit. At the very least, it has expanded my usable volume from just below 9 o'clock with a significant decrease in source volume to boot, to 12 o'clock and only a minor decrease in source volume. A small win, eh!

Update: with the IEMatch set to ultra, the pop on power off can still be heard but is greatly reduced to near negligible levels. Happy to leave the cans attached now. Thanks @hmscott for the suggestion!

 

[PetFju]

Looking good there! I am looking forward to hearing your impressions after a little while with the tubes under load.