[Silver Wolf]

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

I'm certainly enjoying them already, high on my keeper list.... As an early guesstimate they will prolly knock me off my beloved Brimar's lol with thanks @hmscott for suggesting them. Similar sound signature, I guess both British 1960's competing tubes so understandable. Initial impressions, for the higher gain sound floor is very low/quiet which surprised me but the extra push seems to help with bass/bottom end control. To keep it short, I think imaging is very good indeed and mid-range is delightful and meaty. Very organic and inviting with improved dynamics overall, glad I tried them because they may be a new fav.

I wonder, has anyone tried 12BH7A tubes as yet in the TA-20. Just been advised on a nice buy on a matched NOS pair so may try them as well, though I imagine tube protection rails may not fit with taller tubes. Not an issue for my situation, so wondering about giving them a try...price is right though my wallet is empty/tight lol being the time of year it is.

Some of the tunes/playlists I enjoyed in my listening session/s this afternoon, sorry in advance for my eclectic tastes lol... I have been sampling homemade booze as well

 

[hmscott]

I'm certainly enjoying them already, high on my keeper list.... As an early guesstimate they will prolly knock me off my beloved Brimar's lol with thanks @hmscott for suggesting them. Similar sound signature, I guess both British 1960's competing tubes so understandable. Initial impressions, for the higher gain sound floor is very low/quiet which surprised me but the extra push seems to help with bass/bottom end control. To keep it short, I think imaging is very good indeed and mid-range is delightful and meaty. Very organic and inviting with improved dynamics overall, glad I tried them because they may be a new fav.

That's great, and I've found the same, I really enjoy the Brimar 6060's, but the Mullard Mitchum 12AT7's are as good or better for air and dynamics

I wonder, has anyone tried 12BH7A tubes as yet in the TA-20. Just been advised on a nice buy on a matched NOS pair so may try them as well, though I imagine tube protection rails may not fit with taller tubes. Not an issue for my situation, so wondering about giving them a try...price is right though my wallet is empty/tight lol being the time of year it is.

Yup, with the E80CC's I turn the protection bars upside down - legs pointed up, and slide them in around the tubes to at least give the illusion of protection - a reminder to not touch the *HOT* tubes

I've not tried the 12BH7A's yet, I'd compare the pin-outs against some specification sheets - check B+ current requirements, and do some sleuthing to see if anyone else has run them in the TA-20/TA-30... I have a fuzzy recollection seeing someone talking about them for the TA-30, but no link to share right now...

 

[marbert]

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?

I'm afraid the general problem is that xDuoo engineers don't want to strain with inexpensive models. They could provide a delay when turned on, add the relay, but no... Is it so difficult for xDuoo engineers?

For example, recently, I measured the temperature of my MT-601 (attached the results below). Two of the four transistors installed vertically with radiators, while the other two transistors soldered onto the board. In this case, the board becomes a radiator and heats the adjacent elements. As a result - the temperature of the headphone jack 6.3 mm has more than 60 °C (degrees Celsius). Although the jack should not be heated so much.

Keep in mind, this is an open board and when the amplifier is assembled, the temperature will be even higher.

Yesterday I wrote in xDuoo and showed them the results, but they still have not answered.

 

[cirodts]

just for curiosity how do you release the crown where the valves are placed in the TA-20?
With a screwdriver or snap?

 

[hmscott]

just for curiosity how do you release the crown where the valves are placed in the TA-20?
With a screwdriver or snap?

The 2 - protective Metal Frame "Cages" around the tubes up top are a simple 2-legged "plug-in" that is held in with magnets in the legs. It only "hovers" above the tube with a small air gap - there is no contact with the tubes.

They are easy to pull out and set aside when changing tubes. They are made with light aluminum with little mass so they don't hold much heat nor for long, when the TA-20 is powered off they quickly cool to the touch.

 

[cirodts]

so they can be easily extracted without a screwdriver, I would like to extract the right one because it makes a little noise when I put a valve in it.

 

[hmscott]

so they can be easily extracted without a screwdriver, I would like to extract the right one because it makes a little noise when I put a valve in it.

Ah, I see, are you talking about a "Guard" around the socket?

Update - There isn't anything around the socket - the sockets are soldered into the PCB without anything else around it. Your photo suggested a ring around the socket, but it was the beveled edge of the metal top plate reflecting the light.

I haven't taken the Xduoo TA-20 apart, but previous Vacuum Tube PC boards I've seen have that metal shield held on with "tabs" formed into the metal going through the PC board, and either twisted with a pliers to hold them in place, or the "tabs" are soldered onto a pad to hold it in place. (Perhaps this method was ended decades ago )

That is a bit weird that the shield isn't more centered around the socket - that's the point of the tabs going into the PC board holding the shield centered in place.

Let me see if I can find a representative photo showing what I am trying to describe in words.

Of course the first photo I find is a riveted shield onto a socket



The kind I was describing were 2 piece socket/shield parts independently attached to the PCB...which is what your top down photo of the TA-20 socket / shield looks like - a "one-piece" riveted part in the photo above and below would be "pre-centered" and unlikely to be askew as your photo shows.

I've looked for a TA-20 PCB with those 2 sockets / shields, but all I find are photo's of the bottom of the PCB under the bottom plate.

I could ask Xduoo, but I think they are away for their Holiday/Vacation - I haven't gotten replies this week from them yet, probably won't hear back till next week or until after the 1st.

Update: @cirodts , in the Xduoo marketing materials I see Xduoo shows a photo of the tube / socket PCB, and oddly enough, there is no shield...

https://xduoo.net/product/xduoo-ta-20/

You might unplug your TA-20 and using a long nose (thin tines) pliers or a long nose tweezers see if you can move that shield independent from the socket, perhaps it is loose?

Update: No, please don't do that There isn't anything around the socket. The sockets sit naked on the PCB - soldered to it. Please leave the socket be.

 

[hmscott]

Ah, I see, the "Guard" around the socket. I haven't taken the Xduoo TA-20 apart, but previous Vacuum Tube PC boards I've seen have that metal shield held on with "tabs" formed into the metal going through the PC board, and either twisted with a pliers to hold them in place, or the "tabs" are soldered onto a pad to hold it in place. (Perhaps this method was ended decades ago )

That is a bit weird that the shield isn't more centered around the socket - that's the point of the tabs going into the PC board holding the shield centered in place.

Let me see if I can find a representative photo showing what I am trying to describe in words.

Of course the first photo I find is a riveted shield onto a socket



The kind I was describing were 2 piece socket/shield parts independently attached to the PCB...which is what your top down photo of the TA-20 socket / shield looks like - a "one-piece" riveted part in the photo above and below would be "pre-centered" and unlikely to be askew as your photo shows.

I've looked for a TA-20 PCB with those 2 sockets / shields, but all I find are photo's of the bottom of the PCB under the bottom plate.

I could ask Xduoo, but I think they are away for their Holiday/Vacation - I haven't gotten replies this week from them yet, probably won't hear back till next week or until after the 1st.

Update: @cirodts , in the Xduoo marketing materials I see Xduoo shows a photo of the tube / socket PCB, and oddly enough, there is no shield...


You might unplug your TA-20 and using a long nose (thin tines) pliers or a long nose tweezers see if you can move that shield independent from the socket, perhaps it is lose?

@cirodts - I looked at my TA-20 with a flashlight into both tube socket holes in the top plate of the TA-20, and there is nothing in there to rattle, no shield, only the naked socket soldered to the PCB.

So are you saying the socket / PCB assembly makes stress creaking noises while applying pressure to insert / extract the tubes?

I hear that too sometimes if I press too hard - or the tube pins are too corroded - that's why I like buying new tubes with gold plated pins - those slide in / out with less force.

I wiggle the tube side to side, not so much wiggle as "tilt" the tube ever so slightly side to side and then change directions and tilt it side to side the other way while pulling/pushing with gentle force.

Patience helps, I let it happen slowly, then it will release and just "pop/drop out", no squeaking from the socket or the PCB...

It would be a pain to replace the tube sockets soldered onto the PCB, so I take each tube removal/insertion slowly, and I'll hopefully nudge semi-infinite insertions/extractions out of those sockets.

 

[cirodts]

thank you very much for the explanation, my fear is that that little creak may cause the welds to break.

 

[hmscott]

thank you very much for the explanation, my fear is that that little creak may cause the welds to break.

It is probably not the solidly soldered socket pins, instead it is usually the fasteners used to connect the PCB to the chassis, or in this case to the other PCB below the tube/socket PCB:

I highlighted in Yellow the 4 - bolt/screw/nut pairings at the 4 corners where the stress is passed, I would expect those fasteners are where the creaks are coming from.

The sockets are strong - as are the pins passed through the PCB - soldered on both sides of the holes the pins passthrough (pcb through-hole). There is also a "spacer" the bolt is going through to raise the socket PCB above the main PCB - there could be noise generated by the stress of the force applied to those bolts going through the "spacer" too, or the lock washers against the PCB.

The socket tines that open to accept the tube pins can also make a noise, scraping the pins against them also can make a noise, but usually the actual tube pin to socket noise is very hushed.

Again, I hear these same sounds occasionally and when I hear them I - breath out - relax - and use a little less force and add a little more time / patience to the task

Hmmm, I hope Xduoo put a support under the middle of that tube socket PCB, connecting to the PCB under it - like the 4 corners. That is a long enough span that could cause the socket PCB to "bend" down at the middle as pressure is applied unless a center bolt/spacer takes the pressure...

 

[cirodts]

in fact I believe and hope this is it The socket tines that open to accept the tube pins can also make a noise, scraping the pins against them also can make a noise, but usually the actual tube pin to socket noise is very hushed.

 

[PetFju]

i actually considered ordering some new tube sockets while i was at it ordering some new caps for the TA-20. Then i decided i have plenty of time to do that whenever they're worn out, and didn't bother.
However; i did order some new signal caps for the TA-20. Unfortunately really good ones won't fit inside the chassis, so it had to be "lower end" good brands.
I got one set of 8.2uF 400Vdc Jantzen Standard Z-Cap Capacitor and one set of 8.2uF 250V Mundorf MCap MKP Classic Capacitor , as they are recognized brands with units that'll ctually fit. And also might just up the sound a tiny bit

Does anyone have any experience modding these amps in any way like this, and if so; what's your findings?

 

[cirodts]

hallo, I made a video of my problem, noise when applying the valve, what can it be?

 

[hmscott]

hallo, I made a video of my problem, noise when applying the valve, what can it be?

Definitely a "tick" sound, a distinctly different sound than the socket tines scraping by the tube pins, but both are sounds that I am not hearing. You have the Microphone close to the TA-20, closer than my ears, so when I put in tubes I don't hear anything of note, unless I am "not gentle" - thoughtlessly pushing in the tube, as when I am in a hurry. But that sound is a "creak", which I don't hear on your video/audio.

I've heard similar "ticks" when hardware isn't tightened down. Or more accurately, I have heard "ticks" and "clicks", like a screw / nut not tightened fully - enough to be considered "close enough", but there is still one "tick" of play in the fastening hardware. I've cured those by going in and tightening all the hardware I can find around the stress point I am compressing. Nut driver in hand, screw driver set at the ready, and zip up all the hardware, and that gets rid of the sound. I've occasionally found a rivet not completely punched and then I have to replace the whole assembly (socket in this case).

Where did you buy your TA-20? Do you still have time in your return period? Perhaps this is a known thing, not a problem, you could send a link to that video to your seller support email and ask if it is something to be concerned about, as it is concerning enough to you to ask.

 

[cirodts]

aaa

Definitely a "tick" sound, a distinctly different sound than the socket tines scraping by the tube pins, but both are sounds that I am not hearing. You have the Microphone close to the TA-20, closer than my ears, so when I put in tubes I don't hear anything of note, unless I am "not gentle" - thoughtlessly pushing in the tube, as when I am in a hurry. But that sound is a "creak", which I don't hear on your video/audio.

I've heard similar "ticks" when hardware isn't tightened down. Or more accurately, I have heard "ticks" and "clicks", like a screw / nut not tightened fully - enough to be considered "close enough", but there is still one "tick" of play in the fastening hardware. I've cured those by going in and tightening all the hardware I can find around the stress point I am compressing. Nut driver in hand, screw driver set at the ready, and zip up all the hardware, and that gets rid of the sound. I've occasionally found a rivet not completely punched and then I have to replace the whole assembly (socket in this case).

Where did you buy your TA-20? Do you still have time in your return period? Perhaps this is a known thing, not a problem, you could send a link to that video to your seller support email and ask if it is something to be concerned about, as it is concerning enough to you to ask.

Hi, if you turn up the volume of the video you will hear between a tick between a hook and the other of the tube.