Juson Audio JTA35 Tube Amplifier, DAC & HP Amp Review

[fpitas]

KT88 Full Tube Amplifier

View attachment 339929
View attachment 339930

Power output:10 Watts RMS x 2 into 8Ω(Full Tube type) from KT88s, no less

 

[kklarqvist]

There are no output transformers in the Dayton.

Now, as for the titular Juson -- @amirm do "we" know what tube types are under the cage?
One is, of course, most curious.
I am guessing a couple of small-signal tubes. Could be triodes or pentodes. Recent fashion for Chinese-sourced vacuum tube gizmos are pentodes (e.g., the Chinese 6K4 found in the FX-Audio "Tube-03" and its kin).

http://frank.yueksel.org/sheets/095/6/6K4.pdf

I was mistaken, I had the JTA35 photo on the website in my head when I wrote that. By the looks of the website image there are output transformers but that does not seem to apply to the JTA35 depicted in this thread. Seems the one depicted on the website has a different chasis with transformer boxes (empty?).

They list 13P1P (x2), 6P16A (x2) --- pentodes.

 

[mhardy6647]

OK, now I am really curious.
This glamour shot's from an Amazon listing selling this little gizmo.

source: https://www.amazon.com/Integrated-Amplifier-Subwoofer-Headphone-Turntable/dp/B0CD5N6T6Z

So -- it looks like there are four tubes in there.
The ones in the front look, to me (??????), suspiciously like the weird Loktal base direct-heated tubes (designed for battery powered portables, with 1.5 or 3 VDC filaments) used in the bizarre little Nobsound E6 box.

What do you guys think of the newly released Nobsound E6?

Its a super small directly heated 2J27S tube preamp. It uses a 5v dc plug but according to nobsound the anode voltage is stepped up to 105V. If its true then this thing could be an actual tube pre.

www.audiosciencereview.com

Nobsound E6 Direct Heated Vacuum Tube Preamp Class A Stereo Audio Pre-Amplifier

Introduction Nobsound E6 adopts direct heated vacuum tubes, because of difficulties in the control of noise level degree and the balance degree of high, medium and low frequency, and excessive drive current easily affects the balance, this type of tube preamp is rare in the market, but the...

doukaudio.com

The other two tubes look like a couple of metal-based octals(?????????). Perhaps (?????????????) something like the Chinese 6N9(P) - similar to a 6V6 power output tube, or Chinese 6N8(P) - similar to a 6SN7 medium mu dual triode?

6N9P (rando google image)

6N8P (rando google image)

Vacuum Tube 6N8P 1pc Inventory Product for Tube Amplifier Replace 6SN7

Vacuum Tube 6N8P 1pc Inventory Product for Tube Amplifier Replacement 6SN7 6H8C High Reliability, Replace tube 6SN7, 6H8C Application: Parathermal cathode dual triode / low frequency power amplification

www.iwistao.com

Don't make me buy one of these to see what's going on below decks!

 

[mhardy6647]

Power output:10 Watts RMS x 2 into 8Ω(Full Tube type) from KT88s, no less

Triode mode -- that's at least plausible.

 

[fpitas]

Triode mode -- that's at least plausible.

I figured it was triode mode. Still seems like a tiny amount of power. I'm reminded of my pet theory that some people like the peaks clipped off.

 

[AudioSceptic]

If you could reliably hear +1dB at 20 and 20kHz, good luck to you sir I'm surprised by the sharp cut off at 20kHz or so and wonder if the analogue signal is digitised first? $180 is beer money really and do remember this unit has a phono input (which does need refining), aux analogue inputs AND digital too including remote control FFS. PLEASE don't knock it to risk putting the designers off. It can hopefully only get better from here and with luck, any design refinements shouldn't bump the price up hugely..

As said above and I'm going to repeat it - a wonderful FUN 'bedroom/study' system that actually in real life away from SINAD charts ( ) has enough power for a basic living room stereo and low enough noise as it's no worse than FM radio typically.

I confess that I didn't notice the dB scale for the FR: I just assumed those humps were much bigger. Anyway, as you say, this looks like a fun product for (almost) beer money. The VFM is, of course, ridiculous. A nice present for a young music fan, perhaps?

 

[mhardy6647]

Y'all drink pricier beer than do I -- or perhaps just a lot more of it.

 

[fpitas]

Y'all drink pricier beer than do I -- or perhaps just a lot more of it.

Right? More like vintage port money

 

[Sengin]

The question is what is your goal with respect to amps? If you like your amp to add some "distortion that you like" (as you put it), maybe add a little noise too, maybe your speakers can add a little distortion as well, then will you be hearing the music your source is playing or some distorted version of it?

A distorted version of it for sure - I am not making any claims here. Some people hear something they like (perhaps even without realizing what it is) and assume that it is "part of the music my old amp couldn't reveal" or somesuch. I'm just asking if the goal of a tube amp is aligned to the goals of Amir's reviews - it's expected to objectively test poorly as they are designed to add harmonics. But if you are in the market for it, you can't just look at objective measurements because they will all say "it's bad." Perhaps some subjective listening tests would help, but I absolutely understand why they are not done with amps. Or a different review format (e.g. tube amps are 'supposed to' add mostly 2nd harmonics, so a FR that scores well for a tube amp will have as close to only 2nd harmonics added, no extra noise, no random 3rd or 5th, etc).

PS "warmth" does not exist on audio, what you refer to as "warmth" is in fact distortion, even-order harmonic distortion (mostly 2nd harmonic) which our ears perceive as "pleasing", or at least "not annoying".

Right - I tried to be explicit about what I was referring to as both the subjective description (warmth) and the more objective one (saturation/distortion). Tube saturation (2nd harmonic) can be described as a 'sheen' or 'polish' or even 'clarity/detail' (worst is when someone hears this and thinks it is a result of their new headphone/speaker and think they can 'resolve more detail' now) and you can add quite a bit of it before it sounds off or wrong. Tape saturation is mostly 3rd harmonic (IIRC) and adds more of what most people would describe as 'warmth' (though some reserve warmth for just the lower part of the frequency spectrum) - you can't add as much before you take notice, but you can get some good tape saturation in the lower frequencies (really makes a kick sound fantastic imo and I try adding tape saturation to all my kicks [even if it's only on the fundamental] when I'm mixing).

 

[mhardy6647]

Right? More like vintage port money

We actually do drink that on occasion.

 

[fpitas]

We actually do drink that on occasion.

My favorite!

 

[amirm]

We have to take your word for it about the paltry number of reviews spiked by manufacturers, but at the end of the day it’s a policy that does nothing but protect companies and hurt the user base.

No, it hurts me the most as I have to go through the full set of measurements and not be able to publish anything. Usually this means an entire evening for electronics and multiples of that for speakers.

It’s your site, run it how you wish, and this thread isn’t about that (but you offered up the information in the review, remember), yada yada, but I don’t see the logic, or how it benefits “audio science.”

Oh, there’s a dozen products so bad the manufacturer opted to kill publication? That makes the measurements all the more interesting and valuable to us.

It benefits you in the long haul as the companies go and redesign these products and come back with better performance. They do that because I allow them a second chance. This just happened as a matter of fact.

And it is not like you are sitting there waiting weeks for a review as is the norm elsewhere. You are seeing a review almost every day. That less than 1% of the products are rejected should be of no real concern to you.

So yes, I made a conscious decision to put this policy in place. I pay price personally more than any of you per above. I think it is worth it as a carrot to get companies to offer their products for review.

 

[AudioKC]

Good for tube amp, given packaging, I would say awesome value if you into “exoterical” improvement of sound with tubes.

 

[Antagron]

How did it sound subjectively?

 

[majingotan]

Triode mode -- that's at least plausible.

Nope. More like ultra linear mode to me. I currently use a KT88 Triode strapped Class A no global feedback headphone amp, and it only gives 3 watts at 8 ohms transformer tap with 2.4 Vpp input sensitivity.

 

[mhardy6647]

Nope. More like ultra linear mode to me. I currently use a KT88 Triode strapped Class A no global feedback headphone amp, and it only gives 3 watts at 8 ohms transformer tap with 2.4 Vpp input sensitivity.

I'd have thought a single KT88 triode would be good for more than 3 watts, but, no, I didn't look it up!
Maybe SEP? I guess I'll have to look it up... anon.

 

[majingotan]

I'd have thought a single KT88 triode would be good for more than 3 watts, but, no, I didn't look it up!
Maybe SEP? I guess I'll have to look it up... anon.

I don't use the Cayin HA-6A amp, but their specs does show it is most likely triode strapped. Mine is similar as well

Here's the Cayin HA-6A specs:

https://www.moon-audio.com/files/cayin/cayin-ha-6a-manual.pdf

 

[Urib]

This is a review and detailed measurements of the Juson Audio JTA35 stereo hybrid tube amplifier including DAC, Bluetooth, Phono input and headphone out. It was sent to me by the company and costs US $180.
View attachment 339818
As if all that functionality was not enough, we even have a pretty VU meter! And oh, motorized volume control remote control too!
View attachment 339819
There is even subwoofer out!

Overall build feels good and polished. Speaker terminals are oversized for class (good) and we even have built-in power supply. Let's see how it measures.

Juson Audio JTA35 Measurements
Let's start with the power amplifier:
View attachment 339820
Don't expect super clean performance from a tube amp especially at this price and that is what we get. Noise is high and shows up in our SNR tests:
View attachment 339821

Distortion is fortunately frequency independent:
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Crosstalk is poor:
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Frequency response has peaking at the low and upper end:
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Impedance is low though as we see from difference between 4 and 8 ohm. There is a sharp cut off which existed even when I switched to digital input:
View attachment 339824

Here are the power sweeps:
View attachment 339826

If we allow more distortion, power increases with good bit of heardroom:
View attachment 339827

Interestingly we get almost the same amount of power into 8 ohm (we are current limited):
View attachment 339828

Same voltage advantage exists when testing headphone out with more power delivered at 300 ohm:
View attachment 339829

View attachment 339830

Finally, I tested the RIAA equalization using phono input:
View attachment 339831

Kind of strange response with channel mismatch.

Conclusions
It is hard to imagine so much functionality being in such a reasonably priced but quality (physical) implementation. It even went after the soft spot in my heart with that VU meter. The other part of my heart was not pleased with measurements that are lackluster across nearly entire suite. Company support has been fantastic though and when I gave them the option to ditch the review they chose to have it be published anyway! Not enough companies send me products and fewer still don't mind results like this. For this, they need to be praised. Hopefully future products will have better objective performance.

Not having any use for tube products, I can't recommend the Juson Audio JTA35. If you are situated otherwise and looking for a very low cost of entry and high functionality, you may dig what JTA35 has to offer.

Manufacturer Specifications are provided in post #9 below.

------------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

What I understand from this is that when not expansive but popular products like Wiim amp measurements are not being published is because they came out poorly and you gave them the option of not publishing it? Did you gave this option to PS audio as well? I must say that this is disappointing.

 

[farhad]

I voted fine for this. This is an amazing amount of functionality in a small device and the value therefore seems great. The measurements of course show all sorts of failings, but some people do like tube amps making their speakers sound different.

 

[milosz]

I don't know if this has already been mentioned, this thing uses a tube voltage gain stage (preamp) and solid state output of some kind. It also uses tube shunt voltage regulators.

From the Mfg's blurb on Amazon:

2 pieces 13P1P pentode act as a shunt regulator and help maintain a constant voltage output with an increased temperature coefficient and less noise compared to its solid-state equivalent.

2pieces 6P16P Triode-Hexode amplify and imprint their warm tonal quality on signal before being sent to the power amplification stage.