Juson Audio JTA35 Tube Amplifier, DAC & HP Amp Review

[solderdude]

I’m really perplexed by the headphone output figures.

If this does 26w into 8 ohms, it should do 13 watts into 16 ohms, and 6.5 watts into 32 ohms, at least roughly. Somehow only doing 11 mw into 32 ohms makes me think the headphone section isn’t being driven by the same amp as the speaker section, or there’s some resistor or something in the path killing the headphone performance.

If this scaled in power linearly and could do 6.5w at 32 ohms, 3 watts at 64, etc, it would actually be a very compelling product for some colored listening. As it is the headphone output power is just way too ridiculously low to be useful.

It just has a high output resistance to give it a 'tube-y' feel.
Consists of 2 resistors it seems (voltage divider).
To lazy to calculate the output R but it is high for sure.

I suspect it is needed given the poor S/N ratio.

You could always use a hifiman speaker adapter as it can output 14V on its speaker outs (assuming it is not BTL)

 

[oscar_dziki]

Might not be super tube’y as a hybrid. I have both a TA-10R and Liquid Platinum HPA and both do add some flavor but I doubt it’s anywhere near pure tube amps

I might always add some more second and third harmonics with software

 

[Great Sun Jester]

This is why I'm a fan of quality separates, including the DAC. I presume that if you are on a shoestring budget, staying with the phone and earbuds would save you $180.00

 

[ocinn]

I mean no surprise for budget tube product, I’m not even mad about it’s general performance. Buyers of tube amps don’t care

But my god the RIAA curve is inexcusable. In 2023 it legitimately takes effort to screw it up that bad.

There is also no excuse for the crosstalk. Tube buyers can be content with the distortion (which they view as beneficial for some reason) but poor crosstalk is a bad trait, subjectivists and objectivists agree on this

 

[aperfectday]

anyone bought this amplifier? how is the real sound?

 

[Angie87]

 

[mhardy6647]

Is that a big ol' heatsink buried inside a sealed box?

HH Scott, e.g., used the entire (aluminum) chassis of some of their early ss products for heat sinking, which makes some sense, but this appears to be a ticking time bomb -- unless of course I am missing something(?).


The output transistors of this Scott 342C receiver are mounted on the back panel, e.g.,

 

[mhardy6647]

Oh, and a question*:
The 'front' tubes. Are they some sort of Chinese Compactron envelope/base, or are they repurposed Loktal tubes, perhaps even with their shields removed a la the goofy little Nobsound E6 preamp?

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

(Images from the ASR thread linked to above)

What tubes are the front ones, @Angie87 ? I can't quite read what's printed on them in your otherwise excellent photos.
EDIT: Oops! sorry, got it! They're 6p16A, whatever those be. "Triode-hexode" per the writeup at Amazon (i.e., a radio tube). Off I go, tube-spelunking...
______________
* And I apologize if it's been addressed in this thread and I simply missed it! I know I posed the question much earlier in this thread, but not sure it's been answered

 

[mhardy6647]

6p16A from https://www.aliexpress.us/item/3256806052319622.html

So, yes, it does appear to be a de-shielded Loktal like the tube type used in the aforementioned Nobsound E6.

A little google-sleuthing shows another Nobsound product ("B100" amp) that uses the same tube or the (??) interchangeable 12J1S.

The latter is "clearly" (as clear as anything can be when dealing with abstruse old Chinese vacuum tubes) one of the shielded Loktals per

productview_

www.atubesocket.com

Oh, the surreality of products like this amplifier makes my corpus callosum hurt.

 

[mhardy6647]

all righty then. Sorry if no one but me finds this interesting!

Two types of tubes in the JTA-35.
The rear pair are reported by Juson to be 13P1P tubes. These are pentodes and may be used as shunt voltage regulators (cf. PartsExpress's HTA200 hybrid amplifier).

Home

Dayton Audio HTA200 Integrated Stereo Hybrid Tube Amplifier 200 WattsDayton Audio HTA200 Hybrid Tube AmplifierThe perfect solution to bring the rich sound of a tube amplifier to your home audio setup; the innovative design of the HTA200 combines the best of both worlds – the classic sound of...

www.parts-express.com

The front tubes are, as I've already droned on about, the (really) weird ones.
What are they? Well... maybe... maybe (?????) the 6p16A is the same as the 12J1S*. So far, efforts to find datasheets for either tube type, or Russian equivalents of either, have been for naught.

This page cross-references tube types P2000 and RV12, but those appear to be very different in basing/Gestalt. Whether the guts are related... who knows?

https://www.aliexpress.us/item/3256806052319622.html

image from https://www.aliexpress.us/item/1005005493918887.html

EDIT: Dude. curves. I missed this when I looked initially at

https://www.aliexpress.us/item/3256806052319622.htm

I missed the "VIEW MORE" button on the page:

which displays curves.
No pinout, nor other operating parameters/specs, though.

https://www.aliexpress.us/item/3256806052319622.html also cross-references a Russian tube type, 12Ж1n
but I am comin' up blank on that one, too.

Without knowing what they are it's impossible to speculate what (if anything!) they may be used for in this bizarre little amplifier (the JTA-35, that is).
oy, vey.
___________________
* The 6 and 12 'prefixes' would suggest that the former tube is designed for a 6.3 V heater, and the latter for 12.6 V... it's certainly possible that the "12 volt" tube has a center-tapped heater connection (as does, e..g, a 12AX7)... but, again... who da fug knows?!?

 

[mhardy6647]

Beijing electron tube 4J1S 12J1S 12J2S small power amplifier side-heating sharp cut-off five-stage tube

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www.yoycart.com

Says these types are "side-heating" (indirect heated) sharp cutoff "five stage" (pentode?) tube.
No pinout nor characteristics, though.

 

[French Meloman]

There are tube amplifiers with a selling price of more than € or $ 5000 and that have SINADs that are no better if not worse! The big weakness of the device is its low dynamic capacity. The multi-tone test shows stable distortion across the entire audio spectrum, which isn't too bad. Considering the features offered and the very low price of this device, its overall performance is acceptable for a tube technology. As a result, I voted fine.

 

[Yorkshire Mouth]

6p16A from https://www.aliexpress.us/item/3256806052319622.html

View attachment 344325
View attachment 344324

So, yes, it does appear to be a de-shielded Loktal like the tube type used in the aforementioned Nobsound E6.

A little google-sleuthing shows another Nobsound product ("B100" amp) that uses the same tube or the (??) interchangeable 12J1S.
View attachment 344327

The latter is "clearly" (as clear as anything can be when dealing with abstruse old Chinese vacuum tubes) one of the shielded Loktals per

productview_

www.atubesocket.com

View attachment 344326

Oh, the surreality of products like this amplifier makes my corpus callosum hurt.

This is superb - exactly what I’m after.

I loathe valve amps, but must admit they look very special, as do VU meters.

I just need something I can plug into where the valves will light up and the VUs flicker around. I wouldn’t actually be using it to power anything.

 

[Ze Frog]

Not bad really, tube gear is something I'd probably discard measurements to a point if going that route anyway, mainly because tube gear is more about the nostalgia and romance of it. Not to say tubes aren't enjoyable, I quite like a tube amplifier, but I am never under the illusion it's the best for absolute performance. Kudos to the company, transparency is a big plus in my mind and if I was in the market for such a thing I'd consider this company on that alone.