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Juson Audio JTA35 Tube Amplifier, DAC & HP Amp Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 95 37.4%
  • 2. Not terrible (postman panther)

    Votes: 104 40.9%
  • 3. Fine (happy panther)

    Votes: 49 19.3%
  • 4. Great (golfing panther)

    Votes: 6 2.4%

  • Total voters
    254

mhardy6647

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with a pair of old Klipsch bookshelfs …which we all have in storage.
I don't get rid of much -- but I did sell my heritage Klipsch loudspeakers.
They weren't bookshelfs, though -- unless your tastes run to pre-Renaissance codices (codexes?). ;)

 

nothingman

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Over the nearly 2000 reviews, I would say maybe 10 to 12 times. It is a courtesy I provide to companies that volunteer to send me gear. The usual scenario is the company not knowing the emphasis we have on objective performance and what those objectives are. As a result, most products that fall in this category are rather obscure.

Since most of my reviews come from member gear, stuff I have bought, and companies who know their gear will perform, very few fall in this category. I get to provide this without it impacting the work I do in any meaningful way.

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.

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.
 

pavuol

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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.

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.
Amir said "As a result, most products that fall in this category are rather obscure." Personally I am surprised by the high published/unpublished ratio. We know "more than enough" already thanks to this site and the tremendous work behind it, we don't have to know "everything"!
There are many pros of that aproach in fact - you [company] want to get your gear measured by equipment unavaible to you? Go ahead, you risk nothing and the cost of shipment is a little investment for an otherwise costly commercial measurement lab.
Also we shall admit, as critical and nitpicky (but never sarcastic ;)) member comments can be, there shall be some "cheats" like this for companies to not completely lose motivation for sending their products.
 

leebergtally

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It says hybrid and from the images it looks like a driver tube and power tube for each channel. I assume there’s two transformers in the box on back. In most transformer outputs there are taps for 4 and 8 ohms. Btw I looked it up on their website and it looks totally different there. No phono input.
 

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leebergtally

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It says hybrid and from the images it looks like a driver tube and power tube for each channel. I assume there’s two transformers in the box on back. In most transformer outputs there are taps for 4 and 8 ohms. Btw I looked it up on their website and it looks totally different there. No phono input.
I see someone else noted the image discrepancy in an earlier post.
 

nyxnyxnyx

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this is pretty great price for a tube amp if all functionalities work as intended and the build quality is ok.
I once had some headphones tube amplifiers for around this money or even a few times more, and even though the power was quite inadequate, it didn't sound bad to the typical tube-recommended headphones (hd650, beyerdynamics....), so I suspect this will range from "meh" to "alright" in real life scenarios.
 
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Hart

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Interesting...this company sent their product to ASR knowing what they do at ASR. Knowing the outcome. I can only assume they have no test equipment for their own product as the results can only be what they are. What did they think the upside would be? At $180 did they think that any publicity is good publicity? I actually think it's better than that Carver tube amp which is much more more expensive, I guess maybe that's it's forte. So in short it's crappy but not as crappy as something that's really crappy.

And also I don't understand tubes, let's say you could build an amp out of rocks and roofing tar, it would work but it would have very low output and terrible distortion. Would you praise it because it sounded sweet and was old school or exotic? I can appreciate a Model T and it's position in history, however I don't want to drive one. Results may vary.

Lastly it was nice of Amirm to give them the opportunity to not publish, good form.
 
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natna

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The most strange thing is the FR.
If there are tubes in the chain, distortion and SINAD is going to me mediocre by ASR standards.
I have an old tube buffer/preamp, that I tested with 3 different brands (6N3/5670). The sound was ranging from cold and somewhat grainy (chinese generic 6N3) to warm and glorious (NOS GE 5670 5*).
I know that the measurements are going to be nasty...
I rarely use it, but with the right tubes, it pairs perfectly with my old Topping TP20 -II tripath amp and my neutral sounding Crystal acoustics TX-B1 bookshelfs.
 
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mhardy6647

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I am sure it's a hybrid -- and who knows what (if any) purpose the tubes serve in situ? :) There are reported instances (e.g., the "Jaycar" branded hybrid -- sold under many brand names in different territories) of the tubes' filaments serving as resistors in the circuit (and nothing more).

In the present case, my guess would be preamp or buffer (i.e., in this case, I do want to give the mfgr. the benefit of the doubt!).

OK. Here it comes!
mammoth digression ahead... ;)

All this being said ;) I am posting mostly to mention (point out) to all y'all young whippersnappers that it is perfectly possible to build a single-channel tube amplifer using one physical tube (and no other active components) -- or a stereo amp with two tubes. We call these spud amps ("one tubers") ;) There are myriad ways to do this, enabled primarily by the development of specific vacuum tube types to enable very low parts count (i.e., cheap!) amplifiers for low-cost mono or stereo amps for record players and very low cost/entry level hifi as the industry was poised to transition from vacuum tube to soiled solid state.

One route uses a "dual purpose" tube such as the 6BM8 (still much beloved, believe it or not, in certain Japanese audiophile circles). The 6BM8 combines a triode and power pentode in one bottle. Typically two 6BM8s were used to make a single channel push-pull amplifier (one triode as voltage amp, one as splitter, and the two pentodes as PP outputs), but it's perfectly possible to use one 6BM8 in a single-ended spud: triode as voltage amp/driver and pentode as output. Heck, the nutsiest of us ;) might wire the output tube as a triode and make our spud a pseudo-SET ("single-ended triode") amp.

1704471504965.png

source: http://www.tubebooks.org/tubedata/HB-3/Receiving_Tubes_Part_1/6BM8_ECL82.PDF


Another enabling vacuum tube type that jumps to mind for spud amps is a bit uglier. The 60FX5 was designed with enough sensitivity/transconductance to serve as a single (pentode) to take essentially a line level input (specifically a crystal or ceramic cartridge signal from a low-end record player of ca. 1960) and drive a loudspeaker. :) Two of these tubes can be used to build a series-string stereo amplifier with extremely low parts count and no pesky, heavy, expensive power transformer to muck up the profit margin!:cool:

60FX5stereoampresized.JPG

source: https://www.worldradiohistory.com/B...ooks/RCA-Receiving-Tube-Manual-1964-RC-23.pdf
Mind you, the lack of isolation from the AC mains, to modern sensibilities, is a bit outre :eek: -- but it can be done. Not recommending it, of course! Kids, don't try this at home!


OK, I'll stop now!
;) :facepalm:
 

phoenixdogfan

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It's dirt cheap. Seems like the cost of the tubes alone ought to exceed the price of the unit. Almost certainly the tubes are in the front end, and not output tubes.

With a tube amp, the poor SINAD/high noise and distortion is actually kind of the point. Of more concern is the bump in FR below 100Hz, and the .5 db roll off form 2khz to 10 khz. Both of those should be audible. Separation in the phono stage is problematic, but it's a minor miracle they were able to include a phono stage for the price, so hard to complain there. If someone is craving the tube sound in the worst way, don't see how this can be considered a terrible choice.
 

fpitas

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Mind you, the lack of isolation from the AC mains, to modern sensibilities, is a bit outre
People were tougher in those days. Kids these days can't take 117VAC without whining.
 

mhardy6647

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People were tougher in those days. Kids these days can't take 117VAC without whining.
It always kinda made me vibrate...

ahem.
On topic:
EDIT: Ooops, I forgot the topic wasn't the LG Dukebox! I am so ashamed... I'll move the irrelvant comment there. :facepalm:
 
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fpitas

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fpitas

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It's nice to know that this attractive piece of junk electronics is made by honest people.

No one said it was easy!
Cheap. But not easy.
 

fpitas

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DSJR

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It's a little FUN product fellas, not a high end audio confection with sota performance :D

Not sure if it's available in Europe (I admit I haven't looked hard) although AliExpress might sell it).

Would be nice to see inside though... I suspect the valves are in the line buffer if used for actual audio 'work' and the rest is chip based?
 

kklarqvist

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That brick wall on the frequency response is very surprising. How does it do that?
A guess,

Input buffer to ADC - source selector - re-sample at 40kHz precisely fed into DAC (no digital filters) to output stage. The low frequency response is probably the effect of the output transformer if the output stage is tubes. On the back it's printed "hybrid tube amplifier" which usually mean tube input buffer, transistor power but probably reversed for this one (?).

It could all be accomplished with oversampling and digital filters if the device was designed for that FRF — (I doubt it) it goes againt generally accepted ADC/DAC design practices.
 
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