Review and Measurements of New JDS Labs Atom Headphone Amp

[no1boss]

That's a neat little box! .. and I just bought a THX a day before this announcement, heh..

I had actually been waiting for new product from JDS ever since my NFB-11 went silent, so this is kind of a bummer. I guess I'll sell the THX when warranty runs out and maybe then there will even be a Atom DAC+Amp.

Even though the THX is good performance/value, it seems support (as far as repairs etc.) after the product's initial life cycle might be a bit troublesome.

 

[Veri]

I had actually been waiting for new product from JDS ever since my NFB-11 went silent, so this is kind of a bummer. I guess I'll sell the THX when warranty runs out and maybe then there will even be a Atom DAC+Amp.

Quite likely

Also don't forget about March's amp. Looking pretty funky, too.

 

[jackenhack]

Can you please find a scope to measure this beautiful headamp with sine & square waves at 20Hz, 1KHz, 10KHz, 15KHz and 20KHz? You could you the built-in signal generator from the scope, if available or you could use a very good DAC and audiocheck.net or similar website to generate the correct sines and squares.

It's very important to see when the output buffer starts to distort (to bend the sines or to flatten the output signal) and if they get overheated.

Also, Q401 is one of the best devices to test this headamp, right?

I know this is way off topic, but your wish is my demand. A signal from a lab DDS frequency generator, not a "quality" signal, but should give a clue anyway.

This is 2 Vrms at 1 kHz in with low gain setting (I like to play my Sennheiser HD-650 loud).

Here's the square wave at 1 kHz.

Here's a sine wave at 10 kHz.

The square wave at 10 kHz. The post and pre-ringing could be my wonky "flying leads" measurements, the generator or in worst case, bad design from me

All measurements were done without any load.

Here's the 20 kHz sine wave.

And the corresponding 20 kHz square wave.

20 Hz sine wave.

And here's the 20 Hz square wave. I've put markers so you can calculate the 3 dB drop off point

Disclaimer, this is from my old test mule, not the finished product.

 

[bozoc]

Any chance we could see some multi tone tests amirm? That is where the all good stuf is.

 

[jackenhack]

I also bought the THX amp before seeing this review. But I comfort myself with the fact that it has XLR input, and the adventure of taking it apart. I've read the patent, but there's probably a lot to learn from a finished design.

 

[GGroch]

Yeah! But are you saying this is the first transparent amp? Nah. Just more transparent... Transparentier? . Point is there will always be better, and who are we kidding, we'll want that too...

It appears now that from a performance perspective, a well designed headphone amp (and DAC), even a cheap one, can be functionally perfect. The significant breakthrough with the Atom is its power (ability to drive difficult phones) because as Amir's measurements show, there are quite a few cheap amps with low distortion/noise. An earlier thread post called this the "new standard in amps under $300". Is there an actual performance improvement above $300?

So we are at the same place that wristwatches were a few decades ago. Cheap ones can tell time just fine, but a thriving industry exists because aficionados want other things as well. Very few people wear watches with plain black plastic cases.

I just received a Loxjie P20 cheap hybrid tube balanced amp. I am certain it measures a lot worse than the Atom (I would be interested to know by how much and where)...but it is supposed to. The tubes are there to make it euphonic not transparent. It sounds great to me, has a shiny metal case, glows, and tube rolling provides a few more weeks of tweaking fun before I move on. All of these other things mean it really will probably sound better to me....because unlike watches, there is no easy proof of performance around to dispel my illusions.

 

[flipflop]

Any chance we could see some multi tone tests amirm? That is where the all good stuf is.

https://www.audiosciencereview.com/...rasil-dac-inconsistent.3812/page-5#post-91180
https://www.audiosciencereview.com/...rasil-dac-inconsistent.3812/page-4#post-91165

 

[Veri]

I just received a Loxjie P20 cheap hybrid tube balanced amp. I am certain it measures a lot worse than the Atom (I would be interested to know by how much and where)...but it is supposed to. The tubes are there to make it euphonic not than transparent. It sounds great to me, has a shiny metal case, glows, and tube rolling provides a few more weeks of tweaking fun before I move on. All of these other things mean it really will probably sound better to me....because unlike watches, there is no easy proof of performance around to dispel my illusions.

How high do you think output impedance is on the Loxjie?

 

[andreasmaaan]

Any chance we could see some multi tone tests amirm? That is where the all good stuf is.

In post #1 there is an IMD vs level graph. This uses the SMPTE method.

 

[GGroch]

How high do you think output impedance is on the Loxjie?

I have no idea. The spec is not in the manual and I do not think they have a website yet. Loxjie is a trademark of Shenzhen Shuangmusanlin (SMSL, Sabaj) so I imagine there will be one soon. It powers my Hifiman He560 quite well, which is my only balanced phone.

I did just order an Atom as a result of this thread....so my "cheap watches" pile is growing.

 

[Veri]

Loxjie is a trademark of Shenzhen Shuangmusanlin (SMSL, Sabaj) so I imagine there will be one soon. It powers my Hifiman He560 quite well, which is my only balanced phone.

Very interesting. I've been wanting an amp compatible with XLR out for some time now $85 is ridiculously little money for what they offer.

 

[KR8NUX]

Seriously, if you get the Topping D30/D10 and this, you are set for life and probably anything above is diminishing returns.

 

[Jorj]

Seriously, if you get the Topping D30/D10 and this, you are set for life and probably anything above is diminishing returns.

If my kids cared one iota about good audio, I'd get them a D10 (or the Khadas if they had inherited my nerdy tendencies) and this Atom and know that they have gear that it would take years to outgrow, if ever. Those measurement numbers in combination are just simply excellent, and improvements, while desirable, are utterly inaudible.

I am a touch concerned about the potential issues of DC coupling in the Atom. I know next to nothing about it, but I know it can do horrible things to transducers if it goes bad. Is there a real risk here?

 

[trl]

I know this is way off topic, but your wish is my demand. [...]

Thank you, mylord!

If it’s dual spot then being able to compare the input generator signal on probe A vs. the output on probe B would be much easier to spot the differences.

I see that 1KHz has 6.64V and the 20Hz and 20KHz have 6.04V. Also, there are differences on the sines too.

 

[maverickronin]

Is there an actual performance improvement above $300?

A little bit. A few headphones could use more power and most pots are problematic with sensitive IEMs so a better volume control could be useful as well.

 

[jackenhack]

Thank you, mylord!

If it’s dual spot then being able to compare the input generator signal on probe A vs. the output on probe B would be much easier to spot the differences.

I see that 1KHz has 6.64V and the 20Hz and 20KHz have 6.04V. Also, there are differences on the sines too.

Haha! No need to bring in our titles in the discussion honourable Duke @trl.

Yeah, I know that the measurements are all over the place, but you spiked my interest, so I went down the rabbit hole. Thus the different levels. I promise you that the frequency curve is quite sweet up to over 40 kHz. I really shouldn't put out anything until it's done. But I can drive both low impedance headphones like Oppo and higher impedance ones like HD-650 to insane levels without distortion. I experimented with a gain of x15 and plugged in in-ear Etymotics headphones and total silence.
But I'm being more interested in seeing measurements with "real" loads, aka headphones. There's been an upshot of new contenders on the best THD+N throne thanks to @amirm, but that doesn't help if it all goes down the drain when connected to, let's be honest, an electromechanical device with impedance, inductance and reactance. Maybe design a simulation load with the characteristics of, for example, the venerable Sennheiser HD-650, because I love my pair of HD-650 enough not to start pushing the limits of them

 

[amirm]

Maybe design a simulation load with the characteristics of, for example, the venerable Sennheiser HD-650, because I love my pair of HD-650 enough not to start pushing the limits of them

Yes, this is what needs to to be done. It may be difficult though as the headphone distortion tests I have done shows the most effect due to back EMF from the headphone. Throwing out that component may nullify the purpose of the test.

 

[gvl]

Anyone knows if preamp outputs are buffered?

 

[jackenhack]

Yes, this is what needs to to be done. It may be difficult though as the headphone distortion tests I have done shows the most effect due to back EMF from the headphone. Throwing out that component may nullify the purpose of the test.

You're absolutely right. The back EMF is a problem, but it should be able to reproduce. Hell of a lot of measurements to simulate though. Here's my standard test jig when testing output buffers stability when simulating circuits.

 

[amirm]

Anyone knows if preamp outputs are buffered?

I assume they are simply connected to the headphone output possibly with an inline resistor given the fact that they can go to levels way beyond what we need for line out.