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Review and Measurements of New JDS Labs Atom Headphone Amp

Viper Necklampy

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You would get 122 dbSPL if the headphones are rated 98dB at 1mW. If the headphone rating is 98 dB at 1 V RMS the max output would be 106.75 dBSPL.

[EDIT] I ran the numbers using a spreadsheet I have. Looking at your link I see that the website tool has a selection to identify the units. Which 30 Ohm headphones are planning to use?
Thanks, it's the El8 Titanium, i'm waiting for it to ship.. In that site cannot be identified the EL8's, anyway it's 98dB at 1mW, infos online says even 100 or 102dB x1mW, but it's only 98 Audeze says.. So it's 122dB in low gain, it should quite enought even if i listen very loudly sometime, but it says it requires 2,75 Volts rms, in Low gain Atom generate 250mW but i don't know how much Vrms.. I try to avoid High Gain on Atom because amirm on the review says on H gain the results were not as low gain, he didn't show us so i guess he don't wanna show the results :( Also paired with Topping d50 the total SINAD were 109, and cutted to 106dB (Don't ask me why! amirm says that), so i don't know if i would benefit at all the low gain instead of high..
 
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Reyer

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Newbie question:
What would be the proper procedure to shut down the Atom or any other amp using power-off button/switch? Would it be okay to relay the power line to the switch and back to the board or should there be any additional safety circuits to power down it gently?
 

JohnYang1997

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Thanks, it's the El8 Titanium, i'm waiting for it to ship.. In that site cannot be identified the EL8's, anyway it's 98dB at 1mW, infos online says even 100 or 102dB x1mW, but it's only 98 Audeze says.. So it's 122dB in low gain, it should quite enought even if i listen very loudly sometime, but it says it requires 2,75 Volts rms, in Low gain Atom generate 250mW but i don't know how much Vrms.. I try to avoid High Gain on Atom because amirm on the review says on H gain the results were not as low gain, he didn't show us so i guess he don't wanna show the results :( Also paired with Topping d50 the total SINAD were 109, and cutted to 106dB (Don't ask me why! amirm says that), so i don't know if i would benefit at all the low gain instead of high..
Use the gain setting as low as possible. There is no such thing as headroom when it comes to gain setting. Headroom is set by the supply rail and the components themselves. You can have 6vrms input and output 6vrms at 0db gain setting. That's all depending on the input. In real life you use only about 1mw and hardly 10mw. The sinad of all frequencies at 1mw and 10mw is what's important. Don't be blinded by the numbers.
Also don't compare the sinad of dac directly especially the noise part to the amplifier, the noise will be decreased by potentiometer unless you play at maximum volume. And in most cases the noise floor of the amplifier output stage will be higher than the noise coming from dac.
Take closer look at individual distortion harmonics of dac and don't worry too much about thd+n/sinad number of dac.
 

fljoe

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Anyone here using a DAP with their Atom? I am thinking of using my Onkyo DP-X1 with the Atom .. Onkyo headphone out to Atom 3.5mm input. The Onkyo by itself has a hard time driving the Senn HD6XX. Does this sound feasible? Thanks!
 

JohnYang1997

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Anyone here using a DAP with their Atom? I am thinking of using my Onkyo DP-X1 with the Atom .. Onkyo headphone out to Atom 3.5mm input. The Onkyo by itself has a hard time driving the Senn HD6XX. Does this sound feasible? Thanks!
http://ohm-image.net/data/audio/rmaa-onkyo-dp-x1-24-bit
as measurements showed. Single ended output is pure bad. But the balanced output is pretty darn good. Unfortunately atom doesn't have balanced input. So you want to either get thx 789 or get a different dac.
khadas tone board
jds ol dac
smsl su8
db magix ac3 dongle
musiland mu2 dongle
 

ngs428

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Is there an adapter out there that goes from 1/4”male TRS to 2.5mm TRRS female.

I have balanced headphone cables terminating with a male 2.5mm TRRS connection and I want to adapt to a 1/4” TRS female socket (or 3.5mm TRS female) on the Atom.

Options?
 
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amirm

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Newbie question:
What would be the proper procedure to shut down the Atom or any other amp using power-off button/switch? Would it be okay to relay the power line to the switch and back to the board or should there be any additional safety circuits to power down it gently?
I wouldn't worry about how you power it down....
 

tired_guru

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Just have to confirm. This unit not only measures great. It does the justice to many amazing HP from my collection like hd700, he-4, T90 jubilee, dt880 600, he-560 v1, focal clear, meze 99 classics, fostex 909, ar-h1. This is like revelation. I listen mostly to classical recordings and this little guy is seriously audibly transparent. I am extremely picky regarding classical/fusion jazz/acoustic music.

This is like end game. Gobs of power and speed without hint of distortion. There are some amps similar but cost a lot more. Pair it with some neutral dac (grace sdac, d10, khadas tone or d50->this has an advantage of changeable digital filters) and forget about losing money on neverending story. Spend the rest for nice collection of cans instead, to have different one for different genre or when your mood change or when you just want something new/different. But for dac+amp you should use the most transparent combo. Then you can start to compare what different HPs have to offer.

I was thinking about something like thx789 for my he-4 or high impedance HPs (sometimes I love to listen very loud especially with classical) but this has more in high gain than I would ever need, even on some recordings with average low level volume to have great dynamics without ****** compression (loudness war).

So unless you have new he-6se or old he-6, maybe akg k1000 - forget about anything else regarding power reserve. Even t50rp was easy to drive and achieved high SPL in high gain. Even paid almost 200$ importing from USA to EU, it was worth it because there is nothing on the market than can come close to this. Mobility thanks to its small dimensions is another advantage. 2 prongs mains plug will help you to avoid any ground loops between your dac/pc (got terrible issues with schiit asgard 2 and lyr (3 prongs mains plug) + sdac when testing recently, a lot of noises from PC but dead quiet when using it with atom). So there are a lot of advantages for such small amount of money.
 
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tired_guru

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Can someone help me, how much volume i can reach in dB with my headphone according to https://www.headphonesty.com/headphone-power-calculator/ With a 30 Ohm 98db in sensitivity with Low Gain? Looks like ATOM in Low Gain can reach max 250mw in Amirm measurements, (Tell me if i'm wrong) and i don't get the Vrms story, so don't know.. Maybe 122 dbSPL?

It depends on many things. In low gain when you try to get max Vrms (thus max power out), you have to put as much as you can from your DAC. Considering standard 2V (there are dacs with around 3Vrms or even higher, in unity mode you can put about 8,5Vrms on the amp's input according to John), you will have 2V on the output of your amp - this "unity mode", there is no gain applied at all (or it is x1), output stage of an amp works only as current gain (no voltage gain stage in this case).

Now this 2Vrms cannot be taken into calculation for granted. It will occur only if file that you listen will be recorded at 0dBFS level. In real world it will never be (yeah, let's not talk about death magnetic of metallica or other loudness war victims). You can have something near 0dBFS in peaks, but usually it can be somewhere around -3dB or -6dB. For instance for -6dB average, your voltage from max 2Vrms will drop to 1Vrms (x0.5). That's why nice gain like 5-6x is needed not only for some high impedance & low sensitivity HPs, but also for very low level recordings with wonderful dynamics range (classical, jazz, acoustic) and in general well mixed/mastered recordings which are never around 0dBFS, because it sounds simply like total crap. Especially on hi-fi systems.

This kind of info can be find for instance when you listening to youtube in stats for nerds (like -6dB, so you know that there will be max about 1Vrms instead of potential 2Vrms, so voltage drops 2x, your power drops 4x because of U^2 in the equation, your SPL drops significantly comparing to something with like -0.8dB where you can almost get max from your amp in low gain and dac that puts 2Vrms on its output -> now it will be 0.912 x 2Vrms on the output of the dac so on the output of the amp in unity gain mode).

Than you can calculate power U^2/R. Having power calculated it's time to check out sensitivity (remember that dB/mW is usually for low impedance HPs, for high impedance HPs it is usually in dB/V which makes big difference, so you can use just Vrms here but remember this is logarithmic scale). Now you can finally calculate SPL (sound pressure level in real dB) which is real "volume" that you are looking for.

For most of calculations you can you these online calculators but you have to keep in mind what I typed above (selecting proper sensitivity - /mW or /V, knowing what is the gain of amp, max output of your dac and average recording level of your files that you listen to).

Uffff, I hope it clarifies a bit things beacuse this is the topic that is always simplified too much and not so easy to understand with all extra factors. So like you see, a lot of variables before you can tell how loud it will be for certain kind of HPs. But from my lifetime experience for such low impedance & high sensitivity headphones, with 2Vrms on the dac's side you should be more than enough. If the album has very low recording level, you can always use something like replaygain in foobar. This is great solution to retain dynamics range, avoid compression but raise recording level (+ eventually add advanced limiter as extra dsp).
 
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JohnYang1997

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So unless you have new he-6se or old he-6, maybe akg k1000 - forget about anything else regarding power reserve. .
Well even with he6 or k1000, the power is enough. 2vrms at the input is good enough for both at 0db gain setting. And you can output more at higher gain or higher input. And distortion under such load will be low too.
At the technical standpoint, where the atom amp falls short is the high frequency distortion(over 2khz) when using low impedance load(16ohm and less) and outputting high current. That's the limitation of circuits using lme49600. neurochrome hp-1 can be better but still will measure much worse than under high impedance load condition.
In real world, unless you are using 16ohm k1000 or to power an 8ohm speaker, you are free from any distortion.
Tho it will still has characteristic due to relatively high distortion with low impedance load like aeon flow, final e4000, the sound can be a bit bright, not much but still.
 

tired_guru

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Well even with he6 or k1000, the power is enough. 2vrms at the input is good enough for both at 0db gain setting. And you can output more at higher gain or higher input. And distortion under such load will be low too.
At the technical standpoint, where the atom amp falls short is the high frequency distortion(over 2khz) when using low impedance load(16ohm and less) and outputting high current. That's the limitation of circuits using lme49600. neurochrome hp-1 can be better but still will measure much worse than under high impedance load condition.
In real world, unless you are using 16ohm k1000 or to power an 8ohm speaker, you are free from any distortion.
Tho it will still has characteristic due to relatively high distortion with low impedance load like aeon flow, final e4000, the sound can be a bit bright, not much but still.

You got me into calculating it :D I don't have HE-6 right now, but just out of curiosity ...

Atom is able to deliver for 50 ohms HE-6 about 1W of continous power and extremely low 83,5dB/mW sensitivity of HE-6.

This will be only when using high gain and file that is recorded at around 0dBFS, also taking into account that dac is able to pass about 2Vrms - preconditions.

https://www.headphonesty.com/headphone-power-calculator/

Then you have it:

1550140144451.png


About 113dB of SPL. But this scenario is not possible in real life. For average recording level of files, I would go to something at least like -6dB, so your max voltage drops x2. That is much likely scenario, and then it goes like that:

1550140292438.png

107dB of SPL which is still plenty. The problem is that many audiophile recordings can be recorded even lower (not even mentioning classical recordings). But having 1W of pure, continuous power is really a lot. Like you said can be enough for even HE-6. Now you can judge by yourself hifiman's recomendation of having 4 of 5 W per channel if I recall correctly. This can make sense for some dynamics peaks without distortion on some very low recordings.

Let's check out what is going on when you put 5W per channel on HE-6:

1550140618899.png


As a nice bonus you have actual current & RMS voltage needed so you can imagine things better. Yep, this is 120dB of SPL. So this was probably calculated for 120dB threshold. Probably to able to deliver only peaks, uncompressed and undistorted, on very low volume recording level. But in real life this is just crazy and knowing that single digit hifiman can deliver a lot of SPL without hearable distortion - this is also very dangerous, because you don't feel this power/SPL at the beginning until you start losing your hearing. So something like atom can be nice limiter here for your safety too (I went through this with my HE-4 ->very similar to HE-6 in many aspects, also very low sens with 86dB/mW<- and emotiva speaker amp driving them directly from speaker taps with some resistors).

So it all depends on the file in this scenario and its average recording level. But having in mind that natural instruments (not amplified/processed) have natural SPL of about 75 (double bass - quietest of classical/jazz instruments), through violins around 80 during peaks, to 90 for piano (about 100 for grand piano) dB of SPL during classical concert and it is enough to thump small chamber and create enormous emotions, still should be enough to reach this level of SPL even on low level classical recordings.
 
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tired_guru

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And this is how it looks like in reality by mapping audio output in audacity in real time and recording from youtube to check what are the real levels during the track:

1550168549100.png


So after right click on the video and choosing stats for nerds, it says about -2.2dB which is true, but like I thought (but wasn't sure), this is not average content loudness but only the highest peak.

Will do the math for you anyway :> For -21dB level on the DAC's output you will get 0.08*2 Vrms=0,16 Vrms that you can now use for your calculations. For -12dB it will be 0.251*2 Vrms=0,5 Vrms. Do you get the point now ? Forget about your 2 Vrms from the DAC during normal, nicely recorded tracks.

If you applied atom gain here it will be above volatges X 4.5. And this value you could use for power/SPL calculation which would be a lot because it is U^2.

This is example of nicely mastered track, with nice dynamics and beautiful sound, but during the track average level of loudness is somewhere between -21dB and -12dB. Now do the math how much SPL you can get from that.

So having average -16dB level, for HE-6 now you would be able to achieve MAX 86dB of SPL (average voltage on DAC's output 0,316 Vrms) in atom's unity gain mode. And keep in mind that this is not some really low volume recorded track.

That's why you need GAIN section, especially for high impedance, low sensitivity cans.

Uffff, was curious how this looks like from youtube perspective, because I used to listen a lot there for some really nice recorded tracks, especially with nice dynamic range and in HD quality (love the AAC / Opus codec and its advanced model, for me it is as good as FLAC/CD). Now I know. Hope it was interesting reading for you.

Btw. there is no point in looking at stats for nerds content loudness because for instant this track


says it is -0.8dB but having a look at the level meters in audacity during whole track, it has amazing dynamic range with quiet parts around -40dB, average about -20dB, with instant peaks up to -0.8dB. I knew it by using my ears because this is breathtaking experience, you can easily tell when there is such amazing dynamic range, especially when listening to something like this loud. Just wanted to confirm that content loudness info in this case tells nothing about dynamics/quality (only the highest peak level).

1550171264480.png


I can recommend this site to avoid heavily compressed albums, the same album but from different master can sound like death magnetic (metallica, straight, thick, horizontal line, with no dynamics at all) or like something above, with lots of excitement factor in your hi-fi audio chain:

http://dr.loudness-war.info/
 
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JohnYang1997

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Forget about your 2 Vrms from the DAC during normal, nicely recorded tracks.
I guess you missed the point. The whole point was the ability of atom. Atom has 8vrms voltage output, and 200+ma current output. It's always the case no matter the gain setting is. Whether it's loud enough when listening to actual music, it's irrelevant. Of course you need to set higher gain when it's not loud enough while you cranking the volume to max.
 

folzag

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Good explanation of "Stat for Nerds" at Ian Shepherd blog:

"The second percentage reflects the normalization adjustment being used. This is the amount by which the playback volume of the clip has been turned down to prevent users being blasted by sudden changes in volume in comparison to everything else. The value scales in proportion with the Volume slider setting.

The final value is the “content loudness” value, and indicates the difference between YouTube’s estimate of the loudness and their reference playback level. This value is fixed for each clip, and isn’t affected by the Volume slider.

So for example a reading of 6dB means your video is 6dB louder than YouTube’s reference level, and a 50% normalization adjustment (-6dB) will be applied to compensate. Whereas a negative reading of -3dB, say, means it’s 3 dB lower in level than YouTube’s reference, and no normalization will be applied, so the normalization percentage will always be 100% of the Volume slider’s value – YouTube doesn’t turn up quieter videos."
 

tired_guru

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The whole point was the ability of atom.

Hey JohnYang1997,

I didn't miss the point at all. The whole point was about "will my headphone with specific impedance and sensitivity be loud enough on atom" and how to calculate real SPL that you can get (especially when not using high gain because "it has worse measurement result"). Not the maximum one in theory when DAC outputs 2Vrms but using standard songs in real life. That's it, I was just answering some member's question.

Atom has 8vrms voltage output, and 200+ma current output. It's always the case no matter the gain setting is.

True, never said it can't. This not what it's all about - there will be nothing to talk about in this regard, this is obvious. This is max what it can output (actually 2Vrms*4.5 internal gain ~9Vrms, extra voltage drop for lower impdeances), only when certain conditions occur. Not always when you just crank your volume up full scale.

Whether it's loud enough when listening to actual music, it's irrelevant.
It is extremely relevant - this determines usability of certain kind of headphones with the amp.
 
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soundwave76

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My Atom arrived today. Yes, it is quite light and has a plastic feel. The volume knob is not that bad though. Could be more solid and robust with a better feel, but I would improve the plastic case over the volume knob and gladly accept a little higher price.
 

soundwave76

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Is the volume knob light supposed to go off when you turn it all the way left, i.e. power off the device? Mine stays on all the time...? :rolleyes:
 
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