• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Review and Measurements of New JDS Labs Atom Headphone Amp

Joined
Jul 27, 2019
Messages
40
Likes
2
Use low gain unless you really need more power. The Atom measures a lot better in low gain than it does in high gain. There is a little study on ASR about gains which compares the Magni 3 and the Atom in their different gains. To lazy to link it now but you will find it anyway
The problem is that with low gain I get nothing more compared to my onboard built in dac/amp, that's why I bought an external amp in the first place. Plus in games, with full windows volume and Atom on low gain and max volume it sounds really low still like my onboard solution. I don't know if it a headphones' thing, that they are difficult to drive but high gain is the only way to listen loud and comfortable without cranking the volume to max (with low gain)
 
Joined
Jul 14, 2019
Messages
16
Likes
11
The problem is... ...with low gain)
You're using the analogue line out from the computer? Atom low gain is × 1.0, it will be the same volume as analogue out from the PC. I suspect you need to change the connections to use either USB, or S/PDIF via optical or coax to an external DAC to get a true line out signal to the Atom.
 
Joined
Jul 27, 2019
Messages
40
Likes
2
You're using the analogue line out from the computer? Atom low gain is × 1.0, it will be the same or lower as analogue out from the PC. I suspect you need to change the connections to use either USB, or S/PDIF via optical or coax to an external DAC to get a true line out signal to the Atom.
Ah really useful. Yes I use the 3.5mm green out of the motherboard that's why I get the same result volume wise as you say. Is there a USB to rca or optical to rca to use or an external dac is the only way?
 
Joined
Jul 14, 2019
Messages
16
Likes
11
Ah really useful. Yes I use the 3.5mm green out...
That's it then, probably getting somewhere in order of 600mV to 1V signal, with enough current to power undemanding headphones. A line out from a DAC will give you around 2V, but little power. So if the system is not satisfying with the Atom on high gain, maybe check out the Khadas Tone Board (new version coming soon) and Topping D30 or D50s DAC.
 

daftcombo

Major Contributor
Forum Donor
Joined
Feb 5, 2019
Messages
2,134
Likes
1,867
Ah really useful. Yes I use the 3.5mm green out of the motherboard that's why I get the same result volume wise as you say. Is there a USB to rca or optical to rca to use or an external dac is the only way?
Perhaps the Apple dongle (9$) is what you need in-between the computer and the Atom?
 
Joined
Jul 27, 2019
Messages
40
Likes
2
Topping D30 is one of my options to be honest money wise there's not too much difference compared to D10.

So just to be sure. I connect the external DAC via USB (or optical?) with the PC and then the DAC with the Atom via RCA correct? And I will be able to use Atom with low gain and the right volume output right?
 
Joined
Jul 14, 2019
Messages
16
Likes
11
So just to be sure. I connect the external DAC via USB (or optical?)
This is a question of priorities and your system. If you're gaming, I would particularly avoid USB 2.0 because of latency, which may be felt as additional 'input lag' and possibly audio sync issues and stutters. USB 3.0 is less of a problem (I think, but not 100% certain) and so the S/PDIF may be preferable. You have to make a judgement call on how powerful your system is vs the number of devices competing for time on the USB. If you're not gaming, use whichever is the most convenient.
 
Joined
Jul 27, 2019
Messages
40
Likes
2
Gaming is my 100% prio. I have a really powerful gaming rig and currently two USB 3.1 gen 2 ports free and the optical one free too. I remember reading an article here that usb is preferable to optical out but I don't know what is preferred in games vs music for example.
 
Joined
Jul 14, 2019
Messages
16
Likes
11
Gaming is my 100% prio...
I suspect there would not be any discernible difference between the USB 3.1 vs optical S/PDIF, but if you get a DAC that has both, you can try both for the price of one extra cable. iirc Amir wrote something about how USB is excellent if the system is designed properly and will measure slightly better than S/PDIF, but in reality some DACs are better over either optical or coax just due to the specifics of the design. Best thing to do is check the measurements in the reviews.
 
Joined
Jul 27, 2019
Messages
40
Likes
2
I suspect there would not be any discernible difference between the USB 3.1 vs optical S/PDIF, but if you get a DAC that has both, you can try both for the price of one extra cable. iirc Amir wrote something about how USB is excellent if the system is designed properly and will measure slightly better than S/PDIF, but in reality some DACs are better over either optical or coax just due to the specifics of the design. Best thing to do is check the measurements in the reviews.
Ah excellent reference to the reviews section. Regarding the D30 and Atom, Amir proves that they work better over USB and low gain respectively so I guess my question is answered. So, since the external D30 dac over USB, will have more volume output than my green 3.5mm audio out in my motherboard, I will be able to use the Atom with low gain right?
 

Azeia

Active Member
Joined
Jun 13, 2019
Messages
123
Likes
293
Use low gain unless you really need more power. The Atom measures a lot better in low gain than it does in high gain. There is a little study on ASR about gains which compares the Magni 3 and the Atom in their different gains. To lazy to link it now but you will find it anyway
I'd be surprised if it can drive @iazriel's DT 770s at low gain (even with dedicated DAC, as others suggested in the thread) considering that my DX3 has no headroom at high gain for the similarly hard-to-drive DT 990s; not sure how much power the Atom outputs at low, but at high it's about double what the DX3 does at high, so yeah.

I think I found the post you're referring to here; there's a comment from solderdude there that explains things (search on page 1). It seems that for hard to drive headphones it's unlikely you're ever going to get any audible distortion on high gain, if I understand correctly that is. So I would maintain my advice that @iazriel will be best served in high gain since they've got insensitive headphones like mine, even if they buy a DAC (although I'm sure that will improve the situation a bit).

This is a question of priorities and your system. If you're gaming, I would particularly avoid USB 2.0 because of latency, which may be felt as additional 'input lag' and possibly audio sync issues and stutters. USB 3.0 is less of a problem (I think, but not 100% certain) and so the S/PDIF may be preferable. You have to make a judgement call on how powerful your system is vs the number of devices competing for time on the USB. If you're not gaming, use whichever is the most convenient.
Eh, I don't think this could ever be a problem even for computers that are like 20 years old, nevermind modern ones. I've never seen any evidence to back up the various talk about USB 2.0's latency/polling problems in the real world (neither with audio, or with keyboards which is a claim you often hear from people who prefer PS/2 keyboards that use actual interrupts). I mean from a hardware perspective, USB 2.0 is absolutely an inferior bus to 3.0, but even so, I've never seen data to back up that it actually makes a difference in the real world. I think people underestimate just how overkill a modern CPU is for something as simple as USB. Also, if I'm not mistaken, it's the host controller that does the polling, not the CPU.

Lastly, 99% of DACs are USB 2.0, even for high-end professional gear. I've even seen at least one DAC that had USB 3.0 ports that was actually USB 2.0 internally and had claims on the vendor's website about how they have the 3.0 ports just for the sake of supporting USB 3.0 cables which have higher shielding requirements. I can't imagine you getting any benefit from plugging a USB 2.0 device into a USB 3.0 port; you'd be using XHCI instead of EHCI, but again, I haven't seen any info out there that suggests this has benefits.
 

Silou

Active Member
Joined
Oct 5, 2018
Messages
245
Likes
107
I'd be surprised if it can drive @iazriel's DT 770s at low gain (even with dedicated DAC, as others suggested in the thread) considering that my DX3 has no headroom at high gain for the similarly hard-to-drive DT 990s; not sure how much power the Atom outputs at low, but at high it's about double what the DX3 does at high, so yeah.
DT770 Pro 250 Ohm needs 3.02 Vrms 11.87 mA 35.85 mW to get to 110dB SPL
DT990 Pro 250 Ohm needs 3.51 Vrms 13.13 mA 46.07 mW to get to 110 dB SPL
K712 Pro 62 Ohm needs 4.79 Vrms 69.93 mA 334.95 mW to get to 110dB SPL
Hifiman HE6 needs 13.49 Vrms 310.11 mA 4183.45 mW to get to 110dB SPL

I own the K712 and the Atom handles it with ease in low gain. You can see that the Beyers are a lot easier to drive than the K712.

Characteristics: https://reference-audio-analyzer.pro/en/param1.php
Calculator: http://www.digizoid.com/headphones-power.html
 
Last edited:
Joined
Jul 27, 2019
Messages
40
Likes
2
DT770 Pro 250 Ohm needs 3.02 Vrms 11.87 mA 35.85 mW to get to 110dB SPL
DT990 Pro 250 Ohm needs 3.51 Vrms 13.13 mA 46.07 mW to get to 110 dB SPL
K712 Pro 62 Ohm needs 4.79 Vrms 69.93 mA 334.95 mW to get to 110dB SPL
Hifiman HE6 needs 13.49 Vrms 310.11 mA 4183.45 mW to get to 110dB SPL

I own the K712 and the Atom handles it with ease in low gain. You can see that the Beyers are a lot easier to drive than the K712.

Characteristics: https://reference-audio-analyzer.pro/en/param1.php
Calculator: http://www.digizoid.com/headphones-power.html
@Silou Do you use an external DAC along with the Atom or you drive the amp from a motherboard like me? In any case, since it was in my plans to get an external DAC anyway sometime soon, I just made it happen sooner and purchased the Topping D30, I got it on a really nice price too from a European seller in eBay compared to amazon and other stores. Hopefully it will give the necessary improvement in order to drive the DTs with low gain comfortably.
 

Azeia

Active Member
Joined
Jun 13, 2019
Messages
123
Likes
293
DT770 Pro 250 Ohm needs 3.02 Vrms 11.87 mA 35.85 mW to get to 110dB SPL
DT990 Pro 250 Ohm needs 3.51 Vrms 13.13 mA 46.07 mW to get to 110 dB SPL
K712 Pro 62 Ohm needs 4.79 Vrms 69.93 mA 334.95 mW to get to 110dB SPL

I own the K712 and the Atom handles it with ease in low gain. You can see that the Beyers are a lot easier to drive than the K712.

Characteristics: https://reference-audio-analyzer.pro/en/param1.php
Calculator: http://www.digizoid.com/headphones-power.html
I've used that calculator in the past, but this is not easy to read, because you have to power the headphones at a given impedance; when you look at the Atom for instance, it provides 250mW at 300 Ohms, but 125mW at 600 Ohms. Also, from what I understand, low-end frequencies typically require more power than the others, which may account for Amir's comments in the Neurochrome HP-1 review about how "you have not heard clean bass until you power this headphone with this class of amplification", referring to the HD-650.

If those power requirements were accurate for the DT 990, then my DX3 Pro should've been able to drive these perfectly fine since it has 125mW into 300 Ohms at high gain. Because of this discrepancy, I've been looking at the 115dB SPL ratings on the calculator, personally, which is why I always recommend an amp that can do around what the Atom can do in high gain, for these headphones, otherwise you've got zero headroom in my experience.
 

pwjazz

Senior Member
Joined
Sep 21, 2018
Messages
409
Likes
526
Did someone try the preouts of the Atom in combination with powered speakers? I would like to replace my bookshelf speakers with something active, but I am a bit afraid of ground loops :D I use the Tone Board as DAC.
I run a D10 into the Atom and feed a pair of powered JBL 305s from the pre out and I do have ground loops. Plugging both speakers, the amp and my computer monitor into the same power strip helped, but at high volumes I can still detect a hum.
 
Last edited:
Top Bottom