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Review and Measurements of New JDS Labs Atom Headphone Amp

guildenstern

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All my headphones are sensitive. I was going to buy a JDS Labs Objective2 and remove two resistors to turn its 2.5X/6.5X gain into 1X/2.5X. But the company informs me I can buy a 1X/2.5X Atom by asking for those gain settings in my shipping notes. Why on earth don't they mention this option on the Atom page?
Atom comes default with dual gain, 1.0x and 4.5x. So, for sensitive IEMs, you get 1.0 gain in stock Atom. Which is probably fine for most users. Which, I guess, is why JDS doesn't publicize custom gain options. Nice of them to offer to customize for you.
 

half_dog

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All my headphones are sensitive. I was going to buy a JDS Labs Objective2 and remove two resistors to turn its 2.5X/6.5X gain into 1X/2.5X. But the company informs me I can buy a 1X/2.5X Atom by asking for those gain settings in my shipping notes. Why on earth don't they mention this option on the Atom page?
https://jdslabs.com/product/atom-amp/
At Configuration it says:
Dual Gain 1.0x and 4.5x
No need modification to get no gain :)
But if you wish a <1x gain, on both amps you may replace the 273 ohm input resistor (R3 and R7) to something like 4k7, 4k9 or 5k1 resistor. On Atom it can be a little tricky because it's SMD. Both amps has the same project for the gain section.
 

bboris77

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I know that this has been mentioned before, but it would be fascinating to see how the Atom (and other amps) behave when driving very low impedance/low sensitivity headphones. I am thinking 8-16 Ohm range, at 150-250 mA levels. From my research, the Atom should be able to deliver this current within its specs, but it would be interesting if there is any difference in distortion and other aspects of performance.

I am asking for very selfish reasons - I have an Aeon RT Closed on order which is a 13 Ohm, 87-94dB/mW headphone (depending on the source as there are no official specs published). I am aware that this would bring me close to the 120dB sound level which is enough to induce hearing damage, but I just want to make sure that I have enough headroom and am not pushing the amp to the point where performance starts to suffer.
 

Jimbob54

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I know that this has been mentioned before, but it would be fascinating to see how the Atom (and other amps) behave when driving very low impedance/low sensitivity headphones. I am thinking 8-16 Ohm range, at 150-250 mA levels. From my research, the Atom should be able to deliver this current within its specs, but it would be interesting if there is any difference in distortion and other aspects of performance.

I am asking for very selfish reasons - I have an Aeon RT Closed on order which is a 13 Ohm, 87-94dB/mW headphone (depending on the source as there are no official specs published). I am aware that this would bring me close to the 120dB sound level which is enough to induce hearing damage, but I just want to make sure that I have enough headroom and am not pushing the amp to the point where performance starts to suffer.
I'll try my RT open with it with some eq preamp on top. I doubt it will struggle to blow my ears off.
 

Jimbob54

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I'll try my RT open with it with some eq preamp on top. I doubt it will struggle to blow my ears off.

@bboris77

Just tried it. EQ with -3dB preamp >SMSL SU8 DAC (one notch down on volume) > Atom> Aeon RT (Open) . Full vol on low gain was bordering on too loud but not uncomfortable for me for short spell, high gain 12 o'clock was plenty for casual listening- so I am saying it can deliver the juice- for me.
 

bboris77

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@bboris77

Just tried it. EQ with -3dB preamp >SMSL SU8 DAC (one notch down on volume) > Atom> Aeon RT (Open) . Full vol on low gain was bordering on too loud but not uncomfortable for me for short spell, high gain 12 o'clock was plenty for casual listening- so I am saying it can deliver the juice- for me.
Awesome, thank you!
 

bboris77

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Your mileage may of course vary.
I am sure it will be more than loud enough for me as I tend to listen at 85dB which would give me plenty of headroom for transients/peaks at higher dB. I still would like to know what the actual distortion performance is with 8-16 Ohm headphones while pushing moderately high current. I am 99% sure that it will be way below the audible zone. It's just that I am curious since nobody seems to be measuring how headphone amps perform with under-32 Ohm headphones.
 

solderdude

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85 Phon ? 85 dBA average (which is quite loud) or 85dB peak levels (so around 70dB average) ?

Distortion will increase in lower impedances but stay well below the levels of the headphone itself.

It isn't measured that often (16 ohm is and is quite close) because most very low imp. headphones (aside from the Verum and some planars) are mostly IEM's which are very voltage sensitive and draw very little current.
But yes... to find the limits perhaps these days 8 ohm should be the lowest load for headphone amps.
As a side effect it would be really easy to determine the current limits of amps.
The downside is that when you spec this
A: some devices may overheat when the test takes time.
B: Needs to be a high power load.
C: People may want to drive small speakers with it because it was tested with 8 ohm load.
 

bboris77

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85 Phon ? 85 dBA average (which is quite loud) or 85dB peak levels (so around 70dB average) ?

Distortion will increase in lower impedances but stay well below the levels of the headphone itself.

It isn't measured that often (16 ohm is and is quite close) because most very low imp. headphones (aside from the Verum and some planars) are mostly IEM's which are very voltage sensitive and draw very little current.
But yes... to find the limits perhaps these days 8 ohm should be the lowest load for headphone amps.
As a side effect it would be really easy to determine the current limits of amps.
The downside is that when you spec this
A: some devices may overheat when the test takes time.
B: Needs to be a high power load.
C: People may want to drive small speakers with it because it was tested with 8 ohm load.

To answer your question, I meant 85dbA average if I am really in the mood for some loud stuff. Realistically, I listen at 75dB average most of the time unless I am playing FPS shooters where I want to hear footsteps. Of course these are just rough estimates using my iPhone dB meter.

Side note, have you actually measured the max current that the Atom can output? I know that it has been quoted anywhere between 200mA up to 250mA which is what LME49600 is capable of.
 
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solderdude

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O.K. so 85dB average is studio mixing levels (quite loud).
Assuming you listen to well recorded music you might have peaks up to 100dB SPL and assuming you don't boost subbass.
That means to be on the safe side you would need to reach 106dB SPL and will have enough headroom.
AEON = 97dB/V so 9dB of headroom would be needed to be safe = 2.8V = 0.6W

Atom max. output current = 180mA rms (250mA peak) = 2.3V in 13 ohm = 0.4W = 104dB SPL so should be enough for about 90dB SPL average.
 

bboris77

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O.K. so 85dB average is studio mixing levels (quite loud).
Assuming you listen to well recorded music you might have peaks up to 100dB SPL and assuming you don't boost subbass.
That means to be on the safe side you would need to reach 106dB SPL and will have enough headroom.
AEON = 97dB/V so 9dB of headroom would be needed to be safe = 2.8V = 0.6W

Atom max. output current = 180mA rms (250mA peak) = 2.3V in 13 ohm = 0.4W = 104dB SPL so should be enough for about 90dB SPL average.
So, a quick update. I got the Aeons RT Closed and tested them briefly with my El Amp II which is very close to the Atom in performance. Shockingly, I don't even need to go to high gain to get to extreme volumes. When I max out my volume pot in low gain mode (1.0x), they are already too loud for comfort. I am feeding the amp with the Atom DAC that outputs 2V. That means that it is outputting 2V in 13 Ohms, which should give me peaks of 103 dB SPL at 154mA, correct?
 

Aperiodic

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All my headphones are sensitive. I was going to buy a JDS Labs Objective2 and remove two resistors to turn its 2.5X/6.5X gain into 1X/2.5X. But the company informs me I can buy a 1X/2.5X Atom by asking for those gain settings in my shipping notes. Why on earth don't they mention this option on the Atom page?
As a recent Atom buyer, I'd like to know too, although the 1x/4.4 x (which is apparently the default) works fine for most listening; high gain is needed only when source material is recorded low and/or using my 250Ω Beyers (sometimes).
 

magicscreen

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You can use any tube buffer with it.
Most tube buffers have around 0.95x gain or so.
In the light of the Atom, keep it cheap.
Tube buffers just add a little bit of distortion harmonics .
https://www.amazon.com/FX-Audio-TUBE-01-Preamplifier-Black/dp/B01HEQJGPC
Buying something more expensive won't bring more 'magic' just an emptier wallet.
The linked device is a pre-amp though so it has gain and also more 'tube ... ness' than a true buffer.
You can play with both volpots to get more or less 'effect'.
Thank you very much!
After a long hesitation i have bought the Tube-03.
It is great! It adds more musical, pleasant, clearer and detailed sound to the Atom.
 

Godfix

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[QUOTE = "amirm, post: 116434, membro: 2"] Claro. Antecipando o próximo pedido :), também incluí uma foto do transformador AC:

View attachment 17617[/CITAR]
@@ amirm

Estou usando com um Meridian DAC V1 ... Você indicaria outra opção neste orçamento?
 

wemist01

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Recently moved and was surprised to find that my carefully packed Atom had something loose inside. Somehing substantial...

Look at those teardown videos, because the weights at the corners are applied with adhesive. Fortunately, the screws at the bottom unscrewed very easily using a small flathead and the weights pried loose quite easily. Put a DAC on top and it won't blow away!
 

Budgeter

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Recently, I have a weird problem, not sure if it's from Atom amp or not.

Using it with Senn 58x, I leave Atom amp stay on all the time. Sometimes, there is sound channel bleeding (left audio is also hearable on the right, but a bit smaller on the right and vice versa). It happens randomly, but only (?) after a long time of standby (e.g: leaving it there all the night without audio, the problem is there when I use in the next morning). I couldn't find out a way to reproduce the behavior.

When this happens, it seems like a certain frequency range is muted. I play Dota 2 and CSGO, and many type of audio (e.g: attack sound) in the game is muted or feel like under a water pipe. Unplug/Replug the headphones fix it.

Currently, I'm trying different headphones, amps, 3.5 to 6.5mm jacks, to see if it's reproducible or not.
 
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