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Review and Measurements of New JDS Labs Atom Headphone Amp

ehabheikal

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It is going through the amp and volume control.
I am not that into audio stuff, so forgive me if the question is basic,
If i use this as a preamp for a 2v source will it have the power to take it up to 4v or so? or is the volume on the preamp part only down from 2v like passive preamps?
I am mainly interested in a simple high quality pre
 

NTK

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I am not that into audio stuff, so forgive me if the question is basic,
If i use this as a preamp for a 2v source will it have the power to take it up to 4v or so? or is the volume on the preamp part only down from 2v like passive preamps?
I am mainly interested in a simple high quality pre
The Atom amp has a high gain mode that provides a voltage gain of 4.5X. The maximum output voltage is 8.7 Vrms (into loads >150 ohm). Therefore, with the high gain mode, the input limit is 1.9 Vrms max (at which will give the max output of 8.7 Vrms).
https://jdslabs.com/product/atom-amp/#specifications
 

ehabheikal

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The Atom amp has a high gain mode that provides a voltage gain of 4.5X. The maximum output voltage is 8.7 Vrms (into loads >150 ohm). Therefore, with the high gain mode, the input limit is 1.9 Vrms max (at which will give the max output of 8.7 Vrms).
https://jdslabs.com/product/atom-amp/#specifications
And that works on both RCA out as well as the headphone out?
 

magicscreen

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I have managed to burn in my Atom amplifier! :cool:
I put it between the Loxjie P20 and MCTH like a sandwich.
The P20 and MCTH became very-very hot (it is hot summer now) and so the Atom as well.
 

raistlin65

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Question for somebody that knows how to do the math: what would the headphone amp power output be on the Atom with the Apple USB-C dongle used as a DAC given its 1V output?

The reason I ask is people are always asking about the ifi Zen DAC over on Reddit, and we know how it measures

https://www.audiosciencereview.com/...ds/ifi-zen-dac-and-headphone-amp-review.9885/

I've been wondering if the Atom/Apple dongle is the best option in this price range?
 

MRC01

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I think you probably care more about voltage sensitivity than power, but you can compute one from the other, for a headphone of given impedance.

Amir's review showed the Atom delivering 0.25 W into 300 ohms at high gain (no clipping). That's 29 mA of current and 8.6 V. If he used a 2V input for the test, the max gain ratio was 2:8.6 which is 20*log(8.6/2) = +12.6 dB.

If the input voltage were only 1V, that's cut in half, which means the output voltage would be cut in half, which is 4.3 V. This is enough voltage to drive Sennheiser HD600 beyond hearing-damaging levels (115 dB SPL).

Simlar calculations suggest that with a 30 ohm load, the max Atom voltage output is 6 V. That is, the Atom is current limited. Half of this is 3 V which still drives an HD600 to about 112 dB.

In short, it looks like the Atom has enough gain to drive low voltage sensitivity headphones to ear-splitting levels, even if the input is limited to 1.0 V.

Half the voltage is 1/4 the power (into the same load). So for an input limited to 1.0 V, take Amir's power measurements and divide them by 4. That would be 250/4 = 63 mW into 300 ohm and 1100/4 = 275 mW into 33 ohm.

PS: I just noticed that my calculations, which I backed into from Amir's measurements, are almost the same as the figures @NTK posted above from the Atom specs published by JDS.
 
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raistlin65

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I think you probably care more about voltage sensitivity than power, but you can compute one from the other, for a headphone of given impedance.

Amir's review showed the Atom delivering 0.25 W into 300 ohms at high gain (no clipping). That's 29 mA of current and 8.6 V. If he used a 2V input for the test, the max gain ratio was 2:8.6 which is 20*log(8.6/2) = +12.6 dB.

If the input voltage were only 1V, that's cut in half, which means the output voltage would be cut in half, which is 4.3 V. This is enough voltage to drive Sennheiser HD600 beyond hearing-damaging levels (115 dB SPL).

Simlar calculations suggest that with a 30 ohm load, the max Atom voltage output is 6 V. That is, the Atom is current limited. Half of this is 3 V which still drives an HD600 to about 112 dB.

In short, it looks like the Atom has enough gain to drive low voltage sensitivity headphones to ear-splitting levels, even if the input is limited to 1.0 V.

Half the voltage is 1/4 the power (into the same load). So for an input limited to 1.0 V, take Amir's power measurements and divide them by 4. That would be 250/4 = 63 mW into 300 ohm and 1100/4 = 275 mW into 33 ohm.

PS: I just noticed that my calculations, which I backed into from Amir's measurements, are almost the same as the figures @NTK posted above from the Atom specs published by JDS.
Thanks! That's very helpful. So So it is a better alternative to the ifi Zen for single ended use for less money.
 

Harmonie

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@MRC01

So helpful that a dedicated thread, or better, a table or some Excel direct input formula would be beneficiary for the most uneducated (like me) and appreciate dearly

Merci :cool:
 

solderdude

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Half the voltage is 1/4 the power (into the same load). So for an input limited to 1.0 V, take Amir's power measurements and divide them by 4. That would be 250/4 = 63 mW into 300 ohm and 1100/4 = 275 mW into 33 ohm.
It's not quite true for low impedance headphones as the current limiting isn't reached at 1V input voltage but it is an easy rule of thumb ;)
Current is limited to 177mA given the max power rating at 32 Ohm.

At 1V input the output voltage with 4.1x gain will be 4.1V.
At 1V in on 32 Ohm 4.1V is reached as the current is only 130mA so isn't limited yet while it is using 2V in.
So for 32 Ohm output power will be 0.53W
 

raistlin65

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Thanks guys. So the next time somebody asks for a recommendation for an amp/DAC for well under $200, I will share these numbers for the Atom/Apple combo

530mw at 32 ohm
63mw at 300 ohm
 
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when using the headphone amp, does this unit disable the line out section?? and also is the line out act as a preamp where the volume can also be controlled from the dial??
 
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when using the headphone amp, does this unit disable the line out section?
Yes
and also is the line out act as a preamp where the volume can also be controlled from the dial?
I think so, but I can't say for sure ( I'm using a different amp now)
But that's from JDS site :

"PREAMP OUTPUTS
Unplug your headphones and Atom Amp's knob adjusts volume of its RCA preamp outputs, so that you can control volume of your powered speakers"
 

Gradius

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You can also do a simple mod and install a switcher (yeah, it could be a bit better designed).

This way you don't need to plug and unplug all the $%#$!* time.
 

Berwhale

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You can also do a simple mod and install a switcher (yeah, it could be a bit better designed).
I thought about doing this. Are you aware of any pictures or instructions from someone who's done it?
 
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