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Review and Measurements of New JDS Labs Atom Headphone Amp

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Just received my Atom in the post today.
Connected to a random 25$ DVD player in RCA and driving my Magnat 980 LZR.
It is dead silent, and already loud enough at 1/3 of the total volume in low output mode.

Very recommended in this configuration.

I'll try it with the Topping D10 & some DSD files later, should be even better.
 
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Is it normal that with my Atom and DT990pro 250 ohm I can listen to this video at maximum power at maximum gain? it is heard loudly, but it could hold some more volume.

My DAC has 1.75Vrms, can it be voltage failure?

Enjoy the video ... audio hehe
 

GoMrPickles

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How important is their power adapter when it comes to the audio quality? I own few cheaper brands with similar parameters and they would save me some money... however I don't want to sacrifice amp performance just to save a few bucks.
The included power supply came in its own box and is nearly as big as the Atom itself. I don't think you or anyone would need to replace it. It's a beefy piece, 16 V.
 
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Hmm, not sure if it's a fluke, but just now my Atom stayed active (no relay click, LED still lit) after switching it off. I then twisted the knob past the detent and then back off, then the unit turned off as normal.

I'm not worried about it, but it was a bit strange. Anyone encounter the same thing?
I just had the EXACT same thing happen to me. It only happened once and never again. I emailed their support to see what they think. Has it happened to you since?
 

ripvw

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I hooked up my 8-foot RCAs from the Atom to the RCA inputs on my subwoofer. I'm fortunate to have the Presonus T10 sub which includes unbalanced RCA inputs as well as balanced XLR & TRS. The sub does NOT include unbalanced outputs so I'm running XLR to the Presonus Eris E5 monitors. Running the Atom using low gain - the only recommended setting for preamp out - resulted in great sound with no hum but way too much output - it gets plenty loud at the 9 o'clock position on the pot. I will have to play around with the output settings on the sub and monitors to see if I can reduce the gain, but I was very happy with the sound and extremely happy not to have a ground loop issue due to running both unbalanced and balanced cables. There is a ground lift switch on the sub if needed.

The Atom sounds at least as good as the DX7S driving the sub/monitor combo - too bad no remote. I can also report that the Blue Jeans Cable LC-1 RCAs are the best unbalanced cables I've ever used - great connectors and flexible enough not to move the lightweight Atom when installed.

Bring on the Khadas Tone Board...
 
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Ok, I am truly impressed with JDS customer service. They literally replied 10 minutes after I inquired about the relay glitch. Get this, they actually put this potential quirk in their manual on page 6:

"Amplifier does not turn off
Cause: On rare occasion, mechanical relays can stick
Solution: Tap or knock top of enclosure with moderate force to disengage".

LOL, a company which actually tests their products thoroughly and puts relevant stuff in their manuals.
 

jaco61

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This amp is just wonderful, best one out of all I had here and all of them were much pricier up to 500 euros.
Inspired by this informative forum I ordered one directly from Jds Labs to be sent to EU.
So as there is no need for more power and a balanced output this amp does not leave anything more to be desired. The performance is simply fantastic! Best bass I heard out of my E-MU Teak ever, all is wonderful neutral and precise!
It seems even regardless of the higher price here in Europe that the Atom is one of the most remarkable amps around. A stunning little beast ... in just a poor plastic suit ;)
 
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trl

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@NemoReborn I read on the internet that if you move the knob for couple of minutes it can fix a noisy pot temporary, so I tried it and it got a better but after couple of hours it return to make noise, maybe it really noisy pot. Also topping reply to my email and said that the DC offset is less then 4mV , like I thought as this issue happen with different DACs and even without one connected .
Without input source connected to RCA plugs (ideally with input-RCA plugs in short-circuit signal with ground) is the noise still there? If yes, that it's an internal amplifier issue (either the pot, either an internal DC-current flowing between the pot and the GND).
 
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I had a buzz noise when plugged by jack in my Samsung Galaxy.
The noise stopped when the music started (with Foobar app). Then started again a few seconds after the end of the music.
Not sure what was the problem, I'm going to use it in RCA anyway.
 
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I just had the EXACT same thing happen to me. It only happened once and never again. I emailed their support to see what they think. Has it happened to you since?
I faced exactly the same, only at the beginning of using the amp and only once. Never again since then. Working great. Probably some oxidation on the switch or residue of flux. Like there was no contact until it was scraped.

In my opinion the weakest link of this amp is this very small pot regarding durability (rotate cycles) + integration with switch. In time there can be fast degradation of channel balance if you use it extensively (because of very small diameter). Would be great to have another version with smd high precision resistors ladder to have perfect balance and no degradation fo carbon path (or maybe digital PGA series, electronic resistors ladder). But it would be much more expensive (PGA could affect stunning performance of the amp).

Also in high gain please watch out for the limit of max input RMS voltage 2,1V - this will cause clipping, even on low pot volume according to what John wrote to me, this will be voltage input gain stage clipping, so not because of max power output (power supply limitation) but input section with x4,5 gain. So something like DACs with 2,3V RMS can be waste here when in file peaks go up to 0dBFS.

However in low gain there is no limitation (actually it's about 8,5V RMS).
 
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Y
I faced exactly the same, only at the beginning of using the amp and only once. Never again since then. Working great. Probably some oxidation on the switch or residue of flux. Like there was no contact until it was scraped.
Yep, exact same like you! Hope it not will happen again..
 
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Exact same thing happened to me yesterday! Thought it was lemon, not a problem since.
Paris, France.
Happened to me the first 5s of using it. I was scared, turned it off and on, and it was gone.
Haven't heard it during the 10s of hours I used it since.
 

trl

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"
AMIR
November 16, 2018 at 7:37 pm
Given this is DC coupled – is there any DC offset protection? Or any protection circuits beyond the muting relay to protect headphones from damage?
REPLY
  1. JOHN SEABER
    November 16, 2018 at 10:10 pm
    None present; we have shipped thousands of DC coupled amplifiers in the past similarly.
    You can detect DC offset of any amp by listening for a large pop when changing gain, or severe noise when turning the volume potentiometer. If either happens, it’s a good idea to check your source for offset. We’ll add these suggestions to the Instructions guide. Thanks for your thoughts.
"

I probably missed something inside the 33 pag. of this thread, but what opamps are in front of the LME49600? Are LME49600 as output buffers, right?
And what would be the roll of the opamp nearby the pot.?

I wonder because if JDS did the TI's recommended schematic for LME49600, then it has DC-servo, that means there should not much DC on outputs (probably 1mV or so).

However, in my my tests with rolling opamps in LME49600 amplifiers I realized that LME49720 is one of the few opamp where potentiometer is not becoming "scratchy". Instead, with lot of other opamps, potentiometer gets scratchy (tested with ALPS blue 10 KOhms pot.). So, wondering what opamps are inside JDS Atom, because I really think that swapping the 2 opamps from the gain stage might resolve this issue, especially if the "scratchy" noise happens only in the first 10-20 seconds after power ON.
 

trl

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OK, the the LME49600 is in the loop of the the very low-noise NJM2068, so nwavguy news some shit when he said that this is a cheap low noise opamp. :)

I wonder what would be the opamp from the "shadow" of the potentiometer and what would be its role here.
 
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