Review and Measurements of New JDS Labs Atom Headphone Amp

[soundwave76]

^ looks great! Can you share a link to this?

 

[solderdude]

I received my Atom amp two weeks ago. I measured the cups with a db meter and pink noise yesterday.
There is no channel imbalance on my unit.
This is maybe not as good then measuring with a voltmeter, but i cant hear a channel imbalance either.
For what its worth.

(Just a guy from The Netherlands, not an JDS employee )

Channel imbalance is potmeter position dependent and won't be there in any case between 9 o'clock and fully turned right position.
So you won't hear any imbalance unless the volume is set really low, then it will/might be the case.
How MUCH channel imbalance is present below 9 o'clock and fully counter clockwise is very unit dependent.
So you can measure 10 similar amps and get 10 different 'potmeter linearity plots'.
To be more precise, it is volume potmeter component dependent.
There is a considerable difference between individual potmeters.
So much so that Jeremy (garage 1217) has to bin about 30% of all potmeters he buys for his amps as they vary too much in value in the lower part of the adjustment range. He built a simple test device to check for this.
It has to do with manufacturing tolerances of this relatively small mechanical part.
I am guessing JDS labs does not do this and they just pop in what they receive.
A lottery if you will.

(Also just a guy from The Netherlands, not an JDS employee either )

 

[MRC01]

...
To be more precise, it is volume potmeter component dependent.
There is a considerable difference between individual potmeters.
So much so that Jeremy (garage 1217) has to bin about 30% of all potmeters he buys for his amps as they vary too much in value in the lower part of the adjustment range. He built a simple test device to check for this.
It has to do with manufacturing tolerances of this relatively small mechanical part.
...

That's one of the benefits of hand-matching parts, or using higher grade components, why some of the Alps pots are so expensive. Better yet, go to the ultimate volume knob, a stepped attenuator, giving perfect channel balance and lower noise at every position.
However, nobody should expect that in a $100 amp. The Atom's volume pot is not bad, especially for the price. It has a poor/cheap feel to it, not liquid smooth, but it is well balanced from 8:00 all the way to max. I've seen analog volume knobs on $1000 amps that were worse.

 

[jseaber]

The look the same as my measurements. The line shows deviation from 0 dB (ideal). Volume is at max and then reduced step by step. I don't know how the steps represent actual volume control position.

@Irrelephant - Thanks for sharing my measurements! To clarify the x-axis, these are time based intervals; readings were taken every 0.5 seconds as I physically turned the knob from 100% to 0% on each amp. The y-axis values were observed in dBFS for a 1VRMS test signal, and imbalance was calculated by subtracting the Left and Right channel readings.

Atom Amp uses a ubiquitous Alps RK097 potentiometer with 15A taper. This is the same brand, series, and taper used by Objective2, and the same in our Element line (obviously in the vertical orientation). Pot imbalance has been addressed in our FAQ for a decade.

I look forward to hearing your followup.

That's one of the benefits of hand-matching parts, or using higher grade components, why some of the Alps pots are so expensive. Better yet, go to the ultimate volume knob, a stepped attenuator, giving perfect channel balance and lower noise at every position.
However, nobody should expect that in a $100 amp. The Atom's volume pot is not bad, especially for the price. It has a poor/cheap feel to it, not liquid smooth, but it is well balanced from 8:00 all the way to max. I've seen analog volume knobs on $1000 amps that were worse.

Well put. Hand matching is glorious where it can be afforded.

I've been listening to a random prototype at home with perfect encoder attenuation. I'm still not sure we'll bring it to market, as it will be put to shame by anything we build with an analog pot (in terms of Noise). It's frustrating that we can either have fantastic THD+N, or perfect channel balance, but not both in small designs. Stepped attenuators are fine, with their own tradeoffs--size, cost, and limited steps.

Feel free to ask any questions!

 

[Phenylalanine]

^ looks great! Can you share a link to this?

Sure thing:

https://www.ebay.com/itm/20x22mm-Bl...itar-AMP-Effect-Radio-Recorderx1/321748430377

 

[mi-fu]

I had to fashion a very short extension for the potentiometer though.

Would you elaborate on how you did it? I'd like to "upgrade" the knob too

 

[Phenylalanine]

Would you elaborate on how you did it? I'd like to "upgrade" the knob too

I just used a small wooden dowel pin that matches the knob hole diameter and carved the end to match the notch on the potentiometer shaft, but I'm going to have to find something permanent so this is just temporary. It's just jammed in there now with the set screw holding it securely enough to be usable at least.

You could just grind down the bottom of the knob a couple mm and I think you wouldn't need an extension. I bought two knobs just in case I wanted to do that.

 

[maxxevv]

@jseaber

The Atom's AC supply states 16V AC, 16VA, 1000mA.

However, when I put a voltmeter to measure it, it reads 18V AC, 0.6A. which would translate to 10.8VA. So which is which ?

I'm trying to source parts to build a separate power supply replacement for it as the bulbous adapter poses some space issues in my home setup, in case you are wondering.

 

[solderdude]

How did you determine the output voltage ? loaded with the Atom connected ? Under maximum output power or idle ? without any load ?
How did you determine the current ? Did you just connect an AC current meter to the transformer (and basically measure the short circuit current) ? Did you measure the current in series with the Atom switched on ? Was the Atom under max load or idle ?

You are measuring the unloaded (or actual load) output of a mains transformer which is higher without a load or a load below 1A.
With a 1000mA load the measured voltage should be around 16V.
This also depends on the actual mains voltage as well. It is just a simple transformer.

You just need to buy a 16V AC transfomer rated between 16VA to 30VA or so but can also get away with 15VAC 30VA most likely.
Add an enclosure and maybe some fuses and/or filtering while you are at it.

 

[maxxevv]

Thanks for the insight Hans. It was measured unloaded.

The main reason I put up the question was because I couldn't find a 16V AC transformer. Hence, took the multimeter to measure the AC output which totally threw me off .

With regards to fulfilling the 16VA, regardless of voltage, the closest I could find is a Block VC 16/2/18 transformer that comes as 18V AC, 16VA. Would this make sense?

https://uk.rs-online.com/web/p/pcb-transformers/3472717/

Yes, I intend to add a switch with a fuse and mains filter while doing that. Those come quite conveniently in an OTS package though!
No, I won't be putting it together, will be getting a certified electrical engineer friend of mine to do that for me.

Maybe I should ask him with regards to this before I get too far ahead of myself.

 

[solderdude]

You could also look for 15VAC 30VA or something. (Toroids have less stray magnetic fields but higher leakage currents)
something like this (windings in parallel... make sure they are connected in parallel correctly)
or this (with windings in series) which is 18V 15VA

The best transformers are R-cores but are a bit more expensive. These have very low mains leakage.
This particular one will provide you with 15V (use 2 windings in parallel) or 18V (2 other windings in series)

When loaded with the Atom there will probably be around 16VAC on it.
The object of the game is to have enough DC voltage to drop over the regulators.
The regulators output voltage is 15VDC so you need 18VDC minimum on the regulator input and assuming ripple will be 1V or so, 19V DC or higher is perfect.

15V AC will give you about 20 VDC but in reality will probably be around 22 VDC in idle.
16V AC will give you about 21.5 VDC but in reality will probably be around 23 VDC in idle.
18V AC will give you about 24 VDC but in reality will probably be around 27 VDC in idle.

All of these options will work.
The higher the unregulated DC voltage is the warmer/hotter the regulators will become.
There won't be a difference in performance nor sound.

 

[maxxevv]

Thanks Hans, much appreciate the very detailed reply.

 

[daftcombo]

Hi,
The JDS Lab Atom is very powerful. On rock music, with 32 ohms headphones, I barely go furthur than 10 o'clock.
It is even a bit difficult to set the volume as wanted.

 

[MrC]

I have missed the last 20 pages or so of the thread but I am wondering about the Atom not turning off that was mentioned towards the early part of the thread. Is that still a case with anyone?

It happened to me once after a couple of days of owning the amp but didn't happen again until today. Now it doesn't turn off at all, the knob click to off position but the relay doesn't turn off. If I remove power it obviously powers down but powers on as soon as power is reinstated.

I am just wondering if anyone has a fix?

(I am in EU and the amp was delivered to me by a colleague, so I can't send it in to JDS).

 

[PorchSong]

I have missed the last 20 pages or so of the thread but I am wondering about the Atom not turning off that was mentioned towards the early part of the thread. Is that still a case with anyone?

It happened to me once after a couple of days of owning the amp but didn't happen again until today. Now it doesn't turn off at all, the knob click to off position but the relay doesn't turn off. If I remove power it obviously powers down but powers on as soon as power is reinstated.

I am just wondering if anyone has a fix?

(I am in EU and the amp was delivered to me by a colleague, so I can't send it in to JDS).

Give it a whack. . . .seriously. The relay is sticky. JDS suggested this. If it continues to stick, then contact JDS.

 

[MrC]

Thank @PorchSong but that hasn't solved the issue.

I have sent an email to JDS to see if there is a fix that I can apply without sending the amp to them as it is not worth the shipping costs to the US and back, it would be cheaper to get a new one.

 

[MrC]

Just to update, JDS answered very quickly especially for a Sunday and recommended I give it another slap. This slap worked so the amp is happy again.

 

[landco]

JDS Atom vs o2

Why is the jds atom amp cheaper than the o2 when everyone says that the o2 is obsolete and that the atom is better in every way?

What is better in quality? NwAvGuy described in detail all the steps that led him to the development of O2, so I personally have more confidence in him than jdslabs

If jdslabs had the same detailed development blog, there would be more trust.

 

[PorchSong]

JDS Atom vs o2

Why is the jds atom amp cheaper than the o2 when everyone says that the o2 is obsolete and that the atom is better in every way?

What is better in quality? NwAvGuy described in detail all the steps that led him to the development of O2, so I personally have more confidence in him than jdslabs

If jdslabs had the same detailed development blog, there would be more trust.

Because the price of something does not determine its performance. The Atom is built with plastic housing, etc., thus it is less expensive than the O2. But, it outperforms the O2 on objective measurement tests. In fact, it outperforms amps 3-4x more expensive. So, are you suggesting that JDS charge more for the Atom than the O2 as to justify its performance level?

 

[landco]

Because the price of something does not determine its performance. The Atom is built with plastic housing, etc., thus it is less expensive than the O2. But, it outperforms the O2 on objective measurement tests. In fact, it outperforms amps 3-4x more expensive. So, are you suggesting that JDS charge more for the Atom than the O2 as to justify its performance level?

Mr. PorchSong, you did not pay attention to the second part of my question