O2/ODAC Rev. B - JDS Labs Atom - Topping D10s

[HeadphoneXHunter]

Hi guys,

first of all I would like to thank the community a lot for the informative discussions that are going on on the Forum as well as the measurments of various amplifiers and DACs that I was comparing the last few days and found very helpful as well as interesting.

Now to my question. I am using the O2/ODAC Rev. B since 2017 but just recently, when checking my DT 1990 Pros and HD 58xs, I noticed a bit of a hissing sound (exclusivley on the right driver) when using the volume knob between 13 and 15 o´ clock (DT 1990) and between 12 and 14 o´ clock (HD 58X) while playing a test tone 20 Hz - ~100 Hz as well as some songs with longer bass heavy sections (beginng of "bad guy" for example). I was not able to try it at higher SPL, because it would have been unbearably loud. Since it only occurs when using the volume knob and even then is not audible while a song is playing, it was not really bothering me. However, I am curious wether there is a problem with the O2/ODAC or if there is anything wrong with those two headphones. Maybe it is just me, but apart from the reviews on the JDS Labs O2 and the (older?) ODAC I could not find informations about this, which is why I would be very grateful for your opinions.

Last but not least, if, by any chance, it has something to do with the DAC/AMP and not the headphones, would I be able to solve this issue with a switch to the Atom and the D10s or are there similar complaints regarding the Atom? I read both reviews and watched the measurments and was quite impressed. And if I may ask one further question, since the O2 and ODAC are outdated by todays standards, but otherwise still perform as good as years ago, are there any audible differences to the Atom and D10s (or D10/E30 because I know the D10s was just released)? I tried to understand the measurments as much as I can, but some like the SINAD or THD (which I read are "just" numbers that are good to compare overall but do not seem to be the most important thing for the performance, maybe compared to the frequency response?) I do not fully understand, thus cannot use them reasonably when trying to find the best e.g. single ended DACs or AMPs.

Thanks in advance and have a great day!

 

[Bob-23]

a hissing sound

Hallo, Grüße nach Freiburg!
I built the O2 a few times, and as far as I remember, I once had a problem with noise obviously coming from the vol pot (the typical case for hissing vol pots is when there's dc on the pot but that should't be the case with the O2, and the symptoms would probably be a bit different): I resolved the problem by 'cleaning' the pot, and as the pots are closed, by turning volume up an down quickly (amp switched off!), say, 50 or a 100 times, in order to clear away potential abrasion inside the pot. For me it worked. Simply try it out, maybe it helps.

since the O2 and ODAC are outdated by todays standards, but otherwise still perform as good as years ago, are there any audible differences to the Atom and D10s

There's is no doubt that there are amps and dacs out there which measure better - the question is always if this translates into audible differences. The 'progress' that has been made is fascinating - but I guess the point of no audible return has long been surmounted. To me, O2's standard is absolutely sufficient, I get a clean sound, no noise no distortion ( gain 1x & gain 2.5x, listening mainly with HD600 and K702.)
Good luck!

 

[HeadphoneXHunter]

Grüße auch zurück in die Hauptstadt!
Maybe I should give it a try. Eventhough I am not very confident in my crafting skills. So I guess if it doesn´t work out well, I´m just going to give the O2 to my brother and try the above mentioned Atom/D10s-Combo. Since both units are quite cheap, there won´t be any regrets. Eventhough I´m really not into plastic cases that much...

If it were not for the thing I have noticed, I also just would stick with the O2. @Bob-23 since I´ve used the O2 with the Standard 2,5x/6,5x Gain settings, while actually only using 2,5x, did you ever notice a difference between 1x and 2,5x in terms of noise or distortion? Probably not I guess?

 

[Bob-23]

did you ever notice a difference between 1x and 2,5x in terms of noise or distortion?

No, I couldn't hear a difference, but, if possible, lowest gain is usually preferable with most op amps (not with all). Afair, I once heard that you may get distortions at gain 6,5x with the O2. At gain 1x the amp works as an impedance changer.
With regard to 'the progress' that you mentioned, one remark: In terms of repairability we, unfortunately, have to talk about 'regression'. One of the big advantages of an amp like the O2, being hand-soldered with through-hole components: it's easily repairable, and the opamps are socketed, they can easily be swapped. That expands longevity drastically. Today's stuff is so often throw-away-stuff. And too many people got used to it. Decades ago, people expected much longer longevity of their electronic products, and many of the products were crafted well so that they really lasted longer. - And we'll see what life-expectancy, at all, these new well-measuring units have.

 

[3125b]

Grüße aus dem Norden.
Just working the pot shouldn‘t be a problem, if that doesn‘t work it should be replaceable reasonably easily as well.
A few thoughts on a potential replacement amp:
The Atom becomes a lot more expensive if you import it (about 150€), so unless you‘re on vacation in the US, I don‘t think it‘s really worth it. Therefore, the Topping L30 would be my choice. Not only does it have a better case, but also (in my book) better features and of course even more power. Repairability might not be good with that one though.

 

[HeadphoneXHunter]

Grüß Gott
I didn´t even notice the L30...sadly. From the 2 Vrms vs almost 5 Vrms, the L30 should have more than double the power of the atom to be specific whilest still having less distortion, correct? And that power is available undependend of the impedance of the headphone used (300 Ohm, 600 Ohm etc.)? I guess I am going to cancel the order of the Atom than, which hopefully should not be a problem. Not that I would need such amounts of power, but at the same price...a metal case that also measures a bit better...that should be it with AMPs/DACs since balanced is not needed.

Edit:

I indeed calculated 150 € for the Atom with Taxes and shipping included...

 

[3125b]

Amir will measure the L30 shortly I'm sure, it's just releasing this week.
Wolfs measurements look very promising, and JohnYang (the designer) has confirmed that the pot issues are fixed, wich seemed to be the only problem with the L30 pre-production model.
I'm not saying that power is an issue, the Atom has a maximum of 8.7Vrms and with it's proper power supply isn't limited like USB powered options when it comes to supplying current to low impedance loads, in short: more than enough power for all common headphones. It has useful gain settings (1x and 4.5x) with proper 2Vrms input signal and a decent pot.
The case doesn't look or feel great obviously, the E30 (similar to L30) has an aluminium case with a glass front, wich looks and feels better, that's just the way it is.
As far as size is concerned, maybe this will help:

Thats my E30 (same size and design language as L30) atop my Atom amp. They are the same depth.
As you can see I have the volume of the DAC attenuated by 6dB (the D10s doesn't have volume control though) and run the Atom usually about 1/3 to half volume in low gain with my AKG K702, less with my other phones. The HD 600 will need even less voltage for the same volume, it has a much higher impedance but also higher sensitivity than the K702. The 600 Ohm Beyer models will need a little more power though, low gain should still be fine (<2Vrms for normal listening levels).
Power is really not an issue, it's just that the L30 is theoretically even more powerful. In practice, it might not even be, because the high gain setting is only +9.5dB (3x if I'm not mistaken), with a typical 2Vrms input that only gives you 6Vrms output. Anyway, doesn't matter.

Where was I going with this ...
Features, yes.
My biggest pet-peeve with the Atom is the fact, that there is no switch to change between preamp and headphone mode, instead the headphone has to be unplugged. The L30 has a switch. Might not be an issue to you, but it bugs me.
The other thing is, that the Atom has no <1X gain setting, wich means, that with very sensitive headphones, a 2Vrms input signal gets you in the lowest 10% or so of the adjustment range of the pot, where the channel imbalance is prohibitively high (that is normal with analog volume control due to manufacturing tolerances of the pot and varies from one unit to the next, almost all cheaper headphone amps will have that to an extent). So if you ask me, with the Atom a DAC with volume control is almost a necessity. The L30 has a *9.9dB gain setting wich alleviates that particular issue - wich, again, might not concern you at all, depending on the use case.
Of course there is the fact that with a European seller, warranty claims are a lot simpler and cheaper to deal with. Shipping back to the US is probably not worth it. That may not be an issue depending on how JDS handles those international claims, I simply don't know since my Atom has been going strong so far (and probably will for a long time, seems to be a very solidly built amp with aluminium-polymer caps and an Alps pot there isn't much to go wrong).

What I'm saying is, that the Atom is a solid performer and I'm mostly happy with mine. However, I paid 100€ for mine (a friend brought it back with him from a trip to the US) at a time, when there was no comparable domestic option.
If I was buying one now, I personally would go with the L30.
That is not saying that the Atom (or Schiit Magni Heresy) is a bad choice though.

Those are my thoughts on the whole situation, hope it helps.

EDIT: That being said, if you can get your O2 working again, that is probably the best option of them all, a pot should cost 3€ or so. Don't expect to hear any real differences with common headphones, the O2 is not too bad.

 

[HeadphoneXHunter]

It does help. So thanks a lot!