• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Fully Portable Amp that measures better than Objective2?

Roen

Senior Member
Joined
Oct 14, 2018
Messages
389
Likes
104
#1
As the title says, anything measure better than the O2 as well as having lower output impedance?
 

mi-fu

Active Member
Patreon Donor
Joined
Jun 7, 2018
Messages
249
Likes
204
Location
New York
#6
Topping NX4 DSD has a Line-in and functions as a pure amp too. Perhaps it should serve your need?
 

Roen

Senior Member
Joined
Oct 14, 2018
Messages
389
Likes
104
#7
Topping NX4 DSD has a Line-in and functions as a pure amp too. Perhaps it should serve your need?
Perhaps?

But 16 (2.2^2/300) mW at clipping vs. 110 mW at clipping for the O2 @ 300 ohms doesn't seem too convincing. Distortion is also slightly higher at the 16 mW level.
 
Joined
Oct 12, 2018
Messages
74
Likes
26
#8
Roen, your calculations are based on a poorly labeled graph. I scratched my head too when I saw it. Hey, it happens. Note that it should be 4.2V @300 ohm and 2.2V at 30 ohm. Don't have calculator handy but clean power is about 59 mW. I noticed this a couple of days ago, and mentioned it to Amir.
 
Joined
Oct 12, 2018
Messages
74
Likes
26
#9
I didn't want to mention it yet, but as an amp only, the Topping NX3s might fit the bill. It is very similar to NX4 DSD minus the DAC. Otherwise the amp section should measure slightly better than NX4. It is in Amir's queue to test. So, compared to O2, Lithium battery with several times longer runtime, proper relay output protection and no thump. I am told that output impedance is 5 ohm (bummer), which means >40 ohm headphones. O2 uses Nimh with slighly higher voltage so it has more output power (slightly), but don't expect O2 to achieve 120mW at 300 ohms on battery power anyway. Did I mention $50 on Massdrop, $59 on alibaba.

Around 50mW clean power is about the best you can expect from a portable amp.
 
Joined
Oct 12, 2018
Messages
74
Likes
26
#10
Ammend to say ......about the best from a portable amp that doesn't cost $300.

Roen, you should listen to me - I joined two days before you!
 

Roen

Senior Member
Joined
Oct 14, 2018
Messages
389
Likes
104
#11
Roen, your calculations are based on a poorly labeled graph. I scratched my head too when I saw it. Hey, it happens. Note that it should be 4.2V @300 ohm and 2.2V at 30 ohm. Don't have calculator handy but clean power is about 59 mW. I noticed this a couple of days ago, and mentioned it to Amir.
https://www.audiosciencereview.com/...th-and-jds-o2-headphone-amps.3928/post-126360

Based on this, you still get 2.6-ish V at 300 ohm on O2 battery, so still a bit stronger.
 
Joined
Oct 12, 2018
Messages
21
Likes
16
#13
I have an NX4 and it plays my DT880 600ohms plenty loud below max volume, high gain mode. Obviously your loudness preference and use cases will vary, but I think it's definitely worth considering for high impedance cans on the go.

I bought mine from an authorized seller on ebay for around $118 (seller sale + ebay coupon) so if you time it right, you can get a good deal. With the holidays upon us I wouldn't be surprised if you can manage to grab it at that price again.
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
16,205
Likes
11,457
Location
Seattle Area
#14
Sure, if we could get @amirm to review / measure an NX3, that'd be nice too.
As noted, loaner unit is here. It is just that I have a massive pile of gear to review....
 
Joined
Mar 13, 2018
Messages
71
Likes
23
#15
The fiio a5 might fit the bill. It has similar specs and a slightly lower impedance than the O2. I haven't seen anyone measure it though
 
Joined
Oct 12, 2018
Messages
74
Likes
26
#16
https://www.audiosciencereview.com/...th-and-jds-o2-headphone-amps.3928/post-126360

Based on this, you still get 2.6-ish V at 300 ohm on O2 battery, so still a bit stronger.
No, no. I see distortion knee at around 4.8V with O2 on the graph. Now look at NX3s: starts rising around 4.2V but still clean at 5V. Roughly comparable. I'm speaking of 300 ohm.

Nx3s graph:

https://ae01.alicdn.com/kf/HTB1ieLnXLfsK1RjSszbq6AqBXXaA.jpg

Don't know where you read 2.6 VRMS. The trace that dips the lowest is always the 300 ohm.
 
Joined
Oct 12, 2018
Messages
74
Likes
26
#17
A lot of guys are trying to help you out. Is this for a phone as source? Otherwise, a DAC/Amp like the NX4 would be a better proposition.
 

Roen

Senior Member
Joined
Oct 14, 2018
Messages
389
Likes
104
#19
No, no. I see distortion knee at around 4.8V with O2 on the graph. Now look at NX3s: starts rising around 4.2V but still clean at 5V. Roughly comparable. I'm speaking of 300 ohm.

Nx3s graph:

https://ae01.alicdn.com/kf/HTB1ieLnXLfsK1RjSszbq6AqBXXaA.jpg

Don't know where you read 2.6 VRMS. The trace that dips the lowest is always the 300 ohm.
Ah, I was reading the highest trace. Not much experience in reading traces.

Looks like clipping on the NX3s occurs before 4V on the graph you linked? I'm looking at the blue dotted line.

Only thing I don't like about the NX3s is that it won't be good for my sensitive IEMs.
 
Last edited:
Joined
Oct 12, 2018
Messages
74
Likes
26
#20
Yes, I think you're right about the iem's. Not because of sensitivity but because of their impedance. Re Nx3s, starts rising around 4V, graph show 0.0005% at 5V, which is still very good, if the graph is to believed. More to the point, why a portable amp if you are going to plug into D50? Desktop would be a whole other conversation. Amir says JDS Atom almost looks like it is a brother to the D50, and that is, without question, the desktop pairing to get.
 
Top Bottom