• 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.

How to Evaluate Amp in DAC/Headphone Amp Review?

JEntwistle

Member
Forum Donor
Joined
Oct 25, 2019
Messages
58
Likes
64
#1
Sorry if this is an obvious question, but I can't seem to figure it out: In Amir's testing of DAC/Heaphone combo units, is there a way to compare the SNR of the headphone amp of those types of devices? For example, this chart appeared in a recent review of the Dx7 Pro:

1581869563237.png


The RME ADI-2 is there, along with the Topping DX7; but the rest are all headphone amps with no DAC. I recall reading a comment from Amir that he does not like to mix DAC/headphone amps devices with pure headphone amps in charts. But how would one go about comparing the amp portion of the Benchmark DAC3 vs. the RME ADI-2, for example (we have charts of the DAC comparisons for those units)?

As I ask this I am not even sure if I am misunderstanding something here...
 

majingotan

Addicted to Fun and Learning
Forum Donor
Joined
Feb 13, 2018
Messages
869
Likes
799
Location
Laguna, Philippines
#2
Use the headphone jack (4-pin XLR or 6.3mm TRS) and perform measurements from there
 

pozz

Data Ordinator
Forum Donor
Editor
Joined
May 21, 2019
Messages
2,639
Likes
3,814
#4
So that chart there shows you the SNR when the output of the headphone amp, regardless if it's attached to a DAC or not, is set to a very low level of 50 mV. This simulates the low-level signals which feed IEMs.

I'm not sure if that's was the answer you wanted.
 
OP
J

JEntwistle

Member
Forum Donor
Joined
Oct 25, 2019
Messages
58
Likes
64
Thread Starter #5
So that chart there shows you the SNR when the output of the headphone amp, regardless if it's attached to a DAC or not, is set to a very low level of 50 mV. This simulates the low-level signals which feed IEMs.

I'm not sure if that's was the answer you wanted.
This is headphone amp devices, with only a couple DAC/amps shown (RME and Topping). There are many more DAC/amps that have been tested that don't appear on this or a similar chart. For example, the Benchmark DAC 3 is not here, but the non-DAC HPA4 is.

Also, I am not interested in IEMs. Would the 50 mV represent similar performance to over the ear headphones?
 

pozz

Data Ordinator
Forum Donor
Editor
Joined
May 21, 2019
Messages
2,639
Likes
3,814
#6
This is headphone amp devices, with only a couple DAC/amps shown (RME and Topping). There are many more DAC/amps that have been tested that don't appear on this or a similar chart. For example, the Benchmark DAC 3 is not here, but the non-DAC HPA4 is.

Also, I am not interested in IEMs. Would the 50 mV represent similar performance to over the ear headphones?
The 50 mV measurement isn't always made. It's not really necessary unless the amp is especially well-made, so it becomes interesting to look at its noise contribution to low-level signals, or if its a portable design or something meant specifically for IEMs.

My question is what would you really want to compare? Signal-to-noise ratio specifically? It's not really important past about CD quality or so (96dB). For headphones amps you want high power, low output impedance, good linearity and channel balance.

For example, I have a $100 JDS Labs Atom that I use casually at work. It's likely that I will never buy another headphone amp again unless this one breaks. It'll feed current-hungry headphones as well as it does high impedance ones or IEMs.
 
OP
J

JEntwistle

Member
Forum Donor
Joined
Oct 25, 2019
Messages
58
Likes
64
Thread Starter #7
Yes, I'm looking at signal-to-noise. My question is basically how much you might be giving up in performance by getting an integrated DAC/headphone amp vs. separate components (putting aside realistic audibility considerations); e.g.: Topping DX7 Pro vs. a separate DAC + JDS Atom.

In measuring DACs, Amir produces this master comparative chart:
Best Audio DACs Reviewed and Measured.png

This chart includes pure DACs with no headphone amplifier, such as the Matrix X-Sabre Pro, as well as DAC/headphone amps such as the RME-ADI. So for an integrated DAC/headphone amp, is it correct to assume this is measuring the DAC output only?

Then for pure headphone amps, he produces the chart in my original post above.

So what about the SINAD at the headphone output of an integrated unit? In my original example, if I wanted to compare an REM-ADI to a Benchmark DAC3, the master chart shows the relative performance of their DAC outputs, but I don't think there is a chart showing relative performance at the amp output (which I think would be measuring both the DAC and the amp).

I'm not sure if I am missing something or if the data is just not there.
 

pozz

Data Ordinator
Forum Donor
Editor
Joined
May 21, 2019
Messages
2,639
Likes
3,814
#8
Oh, I see you what you mean.

My best answer is to wait a few weeks. @Koeitje and I are putting together an interactive chart of measurements. You'd be able to do those kinds of comparisons on the fly then.

The issue is that there isn't always a separate dashboard or SNR measurement of the headphone section. Sometimes the main DAC dashboard will be same as it would be for the headphone stage if that's what the unit is meant for, as in USB In to 3.5mm Out, sometimes not. Disambiguating these measurements is not always easy with static comparisons.

The answer I'd give you just from having looked at so many of these over and over again is that integrated units are not yet up to what separates can give you, but aren't far off.
 
OP
J

JEntwistle

Member
Forum Donor
Joined
Oct 25, 2019
Messages
58
Likes
64
Thread Starter #9
Oh, I see you what you mean.

My best answer is to wait a few weeks. @Koeitje and I are putting together an interactive chart of measurements. You'd be able to do those kinds of comparisons on the fly then.

The issue is that there isn't always a separate dashboard or SNR measurement of the headphone section. Sometimes the main DAC dashboard will be same as it would be for the headphone stage if that's what the unit is meant for, as in USB In to 3.5mm Out, sometimes not. Disambiguating these measurements is not always easy with static comparisons.

The answer I'd give you just from having looked at so many of these over and over again is that integrated units are not yet up to what separates can give you, but aren't far off.
OK, I will wait to see the interactive measurements. What you have created so far is great, BTW.

My other question is whether the lack of separate dashboard or SNR measurement of the headphone section is a technical issue, or just data that was not a focus of measurement at the time.

Thanks!
 

Koeitje

Addicted to Fun and Learning
Joined
Oct 10, 2019
Messages
818
Likes
919
#10
We will start with the DAC performance and gather feedback on the visualisation. Which we can then easily copy and use for other charts.
 

pozz

Data Ordinator
Forum Donor
Editor
Joined
May 21, 2019
Messages
2,639
Likes
3,814
#11
OK, I will wait to see the interactive measurements. What you have created so far is great, BTW.

My other question is whether the lack of separate dashboard or SNR measurement of the headphone section is a technical issue, or just data that was not a focus of measurement at the time.

Thanks!
I think it's more or less standard to include those now. There's a lot more membership and active attention than there was when I joined, which was only back in May, and way more than back when Amir started posting these reviews in 2016, and the testing procedure has changed a lot from the discussions. So if you see holes in the data it's either because it wasn't the norm to capture it, or because it's not that important relative to the unit's performance. A mediocre unit isn't worth characterizing completely, for example.

I'm fine with that personally since the goal is not to capture every single metric but to evaluate performance in general, which is a more useful, if somewhat messier, way of doing things.
 
OP
J

JEntwistle

Member
Forum Donor
Joined
Oct 25, 2019
Messages
58
Likes
64
Thread Starter #12
I think it's more or less standard to include those now. There's a lot more membership and active attention than there was when I joined, which was only back in May, and way more than back when Amir started posting these reviews in 2016, and the testing procedure has changed a lot from the discussions. So if you see holes in the data it's either because it wasn't the norm to capture it, or because it's not that important relative to the unit's performance. A mediocre unit isn't worth characterizing completely, for example.

I'm fine with that personally since the goal is not to capture every single metric but to evaluate performance in general, which is a more useful, if somewhat messier, way of doing things.
I agree.

For me, the usefulness of the big charts is in narrowing down the set of products you might be interested in. I wouldn't suggest anyone use them as the only selection criteria, but they are good in getting a lay of the land of what's out there.
 
Top Bottom