[fsi22]

This is probably the most correct place for this question.

I recently bought a pair of HD650 and would like to know how do I choose an amp/dac for my pc, laptop and phone.

My understanding of input/output impedance is limited to 1/8 rule/guide and that I need something capable of closer to 2 volts RMS. If anyone can help me understand the very basic important technical factors I would be highly appreciative. Thank you.

 

[castleofargh]

I've tried to explain the power side of things in this post for the hd650 if that's what you're looking for:
http://www.head-fi.org/t/197776/sennheiser-hd650-impressions-thread/27645#post_11806577
keep in mind that all musics aren't recorded at 0db (full scale signal), also if you reduce the gain in an EQ, or use replay gain, the amp will need the to have the ability to compensate for that extra gain and still sound as loud.
 
 
aside from that, an amp with lower distortions will have lower distortions.  one with better crosstalk or slew rate or whatever variable you will see measured, should manifest those differences. so at least measurable differences will exist. how that will be meaningful is for you to decide. one with crappy fidelity will be crap whatever the design if you look for fidelity, but it may feel superior to a transparent amp if the defects sound nice to you and you're really after something pleasing instead of hifi.
 
most pretend that they care about fidelity and then just buy whatever feels nice to them instead of what measures well. you even have such concepts as people calling transparent amps "boring". and some will simply pick whatever they like and call it fidelity often going as far as rejecting measurements or electrical laws when they don't align with their personal opinion of superiority.
so IMO, even before looking into electrical requirements and signal fidelity, one should make his own mind about what he's really looking for. and then avoid lying to himself(and others) about it. ultimately what matters is for you to enjoy your music, so there is almost no bad choices here, only bad excuses. 
at a pure electrical level, a 300ohm headphone is in fact pretty easy to drive. you may have to put more thought into picking the an amp when using IEMs or planars, or speaker amps. that may feel hard to believe when you read the hd650's topic, but I really believe this to be true based on my understanding of electricity.
 
when comes the time to make a choice, of course other parameters will come into play. most will be pepsi vs coca cola kind of choices. where you're not even sure if it really matters or why you have a preference. starting with tube vs solid state. then within each group there actually are several sub groups of components and designs, each with some legitimate pros and cons. as we can't really expect to know everything about amp designs(I certainly don't), we usually end up picking something for the wrong reason. because we got convinced by someone as confident as he was ignorant. or because it looked good, or because a choice needed to be made anyway. the truth being that you can nowadays make very clean sounding devices using almost any technology so it doesn't matter all that much if you can find some measurements to make sure the amp you're looking at is more than a brand name and some eye candy.
tubes will run hot so depending where you live, I'd consider that an important variable^_^. also if you're looking for a colored amp(one that has it's own signature and distortions), tubes still seem like the logical choice.
 
price is also a BS factor in the sense that some components are expensive because they're more expensive to manufacture, not because they make a better sound. with the same idea, some amp manufacturers are in fact 1 or 2 guys in a room making amps from scratch. so obviously they have costs that are very high compared to some big brand making XXXX amps a day in a factory wherever it's cheaper.
 
so all in all, past electrical specs and personal taste(if you're lucky enough to be able to try the amps), everything else could just be random and it wouldn't be harder to pick.
else you can simply ask questions by mail to the manufacturer. within the audio industry, I'd go as far as saying that amp manufacturers feel the most honest/less dishonest of all(IMO!!!!!). if it's a giant brand like sony, don't waste your time the guy answering won't have a clue, but otherwise my personal experiences have almost always been informative, even when they deliberately avoid answering some questions, I find that it's also a meaningful intel.
 
I'm sure you would prefer that I told you "buy XXXXX, it's the best!" but I don't have any such opinion on the matter. so good luck ^_^.

 

[fsi22]

Awesome response.

I've always been technically minded, by that I mean, I have always been someone who tries to understand through reference points rather than subjective reasoning, thats the reason I asked on this group, I had a headache reading the magical nothingness of the HD650 thead.

In terms of what I'm looking for. I'm simply looking for something transparent that will help with the hiss on my pc/laptop and be able to drive 300ohm to what I would get from say ... my IE80 on my phone. I guess I'm tone deaf but I honestly do not hear a difference between tidal hifi and 320kbps mp3.

Finally and sorry if this is a long post, your reply is pretty much what I wanted, not buy x or z but an introduction into understanding the science as that helps me make a far more informed decision. I will have a look at the post you linked.

 

[Rearwing]

I can't give the same sort of answer as castleofargh did (because I don't have the technical or literary skills), but my experiences might help. It took me three years to find the equipment that I now use the most, even though I had the opportunity to have acquired it at the very first meet I went to (I just didn't know it at the time!)
 
My inventory took in tube and solid state amps as I searched for the sound combinations that I felt most comfortable with for long listening sessions. I spent time auditioning kit and this helped enormously in getting me to understand the differences between sound quality and sound colouration. I now have a couple of systems, one for home and one for travel, that give me what I want and that make my music sound fantastic.
 
This is a hobby wherein there are lots of rabbit holes (which can be frustrating at times and enlightening at others), but on the whole it is ultimately satisfying when you find the equipment that allows your ears and brain to hit the aural sweet spot.
 
Best of luck!

 

[fsi22]

I've tried to explain the power side of things in this post for the hd650 if that's what you're looking for:
http://www.head-fi.org/t/197776/sennheiser-hd650-impressions-thread/27645#post_11806577
keep in mind that all musics aren't recorded at 0db (full scale signal), also if you reduce the gain in an EQ, or use replay gain, the amp will need the to have the ability to compensate for that extra gain and still sound as loud.


aside from that, an amp with lower distortions will have lower distortions.  one with better crosstalk or slew rate or whatever variable you will see measured, should manifest those differences. so at least measurable differences will exist. how that will be meaningful is for you to decide. one with crappy fidelity will be crap whatever the design if you look for fidelity, but it may feel superior to a transparent amp if the defects sound nice to you and you're really after something pleasing instead of hifi.

most pretend that they care about fidelity and then just buy whatever feels nice to them instead of what measures well. you even have such concepts as people calling transparent amps "boring". and some will simply pick whatever they like and call it fidelity often going as far as rejecting measurements or electrical laws when they don't align with their personal opinion of superiority.
so IMO, even before looking into electrical requirements and signal fidelity, one should make his own mind about what he's really looking for. and then avoid lying to himself(and others) about it. ultimately what matters is for you to enjoy your music, so there is almost no bad choices here, only bad excuses. 
at a pure electrical level, a 300ohm headphone is in fact pretty easy to drive. you may have to put more thought into picking the an amp when using IEMs or planars, or speaker amps. that may feel hard to believe when you read the hd650's topic, but I really believe this to be true based on my understanding of electricity.

when comes the time to make a choice, of course other parameters will come into play. most will be pepsi vs coca cola kind of choices. where you're not even sure if it really matters or why you have a preference. starting with tube vs solid state. then within each group there actually are several sub groups of components and designs, each with some legitimate pros and cons. as we can't really expect to know everything about amp designs(I certainly don't), we usually end up picking something for the wrong reason. because we got convinced by someone as confident as he was ignorant. or because it looked good, or because a choice needed to be made anyway. the truth being that you can nowadays make very clean sounding devices using almost any technology so it doesn't matter all that much if you can find some measurements to make sure the amp you're looking at is more than a brand name and some eye candy.
tubes will run hot so depending where you live, I'd consider that an important variable^_^. also if you're looking for a colored amp(one that has it's own signature and distortions), tubes still seem like the logical choice.

price is also a BS factor in the sense that some components are expensive because they're more expensive to manufacture, not because they make a better sound. with the same idea, some amp manufacturers are in fact 1 or 2 guys in a room making amps from scratch. so obviously they have costs that are very high compared to some big brand making XXXX amps a day in a factory wherever it's cheaper.

so all in all, past electrical specs and personal taste(if you're lucky enough to be able to try the amps), everything else could just be random and it wouldn't be harder to pick.
else you can simply ask questions by mail to the manufacturer. within the audio industry, I'd go as far as saying that amp manufacturers feel the most honest/less dishonest of all(IMO!!!!!). if it's a giant brand like sony, don't waste your time the guy answering won't have a clue, but otherwise my personal experiences have almost always been informative, even when they deliberately avoid answering some questions, I find that it's also a meaningful intel.

I'm sure you would prefer that I told you "buy XXXXX, it's the best!" but I don't have any such opinion on the matter. so good luck ^_^.

I've read the post, that should be stickied.

Next question is what's for example Opus #11 spec sheet is listed with
Output level: 1.9Vrms(No Load)

and am I correct in my understanding that output impedance should be at least 1/8 of headphone impedance to prevent deviation on frequency response of source? or am I wrong?

Finally do all dac have a flat response?

 

[fsi22]

I can't give the same sort of answer as castleofargh did (because I don't have the technical or literary skills), but my experiences might help. It took me three years to find the equipment that I now use the most, even though I had the opportunity to have acquired it at the very first meet I went to (I just didn't know it at the time!)

My inventory took in tube and solid state amps as I searched for the sound combinations that I felt most comfortable with for long listening sessions. I spent time auditioning kit and this helped enormously in getting me to understand the differences between sound quality and sound colouration. I now have a couple of systems, one for home and one for travel, that give me what I want and that make my music sound fantastic.

This is a hobby wherein there are lots of rabbit holes (which can be frustrating at times and enlightening at others), but on the whole it is ultimately satisfying when you find the equipment that allows your ears and brain to hit the aural sweet spot.

Best of luck!

Thank you.

 

[castleofargh]

I've read the post, that should be stickied.

Next question is what's for example Opus #11 spec sheet is listed with
Output level: 1.9Vrms(No Load)

and am I correct in my understanding that output impedance should be at least 1/8 of headphone impedance to prevent deviation on frequency response of source? or am I wrong?

Finally do all dac have a flat response?

when I find a device with specs like that (or lack of), I forget the device exists and move on. those specs are useless to assess power needs and I'm not a gambler. they had one job, somewhere the marketing decided to put a list of meaningless details while suppressing power into a few loads, I wouldn't even buy that for my IEMs. it's subjective and this DAC/amp might be a little wonder, but I'm not a fan of guessing.
 
most DACs will have a rather flat response(within +/- 1 or 2db over the audible range and the vast majority will do better than that). when it comes to frequency response, the most significant element(which IMO isn't that significant) will be the filter to band limit the signal. different implementations can affect the signal audibly in the trebles if the low pass filter is a gentle slope that starts real soon and you're playing 16/44 formats. what some will describe as "analog sound", and really is a glorified way to say rolled off trebles. a few devices even offer to switch between filters. else again in my opinion, a DAC isn't what you look into when you want to change the frequency response. it's right there in the ineffective EQ department next to cables.

 

[fsi22]

  when I find a device with specs like that (or lack of), I forget the device exists and move on. those specs are useless to assess power needs and I'm not a gambler. they had one job, somewhere the marketing decided to put a list of meaningless details while suppressing power into a few loads, I wouldn't even buy that for my IEMs. it's subjective and this DAC/amp might be a little wonder, but I'm not a fan of guessing.
 
most DACs will have a rather flat response(within +/- 1 or 2db over the audible range and the vast majority will do better than that). when it comes to frequency response, the most significant element(which IMO isn't that significant) will be the filter to band limit the signal. different implementations can affect the signal audibly in the trebles if the low pass filter is a gentle slope that starts real soon and you're playing 16/44 formats. what some will describe as "analog sound", and really is a glorified way to say rolled off trebles. a few devices even offer to switch between filters. else again in my opinion, a DAC isn't what you look into when you want to change the frequency response. it's right there in the ineffective EQ department next to cables.

Thank you for all of that,  easy to understand . I've pretty much set my mind on what to get now. Time to try reading nwavguy blog posts now that I have a basic understanding of what to look out for, for now.

 

[fsi22]

I got my Odac+Objective2 today and blind testing between phone (S6 Edge) and Odac+O2 at the same volume levels, I find the phone very impressive. I've always heard that an amp is necessary, I feel it's less necessary and more of a nicety to have especially if you listen at the volumes I usually do.

The Odac+O2 is a bit cleaner but I would imagine an iphone or most android phones made in the last few years is far better than they are given credit.

 

[icebear]

Get a GSX-Mk2 and be done with the amp part.

 

[sonitus mirus]

  Get a GSX-Mk2 and be done with the amp part.

 
Ha!  Anyone that would spend that much money on a headphone amp would likely never be "done".

 

[Samueru Sama]

I got my Odac+Objective2 today and blind testing between phone (S6 Edge) and Odac+O2 at the same volume levels, I find the phone very impressive. I've always heard that an amp is necessary, I feel it's less necessary and more of a nicety to have especially if you listen at the volumes I usually do.

The Odac+O2 is a bit cleaner but I would imagine an iphone or most android phones made in the last few years is far better than they are given credit.

 
I actually find hard to believe that the odac+o2 is a bit cleaner. How did you set up the blind test? A proper blind test needs a perfectly match volume in both devices and to do so you need a decent multimeter, and also perfectly sync both devices which I find very difficult/impossible, and you need assistance from someone else, because you can't have the slight idea of which device is which.
 
Check the S6 edge plus: https://www.seeko.co.kr/zboard4/zboard.php?id=m_device&page=1&sn1=&divpage=1&sn=off&ss=on&sc=off&select_arrange=headnum&desc=asc&no=54
 
The best way to do the test is to record the phone with the ADC of your PC, but you need a 3.5mm Y splitter, as you need to connect the phone to your headphones (as load) and PC at the same time. Once done, compare the recorded file vs the original one with ABX comparator for Foobar2000, I have recorded several devices that way.
 
Heres a phone (Samsung Galaxy Ace S5830L) with a 80 Ohm load. https://mega.nz/#!xYRGUCrS!2VZ8XLyybwcGcev3YmotpkFMTbQSU0DNImDnH5OFVFI
 
Compare the two files with ABX comparator.
 
By the way, the S6 edge plus max ouputs 0.76 Vrms  "line out mode", that would be 101 dB SPL with the 650s, and in "normal" mode it max outputs 0.428 Vrms (96 dB SPL), but again it's not the same phone, though I doubt that the non plus outputs more voltage.

 

[fsi22]

I actually find hard to believe that the odac+o2 is a bit cleaner. How did you set up the blind test? A proper blind test needs a perfectly match volume in both devices and to do so you need a decent multimeter, and also perfectly sync both devices which I find very difficult/impossible, and you need assistance from someone else, because you can't have the slight idea of which device is which.

Check the S6 edge plus: https://www.seeko.co.kr/zboard4/zboard.php?id=m_device&page=1&sn1=&divpage=1&sn=off&ss=on&sc=off&select_arrange=headnum&desc=asc&no=54

The best way to do the test is to record the phone with the ADC of your PC, but you need a 3.5mm Y splitter, as you need to connect the phone to your headphones (as load) and PC at the same time. Once done, compare the recorded file vs the original one with ABX comparator for Foobar2000, I have recorded several devices that way.

Heres a phone (Samsung Galaxy Ace S5830L) with a 80 Ohm load. https://mega.nz/#!xYRGUCrS!2VZ8XLyybwcGcev3YmotpkFMTbQSU0DNImDnH5OFVFI

Compare the two files with ABX comparator.

By the way, the S6 edge plus max ouputs 0.76 Vrms  "line out mode", that would be 101 dB SPL with the 650s, and in "normal" mode it max outputs 0.428 Vrms (96 dB SPL), but again it's not the same phone, though I doubt that the non plus outputs more voltage.

Volume matched with 1khz and then played tracks. The difference is minute hence I say I'm very impressed with what a phone can do and consider amping an hd650 a nicety and not a necessity.

I have no multimeter and I was simply looking to see how necessary a dac/amp is after all the talk of the hd650 would not be at its full potential without 1.

My personal conclusion after actually listening to them both is an amp is not necessary and the 650 sounds extremely good straight out of my phone and I imagine any new phone would do at least just as good a job.

 

[Samueru Sama]

Volume matched with 1khz and then played tracks. The difference is minute hence I say I'm very impressed with what a phone can do and consider amping an hd650 a nicety and not a necessity.

I have no multimeter and I was simply looking to see how necessary a dac/amp is after all the talk of the hd650 would not be at its full potential without 1.

My personal conclusion after actually listening to them both is an amp is not necessary and the 650 sounds extremely good straight out of my phone and I imagine any new phone would do at least just as good a job.

 
With high impedance headphones the only requirements is that whatever the source is, it needs to output enough voltage for them . They're not affected by high output impedances or small coupling capacitors like low impedance headphones, and they draw very little current, so distortion is going to be inaudable unless you clip the signal, and it is not common in phones to clip at 0 dBFS with high impedance loads.
 
However there are extreme cases, like the audio of my motherboard (an A58M-E), It has output coupling capacitors and are so miserable that there's a noticable roll off even with a 320 Ohm load.
 
http://prnt.sc/db2bus
 
Here's the motherboard recorded playing some music with 32, 320 Ohm loads, and the original file for comparison: https://mega.nz/#!sUgxzRgS!JLTybF_ElfTmROh6pzDngcP8wJoRqA2Sm2V5fZxq-BA
 
foo_abx 2.0.2 report
foobar2000 v1.3.11
2016-11-23 22:00:34
File A: Test-02.flac
SHA1: 7c082b6c71ff44e70763f6be09a75243c3fb7c2a
File B: Test-03.flac
SHA1: d1bbb2d37a64f6a5366062ab52c450ad0b3f09e8
Used DSPs:
Resampler (dBpoweramp/SSRC)
Output:
DS : Speakers (ASUS Xonar DG Audio Device)
Crossfading: NO
22:00:34 : Test started.
22:00:48 : 01/01
22:01:01 : 02/02
22:01:52 : 03/03
22:02:05 : 04/04
22:02:16 : 05/05
22:02:23 : 06/06
22:02:38 : 07/07
22:02:51 : 08/08
22:03:07 : 09/09
22:03:19 : 10/10
22:03:19 : Test finished.
 ----------
Total: 10/10
Probability that you were guessing: 0.1%
 -- signature --
63c739d16140c49b386cc831f6fc8001eb9b9a08
 
 
 
 
But again the S6 edge+ has none of those issues, that's why I said that I find hard to believe that the O2+ODAC sounds "a bit cleaner", you shouldn't have noticed a difference at all, I'm pretty sure that in a proper blind test in which you have no idea of which device is which and volume is perfectly matched with a multimeter, you won't notice a difference.

 

[fsi22]

With high impedance headphones the only requirements is that whatever the source is, it needs to output enough voltage for them . They're not affected by high output impedances or small coupling capacitors like low impedance headphones, and they draw very little current, so distortion is going to be inaudable unless you clip the signal, and it is not common in phones to clip at 0 dBFS with high impedance loads.

However there are extreme cases, like the audio of my motherboard (an A58M-E), It has output coupling capacitors and are so miserable that there's a noticable roll off even with a 320 Ohm load.

http://prnt.sc/db2bus

Here's the motherboard recorded playing some music with 32, 320 Ohm loads, and the original file for comparison: https://mega.nz/#!sUgxzRgS!JLTybF_ElfTmROh6pzDngcP8wJoRqA2Sm2V5fZxq-BA

foo_abx 2.0.2 report

foobar2000 v1.3.11

2016-11-23 22:00:34
File A: Test-02.flac

SHA1: 7c082b6c71ff44e70763f6be09a75243c3fb7c2a

File B: Test-03.flac

SHA1: d1bbb2d37a64f6a5366062ab52c450ad0b3f09e8
Used DSPs:

Resampler (dBpoweramp/SSRC)
Output:

DS : Speakers (ASUS Xonar DG Audio Device)

Crossfading: NO
22:00:34 : Test started.

22:00:48 : 01/01

22:01:01 : 02/02

22:01:52 : 03/03

22:02:05 : 04/04

22:02:16 : 05/05

22:02:23 : 06/06

22:02:38 : 07/07

22:02:51 : 08/08

22:03:07 : 09/09

22:03:19 : 10/10

22:03:19 : Test finished.
 ----------

Total: 10/10

Probability that you were guessing: 0.1%
 -- signature --

63c739d16140c49b386cc831f6fc8001eb9b9a08




But again the S6 edge+ has none of those issues, that's why I said that I find hard to believe that the O2+ODAC sounds "a bit cleaner", you shouldn't have noticed a difference at all, I'm pretty sure that in a proper blind test in which you have no idea of which device is which and volume is perfectly matched with a multimeter, you won't notice a difference.

Very useful information, thank you for that. My onboard audio from both laptop and pc have very bad hiss. What would cause that?

So the multimeter would produce a perfectly objective datum and, if my volume is even slightly higher on one it will give the impression of greater dynamic range over the other. Am I correct in my understanding?

I doubt there would be too much of a difference between votages with S6 Edge + and Edge, I would think there would be a difference between EU and the rest of the world Samsung phones in general because of EU phones being volume capped.