Review and Measurements of Teac HA-501 Headphone Amp

[GGroch]

Just an observation , and for @amirm 's consideration in future reviews for DAC Amps / HF amps......Do the subjective listening tests as a base note before any measurements are taken. Note down all your listening observations first.....

You make a valid point, but there is a unique benefit to doing subjective listening tests after measurement.

Most of the products Amir measures have already been subjectively reviewed elsewhere without measurement. I understand Amir has excellent hearing but I do not believe he claims any special powers in this regard, so any subjective listening before measurement would be from a similar perspective of what is already available.

One of the most common questions after a product's measurements are posted, is "Can I hear the anomalies that you measured." Testing first, then listening, provides Amir with guidance as to what specifically to listen for. This is a different, more specific perspective than is available elsewhere. In the case of the HA-501, it appears the measured shortcomings were not audible. You're right, additional information provided by measurement will influence the subjective experience to some degree, but that can be a good thing if it provides more focus.

I guess it is in some ways like my annual medical checkups. They usually tell me I can take the blood test before or after my office visit. I usually choose to visit after the blood results are in so the Doc knows what to look for.

 

[Frank Dernie]

All that Amazon stuff are often not brand new items but refurbished or pre-owned or returned items, don't trust Amazon (Edit: based on my own experience)!!

I haven’t had anything obviously second hand from Amazon which was claimed to be new.
OTOH I can imagine returned “in as new condition” will inevitable be supplied from time to time since there is a legal obligation in many countries for vendors to give the money back on items customers return. This is a luxury increasingly many people seem to exploit these days including a good number of members of this forum.
It is pretty inevitable that if an item was just returned but not faulty that the next customer is going to get it “In as new condition”
It hasn’t happened to me yet.

 

[Shadrach]

Just an observation , and for @amirm 's consideration in future reviews for DAC Amps / HF amps.

i) Do the subjective listening tests as a base note before any measurements are taken. Note down all your listening observations first.

ii) Then move on to the measurements.

iii) And then reconcile them.

Doing the current measurements and then moving on to subjective listening tests will inevitably introduce "affirmation bias" in the listening tests. I seem to detect that in some of the comments of the tests.

Even if its not the case, I would think it helps to keep reviews that wee bit more balanced.

Why on earth do think what amirm may or may not hear has any relevance to what you may or may not hear?
It's kind of the point of subjectivism. There are plenty of forums where you can read subjective reviews of equipment.
This is not meant to be in any way rude to amirm and I believe he will completely understand, but I would rather he left out any subjective comments about sound quality, or even whether, or not he can hear obvious distortion.
If people think they can hear above the accepted 'it may be audible limit' then a forum such as this probably isn't for them.
There are already an awful lot of closet subjectivists on this forum.

 

[pkane]

This is a review and detailed measurements of the Teac HA-501 headphone amplifier. It is on kind loan from a member. The HA-501 in black costs $549 including Prime shipping from Amazon. Oddly, the silver color is much cheaper at $354! Black anodizing must have become very expensive. The black does look a lot nicer though so it would be tough to settle for silver.

The HA-501 is one of the most attractive desktop audio products. If you are a fan of the 1970s and 1980s hi-fi gear, the Teac is the best way that look could have been modernized yet hold its retro appeal:

View attachment 25419​

The controls feel fantastic and the head of the class for sure.

Controls are not unusual other than addition of "damping factor" which simply adds a resistor in the path of the headphone output (measurements later).

The other odd thing is the auto-muting. When you unplug the headphone, the red audio mute LED comes on and will not go off until you turn the volume all the way down to infinity and then back up. This is to assure you never plug in a headphone and have it play at exceedingly high levels. I am not sure that is worth the effort it takes to reset it every time if someone has multiple headphones they use often.

The back panel shows the generous inputs and outputs:

View attachment 25420​

If it were up to me, I would make balanced XLR inputs mandatory on every headphone amp. So useful in getting around ground loops.

Nice to see switch selectable pass through RCA outs.

Being a proper audio companies, regulatory certifications are there and can be relied upon to mean this is a safe device that doesn't spit out a bunch of RF.

Overall, a headphone amplifier doesn't get much nicer than this from look and feel point of view.

Headphone Audio Measurements
Let's start with our dashboard output, driving the HA-501 using XLR inputs (same input was used for all the tests):

View attachment 25421

I set the volume to pass through (4 volt in, 4 volt out). Even at this reduced volume level, the amount of distortion is quite high for a top of the line headphone amplifier. The distortion is from third harmonic which sets the SINAD by itself to 83 dB. As a way of comparison, the Massdrop THX AAA 789 clocks at 117 dB while producing 5.8 volts output! That is an incredible gap in performance.

Signal to noise ratio is spec-compliant:
View attachment 25422

The 50 millivolt output which measures how well an amp drivers ultrasensitive headphones is not so good though:

View attachment 25423

Measuring THD+N versus frequency at my standardized 5.8 output level shows how much more the distortion rises with volume:
View attachment 25424

Even at 2 volt output the HA-501 is not competitive.

Intermodulation distortion distortion versus output power shows the same:

View attachment 25425

But also indicates that the HA-501 has more power than THX 789's single-ended output. We can see this clearly in THD+N versus output power at 300 ohm:

View attachment 25426

Switching to 33 ohm for a more current limited load we get:
View attachment 25427

Here, the rise in distortion is more severe but we still have ample amount of power at 1.4 watts.

Channel imbalance is very good until the end:
View attachment 25428

Finally, output impedance is very good at high damping factor setting:

View attachment 25429

The amount of resistance at low damping factor is still modest at 6.2 ohm. I thought it would be higher than it is.

Headphone Listening Tests
As usual, I start my listening tests with the Sennheiser HD-650. As the measurements predict, there was more than sufficient amount of power to drive these to produce excellent bass (they sound anemic otherwise). The authority and clarity erased any memory of less than excellent measurement graphs.

The situation was nearly the same with Hifiman HE-400i. There was plenty of power although I thought maybe at the limit it got a tiny bit distorted. Never mind as I could not listen at that level for more than a couple of seconds.

Using the HE-400i, I played with the damping factor. It makes quite a bit of difference going from High to Low, causing both the level and bass response to suffer greatly in Low setting. Of course this is not the main use of it but thought it was a good tool to measure the effect of high output impedance subjective.

Conclusions
The Teac HA-501 nails a number of my review criterias from look, feel, safety, reliability and amount of power. Subjectively it also meets its target of producing ample power to drive just about every headphone you throw at it.

Objectively it is far from top of class given the game changing headphones amps: Massdrop THX AAA 789 and JDS Labs Atom. These two amps have basically left everything else in the dust. Where they lose to Teac though is in overall feel and look. Even the THX falls behind by good few points.

So you have a choice to make: go with heart that is pulled by the look and subjective sound quality or engineering excellence as represented by the competitors. I am not here to solve that equation for you. I want both and Teac HA-501 doesn't have both.

------------
As always, questions, comments, recommendations, etc. are welcome.

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I happen to have THX AAA 789 and HA-501 on hand, so will try a comparison a bit later. For now, HA-501 doesn't appear to be as bad as what you've found. Here's what I get using REW (0-22.4kHz range):

THD+N of about -95dB. The difference appears to be in the third harmonic, which is lower than the 2nd in my measurement, and much higher in yours. Also, the 60Hz mains frequency and its harmonics are more prominent in mine. I'll need to look into better power supply or see if I have any ground loops.

 

[JohnYang1997]

I thought it was ud501.
Come on, someone get amirm a ud501 to measure.

 

[JohnYang1997]

That's just heckling from the sidelines and not remotely useful commentary, is it? It's not a D/A converter. It simply a headphone amplifier.

The S/N is pretty good at @109dB and as you can see, the power supply noise contribution is very low in this product. It is the THD that kills it. That said, I'd like to see it tested against its specifications (1V in 1V out) before condemning it. After all, if it meets advertised specifications, there is absolutely no justification in calling it out.

View attachment 25437
Some good shots of the internal construction here: http://www.hifishock.org/gallery/electronics/teac/headphone-amplifier/ha-501-3-teac/

View attachment 25436

They make great fanfare of the NJR Muses 8920, a current flavor-of-the-month opamp used in this product (pdf attached).
http://audio.teac.com/product/ha-501/

Consider we are simply amplifying/buffering a line stage to drive headphones. Do we seriously need this level of complexity (that's just one channel in the foreground)? Do we really need a discrete Class A power amp for headphones when an opamp and a buffer stage will do?

Just checking. Are you sure that 8920 is only doing buffering? Or it's the gain stage or it's differential amplifier to sum the xlr input?
I personally think half of the 8920 does summing and the other half provides gain. And the soic8 opamp provides feedback for the discrete output stage.

 

[JohnYang1997]

Why on earth do think what amirm may or may not hear has any relevance to what you may or may not hear?
It's kind of the point of subjectivism. There are plenty of forums where you can read subjective reviews of equipment.
This is not meant to be in any way rude to amirm and I believe he will completely understand, but I would rather he left out any subjective comments about sound quality, or even whether, or not he can hear obvious distortion.
If people think they can hear above the accepted 'it may be audible limit' then a forum such as this probably isn't for them.
There are already an awful lot of closet subjectivists on this forum.

I don't think he's being rude. In fact it's a very good point. I'm not saying amirm is doing it wrong and we shouldn't trust but it's a better way for subjective evaluation. Sure we can ignore the listening part but that's half of the evaluation. And we do prefer someone can provide non-biased subjective tests.

 

[invaderzim]

All that Amazon stuff are often not brand new items but refurbished or pre-owned or returned items, don't trust Amazon (Edit: based on my own experience)!!

Were these items that were sold by Amazon or a 3rd party through Amazon?

I am no fan of Amazon but I can't imagine them selling items as new that were refurbished. I've seen plenty of un-boxing videos online where people buy unseen lots of Amazon returns that would indicate if the item is opened at all it goes into those rather than back on the shelf.

Now, with items sold by 3rd parties through Amazon I could easily see used and questionable items being sold.

 

[maxxevv]

You make a valid point, but there is a unique benefit to doing subjective listening tests after measurement.

Yes I agree but to be perfectly unbiased, its has to be 2 pronged. I wasn't asking for a subjective review though, I was suggesting for a better sequence to reduce any bias in subjective observations that Amir is making in the listening portion.

Why on earth do think what amirm may or may not hear has any relevance to what you may or may not hear?
It's kind of the point of subjectivism. There are plenty of forums where you can read subjective reviews of equipment.
This is not meant to be in any way rude to amirm and I believe he will completely understand, but I would rather he left out any subjective comments about sound quality, or even whether, or not he can hear obvious distortion.
If people think they can hear above the accepted 'it may be audible limit' then a forum such as this probably isn't for them.
There are already an awful lot of closet subjectivists on this forum.

You're missing the point.

i) Have you actually read beyond my first 2 sentences ?

ii) Has Amir ever done more than look out for obvious flaws in the output listening portion ? Answer: NO.

iii) Am I asking him to do anything more than what he has always done ? IOW: A subjectivist review of an device ? Answer: NO.

 

[Tks]

You make a valid point, but there is a unique benefit to doing subjective listening tests after measurement.

Most of the products Amir measures have already been subjectively reviewed elsewhere without measurement. I understand Amir has excellent hearing but I do not believe he claims any special powers in this regard, so any subjective listening before measurement would be from a similar perspective of what is already available.

One thing I must disagree with, at least from an outside perspective, is this notion that he has "excellent" hearing. Safe to say he's not in his late teens, or I would even guess 20's. Also he really enjoys listening to music quite loudly and defend that stance a few times saying there is no damage he's doing.

The one thing about his hearing that I believe would be excellent, is perhaps how self-trained he has become simply due to the breadth of all that he has heard.

The reverse proposal (to have him listen first, and then measure) I believe (as a gamble) would illustrate that he would be far from "excellent" hearing from a "natural" point of view.

I don't say this as an offense to him, it's just my take on a few statements and deduction of ages' effect on the auditory system.

 

[Tks]

I thought it was ud501.
Come on, someone get amirm a ud501 to measure.

No problem, just send him a unit

 

[amirm]

One thing I must disagree with, at least from an outside perspective, is this notion that he has "excellent" hearing. Safe to say he's not in his late teens, or I would even guess 20's. Also he really enjoys listening to music quite loudly and defend that stance a few times saying there is no damage he's doing.

I don't listen to music loud. For my continuous listening, the levels are quite low. It is usually -20 to -40 dB on DX3 Pro. I do occasionally turn up the volume on a track or two but that is not my normal listening.

The one thing about his hearing that I believe would be excellent, is perhaps how self-trained he has become simply due to the breadth of all that he has heard.

That is only the recent experience. My training was professionally done starting in 1998 when I started to manage the audio compression team at Microsoft. I was shocked despite being an audiophile for decades that I could not hear the difference between 128 kpbs compressed music and the original. I started to formally train myself and then became walk in the park to hear compression artifacts far, far less audible than that. I developed a skill to put aside the music for what it is, and drill into specific artifacts. In a number of tests we performed at Microsoft, I could easily beat all audiophiles.

Of course my high frequency hearing has degraded due to age. But in double blind tests offered as challenges in public, I am one of the few who takes them and passes them. Here is one of many examples:

MP3 versus original on a track from the late Arny Krueger:

foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/07/19 19:45:33

File A: C:\Users\Amir\Music\Arnys Filter Test\keys jangling 16 44.wav
File B: C:\Users\Amir\Music\Arnys Filter Test\keys jangling 16 44_01.mp3

19:45:33 : Test started.
19:46:21 : 01/01 50.0%
19:46:35 : 02/02 25.0%
19:46:49 : 02/03 50.0%
19:47:03 : 03/04 31.3%
19:47:13 : 04/05 18.8%
19:47:27 : 05/06 10.9%
19:47:38 : 06/07 6.3%
19:47:46 : 07/08 3.5%
19:48:01 : 08/09 2.0%
19:48:19 : 09/10 1.1%
19:48:31 : 10/11 0.6%
19:48:45 : 11/12 0.3%
19:4
8:58 : 12/13 0.2%
19:49:11 : 13/14 0.1%
19:49:28 : 14/15 0.0%
19:49:52 : 15/16 0.0%
19:49:56 : Test finished.

----------
Total: 15/16 (0.0%)

This one was a test of high resolution audio versus CD rate as offered by AIX records (but used for MP3 testing):

foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/07/31 15:18:41

File A: C:\Users\Amir\Music\AIX AVS Test files\On_The_Street_Where_You_Live_A2.mp3
File B: C:\Users\Amir\Music\AIX AVS Test files\On_The_Street_Where_You_Live_A2.wav

15:18:41 : Test started.
15:19:18 : 01/01 50.0%
15:19:30 : 01/02 75.0%
15:19:44 : 01/03 87.5%
15:20:35 : 02/04 68.8%
15:20:46 : 02/05 81.3%
15:21:39 : 03/06 65.6%
15:21:47 : 04/07 50.0%
15:21:54 : 04/08 63.7%
15:22:06 : 05/09 50.0%
15:22:19 : 06/10 37.7%
15:22:31 : 07/11 27.4%
15:22:44 : 08/12 19.4%
15:22:51 : 09/13 13.3%
15:22:58 : 10/14 9.0%
15:23:06 : 11/15 5.9%
15:23:14 : 12/16 3.8%
15:23:23 : 13/17 2.5%
15:23:33 : 14/18 1.5%
15:23:42 : 15/19 1.0%
15:23:54 : 16/20 0.6%
15:24:06 : 17/21 0.4%
15:24:15 : 18/22 0.2%
15:24:23 : 19/23 0.1%
15:24:34 : 20/24 0.1%
15:24:43 : 21/25 0.0%
15:24:52 : 22/26 0.0%
15:24:57 : Test finished.

----------
Total: 22/26 (0.0%)

These are very difficult tests to pass. They require extreme attention to what could be distorted and focusing on them after some trial and error. Once there though, you can see extremely good success rate.

Bottom line: I have training that allows me to listen through the music and focus on different aspects of it. If such issues are at very high frequencies, then yes, you can't rely on me. Otherwise, my skill levels are well above average not because I was born with it, but because I have spent hundreds of hours testing for artifacts in audio in controlled listening tests (where one would know if the answer is right or wrong).

I don't say this as an offense to him, it's just my take on a few statements and deduction of ages' effect on the auditory system.

No offense. I think it is best to ask me about such things rather than reading the tea leaves.

For many audiophiles that are as old as me and older, it is good news that one can be a critical listener, able to hear small impairments well above general public despite losing high frequency hearing.

 

[amirm]

I happen to have THX AAA 789 and HA-501 on hand, so will try a comparison a bit later. For now, HA-501 doesn't appear to be as bad as what you've found. Here's what I get using REW (0-22.4kHz range):

Thanks. What is the input source and what was the input and output voltages?

 

[amirm]

thank you for the work and this review! ive always been wondering if teacs hpa is worth the 500... now i know.
one suggestion: i know this is a science forum and from an objective scientific point of view its correct to compare every newly tested device to top-measured devices, but as far as it goes for "recommendations" (wich, i guess, go for folks beeing interested in BUYING this/any hpa), Massdrop THX AAA 789 is simply NOT AVAILABLE (or is it?) and i really wonder if it ever will be again... so, from someone whos interested in bying a hpa and his perspective point of view, it simply makes no sense to recommend the THX789 over and over again. I SIMPLY CANT BUY IT... (can i?)

Well, you can buy it. I bought one in the second run from massdrop. I remember once wanting to buy a Honda minivan. There was a massive shortage on them. You put your name and deposit and then waited for a call from the dealer. Once there, the first one to get to the dealership would get the van. We got the call one day early in the morning and we ran out half-dressed and were the first one in the dealership and got the unit! That shortage did not stop anyone from reviewing and giving high scores to Honda Minivan. We also overpaid to get the said van.

But yes, I hear you and in every breath I also mention JDS Labs atom which is available. The Atom does not have balanced input though so I am forced to use the THX as a reference.

Ultimately the data is what you want to go by. My conclusions are a personal opinion. And that opinion is that the general public and manufacturers should know that the THX implementation in that amp is cleaning their clocks. They need to wake up and either improve their own solution as JDS Labs has done or license the THX technology as companies like Benchmark have done.

People also read these reviews for years to come and such shortages may not be in place then.

 

[amirm]

Just an observation , and for @amirm 's consideration in future reviews for DAC Amps / HF amps.

i) Do the subjective listening tests as a base note before any measurements are taken. Note down all your listening observations first.

ii) Then move on to the measurements.

iii) And then reconcile them.

Doing the current measurements and then moving on to subjective listening tests will inevitably introduce "affirmation bias" in the listening tests. I seem to detect that in some of the comments of the tests.

Even if its not the case, I would think it helps to keep reviews that wee bit more balanced.

Thanks for the point of view. I don't want to put the subjective review first as that would elevate its level above objective data (it becomes an afterthought as it has in stereophile reviews).

While your point in general is valid, in practice is not an issue for the type of listening tests I do:

1. Single device testing as is done here. Here, I simply turn up the volume as high as I can tolerate. A few things happen during this depending on device capability. Some run out of power early in which case I report it as anemic, lacking bass, lacking detail, etc. They are all just saying there simply is not enough power to drive the headphones satisfactorily in my opinion. Or at best there is no headroom for music that is recorded less loud, headphones that are less efficient than mine, etc.

Alternatively, there is distortion as levels go up in which case I explain that.

So one way or the other, it is not searching for elusive qualities that could easily be biased.

2. Double device testing. Here I use an AB box and am comparing the review device against a reference I have. In this test, I usually am searching for signs of distortions not necessarily at max volume. The test is blind so advance information doesn't aid in putting down one or the other device.

What the information does is inform the areas of deficiency. Let's say SNR is poor. I could test for example for noise levels with appropriate clips and settings. This is what I like members to do. Don't go into your subjective evaluations blind, pun intended. You will definitely be biased by marketplace and internet chatter. You will think that a tube device must be sounding warm because it glows that way. Instead seek out measurements, and use that as the basis of what the issues might be. If power is not there, then test for that in your listening tests to make sure it is good enough for you.

Use my measurements as a compass for your listening test travels.

 

[Shadrach]

I don't think he's being rude. In fact it's a very good point. I'm not saying amirm is doing it wrong and we shouldn't trust but it's a better way for subjective evaluation. Sure we can ignore the listening part but that's half of the evaluation. And we do prefer someone can provide non-biased subjective tests.

 

[Willem]

Well put, Amir. I am not into headphones, but my take home from some of these recent measurements and subjective observations is that they confirm my experience that power is just about the most important variable, provided it is reasonably clean, of course.

 

[pkane]

Thanks. What is the input source and what was the input and output voltages?

Source was Holo Spring DAC on balanced output. Balanced input 3.5v, output of 1.95v.

 

[amirm]

Ah, try 4 volt out, 4 volt in as I tested and let's see if the results are similar.

 

[amirm]

Also, my dashboard output load is 600 ohm.