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Review and Measurements of Teac AX-501 Amplifier

amirm

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#1
This is a review and detailed measurements of the Teac AX-501 integrated power (speaker) amplifier. It is on kind loan from a member. The AX-501 is part of the reference series from Teac so doesn't come cheap as desktop products go. I see the price at USD $999 on Amazon plus $35 shipping. There is a discount for silver a USD $899 but Amazon doesn't sell it for some reason.

When I reviewed the Teac HA-501 Headphone Amplifier, I heaped praise over its modern retro look. The AX-501 takes that to an entirely different level with addition of a couple of super cute, yellow background VU meters:

Teac AX-501 Integrated Amplifier Audio Review.jpg

What is that? I should have took the shot with the VU meters working and the light turned on? Well, the owner played a cruel joke on me by not supplying me with the remote and leaving the setting to off for the VU meter!!! :D

The controls are almost as nice of the HA-501 with the exception of the volume control which feels a bit stiff and has some slack in it. Otherwise, there is nothing to fault it as far as I am concerned.

Here is the back panel:
Teac AX-501 Integrated Amplifier Back Panel Audio Review.jpg

XLR inputs should be mandatory in this price range and I am glad to see then included here (that is the way I ran all of my tests).

The AX-501 uses a class-D amplifier and runs as cool as you could get in my testing. I don't think it ever got even warm.

Class D also means light weight and that is NOT the case here. The AX-501 is a very hefty unit for its size. This means it stays put no matter how heavy your cables are.

Notice the lawyers getting their hands on the unit as to indicate the class of speaker wiring you are supposed to use! But hey, it is good to know the unit has been through corporate filter of certification and regulation.

Even though Teac is a Japanese company, the AX-501 is made in China.

Power Amplifier Measurements
Let's start with our usual 5 watt dashboard view using XLR inputs:

Teac AX-501 Integrated Amplifier Audio Measurements.png


Even though Teac specs the AX-501 at 1 watt, we see the same performance at 5 watts which is nice. Distortion and noise as stated in SINAD dB puts the AX-501 above average (of 74 dB):

Teac AX-501 Integrated Amplifier SINAD Audio Measurements.png


It loses to SONOS Amp using its digital input and ever so slightly outperforms the Amazon Link Amp.

Signal to noise ratio matches company spec:
Teac AX-501 Integrated Amplifier SNR Audio Measurements.png


Frequency response shows identical output for both channels which is a relief as poorly made class-D amps differ in this regard:
Teac AX-501 Integrated Amplifier Frequency Response Audio Measurements.png


Roll off is early for my taste. I like to see flat response to 40 kHz. That said, early filtering seems to help bring stability to performance of the low cost class D amps and I saw that here as I measured power output:

Teac AX-501 Integrated Amplifier Power Audio Measurements.png


There is a broad operating range where performance is good between 1 and 30 watts. We then run out of juice and clipping occurs at 88 watts. Rated output is 100 watts although higher resolution measurement may have gotten us closer.

The Amazon Link Amp has more power and SONOS even more. You are guaranteed to hear distortion when an amp reaches its max power rating so on this all important metric, the Teac AX-501 loses to its cheaper rivals. And of course we are worlds away compared to reference amps like those based on Hypex NC-400.

I have added a new test to my power amplifier suite and that is intermodulation distortion relative to measured power. I ran it against the recently reviewed Klipsch PowerGate Amplifier:

Teac AX-501 Integrated Amplifier IMD versus Power Audio Measurements.png


We see more evidence of the stability and clean performance of Teac AX-501 as switched/class D amplifiers go. The IMD graph is also more revealing of distortion set it around 7 to 8 watts and climbing before final clipping.

Headphone Amplifier Measurements
I ran a sampling of my headphone tests starting with power versus distortion using 300 ohm load:

Teac AX-501 Integrated Amplifier Headphone 300 Ohm Power Audio Measurements.png


Wow, this is impressive amount of output power at such a high impedance. I wonder if we are just looking at the output of the power amplifier, reduced with an in-line resistor. Here is the results with 33 ohm load:
Teac AX-501 Integrated Amplifier Headphone 33 Ohm Power Audio Measurements.png


Oh, this is not nearly as good. The reason is this:

Headphone Amplifier Output Impedance Measurements.png


Sadly, we have a high value resistor in series with the output to the tune of 58 ohm. I don't like to see a value much more than 10 ohm and ideally, down to 1 to 2 ohm.

Best use would be high impedance headphone with relatively flat impedance graph versus frequency. Otherwise some "color" will be imparted on the sound (for good or bad).

Conclusions
Personally I think Teac has nailed the look and feel of such a desktop product. The AX-501 is in an entirely different class, rivalling Nagra when it comes to switch-gear and meters. In that regard it is a "bargain."

The power amplifier seems competent without hairy corner cases. It is above average in performance but not rising up to the levels I like to see for $1,000. As I noted in the review. power is everything and there are much better choices in that regard such as SONOS Amp. At nearly half the price, it delivers more than twice the power plus a bunch of other features such as included streaming/DAC. It doesn't look nearly as nice as Teac AX-501 though.

The headphone output is a checklist item although it should sound very good with high impedance headphones (I did not test).

The AX-501 runs cool and should be quite reliable and safe giving its pedigree.

Overall I 'like" the Teac AX-501 but can't recommend it on performance or value. We should be able to do better for $1,000 so the search continues.

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

Major issue: my pink panther models have given me notice that they like to go on strike if I don't increase their pay. They say the original agreement did not at all call for daily reviews. Apparently they go through a lot of work with make up and such to look good on camera. So let's raise some funds so that I can pass on the same to my "talent" using:

Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 
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#4
I believe it is based on this Module Annaview ALC0240, which also suffers from increased distortion with increased frequencies like the ICE POWER modules which power other teac amplifiers, I'm curious if you can do a frequency vs distortion at a specific power output (1w or something like that). Hypex doesn't suffer from this in their UCD/n-core lines, but I'm not really sure how much of it's audible. Still holding out for an affordable set of diy amplifiers that have greater than 96db sinad for my lx mini's :)
 

amirm

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#6
I believe it is based on this Module Annaview ALC0240, which also suffers from increased distortion with increased frequencies like the ICE POWER modules which power other teac amplifiers, I'm curious if you can do a frequency vs distortion at a specific power output (1w or something like that).
Ah shoot. I measured that but forgot to post. :)

Teac AX-501 Integrated Amplifier THD vs Frequency Audio Measurements.png
 

amirm

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#8
Please do the AX-505, it's based on the tuned nCore modules. Actually, please do the NT-505 too, it's dual AKM4497eqs. Teac products just look oh so good.
We need to find someone who has bought one as they are beyond my budget to purchase for testing.
 
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#9
We need to find someone who has bought one as they are beyond my budget to purchase for testing.
I've got the NT505 but the shipping to and from you would be costly as I'm from the great white north. I've been considering the AX-505 though and would love to see if they've done a good job with the nCore's.
 

restorer-john

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#10
It's very cute looking.

Here is a closeup of the smps/amplifier PCB section. Of serious concern are the CapXon capacitors which in my experience are one of the absolute worst for venting and premature catastrophic failure. It shocks me that a respected manufacturer would consider using such poor quality capacitors.

smps amp.JPG


capxon.JPG


Here is another above shot:

1556669357120.png


Edit: The Class D amp section PCB appears to be an Abletec/Anaview (similar to the ALCO-240) module, but clearly put together in China. What's happened to these once great companies like Teac? Can't they design their own amplifiers anymore- do they all have to buy some off-the-shelf solution on a board?

Here's the module that looks remarkably similar... (DIYers buy these modules, stick them in boxes and say they 'built' an amplifier a-la Hypex) Also the date code on the above PCBs is 22nd June 2010. So it is a nearly decade old Class D design.

1556671439644.png


link to data sheet:
www.anaview.com/sites/default/files/PDS%20ALC0240-2300-I.pdf
 
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jackenhack

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#11
The attenuation of switching frequency is too little for my taste (note the above is without AES filter).
I don't understand why it's so hard to filter out way out of band noise in the design of a Class-D amplifier? It's so far away from the audio band; you don't need a steep filter. A straightforward low-pass filter without any special components would suffice. Well, as long as it's under 50kHz, it won't heat up my Elac Jet tweeters.

Still no great contender of all the amplifiers tested so far. I might have been spoiled by the measurement of the Massdrop THX headphone amplifier, but it shouldn't be impossible to get better results. It's kind of funny that the best-measured amp tested so far is a DIY kit.
This forum has spoiled me. I'm thinking of simplifying my livingroom setup by buying the KEF LS50 Wireless speakers connected to Roon, replacing my home built ProAc 2.5 Clones. But I want a verification by @amirm before purchasing anything. But this time, I'm going by ear.
 

amirm

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#12
This forum has spoiled me. I'm thinking of simplifying my livingroom setup by buying the KEF LS50 Wireless speakers connected to Roon, replacing my home built ProAc 2.5 Clones. But I want a verification by @amirm before purchasing anything. But this time, I'm going by ear.
Oh, no, I feel betrayed! :D
 

jackenhack

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#13
Of serious concern are the CapXon capacitors which in my experience are one of the absolute worst for venting and premature catastrophic failure
I've repaired a lot of stuff where that cheap brand has failed. Designed by engineers, finished by the penny pinchers of the economy department. Every failed unit is a lost customer. I don't get it. How hard can it be to install quality caps in a power supply?
 

vkvedam

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#15
Major issue: my pink panther models have given me notice that they like to go on strike if I don't increase their pay. They say the original agreement did not at all call for daily reviews. Apparently they go through a lot of work with make up and such to look good on camera. So let's raise some funds so that I can pass on the same to my "talent"
My favourite part of the review :)
 

confucius_zero

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#17
We should be able to do better for $1,000
I wonder what made you come to this opinion as it occupies a space close to the nad 7050 and marantz HD1 which share the same price bracket. All 3 are part of the top tier of the current chart. It also shows a well extended FR in the low end
 

GioF71

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#18
Thanks @amirm for the review.
This was one of my most desidered solutions for my desktop. Teac is a respected brand, its width is not excessive, and it has balanced input as well as some other RCA inputs. It was almost ticking all the boxes, but
a) declared power left something to be desired
b) lack of objective reviews
c) from one review I saw from an Italian reviewer, the movement of those (albeit very nice-looking) vu-meters depends on the output volume and at normal listening levels (at least for a desktop use) they barely move. They would have been a continuous disappointment.
d) not cheap

So I kind of left my heart on its gorgeous asthetics but I can't be happier with my Nord Acoustics NC502MP!!!
 

restorer-john

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#19
the movement of those (albeit very nice-looking) vu-meters depends on the output volume and at normal listening levels (at least for a desktop use) they barely move. They would have been a continuous disappointment.
They may be calibrated for 0dB at full (rated) output level. As such, they'd only be swinging significantly when very loud.

Or, they may just be pretty moving coil meters to look 'cool'.
 

PierreV

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#20
I wonder what made you come to this opinion as it occupies a space close to the nad 7050 and marantz HD1 which share the same price bracket. All 3 are part of the top tier of the current chart. It also shows a well-extended FR in the low end
I think the expectations were too high to begin with because of the number of DACs/Headphone Amps that delivered excellent measurements.

If we look at the summary chart, with the exception of the Hypex kit and the Neurochrome (which are definitely balanced single-purpose devices), we now have 3 devices that were panned (Marantz, Accuphase and now Teac) in the top tier... The Sonos being a weird exception seems to be awful in some scenarios and quite decent in others.

We have to accept that as the reality. I know some people like to focus on a single number out of context, say 110+ for the Khadas Tone Board and 85 for the Marantz and then rant about how low the brand has fallen and how much of a genius the KTB "designer" is. What is lost here is that something like the KTB is essentially a single component of all these integrated systems. Packing those components together in a convenient box is where the problems/losses start to show up. From the spec sheets, and assuming neither Hypex or Marantz are outright bull****ters, the pure amp component in the Marantz will measure, stand-alone, much better than the integrated solution.

And the proof is right here too: look at where topping/smsl can be found when we are talking more integrated devices or power amps...

It's all relative. The KTB is a wonderful alternative and a bargain compared to so-called high-end DACs if you need/want a stand-alone DAC. It is also incredibly inconvenient, limited and expensive on the whole compared to a decent AVR at $1000-$1500. Topping seems to implement some stuff really cleanly but is clearly incompetent in some types of things/more component designs.

We need to reset our expectations. DAC is "solved" in terms of audibility. The rest is not clearly solved (but maybe is in terms of audibility).

BTW, we keep talking about ABX testing and making fun of subjective testers. But I think it would also be interesting to ABX a power amp with 110 sinad vs an integrated with 85 sinad on reasonably easy to drive speakers. If one can't reliably tell the difference, it would show that the "more slam, more palpable" subjective bias has been replaced by the "but I have more sinad" objective bias...

And, tbh, I find the capacitor observation that @restorer-john made more disturbing than the lack of a few dBs here and there...
 
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