AIYIMA A70 Mono Amplifier Review

[EddNog]

It's ugly, but at least it's symmetrical in design!

As for seemingly duplicated subwoofer controls, it's because the large dial on the front controls the low-pass frequency crossover point of the speaker-level outputs on the back, whereas the small knob on the back controls the low-pass frequency crossover point of the RCA LFE output.

You know, so if you wanted a really huge active subwoofer for the deep subbass, you can attach that to the LFE, and then separately you can drive a smaller passive subwoofer from the speaker level outputs for the upper bass. Or something. I don't know, I made this last part up, I'm not actually recommending it.

-Ed

 

[EddNog]

ieema?? A bit like View attachment 400441???? I'm guessing though!

Best chuckle I've had today by far. Thanks so much for this post.

-Ed

 

[Yevhen]

Is there a beter way to rate the amplifier with one number as the alternative to SINAD at 1kHz?


''Good'' amplifier, SINAD 94dB

''Bad'' amplifier, SINAD 89dB

 

[Multicore]

Is there a beter way to rate the amplifier with one number as the alternative to SINAD at 1kHz?


''Good'' amplifier, SINAD 94dB

View attachment 400539
View attachment 400542



''Bad'' amplifier, SINAD 89dB

View attachment 400541
View attachment 400544

Sinad is like a Wine Spectator rating. There's way too much complexity involved to bundle into one number.

 

[tomtoo]

Not see where the tpa3255 can play his good parts in mono mode here. In theory it could go down to 2ohms. But not testet ? At 2ohms it could be interesting as a sub amp. But no info ? Not happy with the info at the moment. From my point of view a tpa3255 in mono makes only sense at 2ohms. You know more? Cool tell me?
At 2ohms it should be in the 400W region. Not bad for a 100$ amp. And who cares about +1 db at 30k if you use it as a sub amp? Two 15inch in parallel at 400W can be bad . So from my point of view its a little the wrong test. Testing a sports car on the dirt track and vice versa.

 

[JDS]

This is a review and detailed measurements of the AIYIMA A70 Mono TI TPA3255 based class D amplifier. It was sent to me by the company and is on sale for US $116.
View attachment 400113
The on/off and input type selectors have good quality feel to them as do the rotary controls. Right one is volume but left one had my scratching my head. Subwoofer frequency? That is something you set once so you don't need front adjustment. Even if you did, what is one in the back that has the same name?
View attachment 400114
As is, measurements showed that neither made a difference in frequency response of the speaker output. If you however toggle a switch underneath, the front control at least becomes active, setting the high frequency roll off. I could not figure out what the back control did. Reading the instructions didn't help but my conclusion was that the switch turns the amplifier into one that drives passive subwoofer (woofer and no amp). Passive subs have fallen out of favor in US at least for more than two decades. You can get ultra low cost subs that are active. AIYIMA has seemed to gone to great lengths to implement such a functionality with dedicated front and back controls. It is quite puzzling to me. Hopefully you all didn't talk them into this!

Nice to see trigger input so amp can be woken up by the source having the same output. And inclusion of extra gain for RCA solves the battle of what the gain should be by default. I like the default of it being off. But some want higher gain (which brings with it more noise and potentially channel imbalance).

I forgot to take a picture of the power supply but it is GaN based, 48 volt @ 5 amp for total of 240 watts in a relatively compact package. In use neither the power supply, or the case (top or bottom) warmed up let alone get hot. Either thermal management is very good or hot stuff inside care isolated from the case.

Note that there is another AIYIMA A70 amplifier (without mono). As with that unit, the mono version here implements post-filter feedback (PFFB) so should have high level of isolation from load/speaker dependency compared to units without. We will measure this.

AIYIMA A70 Mono Measurements
Let's start with XLR input at max volume:
View attachment 400116

Distortion is at inaudible -110 dB so noise dominates SINAD at 94 dB, placing the A70 mono at the top of the "competent" group of amplifier we have tested:

View attachment 400118
View attachment 400119

RCA input is similar despite higher gain:
View attachment 400120

I am happy to see 25 dB gain here as that is what I think companies need to target unless max power is not reached with 2 volt input.

Frequency response test shows that PFFB is working, sans a bit of increased output impedance:
View attachment 400123
Given that the 4 ohm also peaks at 20 kHz, the 8 ohm peak is now 1 dB higher than mid frequencies which may be audible to some young people.

SNR is excellent and matches spec fully:
View attachment 400124

I was surprised by the increasing intermodulation distortion in low frequencies in multitone test:
View attachment 400125
It is not something I have seen in other implementations. Fortunately our hearing threshold is pretty high at lower frequencies so likely not audible. The rise in the same at higher frequencies is typical:
View attachment 400126

Let's measure available power:
View attachment 400127
View attachment 400128
View attachment 400129

Sweeping at different frequencies we see the jump in distortion at lower end of the spectrum (20 Hz):
View attachment 400130
On positive front the curves are much smoother and don't rise as much as some other implementations.

Power is nicely maintained across full audible spectrum (with a degree of error):
View attachment 400132

I went to test the amp with my Loadbox reactive load but sadly, found the load box not communicating with the PC anymore.

Here is the impressive warm up performance:
View attachment 400133

I didn't take a thermal image because as I noted in the intro, the amp and its supply were at room temperature more or less.

Conclusions
AIYIMA A70 MONO amplifier brings highly competent performance to the table with performance that beats majority of amplifiers I have tested. Yet it costs so little. Having balanced input, selectable gain for RCA and trigger are much appreciated. I am at a loss as to what the subwoofer features are about but fortunately, they are disabled using a switch. To be clear, what we/I want is to roll off the main output and have an unmodified output for sub. The sub will have its own filtering. It is the mains that needs filtering.

I am going to recommend the AIYIMA A70 Mono amplifier.
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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Sure, most "ready to wear" subwoofers nowadays are active. But for my HT I home brewed an infinite baffle box (2 x 15" drivers) that mounts under the floor, and tuned it with Dirac. So all I need is a reasonably powered, quiet Class D mono amp. This one falls a little short on power for my system, but otherwise seems like a reasonable compromise.

 

[amirm]

Is there a beter way to rate the amplifier with one number as the alternative to SINAD at 1kHz?

The Cambridge was knocked down due to poor performance of its DAC. If it were an amp only, it would get a "recommended" ranking as well.

 

[pma]

Is there a beter way to rate the amplifier with one number as the alternative to SINAD at 1kHz?

You are absolutely right, 1kHz 5W SINAD can be called as almost pointless number. And its use as a sound quality comparison number confuses crowds of laymen ASR readers.

 

[Talisman]

Aiyima always follows Fosi's lead—where Fosi goes, they follow. It makes me smile a bit. Since the V3, they've started cloning Fosi’s ideas and innovations, both in terms of technical solutions and implementations. Of course, competition benefits consumers, but I always get the feeling they’re like that classmate who doesn’t have ideas and peeks at the smarter student’s paper.

 

[TonyJZX]

i kind of agree... companies respond to each others product lines if there's success ie. sales to be seen

HOWEVER I would give kudos to Aiyima for doing this 'subwoofer amp' thing too - they saw how maybe selling single units as sub amps could be useful?

Its their odd implementation of it i'm not a fan of

in the original thread the Aiyima rep. tried to explain what the front panel and rear sub output does but yeah... I mean... if you are trying to make complex products then you need to follow it up with clear usage diags or whatever on your site AND in your manuals

I dont think Aiyima wins anyone over with their implemenation of whatever they thought was going on with this unit.

It reminds me of that Douk A100 whatever that was announced here. I'm shaking my head with both these devices.

 

[MCH]

Aiyima always follows Fosi's lead—where Fosi goes, they follow. It makes me smile a bit. Since the V3, they've started cloning Fosi’s ideas and innovations, both in terms of technical solutions and implementations. Of course, competition benefits consumers, but I always get the feeling they’re like that classmate who doesn’t have ideas and peeks at the smarter student’s paper.

Probably, but fosi also got very much inspired by the 3e audio boards, and let's not forget that Aiyima were the ones that bring the tpa3255 to the masses and particularly to this forum with the original A07. One could argue that all these amps are descendents of it.... credit to where it is due.

 

[AIYIMA]

Thank you all audio enthusiasts for your attention to A70 Mono! This is an explainer video about active vs passive subwoofers, click on the link to learn more.

If you have any questions, please leave a comment and let’s enjoy music together!

 

[gvl]

Is there a metric to rank pride of ownership?

 

[catch22]

You are absolutely right, 1kHz 5W SINAD can be called as almost pointless number. And its use as a sound quality comparison number confuses crowds of laymen ASR readers.

''Good'' amplifier, SINAD 94dB
View attachment 400539
''Bad'' amplifier, SINAD 89dB
View attachment 400541

1KHz 5W SINAD has long been used as the single metric for ranking.
These two graphs however is a good example that the 1kHZ 5W SINAD is not always a good represention of SINAD across the spectrum.

Can the single SINAD metric be bettered?
To replace the 1KHZ SINAD with the average SINAD across 0Hz to 20KHz?

 

[beefkabob]

Multitone is unacceptable IMHO.

 

[EJ3]

It seems to be "not BAD" but what the controls actually do and how, is an issue.

 

[mhardy6647]

Pink panther wants pink knobs, that is how the universe is running.

I mean... there are options... on the aftermarket.
e.g.,

Knob - Small, Indicator Line, set screw | Antique Electronic Supply

The P-K380 is a high quality Davies 1510 clone. This classic design can be found on countless pedals, synths, amps and other equipment. The set screw uses a metal insert for additional stability and durability. This knob has an infilled painted indicator and fits 1/4" (6.35mm) pot shafts. The...

www.tubesandmore.com

Knob - Chicken Head, Push-On, for knurled shaft | Antique Electronic Supply

High quality black plastic chickenhead knob. 1-1/4" in length. Push-on for split knurled shaft.

www.tubesandmore.com

 

[Multicore]

ieema?? A bit like View attachment 400441???? I'm guessing though!

I've decided to go with aye-EE-why-EE-mah

 

[Robbo99999]

I've decided to go with aye-EE-why-EE-mah

Ha, I really don't know how it's supposed to be pronounced!

 

[ampguy]

My feeling is this is an amp for those that like to tinker. The dual sub filters will likely be may be redundant with the subs filters, but will let folks listen to both filters, and may actually prefer say the amps to the subs.