AIYIMA A20 Stereo 2.1 Amplifier Review

[Tontom]

It's not 12 dB/octave for me.
I measured 6 dB.
I actually assumed they used the same filters as, for example, the Wiim Ultra (24dB/octave).
I'm still considering whether to send mine back.

 

[caught gesture]

No need to ask Aiyima. Here is Amir's measurement.

Here is the calculated response of a 1st order HPF with 80 Hz cutoff frequency. The filter in the unit Amir tested was 1st order.
View attachment 493230

Spoiler: Python code

import numpy as np
from scipy import signal as signal
import matplotlib.pyplot as plt

norder = 1
hpf = signal.butter(norder, 1.0, btype='high', analog=True)  # For the filter, cutoff frequency is normalized to 1

wc = 80.0  # Actual required filter cutoff frequency
w = np.logspace(np.log10(10.0), np.log10(100000), 200) / wc
w, h = signal.freqs(*hpf, worN=w)
ymin, ymax, ystep = (-5.0, 5.0, 1.0)

fig, ax = plt.subplots(figsize=(8, 6))
ax.semilogx(wc*w, 20 * np.log10(abs(h)), '-', markersize=2, markeredgecolor='k')
ax.set_title('Butterworth order {:d} HPF frequency response'.format(norder))
ax.set_xlabel('Frequency, Hz')
ax.set_ylabel('Amplitude, dB')
ax.set_yticks(np.linspace(ymin, ymax, int((ymax-ymin)/ystep)+1))
ax.set_ylim(ymin, ymax)
ax.margins(0, 0.1)
ax.grid(which='both', axis='both')
ax.axvline(wc, color='green', lw=1, ls='--')
ax.axhline(0, color='k', lw=1)
fig.savefig('hpf_fr.png')
plt.show()

Aiyima says it is a 2nd order HPF at 12dB/octave. That’s what I hope it is as that is the same as the LPF on my sub. Who is correct?

 

[Tontom]

We'll see.

 

[Sir Sanders Zingmore]

I'm feeling like Amir should start putting a disclaimer on his reviews as this needs to be noted in almost every amplifier review it seems: the way Amir rates power is not how any manufacturer (or any other reviewer to my knowledge) rates power and you can't compare Amir's power rating to anyone else's. It's also somewhat iffy to compare between Amir's reviews as his method of taking power at the "knee", where the amp's distortion starts to increase rapidly, is inherently subjective and done by eyeball. To be clear, I have no issue with Amir's method as I understand the reasoning and it's consistent enough between reviews, but it does cause this issue where Amir's ratings are often very different from the manufacturer's specifications and we get these comments.

Let's look at the actual graphs shall we:

I'm unclear why there isn't agreement between the max power bar chart and the power versus distortion chart, as we can plainly see that the amp reaches about 200W before hitting 1% distortion (-40dB THD+N). Rating power at 1% distortion is common. We are still short of the 250W rating, but I don't see in Aiyama's specs how they did the rating so it may have been taking at an even higher distortion figure.

While not specifying the conditions for the power rating is bad practice, based on the graph this amp almost certainly can put out 250W into 4ohms as long as you allow for a fair amount of distortion.

Amir’s max power bars clearly show max power at 1% THD into 4ohms is about 175W. Miles short of the claimed 250w

It looks like we are getting a bit more than 100W into 8ohms on Amir's testing at 1%. Still falls a bit short of the spec, but pretty close

Sorry but how is 100w “pretty close” to the claimed spec of 150w?

 

[Tontom]

I also feel a little cheated by AIYIMA

 

[fwwwk]

Aiyima says it is a 2nd order HPF at 12dB/octave. That’s what I hope it is as that is the same as the LPF on my sub. Who is correct?

Essentialy my do or don’t. What are we missing here? Measuring amplification over 1/2 x frequency shouldn’t be a thing to discuss and I can not see a possibility for different measuring devices to variate this much either.

 

[Mark185]

The high-pass filter (HPF) is 12 dB/octave, and the low-pass filter (LPF) is 24 dB/octave. Initially, we planned to make the HPF 24 dB/octave, but due to the difficulty of ensuring potentiometer consistency in a fully balanced circuit, after multiple tests and adjustments, we ultimately changed the HPF to 12 dB/octave. We sincerely apologize for any confusion this may have caused.

This is the high-pass filter response curve measured in our lab using professional AP instruments, provided for your reference.
View attachment 493490

Sorry @AIYIMA but the A20 I purchased measures 6 dB/octave. I do not have Audio Precision but I am an electrical engineer and know how to use my test equipment. Your A20 amplifier is only 6 dB/octave on the high pass filter on the amplifier I purchased. I am also confused by your statement about a low pass filter. There is none.

I have purchased and praised other audio products you have made but this one does not live up to the marketing claims.

 

[AIYIMA]

Hi, sorry ... what Low Pass Filter? I missed that, how is this implemented? Thanks

 

[AIYIMA]

Hi, sorry ... what Low Pass Filter? I missed that, how is this implemented? Thanks

Hi!
The LPF (Low Pass Filter) here refers to the fixed low-pass filter on the SUB OUT output.
Anything above the 20–200 Hz range gets rolled off at 24 dB/oct, and this LPF is fixed, so it can’t be adjusted.

If you have any other questions, please feel free to ask — happy to help!

---

 

[caught gesture]

If you have any other questions, please feel free to ask — happy to help!

---

Any comment or further data on the HPF? Some people are insisting that it is a 1st order 6dB/octave filter after measuring it themselves.

 

[Tontom]

I think I'll keep the A20 after all, because the amplifier itself is really good.

I've set the high-pass filter (HPF) to 120 Hz to relieve my KEF LS50 speakers of low-frequency strain. I've set the subwoofer to 110 Hz for better crossover. I then had the 'Wiim Pro Plus' calibrated using RoomFit.
With the control set to 120 Hz, this means:

-3 dB at 120 Hz
-6 dB at 60 Hz
-9 dB at 30 Hz.
This is already a significant reduction, as the energy requirement in the bass range increases quadratically.

 

[RafaRafita]

Hi everyone, Can anyone compare it to the Fosi Audio ZA3? How does it compare in terms of quality and technical specifications?Moreover, has anyone owned both amplifiers and compared their sound quality? Should I consider upgrading to the A20 if I have the ZA3?What are your thoughts on this? Many thanks in advance. Best regards to everyone.

 

[ziggurcat]

Hi everyone, Can anyone compare it to the Fosi Audio ZA3? How does it compare in terms of quality and technical specifications?Moreover, has anyone owned both amplifiers and compared their sound quality? Should I consider upgrading to the A20 if I have the ZA3?What are your thoughts on this? Many thanks in advance. Best regards to everyone.

You can check out the review, and compare:

Fosi Audio ZA3 Amplifier Review

This is a review and detailed measurements of the Fosi Audio ZA3 stereo amplifier with balanced XLR inputs. It was sent to me by the company and costs US $149.99 with 48 volt power supply. The amplifier has really dressed up from its earlier origins of common enclosures in budget class...

www.audiosciencereview.com

 

[RafaRafita]

You can check out the review, and compare:

Fosi Audio ZA3 Amplifier Review

This is a review and detailed measurements of the Fosi Audio ZA3 stereo amplifier with balanced XLR inputs. It was sent to me by the company and costs US $149.99 with 48 volt power supply. The amplifier has really dressed up from its earlier origins of common enclosures in budget class...

www.audiosciencereview.com

Yes, I know, thank you, but I'm talking about a fair comparison of Fosi Audio ZA3 vs AIYIMA A20.

 

[RafaRafita]

I'll add that this is about listening. Not just the technical specifications on paper. Of course, I expressed myself, sorry!

 

[caught gesture]

I'll add that this is about listening. Not just the technical specifications on paper. Of course, I expressed myself, sorry!

It’s an amplifier without any audible distortion. Level matched with blind testing, you won’t hear a difference.

 

[RafaRafita]

Thanks

 

[SMen]

I'll add that this is about listening. Not just the technical specifications on paper. Of course, I expressed myself, sorry!

I don't have these two units, but I would be very surprised if you were to be making any meaningful kind of upgrade by changing from one to the other ... in fact probably in this instance just looking at the specs would probably be enough (in this specific instance ... especially as the Aiyima does not seem to be properly PFFB). They are not far apart in price either ... maybe the difference is explained in the filter. I'd stay happy with the Fosi.

In fact, it probably is all about the filter, and whether you have a need for this, rather than listening vs technical specs.

 

[obsessive9119]

Hi everyone, Can anyone compare it to the Fosi Audio ZA3? How does it compare in terms of quality and technical specifications?Moreover, has anyone owned both amplifiers and compared their sound quality? Should I consider upgrading to the A20 if I have the ZA3?What are your thoughts on this? Many thanks in advance. Best regards to everyone.

I have the ZA3 and was considering switching to this for the HPF and (I was hoping) better on paper performance. The A20 has slightly less power and no better perf for the most part, so personally I won’t be “upgrading”.

 

[RafaRafita]

I understand, thank you for sharing this information. Also, what kind of operational amplifiers (OP-AMPs) are you using? Are they stock or something else?