Op-amp Rolling Using AIYIMA A07

[pma]

I have made my homework and re-measured AIYIMA A07 with NE5532, LME49720 and OPA2134. My measuring system has been improved since the time of my first measurements of the A07. However, no breakthrough findings, but good enough to debunk some strange myths.

I measured the A07 supplied from SMPS (Meanwell RS-100-24) set to 27Vdc output and the amplifier was loaded with 4R7/200W resistor.

Below are the results.

1. THD vs. output voltage with 3 opamps:

It can be seen that the plots are almost identical. BTW, very good result.

2. THD vs. frequency at 20W/4.7ohm @BW48kHz

Again, the plots are identical, only at very low frequencies NE5532 is lower due to its lower noise. I do not like that result very much (THD rise with frequency), however it is typical for TPA3255 class D amps measured with BW48kHz. I would like to add that the NE5532 is a better choice for AIYIMA A07 than the LME49720. The reason is that 5532 has lower input current noise than 49720. The thdfreq plot of 49720 x 5532 is similar to 2134 x 5532 plot. 2134 has higher input voltage noise than 5532. Once again, 5532 is the technical winner due its versatility. But nothing to be audible.

Next plot is THD vs. frequency measured with 90kHz bandwidth. We can see how the distortion proportionally rises with frequency, if we demask the usual trick with 20kHz BW limited THD or THD+N. However, this has nothing in common with the opamp used.

So, if we use decent opamps, we can get nothing from opamp swapping in this or similar amplifiers. Nothing but troubles, if we used improper parts. People just want to play with and they need to have certain beliefs, that's all.

P.S.: 5W "benchmark"

SINAD = 87.5 dB (NE5532)

 

[pma]

I think this is quite interesting - though the amp is supplied from the SMPS which usually adds quite high artifacts at 70-80 kHz, the extended BW measurement is quite clean, even if I use no LPF measuring filter. The 2 big capacitors are only to eliminate output Vs/2 DC voltage from the single supply bridged A07 design.

 

[SnakeLord]

But what about some discrete class A high-end opamps like Bursons, Sparcos and so on? Yours are just too similar on the paper.
I mean you cant really expect an moist sound with bigger soundstage from some cheap IC LME49720.

And whats the point of making the rolls on this limited cheap amp? You clearly need an Apollon or Audiophonics Hypex/Purifi with custom buffer to have a benefit from rolling.

Also why not using an DAC/HP amp for the rolling? Thats where the real magic happens! Its day n night!

 

[DVDdoug]

But what about some discrete class A high-end opamps like Bursons, Sparcos and so on? Yours are just too similar on the paper.

What's the audio problem you expect to fix?

Op-amps are not critical in line-level audio applications. It's usually the least-critical circuit in the amplifier and it makes the least difference. People swap op-amps because they are often in a socket and it's easy. And since they aren't critical it usually works. Swapping a MOSFET requires soldering and if you don't choose a compatible MOSFET bad things can happen. Unsoldering and replacing the main chip in class-D amplifier is very difficult and you probably won't find a compatible drop-in replacement.

If you are making a high-gain preamp (a phono preamp or a microphone preamp) any noise generated in the op-amp gets amplified so you generally want a low-noise op-amp.

I mean you cant really expect an moist sound with bigger soundstage from some cheap IC LME49720.

Amplifiers don't affect soundstage (in Controlled Audio Blind Listening Tests) unless the left channel is louder than the right or there is some other gross defect.

And whats the point of making the rolls on this limited cheap amp? You clearly need an Apollon or Audiophonics Hypex/Purifi with custom buffer to have a benefit from rolling.

Again, what do you think is wrong with the "cheap" amp? If you can't hear a defect there's nothing to improve.

Also why not using an DAC/HP amp for the rolling? Thats where the real magic happens! Its day n night!

You'd be surprised how those "night and day" differences go-away in a controlled blind listening test.

And there's no "magic". With electronics there is ONLY noise, distortion, and frequency response. (With speakers it's mostly frequency response but room acoustics complicate things.) Audiophoolery explains the characteristics of sound quality.

 

[capslock]

Wow, - 97 dB HD3 without PFFB is quite an achievement. When did you buy these amps?

Back in 2021 they looked like this makeing me wonder if Aiyima added some PFFB without advertising:

'AIYIMA A07 TPA3255 Review (Amplifier)'

Jan 1, 2021

This is a review and detailed measurements of the AIYIMA A07 desktop amplifier based on TPA3255 class D amplifier chip. It was kindly purchased new by a member and drop shipped to me. The cost is US $72 on Amazon including prime shipping. And as of this shipping, it also included a 32 volt, 5 amp switching power supply. Member also purchased and sent me a 48 volt/3 amp power supply which I also tested.

The case is standard budget audio affair:

The volume control feels cheep but does the job. The back panel terminals were way too small for my binding posts...

• amirm
• Replies: 2,270
• Forum: Stereo and Multichannel Amplifier Reviews

• 

 

[Nzama]

What's the audio problem you expect to fix?

Op-amps are not critical in line-level audio applications. It's usually the least-critical circuit in the amplifier and it makes the least difference. People swap op-amps because they are often in a socket and it's easy. And since they aren't critical it usually works. Swapping a MOSFET requires soldering and if you don't choose a compatible MOSFET bad things can happen. Unsoldering and replacing the main chip in class-D amplifier is very difficult and you probably won't find a compatible drop-in replacement.

If you are making a high-gain preamp (a phono preamp or a microphone preamp) any noise generated in the op-amp gets amplified so you generally want a low-noise op-amp.


Amplifiers don't affect soundstage (in Controlled Audio Blind Listening Tests) unless the left channel is louder than the right or there is some other gross defect.


Again, what do you think is wrong with the "cheap" amp? If you can't hear a defect there's nothing to improve.


You'd be surprised how those "night and day" differences go-away in a controlled blind listening test.

And there's no "magic". With electronics there is ONLY noise, distortion, and frequency response. (With speakers it's mostly frequency response but room acoustics complicate things.) Audiophoolery explains the characteristics of sound quality.

What about time and phase?
Isn't it part of our perception and one that gets usually messed up with amplification and reproduction with speakers?

 

[SnakeLord]

What's the audio problem you expect to fix?

In particular i am looking for some really deep, tight, hot and moist bass which will satisfy and please my ears.
I cant get no satisfaction.

 

[NotInYourHead]

In particular i am looking for some really deep, tight, hot and moist bass which will satisfy and please my ears.
I cant get no satisfaction.

That'd be the room's fault (or speakers, if their low end is lacking).