AIYIMA A70 Stereo Amplifier Review

[AIYIMA]

 

[AIYIMA]

 

[JSmith]

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Love your companies work Aiyima, but please don't go down the Fosi path of promoting this op-amp rolling nonsense.


JSmith

 

[Talisman]

Love your companies work Aiyima, but please don't go down the Fosi path of promoting this op-amp rolling nonsense.


JSmith

I understand what you feel, but these companies are not scientific promotion bodies, they have to make money, by granting this possibility they can offer a well-designed product and at the same time attract all the users who like to mess with the design without this creating a disadvantage for us

 

[JSmith]

attract all the users who like to mess with the design

True... but then I've pointed out this aspect to Fosi before (fallen on deaf ears), that they should be careful directing customers to modify a product that is meant to be "fit for purpose" to start with and what implications this may have for them in certain countries (depending on the local consumer laws).


JSmith

 

[Doodski]

True... but then I've pointed out this aspect to Fosi before (fallen on deaf ears), that they should be careful directing customers to modify a product that is meant to be "fit for purpose" to start with and what implications this may have for them in certain countries (depending on the local consumer laws).


JSmith

Anything electronic that I released back to a customer that had been MODed, had a mains transformer tampered with or was not 100% like new in safe operation was released as, "For test purposes only." That way I was not responsible for any further operation of that unit that the customer was responsible for. The insurance can be nulled and voided in some circumstances I was advised although I don't know the specifics of that. So selling gear that is made to be tampered with by non experts seems like a recipe for disaster llegally speaking.

 

[AIYIMA]

This is a power amplifier board taken directly from a mobile phone. We guarantee that no components will be modified.

 

[Mnyb]

Anything electronic that I released back to a customer that had been MODed, had a mains transformer tampered with or was not 100% like new in safe operation was released as, "For test purposes only." That way I was not responsible for any further operation of that unit that the customer was responsible for. The insurance can be nulled and voided in some circumstances I was advised although I don't know the specifics of that. So selling gear that is made to be tampered with by non experts seems like a recipe for disaster llegally speaking.

The opposite of the seal/sticker with “no user serviceable parts inside”

I’m quite sure that a dunning Kruger affected tinkerer that’s the target for such a product could not keep the butter fingers away from other stuff while the case is open , not just the op-amp

I’m more concerned that making the general amp design safe to operate with a range of op amps migth not be the optimal design for,the circuit at hand ?
Said butterfingers will not stick to the recommended list of optional Op-amps but read what some guru said out of context on some website and stick whatever fits the socket in there .

 

[Doodski]

I’m more concerned that making the general amp design safe to operate with a range of op amps migth not be the optimal design for,the circuit at hand ?

As @solderdude stated clearly a couple of days ago regarding OP amps and the OP amp peripheral circuitry the ratio of the peripheral resisters and reactance too if used in the OP amp circuit peripheral determines the gain of the circuit. Not the bare OP amp total specification for maximum gain. So OP amps can be swapped without changing the gain of the OP amp circuit once it is calibrated from the factory by selecting peripheral parts for the OP amp circuit gain level. It's amazing that this is the way and is what makes it OK for newbies to experiment with OP amp rolling and test drive different OP amps. I had somehow forgotten this information from my OP amp education comprised of a couple of months of study decades ago. Thank you @solderdude for bringing me back up to speed on such fundamental theory of OP amps. It is safe to swap the OP amps providing the rest of the PCB circuitry is not tampered with.

 

[Xcaliber]

Most of these cheap TPA3255 amps with small footprint is ideal for desktop, workshop, kitchen, and garage for casual listening, very good pairing with low budget or old bookshelf speakers. At least for me the main attraction of these little amps is the price point, and I feel the original A07 and TB10D are still the king of value and sounds damn good for the money.

This new A70 with 48v10a power brick cost 4x more than A07 and TB10D! but it surely ain't going to sound that much better/louder/cleaner in the real world application, could it? The power output is on par with most other cheap TPA3255 running on'wimpy' 32v/36v5a so what is the compelling reason to pay 4x more for something that have no practical improvement in the real world?

Beside, do people actually use this stuff as their long term primary amp to feed their $1K~3K speakers?

 

[Mnyb]

As @solderdude stated clearly a couple of days ago regarding OP amps and the OP amp peripheral circuitry the ratio of the peripheral resisters and reactance too if used in the OP amp circuit peripheral determines the gain of the circuit. Not the bare OP amp total specification for maximum gain. So OP amps can be swapped without changing the gain of the OP amp circuit once it is calibrated from the factory by selecting peripheral parts for the OP amp circuit gain level. It's amazing that this is the way and is what makes it OK for newbies to experiment with OP amp rolling and test drive different OP amps. I had somehow forgotten this information from my OP amp education comprised of a couple of months of study decades ago. Thank you @solderdude for bringing me back up to speed on such fundamental theory of OP amps. It is safe to swap the OP amps providing the rest of the PCB circuitry is not tampered with.

Not always there could be bandwidth concerns it can get unstable and oscillating, maybe due to parasitic coupling or peripheral components that would not bother one amp but do bother some other op amp ?

Also nois can differentiate them ?

 

[tmtomh]

If I'm Aiyima, my takeaway is that there's no point in posting an image of the internals because the folks who are interested won't believe it anyway.

This is a power amplifier board taken directly from a mobile phone. We guarantee that no components will be modified.

View attachment 356049View attachment 356051

Nice - thank you!

 

[Xcaliber]

But they have advantages. I am looking for a more powerful desktop amp to drive my KEF R3. Naturally the Apollon Audio et al amps are way bigger due to the internal PSU. They dont really fit on my desk but having a PSU on the ground would be OK.

When portable amps are too big to fit on the desk, a short trip to homedepot to get a few L brackets to mount the amp Under the desk may be the ticket.

 

[Doodski]

Not always there could be bandwidth concerns it can get unstable and oscillating, maybe due to parasitic coupling or peripheral components that would not bother one amp but do bother some other op amp ?

Yes, you are correct.

Also nois can differentiate them ?

This is an aspect of OP amps that I am not thoroughly educated in anymore. I have forgotten details and some theory of OP amps. But it makes sense that anything different can differentiate them apart from one another. OP amps are a intriguing device in that they are so immune to bad stuff, reject bad stuff and can do so many functions just by swapping out peripherals and changes in the circuit layout. I need to get a proper OP amp theory textbook and refresh everything in my mind before I get to talking fancy like a expert on OP amps. Maybe @solderdude if he has the time can follow up with this thread and get us properly informed.

OK, I searched my bookmarks and have a link for a textbook in PDF format written by Thomas J Floyd and titled Electronic Devices Electron Flow Version. This will require sleep and then a little bit of time for a very basic refresher on OP amps. I was thinking of the textbook written by the same Floyd author titled Semi Conductor Devices Fundamentals which is what I actually studied decades ago and it has almost ~900 pages of ~1500 pages devoted to OP amps where the PDF I have now is only maybe a couple hundred pages I'm guessing.

Even a low budget amp like the Aiyima A70 OP amp circuitry will be a decent design. OP amps are just that way.

 

[Mnyb]

Yes , I just saw the sockets on the picture some will fiddle .

Was it not fad of using high speed op-amp for tinkering ?

I don’t know details about electronics but many op have different applications they are more suited to and some are more general purpose. (I’m an EE I have BsC in control and maintenance specialised in electric power and motors, know just enough to be dangerous regarding circuit design )

For human listening it’s been good since the NE5532 and it’s siblings where invented there is som kernel of truth to some audiophile nonsense the ua741 one of the very first op’s where miss used in audio application and it was a stretch .

Now we have even better ones , so it’s strange to obsess so much about them ? Just let them be

 

[MCH]

This is a power amplifier board taken directly from a mobile phone. We guarantee that no components will be modified.

View attachment 356049View attachment 356051

Thank @AIYIMA:GUO for sharing. Love those smd caps on through hole footprints. Got the inspiration from the max thread?
There are quite some unpopulated parts, are you aiming at v2 with some additional feature?
Thanks!

 

[Doodski]

Was it not fad of using high speed op-amp for tinkering ?

Yes, the slew rate and the resulting upper frequency response of the OP amps was/is cool and maybe is more so for some of the more fluent newbies that OP amp roll. They expect better highs and stuff I guess. I think it's cool that they get their feet wet in electronics by OP amp rolling Aiyima amps like the A70 and checking out the PCBs and whatever they do when inside there mucking about. I think they need to start somewhere and even if it's fantasy it's still getting experience.

 

[trungdtmc]

Thank @AIYIMA:GUO for sharing. Love those smd caps on through hole footprints. Got the inspiration from the max thread?
There are quite some unpopulated parts, are you aiming at v2 with some additional feature?
Thanks!

If I'm not wrong, those 4 capacitors are signal coupling capacitors, not decoupling capacitors for the main power source. Using x7r in that position maybe not good idea
Another problem is the heat dissipation of the inductor. I noticed that the measurement results were very different between when first turned on and after hot use on the A07 Max

 

[T&T]

This is a power amplifier board taken directly from a mobile phone. We guarantee that no components will be modified.

View attachment 356049View attachment 356051

Nice pictures, who much will be this A70 without the power supply?

 

[Walter]

Calling it so, does a complete dis-service and is a slur against an actual brick

You've clearly never seen the bricks they use here in Cambodia!