AIYIMA A70 Stereo Amplifier Review

[lewdish]

I wish they would just make a multichannel power amp w/ no bells & whistles other than a 12v trigger

 

[Roland68]

Lol, and why would you take the Topping over the Aiyima?

Where should I start...?
- 1 x TPA3255 per channel
- Topping understood how to correctly wire the input of the TPA3255 (also applies to the output)
- Therefore almost equivalent performance on RCA and XLR
- Designed for 52 volts
- Much higher performance when you need it
- Even higher performance is possible because the power supply is undersized for 2 x TPA3255
- Very stable and insensitive operation, both with capacitive and inductive loads
- Extremely good channel separation
- Very load-independent frequency response and stable operation
- As with almost all topping devices, an extremely well-developed and low-noise power supply, especially for the small signal range

As I said, I'll be happy to take it from you for the price. Would save me the trouble of assembling two TPA3255 EVM boards myself.

 

[Bruce Morgen]

A70 has started pre-sale, and you can get a 10% discount for pre-sale.

AIYIMA A70

AIYIMA's latest TPA3255 power amplifier has PFFB function and is equipped with 48v5a GAN power supply. Parameter:Chipset: TPA3255+NE5532Replaceable operational amplifier chips: RT3609SM, OPA2604, OPA2134, LM4562, JRC5532, OP275GSZ, OPA1612, MUSES01/02/03...

www.aiyima.com

IMO there needs to be a no-PSU purchase option. Many veteran "chip amp" users already own suitable PSUs.

 

[Kevinfc]

I gave the answer. It makes little sense to get the half power supply just to save $30.

I understand the logic and agree. Even if the 5a power supply had better numbers, I’d have no interest in buying it. There’s plenty of other amps offering a smaller power supply with similar features using that chip. To me, the point of the A70 is more features AND much more power.

 

[Kevinfc]

IMO there needs to be a no-PSU purchase option. Many veteran "chip amp" users already own suitable PSUs.

At that price I’d bet you’re stuck with buying one with a 5a supply and replacing it. Maybe you can find one on a Chinese website.

 

[Kevinfc]

Personally, I’d like to get my hands on just the 10a power supply

 

[sejarzo]

Personally, I’d like to get my hands on just the 10a power supply

I wonder what they will go for on the Aiyima site when they do start selling it on their power supply page. My guess is $65.99 as it carries a $30 premium when purchased with the amp over the 48v/5A PSU, which now sells separately for $35.99.

 

[Kevinfc]

I wonder what they will go for on the Aiyima site when they do start selling it on their power supply page. My guess is $65.99 as it carries a $30 premium when purchased with the amp over the 48v/5A PSU, which now sells separately for $35.99.

Good call, I’ll keep an eye out on their website.

 

[restorer-john]

In what world would this term a problem? Sorry but that sounds a little bit like woke BS to me. The term Chi-Fi is used across all of the internet regarding Chinese hifi products. Some people just try to get offended by everything.

I agree, and Chi-Fi is a cute term, but carries with it a somewhat derogatory element due to all the bargain basement stuff sold by the millions. Just call it Chinese HiFi if you want, just like US HiFi, Danish HiFi, whatever- nobody can complain about that.

 

[sejarzo]

Good call, I’ll keep an eye out on their website.

Unsure if it will be that cheap, though, as their main competitor is selling a 48V/10A GaN supply for $89.99 now. Yowza.

 

[Multicore]

TL;DR version:
It is a limitation of Amir's reactive load box, and it prevents the reactive load testing on some amplifiers due to the design of these amplifiers. This limitation is not relevant to the vast majority (99%+) of passive loudspeakers, which are what these amplifiers intended to drive.

More detailed version (will need some basic understanding of electrical circuits):
The TI class-D amplifier chip that does the majority of the work in this amplifier can operate in 3 different modes:
View attachment 355026
The TI TPA 3255 chip used by the A70 has 4 amplifier sections. It can drive 4 speakers in its SE (single-ended) mode; 2 speakers in its BTL (bridge-tied load) mode, or simply bridged mode; and 1 speaker in its PBTL (parallel bridge-tied load) mode. The A70 is configured to operate in the BTL mode.

In the SE mode, one side of the speaker (usually the negative terminal), is connected to electrical ground inside the amplifier. In the BTL mode, Output B is configured to have its output at the reversed polarity of Output A (similar for outputs C & D). The combined output of OUT A and OUT B doubles the voltage output to the speaker. By "bridging" together outputs A & B, the amplifier can double its output voltage capacity without having to increase the power supply voltage as in the SE mode (i.e. use the same power supply). The output current limit of the BTL mode remains the same as SE mode, and since 2 amplifier sections are together driving the speaker, the "apparent load impedance as seen" by each amplifier section is half that of the speaker. That's why for bridged amplifiers, the rated minimum speaker impedance is usually twice that when they operate in the single ended mode.

To counter the output current limitation, in the PBTL mode the amplifier is configured to 2 BTL sections in parallel (each providing half the demanded output current), thereby doubling the current output capacity. The minimum required speaker impedance in the PBTL mode is the same as in the SE mode, but with output power is increased by ~4X.

The issue with Amir's complex load is that it expects the negative output of the amplifier to be connected to the electrical ground. Since this is not the case with the BTL or PBTL modes, the complex load box doesn't work all the time for bridged amplifiers. This is not a problem with the vast majority of passive speakers as they don't need nor expect the negative amplifier output to be at electrical ground. Exceptions may include some electrostatic speakers and the older Polk SDA (don't know about the current ones).

OMG. Thank you! What a fine education you can get at ASR. It's really amazing and gratifying. I understand almost all of what you wrote. Only a couple of points...

The issue with Amir's complex load is that it expects the negative output of the amplifier to be connected to the electrical ground.

How does that happen? I would imagine a load box to be a network of high power resistors, capacitors and inductors. Why would that expect something?

Does this have something to do with the connection between one side of a signal path and safety ground?

 

[Chilli]

This is a great little amp and measures very well. Good job Aiyima. I
'm OK with the sub out, myself. I think it might suit those who need to diy or cross a driver higher, but less so for this who have a proper sub, and you can just set it high. I feel the criticism in this is a tad harsh. However, we all have different needs, so each to their own.

 

[restorer-john]

So what about solid, sincere or even emphasized hi-fi? And how comes, that here it is not China which comes into customers’ minds immediately?

Not sure what you mean.

There's absolutely no issue with using the country of origin as a partial descriptor. Or even an area within a country.

East coast vs west coast sound in speakers was a commonly used term. UK sounding was another. I don't think we ever (in Australia) had a big enough industry to get a "sound" or quality descriptor.

Right now, Chinese HiFi still has a baragin basement, stripped down, anodised and extruded connotation attached to it, with dubious ergonomics and often dreadful physical design, BUT that is changing fast. In the last 5 years, the offerings have improved exponentially, although the prices have gone up with the quality.

I don't know what it will take to establish an actual Chinese HiFi brand that can stand on its own on the world stage, if that can be done. It takes decades. It took the Japanese 30 years after WWII to get their HiFi brands totally accepted to the point they were a number one choice, not a cheap alternative.

 

[Lambda]

GaN semiconductors, e.g. diodes and transistors, are significantly more efficient. This allows smaller, cooler and more powerful switching power supplies to be built, but above all more efficient ones. This can improve the efficiency by 5-10%, which would also be the measurable difference.
Information about gallium nitride / GaN semiconductors can be found online.

I know what GaN semiconductors are and i have used them multiple times.

GaN has become a blanket marketing buzzword.
They are not "more efficient" but if done right they can be used to make Smaller converters or more efficient ones

So why should the user care how they get the efficiency and power density. and how would you test this?
what matters is that the whole system performs to spec

 

[Ze Frog]

Another extremely impressive product given the price. Hopefully the aesthetics will improve over time though. The WIIM amp for instance is a really handsome beast and I think that's one thing that will sell these kinds of things more.

 

[restorer-john]

I know what GaN semiconductors are and i have used them multiple times.

GaN has become a blanket marketing buzzword.
They are not "more efficient" but if done right they can be used to make Smaller converters or more efficient ones

So why should the user care how they get the efficiency and power density. and how would you test this?
what matters is that the whole system performs to spec

A 480W SMPS brick sitting on shag rug under the sofa that doesn't catch fire and burn your house down is kinda important.

These outboard supplies are getting ridiculous- look at the "amplifier" and its power supply- it's stupid looking if you ask me.

 

[Walter]

As Amirm says , at this price range, it makes little sense to skimp on the power supply to save $30. Maybe if you are buying it for nearfield use and you have efficient speakers, where you know you will never drive it near its limits. But then if you ever decide to repurpose it, you've lost the extra flexibility the higher amperage PSU provides, so...

 

[Kevinfc]

A 480W SMPS brick sitting on shag rug under the sofa that doesn't catch fire and burn your house down is kinda important.

These outboard supplies are getting ridiculous- look at the "amplifier" and its power supply- it's stupid looking if you ask me.

This one doesn’t look very large, particularly for a 10a. I can’t find any similar brick power supply, they’re all 48v 5a. That in itself is an innovation for this product.

Like you I have mixed feelings about an outboard power supply, but it’s for aesthetic reasons only.

 

[dzerig]

Whatever happened to the days of manufacturers giving their power at so many watts with such and such distortion? Too many companies refuse to give the real power (here it is 77 watts) of their gear.

 

[dzerig]

With this kind of performance, it will be interesting to see what a 8,11, or 16 channel multichannel amplifier could look like, using TI Class D chips and a integrated power supply, sort of like a modern Lexicon DD8.

On the other hand 4 x 220 = $880 at which point the NC252MP seems to be a better deal at “just” 2x the price.

It would look like 4 to 6 power bricks attached to a small box.