AIYIMA A70 Stereo Amplifier Review

[Audionaut]

because the bass sounds like it's not DC-coupled

How does a not DC coupled Bass sound?

 

[Zoli64]

I'd be interested in this too, is it really worse, does the bass transmission of the factory condition drop? I also noticed a slightly duller sound in the high notes, not as crystal clear.

 

[antcollinet]

I used the balance on RME ADI-2 PRO FS R to switch between amplifiers.

So each amp was playing to a different speaker postioned differently in the room. That will make a huge difference to the sound even the amps are identical.

o you have to volume adjust, which I did by ear,

Also completely useless for a valid comparison. The whole point of accurate level matching is that even 1dB of difference or less is often not detectable as a volume difference - but is typically percieved as a quality difference. "Slamminess" of the bass would be a typical perception created from a small level difference. For a valid comparison you need to be matching to 0.1dB which can only be done with a volt meter at the speaker terminals using a test tone.

or just use my phone as a level meter

Not accurate enough. Volt meter needed.

even if steady-state measurements end up being nearly the same

A sine wave is not steady state. Even if it were, a square wave would be just as steady state. Look at the multitone signal in the time domain - does that look steady state to you?

 

[Nam]

I tried a Mean well lrs-350-36 power supply with Aiyima A70. I hear noise from the speakers at a distance of 1 meter when rotating Aiyima A70's volume knot. That does not happen when using Aiyima's bundled power supplies (48V5A and 36V6A).
And Mean well lrs-350-36 runs warmer than Aiyima power supplies. I mostly listen to music at moderate level, room size 4.5m x 6.5m x 5m.

Edit: I hear noise at the speakers when rotating Aiyima A70's volume knot with Aiyima 48V5A PS too, noise is much lower than using Mean well lrs-350-36. I recommend running Aiyima A70 at max volume because the volume pot seems low quality.

 

[Roy_D]

Not excited, but a good move in the right direction.

- Single ended input is worse than A7 Max, Fosi V3 & ZA3.
- Subwoofer output practically unusable for most users. Regular active stereo line output will be a much more usable solution that can also be used to connect a subwoofer.
- 10 Amps GaN PSU brings nothing to the table. The Fosi V3 with their "ordinary" 48V/5A PSU has more power in 4 and 8 Ohms and is cool to the touch in normal operation.
- Price wise, it is too close to the Topping PA5 II territory, but the measured results are a joke, in comparison. Apart from the raw power that is the inherent difference between the TPA3251 and TPA3255 chips inside these amplifiers.

I'm eagerly awaiting for PFFB answer from Fosi.

What are the reasons the subwoofer out on the A70 is less usable to connect a subwoofer?

 

[Audionaut]

What are the reasons the subwoofer out on the A70 is less usable to connect a subwoofer?

Picture from Aiyima itself.
200 - 800 Hz maybe a Joke

 

[Roy_D]

Picture from Aiyima itself.
200 - 800 Hz maybe a Joke

Ah so less than useful low pass filter setting but still it cuts out 95% of remainder of the audible spectrum so better than just a straight output without. But could have been done better yes.
The amp's volume control does affect it though?

 

[JLB321GO]

The sub crossover frequency can be set anywhere between 150 Hz and 600 Hz.

How can that make any sense???

 

[john61ct]

What are the reasons the subwoofer out on the A70 is less usable to connect a subwoofer?

Just set to max to bypass and use the LP filter on your subwoofer controls

...

The amp's volume control does affect it though?

Yes the sub line-level out is volume controlled by the main knob

 

[john61ct]

200 - 800 Hz maybe a Joke
View attachment 453439

My understanding is the pic is not accurate

The sub crossover frequency can be set anywhere between 150 Hz and 600 Hz.

How can that make any sense???

If you watch Erin/EAC video

at around 11min, there are two FR graphs showing the actual results of the min vs max settings

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the lowest "150Hz" setting starts to drop at 50Hz, by 150Hz the output is down to ZERO

the highest "600Hz" setting starts to drop at 200Hz, by 600Hz the output is down to ZERO

So other manufacturers might actually label these settings with much lower numbers.

Obviously a HP filtering on the Main full-range speaker pair would be nice, but such a feature is in reality non-existent on "power only" chip amps.

So, assuming that is not needed in this use case

the A70 LP filter COULD be used with a external amps + Passive speakers to drive a "mid-bass" woofer in the say 80Hz - 300Hz range

and / or a subwoofer in the say 20Hz to 120Hz range.

I personally would want stereo L/R signals for the former rather than mono.

And this whole scenario is a pretty artificial one created just to answer "what were they thinking?"

Maybe using with a small bookshelf "satellite style" main pair, or a soundbar? @AIYIMA ?

Most westerners are using powered subs that include the bass management filtering features already.

So as repeatedly stated above, just set it to its highest frequency to in effect disable it and let your sub handle the LP filtering

 

[antcollinet]

the lowest "150Hz" setting starts to drop at 50Hz, by 150Hz the output is down to ZERO

the highest "600Hz" setting starts to drop at 200Hz, by 600Hz the output is down to ZERO

No, they are not down to 0, they are down to -3dB. Which is precisely the level which is considered the corner frequency/cut off point for a filter.

So - for example - a 3kHz low pass filter will have dropped to -3dB when the frequency drops to 3kHz.

So the amp has a 150Hz to 600Hz cutoff filter - and is pretty much useless for sub integration.

 

[john61ct]

Those numbers are above my understanding, but I'll keep learning

> pretty much useless for sub integration

as stated IMO that is the case no matter the LP details, sub line out should be full spectrum

The need for filtering (if any) is HP with the main pair

 

[Roy_D]

No, they are not down to 0, they are down to -3dB. Which is precisely the level which is considered the corner frequency/cut off point for a filter.

So - for example - a 3kHz low pass filter will have dropped to -3dB when the frequency drops to 3kHz.

So the amp has a 150Hz to 600Hz cutoff filter - and is pretty much useless for sub integration.

I have never heard of any manufacturer putting a 3db per octave filter for subwoofer crossover so very much doubt this is the case that @AIYIMA did that here?
The 150/600hz indication were endpoint ones, where those frequencies were starting to near the relative noise floor and not onset of filtering frequencies!?

 

[john61ct]

The mono version A70 is 12dB/octave

I have not seen the slope spec for the stereo one.

 

[somebodyelse]

I have never heard of any manufacturer putting a 3db per octave filter for subwoofer crossover so very much doubt this is the case that @AIYIMA did that here?
The 150/600hz indication were endpoint ones, where those frequencies were starting to near the relative noise floor and not onset of filtering frequencies!?

I've no idea where you got a slope of 3dB per octave from, unless you're confusing the slope with the definition of the corner frequency. The filter response will always be at -3dB at the corner frequency by definition, no matter what its slope is.

 

[Roy_D]

I've no idea where you got a slope of 3dB per octave from, unless you're confusing the slope with the definition of the corner frequency. The filter response will always be at -3dB at the corner frequency by definition, no matter what its slope is.

 

[john61ct]

Here are Erin's graphs, the yellow is the lowest "150" setting, the blue is the "600" highest.

https://imgur.com/uT8FuXB

my interpretation:

the lowest "150Hz" setting starts to drop at 50Hz, by 150Hz the output is down to ZERO

the highest "600Hz" setting starts to drop at 200Hz, by 600Hz the output is down to ZERO

I did not mean 0dB, I meant the 150/600Hz are not the points where the filters start, but where they have finished

50Hz and 250Hz might be better labels, where the filters' impact has begun?

 

[somebodyelse]

@Roy_D posting a screenshot of the earlier post quote doesn't help - I had already read that, and it doesn't mention a slope of 3dB per octave. Going back to the original sub out measurement in post #1 we see a low pass that is 3dB down at ~150Hz (eyeballing a log scale) which matches the '150' lowest setting. Given the scale we can't really judge the slope, but for a sub out it's a very odd choice of frequency range.

 

[somebodyelse]

Here are Erin's graphs, the yellow is the lowest "150" setting, the blue is the "600" highest.

https://imgur.com/uT8FuXB

my interpretation:

the lowest "150Hz" setting starts to drop at 50Hz, by 150Hz the output is down to ZERO

the highest "600Hz" setting starts to drop at 200Hz, by 600Hz the output is down to ZERO

I did not mean 0dB, I meant the 150/600Hz are not the points where the filters start, but where they have finished

50Hz and 250Hz might be better labels, where the filters' impact has begun?

I'm not seeing the image, but assume it's from Erin's Youtube review of the A70 at the 11:36 mark. Look at the scale on the left hand side - the bottom of the chart is at -3dB, not zero output. The markings match the definition for a filter's corner frequency.

 

[john61ct]

the bottom of the chart is at -3dB, not zero output.

As I stated I do not know dB units, in research googling it seems very confusing, totally different meanings in different contexts.

> filter's corner frequency

This also means nothing to me, so I will just refrain.

I apologize for my ignorance.