Aiyima A70 Mono

Aiyima’s new Mono block amplifier has a few (maybe too many) new tricks

So this latest Amplifier from Aiyima has me a bit conflicted. I do like clean unfussy designs and I thought Aiyima did a great job with their previous amplifier the A70. With that Amplifier I felt Aiyima jumped back ahead of their great rivals Fosi Audio at least as far as class D Stereo Amplifiers.

But as you see in the photo below the A70 Mono has a different design again:

I was intrigued when Aiyima offered to send me a pair of their new A70 Monoblock’s. I do love to see competition and these 2 companies have been battling it out for a few years now with some great upgrades to their product lines. Obviously, Monoblocks is the latest battleground between these 2 companies, with the Fosi Audio V3 Mono’s been recently launched, and now we have the A70 Mono’s.

So with the A70, as you will see, you get a feature rich device but does it have the right features for you or even the right features for a Monoblock? And does it have what it takes to have a place in your audio setup.

Read on to find out.

Before I get into the features, lets see what you get in the box.

Unboxing

So the A70 Mono comes in a nice box obviously each Monoblock comes in a separate box:

Note: So the outside of the box clearly says 300W x 1 - I think all these audio companies really should be more realistic with either the specifications or their power supplies. This is not just Aiyima but the majority of audio companies (from every continent) exaggerate their power specifications based on a max power possible but not necessarily the power you get with power supply supplied in the box.

Opening it up you get the manual, warranty and of course the A70 Mono and its power brick:

I got the 48V 5A GAN power supply:

Using Aiyima own Power specifications - potentially when using the Mono block with a subwoofer you can get 300W output but the max power in ‘Full range’ amplifier mode with a 4 Ohm speaker is 280W, but I guess the 300W comes from the maximum power when driver a passive sub-woofer:

What is on the Front

Looking at the front you immediately get the idea this is no ordinary monoblock:

And my initial thoughts on the A70 Mono was, that this is nothing like the A70, it has too many buttons / dials and options especially for a Monoblock. Does a Monoblock needs 2 large dials on the front? Most monoblocks will not have any dials as the mono ‘pair’ will be fed by and controlled by a separate preamp. In fact as you will see mostly I my daily usage over the past few weeks I didn’t use either of these dials as I set the volume to Max on both as the only way to volume match both amplifiers.

Features over function

In my recent A70 review I covered a little bit of my history trying various Aiyima products and how they have the tendency to have some ‘zig/zag’ progress, adding some great ‘clean’ audiophile friendly features in one release but then in subsequent releases adding lots of extra supplementary features that are at best niche features on top of that clean design.

I do think this comes from Aiyima serving multiple markets, as they sell lots of ‘diy’ audio products and amplifier boards to enthusiasts rather than focus directly on the audiophile market. So instead of just functioning as a classic Monoblock, Aiyima have effectively decided to add extra features and turned this device into a 2 in 1 device with 2 very different capabilities (a sort of ‘Jekyll and Hyde’ device).

But after using it for a few weeks now, I think there is still a lot to like with the A70 Mono blocks specifically the very clean sound, so lets get into the features of the A70 Mono’s.

Feature overload or useful extra options?

I think the key to understand the A70 Monoblock is to flip it over and look at the switch on the bottom:

This switch effectively turns this ‘Jekyll and Hyde’ device into either a Jekyll or a Hyde, where you can use the A70 Mono’s as either a classic Monoblock amplifier “FULLRANGE” or as a passive Subwoofer amplifier “SUB”.

A70 as a ‘classic’ Monoblock amplifier

As a Monoblock Amplifier the A70 Mono does everything you should expect from a Monoblock (and more) with RCA, XLR inputs, a 12V Trigger and even a +6db gain switch to ‘match’ the levels between RCA and XLR should you need too.

Looking at the back you can see these options - with the RCA, XLR and that 6Db switch on the left:

And the trigger input and the speaker binding posts the right hand side.

Internally, one of the key features of the A70 Mono is that it has that same PFFB circuit that helped provide perfect linearity to the A70 which thankfully now seems like a standard features in these class D amplifiers.

So, I have mainly being using this as a Monoblock and I think it is actually a better device than the Fosi Audio V3 Mono - specifically because of the proper trigger input, but I also think the slightly larger size means it runs cooler especially if installed inside a cabinet. I had some problems with one of my V3 Mono’s when powering my Kef LS50 Meta’s (it got very hot after 4 or 5 hours) but I had no similar problem with either the A70 or with the A70 Monos.

I also really like having real trigger inputs rather than the signal detection that the V3 Mono’s utilise.

So, here is a photo comparing the sizes of the original A70, the Fosi Audio V3 Mono’s and the A70 Mono’s:

And what they look like from the back:

If Aiyima had just left this as just a mono amplifier I think it would be a great success but Aiyima really want to “One up” Fosi Audio with more features, and they decided the way to do this with the A70 Mono was that ‘switch’ on the underside and to turn the amplifier into a passive subwoofer amplifier.

Since, Aiyima are selling the A70 Mono at a very similar price point to the V3 Mono’s I imagine the idea is the extra features are enough to swing peoples purchases decisions towards the A70 Monoblocks, but they also add some complexity.

So let’s have a look at those subwoofer features:

A70 Mono’s controlling an active Subwoofer

So there is an active subwoofer output on the back of the A70 Mono’s allow for example 2 A70’s to have 2 separate subwoofers attached.

So, when trying to correct room ‘modes’ (especially without Room correction EQ) utilising multiple subwoofers are vital, so I can imagine utilising 2 active subwoofers with different “low pass filter” in different positions with your room can help removing sub-bass issues, so this configuration is potentially pretty useful, but it is unusual to have 2 separated subwoofers connected from Left and Right channel only bass. I briefly tested this, and it worked well if a little old-fashioned. My preference for subwoofer management is to use a device with dedicated room correction with bass management e.g. a Wiim Ultra or a Minidsp feeding room corrected RCA input into each mono block and separately feeding a subwoofer.

But the A70 Mono does implement a “low pass filter” for the bass frequencies sent to the active subwoofer outputs. With configuration from 40Hz to 200Hz via a dial on the back next to the active subwoofer output. While this is partially useful most active subwoofers has their own “low pass filter” control so it is a pity this dial isn’t a “high pass filter” on the speaker outputs.

Note: The A70 “SW-Freq” dial on the front is not for the active subwoofer but instead for controlling the passive subwoofer capabilities, so let have a look at the’passive’ subwoofer control:

A70 as ‘Passive’ Subwoofer Amplifier

So when in subwoofer mode, both dials on the front become useful. The frequency of this passive low pass filter is controlled with the “SW Freq” dial on the front of the A70 Mono and obviously the volume controls the passive subwoofer volume. If you own active subwoofer you will recognise both of these controls (typically on the back of an active subwoofer).

I did a little bit of research into passive subwoofers (as all subwoofers I have are active subwoofers) and it seems that especially on DIY forums that building your own passive subwoofer or rescuing older active subwoofer with blown amplifiers is very popular and therefore a passive subwoofer amplifier is actually a very popular option for some people.

Internals

Looking at the internals - you can see a very clean design with some high quality components, specifically Aiyima mentioned the Rubycon 63V3300f filter capacitor, the Nichicon Audio capacitor and the WIMA capacitor+ Mono mode inductor: There are also many options for replacing op-amps, if that is your thing.

On the back you get a large heat-sink covering the TPA3255 chip:

Specifications and Measurements

Measurements

Note: The following measurements were provided by Aiyima - If I see updated measurements on ASR soon, I will update this review

First the Frequency Response shows an almost perfectly flat response, which is what you should get with a class D amplifier when PFFB has been implemented (removing any loud dependency issues):

The SINAD score shows 96 dB from the Balanced XLR input which is a very respectable score and is aligned with what Amir over at ASR found for the A70 when he measured that amplifier, so that value is very believable:

My setup

I thought it would be fun or useful to show briefly how I was mainly was using the A70 Monos for the past few weeks, so in this photo I have WiiM Pro feeding a Fosi Audio ZD3 pre-amp / DAC via optical (in the lower shelf) as the ZD3 has both RCA and XLR outputs and with the A70 Mono’s having both RCA and XLR inputs I thought I would add a little bit of tube fun to the setup by routing the RCA output through a Aiyima T1 Pro Tube Pre-Amp - the A70 Mono’s ultimately feed a pair of Kef LS50 Meta and a single Kef Subwoofer:

Zooming in a bit:

I mostly do like a clean neutral response so the L/R XLR outputs directly into the A70’s provides very neutral sound, but I think everyone needs a little bit of tube warmth every so often, so feeding the RCA output from the ZD3 into the T1 Pro and then out into the RCA inputs of each A70 was a nice options:

Here is a diagram I put together of this overall setup: Note: I also have a Schiit Midgard which has both XLR and RCA inputs and outputs and I did for a while feed the ZD3 XLR output into this midgard before feeding it into the A70’s Mono’s.

Some final thoughts

Here are my thoughts on what might have been better with the A70 Mono’s:

2 Separate devices

I would have loved Aiyima to actually provide 2 separate devices. A full range monoblock amplifier (without the 2 dials on the front) and a separate passive subwoofer amplifier. That subwoofer amplifier device would resemble this A70 Mono with mostly the same controls, though it could have had one single volume control on the front and just had the subwoofer frequency control on the back.

High Pass Filter on speaker outputs

Now that PFFB is standard with these class D amplifiers the next thing that needs to be added to these amplifier that have active subwoofer output is a proper High Pass filter. If you follow channels like Erin’s audio corner you can see that bookshelf speakers often struggle with distortion when fed lower (sub-bass) frequencies, implementing a high pass filter, instead of or as well as a low pass filter on the subwoofer output would massively improve this situation. As for the speaker output when using a subwoofer there is no need to pass ’low bass’ frequency to the main speakers so a high pass filter would be ideal, but we are still waiting for this feature in this price range.

This has to be the next audiophile ‘battleground’ feature between Aiyima and Fosi Audio.

Rating

I have given the Aiyima A70 Monoblock’s an overall pragmatic rating of 4-stars. As a pure monoblock it performs excellently and would get an easy 5-star rating especially how well it sounds from the XLR inputs and those useful extra options like 5-volt triggers are great.

But I have taken off 1-star due to added complexity added to support a ‘single device’ acting as 2 to support both active and passive subwoofers with the 2 dials on the front and the 2 different SW frequency adjustments (depending on whether you are running an active subwoofer or a passive subwoofer).

Conclusion

I fell Aiyima have made a sideways step with the A70 Mono’s after the incredible good A70’s. But in power amp Monoblock mode this is a great device with XLR and RCA inputs as well a trigger (assuming you leave the volume at max ) but then the addition of support for passive subwoofers seems like a second product ‘grafted’ onto the Monoblock rather than a logical extension of the product.

But if you are looking great sounding Monoblocks with XLR / RCA inputs with triggers, PFFB support, swappable op-amps and excellent heat dissipation design the A70 Mono’s are a great choice.