AIYIMA A70 Mono Amplifier Review

[john61ct]

Also sorry, I can go either SE RCA or balanced XLR from pre-amp

Would that choice affect SPL (current delivery) from the speaker outputs?

 

[harkpabst]

I will be HP filtering the LS50s, maybe as high as 150-200Hz and using room correction / subwoofer integration (to address elsewhere)

Very good plan. But if you do that you're not gonna need a load of power to drive the LS50s.

Am I right this A70 Mono version will be better for these speakers specifically since they are rated down to 2 Ohm?

I'd say you worry too much. At no frequency does the impedance come anywhere near 2 Ω. According to Stereophile the absolute minimum is 4 Ω at 200 Hz and then most critical combination of impedance magnitude and phase angle occurs at 135 Hz. When using a 200 Hz high pass filter, this will become almost meaningless.

KEF LS50 Anniversary Model loudspeaker Measurements

Sidebar 3: Measurements I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the KEF LS50's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield and spatially averaged room responses. My estimate of the KEF's voltage sensitivity was...

www.stereophile.com

This is a rather recent review, but some things have changed in the meantime. This amp doesn't look very attractive to me. The current regular price is $160 per piece including the PSU, that's $320 for the stereo pair (obviously).

Even if you don't care about best sound quality so much, look at what a 3e Audio A7, which is technically vastly superior, costs (and take note of the announced special offer):

Not (yet) available through Amazon, but AliExpress only. But this is a much better performer and confirmed.to be rock solid even into reactive 2 Ω loads! PBTL and the best PFFB implementation so far. This lowly chip amp beats some Hypex based amps in IMD performance, at least up to 7 or 8 kHz (are you worried about 2nd or 3rd order distortion of a 10 kHz signal, where the NC500MP performs slightly better ).

In fact, even the more value oriented 3e Audio A7se (no PBTL).could drive the LS50 from 150 Hz upwards, but I would probably still pick the higher spec model, just in case ...

 

[john61ct]

> I'd say you worry too much

Yes I may be splitting hairs, but I'm trying to increase my understanding as well as optimizing the SPL for these lower impedance "current hungry" speakers with relatively inexpensive amps.

> At no frequency does the impedance come anywhere near 2 Ω

The actual lowest impedance exhibited by these OG LS50s is not so much a direct factor in why I seek amps rated to handle down to 2Ω.

My understanding is that each channel should have its own TPA325X, and the implementation should use PBTL mode.

The result of this should allow the amp to be rated by the manufacturer for 2~8Ω speakers, and power output nearly doubling going from 8Ω down to 4Ω.

Please confirm that the Mono version of A07 does match this profile, and the Stereo version does not.


> if you do that you're not gonna need a load of power to drive the LS50s

I am HP filtering specifically to increase the effectiveness of the current delivered (even just a little, and within the bounds of SQ and safety), and if that means I spend a bit more on "overkill", not using all the amps' current potential, so be it, a little headroom causes no harm amirite?

I'm even (maybe) willing to pay for two stereo power amps, but using each as a mono amp, for overall value/$ in future flexibility, but **only if** that path delivers just as much current as amps designed to be monoblock.

So - within the context of the Aiyima line, do you think the Mono version of A07 will deliver (even a little) more current than any other amp they offer?

Thanks very much for this suggestion as well, hopefully it gets put through Amir's process soon!

Even if you don't care about best sound quality so much, look at what a 3e Audio A7

 

[harkpabst]

My understanding is that each channel should have its own TPA325X, and the implementation should use PBTL mode.

Well, yes, that's the short version. Each TPA3255 chip has 4 power outputs. They can be configured to implement 4 channels (in single ended mode, SE) or 2 channels (in bridge tied load mode, BTL) or 1 channel (in parallel bridge tied load mode, PBTL). If all you want is an amp that safely doubles it's output power into 4 ohms compared to 8 ohms, the BTL configuration is actually well sufficient.

Here is one example, the WiiM Vibelink Amp:

The Vibelink Amp is not for you, because it has a built-in PSU. I only mention it as an example of an amp that clearly doubles it output power into 4 ohms and (thanks to its overall good design) surprisingly is even stable into 2 ohm loads (not recommended by WiiM).

PBTL is potentially able to double the power output into 2 ohms, compared to 4 ohms, again. But for this to work, the power supply and the output filter must be up to this task as well. Unfortunately, Amir could not test the A70 with his reactive load box, so we don't know for sure how it deals with such low loads in practice.

Please confirm that the Mono version of A07 does match this profile, and the Stereo version does not.

I can't because I'm not familiar with the family of AIYIMA amplifiers.

You don't need a mono amp to get PBTL. A stereo amplifier can implement PBTL just as well, if it uses two TPA3255 chips. And these designs do exist, of course. Two examples:
3e Audio A5
3e Audio A7

Thanks very much for this suggestion as well, hopefully it gets put through Amir's process soon!

Yes, Amir did already test the 3e Audio A7 and it's little brother, the 3e Audio A5. There is also the 3e Audio A7 Mono, but the only difference between one single 3e Audio A7 and a pair of 3e Audio A7 Mono is the fact that you can (and more or less must) use two PSUs for a pair of A7 Monos.

Here are the relevant power delivery plots published by Amir.

3e Audio A5

3e Audio A7

My point is: One 3e Audio A7 stereo amp is guaranteed to supply more power into 8 ohms, 4 ohms and 2 ohms than a pair of A70 Monos and it offers much better distortion numbers and it will cost you about the same or even less than a pair of A70 Monos. So, if you don't even want to make use of the "unique selling point" of the A70 Mono, the high pass filtering and subwoofer output of the A70 Mono (and I think it is a very wise move to use an external crossover for that), then why go for the clearly inferior offer at the same price?

I am HP filtering specifically to increase the effectiveness of the current delivered (even just a little, and within the bounds of SQ and safety), and if that means I spend a bit more on "overkill", not using all the amps' current potential, so be it, a little headroom causes no harm amirite?

Short comment on this: High pass filtering the OG LS50 at 150-200 Hz will actually increase the sound quality, if the subwoofer/s can play up that high. LS50 (Meta or OG) are really super high quality speakers. Their biggest (relative) weakness is intermodulation distortion below 200 Hz. High pass filtering removes this weakness and potentially further improves their already superb midrange clarity.

I've been running LS50 and LS50 Meta with two Lyngdorf BW-2 subwoofers crossed at 200 Hz for a couple of years. The result was really outstanding!

One last note: According to the forum rules we (or more specifically I) should not be discussing these topics in a review thread. I have no intention to talk down AIYIAMA products. But I feel like I have to point out my opinion that this amp is not the best you can get for your money, taking into acount your particular use case.

 

[john61ct]

Thanks SO much for such a detailed response, especially wrt BTL vs PBTL modes and HP filtering my LS50s

If all you want is an amp that safely doubles it's output power into 4 ohms compared to 8 ohms, the BTL configuration is actually well sufficient.

No that is just a starting point.

What I am after is the maximum current delivery into low impedance, neither fine SQ nor cost consideration are as great a priority.

Thanks also for the points about other maker examples, Wiim and 3e, to be researched and discussed in other threads.

> if you don't even want to make use of the "unique selling point" of the A70 Mono, the high pass filtering and subwoofer output of the A70 Mono

FYI no chip amp does any HP filtering at all, and if there is any filtering for sub output obviously LP only and only relevant for amps/subs without such controls, long obsolete in the west.

 

[harkpabst]

FYI no chip amp does any HP filtering at all, and if there is any filtering for sub output obviously LP only and only relevant for amps/subs without such controls, long obsolete in the west.

I know that I said I don't know nothing about the AIYIAMA amplifiers. And yes, you're right, the A70 Mono does not provide high pass filtering of the main speakers (sorry, I got confused). But e.g. the Douk Audio A5 does.

Douk A5 Budget Stereo Amplifier Review

This is a review and detailed measurements of the Douk Audio A5 stereo class D amplifier. It was sent to me by the company and costs US $99.99 as of this writing on Amazon including free shipping. I really like the look of the unit. The control on the right turns the amp on and adjusts the...

www.audiosciencereview.com

That's not a recommendation on my part at all, just a simple fact.

Ideally, even the LP filtering should not be provided by the (active) subwoofer. A capable pre-amp or pre-processor will perform the HP filtering to the mains and the LP filtering of the sub. In my case the (relatively pricey) Lyngdorf TDAI-1120 does it all, but the WiiM Ultra is probably the most affordable product that does all this is one single tiny box. Just connect it to the LFE input of your subwoofer and it will split frequencies evenly between mains and sub using a Linkwitz-Riley 4th order digital crossover.

WiiM Ultra Streamer Preamp Review

This is a review and detailed measurements of the WiiM Ultra network streamer, DAC, phono stage and preamplifier. It was sent to me by the company and costs US $329. Physical attribute are modern and attractive enough. Alas, I can't say the same thing about the graphical interface. Icons seem...

www.audiosciencereview.com

 

[john61ct]

Douk Audio A5 does

Love it, exception proves the rule

I'll look at Wiim, just been wary of DSPs in my so-far analog-audio zeitgeist.

Is the Ultra the main one worth lookin at?

> Lyngdorf TDAI-1120

WOW! I happen to be related to the Steinway family, since before they got bought out (by CBS/SONY?) fond memories playing at the "village" in Astoria, visiting the dealers around Europe, summers at the compound on Long Pond...

I also have recently started down the rabbit hole of "Pure Digital" amplification, DDX/STA chips, PowerDACs etc

so this is a very interesting company to me!

As with other thread diversions, to be discussed elsewhere...

 

[john61ct]

Ideally, even the LP filtering should not be provided by the (active) subwoofer. A capable pre-amp or pre-processor will perform the HP filtering to the mains and the LP filtering of the sub.

...WiiM Ultra is probably the most affordable product that does all this is one single tiny box.

I found a NOS Outlaw ICBM-1

all-analog, built for purpose, supports stereo mid-bass / woofers / subs, and at a much lower price

I think will give me a lot more flexibility, does not lock me into the Ultra as my pre-amp

What say you?

Or anyone of course, all feedback welcome