3e audio A7/A7 Mono Amplifier Review

[harkpabst]

However, the A7's actual continuous power output per channel is 100-120 watts at 2 ohms and 135-160 watts at 4 ohms. The latter figure only applies with an additional large heatsink and good airflow.

How did you find out about these numbers?

Edit:
And how is an amplifier that is NOT rated for 2 ohm loads (and has not been tested by Amir into this load) going to help with a 2 ohm subwoofer?

SMSL A300 Stereo Amplifier Review

This is a review and detailed measurements of the SMSL A300 stereo class D amplifier. It is on kind loan from a member and costs US $196. The A300 is slick looking with flush volume control and switches. Alas, I am not a fan of the blue LED display from aesthetic point of view. It is nice...

www.audiosciencereview.com

 

[Roland68]

Thank you! so there is a drop in power into 2ohms? I will check out the SMSL A300. Much appreciated!

How did you find out about these numbers?

No, there is no drop in performance; it's only about the heat that can be dissipated continuously. The first set of figures comes directly from 3E Audio, the latter is based on our experience and measurements with additional heat sinks on TPA3255-based PBTL amplifiers.

Edit:
And how is an amplifier that is NOT rated for 2 ohm loads (and has not been tested by Amir into this load) going to help with a 2 ohm subwoofer?

SMSL A300 Stereo Amplifier Review

This is a review and detailed measurements of the SMSL A300 stereo class D amplifier. It is on kind loan from a member and costs US $196. The A300 is slick looking with flush volume control and switches. Alas, I am not a fan of the blue LED display from aesthetic point of view. It is nice...

www.audiosciencereview.com

He had previously asked about two 4-ohm subwoofers, which he might want to connect together to create a 2-ohm system.
But I explicitly pointed out with the A300 that it only supports 4 ohms, so what's the problem?

 

[peng]

I'm sorry if my tone came across as patronising, that surely wasn't my intention.

I still think we really don't know how much of an objective difference might be there in this scenario. It all depends on the speakers. More perceived top end could absolutely be perceived due to load dependency. We audiophiles (yes, I do call myself a audiophile) tend to happily jump on the slightest difference we were happy enough to recognize (at least we think we did) and exaggerate the results.

No I welcome your remarks as usual, regardless.

I also think we don't know how to quantify such potentially audible differences objectively, and understand that different people may interpret subjective expressions differently, such that what one perceives "clearly" may be "subtle" or insignificant to others, even if they heard exactly the same difference, lol.

 

[harkpabst]

He had previously asked about two 4-ohm subwoofers, which he might want to connect together to create a 2-ohm system.
But I explicitly pointed out with the A300 that it only supports 4 ohms, so what's the problem?

I'm a bit baffled by your unusually harsh tone. Sorry, I didn't check all postings by @StephenMarkLay in other threads. I still don't see him requesting 400 W of continuous power output anywhere.

Did you also test the A300 for its continuous power output?

 

[SMen]

That's possible, but practically speaking, I doubt the difference would be audible to most people, of the more than 10 metrics Amir typically measured, the one below is one that is a reliable indicator:

This graph shows in the 20-20000 Hz (assuming the op cannot hear the 2nd and higher harmonics of 10 kHz, and the IMD due to the ultrasonic frequencies are high enough to be audible neither), between at 0.05 W to over 100 W into 4 ohms and likely better into 8 ohms, distortions plus noise would be at below -55 dB or <0.2 %.

So, PBFB or not is not likely going to make the " a clear and obvious difference" the op thought he was hearing, unless it wasn't truly an apple to apple comparison.

View attachment 511423

Yes, I agree - it's a question of degree ... We have all listened ourselves to compare amplifiers, and so "clear and obvious" claimed differences raises obvious alarms... but equally with PFFB vs No PFFB and not to mention other attentions to design details that I suspect elevates 3e's price a bit, going the other way and saying 'there is no audible difference' might be going too far the other way.

I listened to a fascinating interview with Peter Comeau, the loudspeaker designer, and he likened our brain/hearing mechanism to a sophisticated equalizer ... where our brain tries really hard to interpret for us - it is a different thought process to being 'fooled'. But initial impressions can change once we settle down and don't try too hard to listen. Just my opinion on it.

 

[SMen]

PFFB is not only about reducing distortion, but much more about reducing the output impedance.

A low output impedance over the entire audio frequency range is required for the amp to be not load dependent. Practical load dependency as observed with class-D chip amps without PFFB changes the measured frequency response of the speakers. Not just in the upper highs but - depending on the impedance response of the speaker - starting in the upper mods.

I won't overstate this, but our hearing is actually sensitive to loudness variation over frequency.

I just want to +1 on this because I think you have nailed it!

 

[SMen]

**This is wrong, we are negatively biased. A probably apocryphal test years ago describes a room full of scientific audiophiles who were told they would be comparing the sound of a system swapping out standard and audiophile power cables. Unsurprisingly none of the listeners heard a difference. The story goes that what was actually being switched was speaker polarity, an easily audible change. The scientific types were blinded by their scientific bias to real audible differences.

Fantastic! I love this. Bias works both ways!

 

[peng]

Fantastic! I love this. Bias works both ways!

Either way, it seems to show that we are so biased lol!! To the point we could be fooled so easily, and that may not always be a bad thing either.

 

[GGroch]

.......To the point we could be fooled so easily, and that may not always be a bad thing either.

Yep, often not a bad thing, evolution favors it. Our successful ancestors did not wait to fully analyze all aspects of whether the dark shape charging and growling at them was a bear or not, they just took off running.

The term Cognitive "Bias" is too negative. I prefer "Predictive Perception" which hints at our senses being clever, if not particularly accurate.

 

[StephenMarkLay]

I'm a bit baffled by your unusually harsh tone. Sorry, I didn't check all postings by @StephenMarkLay in other threads. I still don't see him requesting 400 W of continuous power output anywhere.

Did you also test the A300 for its continuous power output?

I didn't mean to start an argument . But yes the plan would be for two 4ohm drivers with one mono amp. But super high power isn't necessary. It is strictly for music in a medium room. No HT or extreme volumes are necessary. I plan on using two fairly sensitive woofers so likely 200w is enough,

 

[harkpabst]

I didn't mean to start an argument . But yes the plan would be for two 4ohm drivers with one mono amp. But super high power isn't necessary. It is strictly for music in a medium room. No HT or extreme volumes are necessary. I plan on using two fairly sensitive woofers so likely 200w is enough,

One thing is for sure: A single A300 won't do that. Two of them, each in BTL mode, will (and their poor measurements won't matter too much in the sub bass region. They will also set you back roughly 300 to 350 quid. That's A7 (stereo) territory.

 

[Roland68]

I'm a bit baffled by your unusually harsh tone. Sorry, I didn't check all postings by @StephenMarkLay in other threads. I still don't see him requesting 400 W of continuous power output anywhere.

Did you also test the A300 for its continuous power output?

That wasn't meant to be harsh, but I'm not a native English speaker, so it's just being direct.
I never mentioned 400 watts of continuous power for the A300, do you see what I find odd?

We have several A300s running as subwoofer amplifiers in BTL mode, partly because of their affordable price of €160-200 each. I tested one with 250 watts for 10 minutes, but my load resistors couldn't handle any more.
The A7 can't compete in that specific application, which isn't a bad thing, and it would also be more expensive.
This is partly due to the slightly more efficient Infineon Merus technology, which, however, doesn't deliver such good measured values and is more load-dependent in the high-frequency range.

I didn't mean to start an argument . But yes the plan would be for two 4ohm drivers with one mono amp. But super high power isn't necessary. It is strictly for music in a medium room. No HT or extreme volumes are necessary. I plan on using two fairly sensitive woofers so likely 200w is enough,

With the A300 in BTL mode, you'll naturally need one amplifier per subwoofer.
You can also test whether one A300 in stereo mode is sufficient for both subwoofers, and if not, switch to BTL.

Inexpensive alternatives for subwoofer amplifiers are the IcePower modules (DIY) and amplifiers from the PA sector, which are often available used at very low prices. Sylph Audio offers an extremely good and affordable DIY alternative with the SE800 module, delivering up to 600 watts at 4 ohms.

An A7 or two A7 mono modules would also be possible, but you'd have to test that, and the power output would be more limited.

 

[StephenMarkLay]

Thank you both for addressing my questions. Very much appreciated!

 

[ioskyr]

Hello to the forum. Could I pick your brains concerning the A7? I just received my A7 stereo amp. I looked inside the vents under it, and I noticed that it might be missing a component on the pcb. Next to the flat wires inductors(7R0), in the pictures posted here, there is a black rectangular component (HF3FF). There is nothing there on my amp (attached photo). Is that normal, a revision of the amp without it, or I should be worried about it. I haven’t plugged it on yet. Thank you in advance.

 

[Dave TR3A]

Hello to the forum. Could I pick your brains concerning the A7? I just received my A7 stereo amp. I looked inside the vents under it, and I noticed that it might be missing a component on the pcb. Next to the flat wires inductors(7R0), in the pictures posted here, there is a black rectangular component (HF3FF). There is nothing there on my amp (attached photo). Is that normal, a revision of the amp without it, or I should be worried about it. I haven’t plugged it on yet. Thank you in advance.

Perhaps you ought to direct that question to 3e Audio or the seller for a definitive answer. 3e Audio provides a "Contact Us" page on their web site and give an e-mail address ([email protected]).

 

[Roland68]

Hello to the forum. Could I pick your brains concerning the A7? I just received my A7 stereo amp. I looked inside the vents under it, and I noticed that it might be missing a component on the pcb. Next to the flat wires inductors(7R0), in the pictures posted here, there is a black rectangular component (HF3FF). There is nothing there on my amp (attached photo). Is that normal, a revision of the amp without it, or I should be worried about it. I haven’t plugged it on yet. Thank you in advance.

That's absolutely correct.

If you look more closely, you'll see that there's a component there, just much smaller. It used to be a relay, now it's a transistor acting as a switch.

Addendum: On newer devices, this area appears to be completely empty.

 

[ioskyr]

That's absolutely correct.

If you look more closely, you'll see that there's a component there, just much smaller. It used to be a relay, now it's a transistor acting as a switch.

That particular part of the PCB is totally empty. I just checked again.

 

[Roland68]

That particular part of the PCB is totally empty. I just checked again.

I had already corrected it; apparently, this area is completely empty on newer devices.
So you can try it without worry.

 

[john61ct]

The first set of figures comes directly from 3E Audio, the latter is based on our experience and measurements with additional heat sinks on TPA3255-based PBTL amplifiers.

Is this for the Stereo or Mono A7 ?

 

[john61ct]

Perhaps you ought to direct that question to 3e Audio or the seller for a definitive answer. 3e Audio provides a "Contact Us" page on their web site and give an e-mail address ([email protected]).

Apparently you get a quicker response from their Ali store