3e audio A7/A7 Mono Amplifier Review

[Dave TR3A]

I noticed when power is toggled (also possible from an external trigger) the 3e amps stay on for a while. But I guess they would turn off on you when the signal level is not high enough.

Curious though, did you try a different model like the A5? Did you maybe try to go to XLR in, bypassing the opamp and using only those 20 db, with rca voltage? That's so much less gain on the amp side, it should require your preamp to send significantly more. Well, not 90 -> 106db more but maybe enough to have the autosensing working reliably.

@Ruediger Although the pre-production unit sent to Amir for testing had a 12V trigger, the production units don't have that. This photo shows that there is no 12V trigger input on the back panel of the A7.

I found that the A7's "autosense" would turn off the amp that served my tweeters. I guessed that was because the signal going to the tweeters was so small. I didn't measure the magnitude of the signal, but it would have been well under 50 mV --- perhaps less than 10 mV.

The signal to my amps is provided by a MiniDSP Flex Eight DSP. It does not have XLR outputs, just RCA. This diagram shows the configuration I used:

I tried a PAM158 (an 8-channel amp where each channel is similar to an A5). I wrote of my experience with that amp in this post. @3eaudio replied to that post and I'm hoping they'll get back to me about the noise that I heard from the PAM158 (and that I didn't hear with the A7). I'd really like for the PAM158 to be a viable choice for my system.

 

[Ruediger]

@Ruediger Although the pre-production unit sent to Amir for testing had a 12V trigger, the production units don't have that. This photo shows that there is no 12V trigger input on the back panel of the A7.

What I meant by external trigger is one of these devices that you insert into the powerline or at the powerplug. It will turn the unit on by 12v trigger, but autosensing will then turn it off later - as you experienced.

I see something like this with a subwoofer. Autosensing is too insensitive, it often won't turn on by itself. But when turned on manually it stays on with the same signal.

But a good old knob, dipswitch or similar would be best for sensitivity adjustment.

 

[astamixa]

Hello everyone! Excuse my pidgin English. It's not my native language.
In January 2025, I received two 3E Audio A7 Mono amplifiers from the first batch. They have poor auto-on/off sensitivity, and it's impossible to disable 5 min sleep mode. For a year and a half now, they've been working perfectly in my system with power supplies I built myself.
Recently, I had some free time and decided to update them. I sent an email to 3E Audio, and they told me that I would need a programmer to update the firmware of the STM32 microcontroller, and that I would also need to remove one small SMD resistor on the PCB, which was already mentioned here. Afterwards, they kindly provided a picture of the PCB showing the contact pads for programming the microcontroller, along with the latest firmware.
I purchased a Chinese V2 programmer for $3. To use it, I needed to install a USB driver and the free ST-Link Utility software from the STMicroelectronics website on a Windows PC. The amplifier is equipped with an STM32G030F6P6 microcontroller in TSSOP20 package with 20 pins. I installed 0.1" single-row male pin header (2.54 mm) into the PCB holes to connect the programmer. To update the firmware, the programmer connects to four of the five installed pins. The update went smoothly in a few seconds. Removing the SMD resistor was a bit of a challenge! The components in this part of the board are 0402 size and are quite tightly packed. Removing them required the use of a microscope. I've attached a short video comparing the components with a wooden match head. In return, now I have a fully updated version of the A7 Mono with the ability to disable sleep mode, 20-minute sleep time, and high sensitivity to low music volumes without turning off the amplifier.
Many thanks to @3eaudio for a wonderful product and caring customer service!
Good music and pleasant summer evenings to everyone!

Update: the firmware is universal for the entire range of A5se/A5/A7se/A7 and A7 Mono, as follows from the file name - A5x_A7x.

 

[Dave TR3A]

Recently, I had some free time and decided to update them. I sent an email to 3E Audio, and they told me that I would need a programmer to update the firmware of the STM32 microcontroller, and that I would also need to remove one small SMD resistor on the PCB, which was already mentioned here. Afterwards, they kindly provided a picture of the PCB showing the contact pads for programming the microcontroller, along with the latest firmware.
I purchased a Chinese V2 programmer for $3. To use it, I needed to install a USB driver and the free ST-Link Utility software from the STMicroelectronics website on a Windows PC. The amplifier is equipped with an STM32G030F6P6 microcontroller in TSSOP20 package with 20 pins. I installed 0.1" single-row male pin header (2.54 mm) into the PCB holes to connect the programmer. To update the firmware, the programmer connects to four of the five installed pins. The update went smoothly in a few seconds. Removing the SMD resistor was a bit of a challenge! The components in this part of the board are 0402 size and are quite tightly packed. Removing them required the use of a microscope. I've attached a short video comparing the components with a wooden match head. In return, now I have a fully updated version of the A7 Mono with the ability to disable sleep mode, 20-minute sleep time, and high sensitivity to low music volumes without turning off the amplifier.
Many thanks to @3eaudio for a wonderful product and caring customer service!
Good music and pleasant summer evenings to everyone!

Impressive! Kudos to you @astamixa for your skills and to @3eaudio for the support they provided.

 

[astamixa]

Impressive! Kudos to you @astamixa for your skills and to @3eaudio for the support they provided.

Thanks, @Dave TR3A ! Life is about learning and discovering new things. And It's exciting, wonderful, and rewarding. ASR Forum is a wonderful place! Thanks a lot to @amirm and many other members, I've learned so much useful information. Kind regards to Ontario region!

 

[Ruediger]

Kudos to your skills!

And good to see 3e audio giving support.

 

[Link01]

It's great that you received the support from the manufacturer and all, but this is 2026, updating a firmware should not be this difficult and that is a design problem to begin with.

 

[petergobbler]

Looking at the measurements of this unit and how it handles 2 ohm resistive and inductive loads am i correct to assume this unit could drive a pair of power hungry electrostatic speakers? Like some older Martin Logan electrostats (like the Sequel 2,SL3,Quest) for example that dip well into 2ohms range with a mixture of capacitive/inductive loads? Have anyone tried this amp in such a setup?

 

[john61ct]

that dip well into 2ohms range

Does that mean "while staying above 2Ω" ?

And do you intend to already be pushing for maximum power and current, big space high SPLs?

If so, even if not blatantly overheating you may not be leaving enough headroom for transients at low distortion

 

[petergobbler]

Does that mean "while staying above 2Ω" ?

And do you intend to already be pushing for maximum power and current, big space high SPLs?

If so, even if not blatantly overheating you may not be leaving enough headroom for transients at low distortion

Just for example:

MartinLogan Sequel II loudspeaker Measurements | Stereophile.com

Sidebar 3: Measurements Electrostatic loudspeakers have gained a reputation for being hard to drive, so it was with my bump of curiosity piqued that I measured the load represented by the Sequel II. Fig.1 shows the result. A well-damped peak at 33Hz reveals the woofer tuning, while the overall...

www.stereophile.com

I don't have more detailed measurements than this at the moment.

 

[john61ct]

The next question is just as important.

If you are only using say 80% of rating IMO it will be OK

 

[petergobbler]

The next question is just as important.

If you are only using say 80% of rating IMO it will be OK

80% of 240W-ish watts is still a lot of watts.

 

[john61ct]

Yes. but 240W is the rating for at what distortion level? what impedance? And not fluctuating...

 

[Ruediger]

Looking at the measurements of this unit and how it handles 2 ohm resistive and inductive loads am i correct to assume this unit could drive a pair of power hungry electrostatic speakers? Like some older Martin Logan electrostats (like the Sequel 2,SL3,Quest) for example that dip well into 2ohms range with a mixture of capacitive/inductive loads? Have anyone tried this amp in such a setup?

The graph shows a wide area between 2 and 4 ohms where quite some energy flows. And a dip lower in the high region where it's only a little. Doesn't look like a problem for these amps.

But the thought should start with a calculation of the needed watts. It's often a lot less than we think. Should the A7 max. output be challenged (highly doubt that) it's a task for bigger amps like Hypex, Purifi, Icepower..

 

[Alannn]

Yes. but 240W is the rating for at what distortion level? what impedance? And not fluctuating...

 

[Ruediger]

I forgot the A7 mono is not just half a unit. Pair those with the 48v10a psu and have a whole lot of power.

 

[john61ct]

And accepts an even higher voltage, which has an "even bigger" impact.

But for me I'd want to only do that - max 51V - when I "needed" it, otherwise keep it lower for longevity.

 

[peng]

Bait and switch is (IMO) any situation where one thing is promised in order to secure a sale, and a different thing is supplied.

In this case they are baiting people in with promises of "audio grade capacitors of a particular type" then switching them for something else. But regardless of terminology, it is dishonest marketing/sales, and I have a low tolerance for dishonesty.

It is why I am here at ASR.

I would like to know if my pair of mono bought last Dec from Amazon.ca have the OPA1656 or OPA1612 but the number on the chip cannot be seen through the square hold, and I am sure even if I pull it out the quality of the printing is just too poor to be seen. I can see the caps are Rubycon not the Elna they advertised at the time (and still do iirc).

Is that anyway to know which opa I have. Not that I think I can hear a difference, just curious, the 1612 seems to cost a lot more on per unit basis.

 

[Roland68]

I would like to know if my pair of mono bought last Dec from Amazon.ca have the OPA1656 or OPA1612 but the number on the chip cannot be seen through the square hold, and I am sure even if I pull it out the quality of the printing is just too poor to be seen. I can see the caps are Rubycon not the Elna they advertised at the time (and still do iirc).

Is that anyway to know which opa I have. Not that I think I can hear a difference, just curious, the 1612 seems to cost a lot more on per unit basis.

View attachment 556228

Why don't you post a high-resolution image of the area?

 

[LambdaCDM]

I would like to know if my pair of mono bought last Dec from Amazon.ca have the OPA1656 or OPA1612 but the number on the chip cannot be seen through the square hold, and I am sure even if I pull it out the quality of the printing is just too poor to be seen. I can see the caps are Rubycon not the Elna they advertised at the time (and still do iirc).

Is that anyway to know which opa I have. Not that I think I can hear a difference, just curious, the 1612 seems to cost a lot more on per unit basis.

Use zoom and constant light.

Spoiler: Result