3e audio A7/A7 Mono Amplifier Review

[harkpabst]

Possibly - we don't have measurements, but since the A5 can happily drive 2ohm loads, I'd be surprised if the A7SE couldn't also:

We don't have independent measurements of the A5se and the A7se, but we do have ASR measurements of the A5 and the A7.

Why would you assume the A7se to perform equally well into 2 ohm loads as the A5 when 3E AUDIO explicitly don not state this?

 

[peng]

At 1220 Hz I wouldn't be concerned about the power or current demand either. But I'd like to make sure that the amp's output impedance is as low as possible and that would lead me to the A7 or the A5, if the power output is sufficient.

No disagreement, I had a typo in that post, fixed now.

 

[peng]

Possibly - we don't have measurements, but since the A5 can happily drive 2ohm loads, I'd be surprised if the A7SE couldn't also:

View attachment 503703

The 3e SE versions can certainly hande 4 ohm nominal with dips down to 2 ohm but not 2 ohm nominal. I know what that IEC standard said about nominal, but don't think manufacturers follow it, not rigidly anyway. If such dips are very wide, trough like, then it could be a problem but in most cases such low dips tend to be narrow.

 

[Roland68]

The A7 SE is rated for 4 ohm load so it can handle thise dips. Just about any 4 ohm nominal speakers will have dips below 4 ohms. The BMR’s impedance is not the issue, but the sensitivity is a bit low for sure. Get the 10 A brick that will help.

I generally agree, but impedance dips down to 2.9 or even 2.5 ohm are not acceptable for a 4 ohm rating. IEC 60268-5 and EIA/RS-299-A require the actual minimum impedance to be no lower than 0.8 times the nominal impedance.

I'm not pointing at Dennis Murphy, not at all. But I do recommend to rather go with the 3E AUDIO A7 in favor of the A7se in this case.

Possibly - we don't have measurements, but since the A5 can happily drive 2ohm loads, I'd be surprised if the A7SE couldn't also:

We don't have independent measurements of the A5se and the A7se, but we do have ASR measurements of the A5 and the A7.

Why would you assume the A7se to perform equally well into 2 ohm loads as the A5 when 3E AUDIO explicitly don not state this?

The A5 and A7 each use one chip in PBTL per channel and are therefore capable of handling 2 ohms.
The A5se and A7se use only one chip per device in BTL and are therefore only designed for 4 ohms.

The A5se and A7se can certainly handle loads down to 2 ohms in most cases, but this is far from ideal.
Significant heat generation and sonic degradation, depending on the complexity of the low-impedance load, are the result.
It should also be understood that this operates the amplifier and the TPA3251/55 chip outside of their specifications and may overload them. This can lead to failure, potentially damaging or destroying the speakers.

Furthermore, the power output at 2 ohms can drop significantly compared to the A5/A7, possibly even below the power output at 4 ohms.

Especially at higher power levels, the load in the A5 and A7 is distributed across two ICs and a heatsink twice the size.

If you're still unsure which speakers to buy, or if your speakers have an impedance below 3.5 ohms, particularly at low frequencies, I would always recommend the A5 or A7.

 

[antcollinet]

Let's take a step back here. A narrow band dip in impedance to 2ohm, does not turn a 4ohm impedance speaker into a 2ohm one.

Current limitations on impedance dips are only going to start to become an issue:
1 - When trying to output full power from the amp
2 - When a high proportion of that power is at the specific frequency of the dip.

This will certainly be a problem for single-tone test signals testing for full power, but it is unlikely to be a significant problem for real music which spreads its spectral power over the whole audio bandwidth, and more often than not is played at levels well within the capability of the amp.

I would certainly go for one of the PBTL models myself - but if I were already an owner of an SE, then I'd fail to lose sleep over it - even if I had speakers dipping below three ohms. This is especially the case for one rated for 230W into 4 Ohm. Which - even if current-limited at that point, will still be able to output 115W into 2 ohm without breaking a sweat.

 

[peng]

The A5 and A7 each use one chip in PBTL per channel and are therefore capable of handling 2 ohms.
The A5se and A7se use only one chip per device in BTL and are therefore only designed for 4 ohms.

The A5se and A7se can certainly handle loads down to 2 ohms in most cases, but this is far from ideal.
Significant heat generation and sonic degradation, depending on the complexity of the low-impedance load, are the result.
It should also be understood that this operates the amplifier and the TPA3251/55 chip outside of their specifications and may overload them. This can lead to failure, potentially damaging or destroying the speakers.

Furthermore, the power output at 2 ohms can drop significantly compared to the A5/A7, possibly even below the power output at 4 ohms.

Especially at higher power levels, the load in the A5 and A7 is distributed across two ICs and a heatsink twice the size.

If you're still unsure which speakers to buy, or if your speakers have an impedance below 3.5 ohms, particularly at low frequencies, I would always recommend the A5 or A7.

Agreed with what you are saying, but the key point some of use are making is, 4 ohm rated amplifiers can be suitable for speakers that have 4 ohm nominal impedance but also have dips to around 3 ohms or even lower. Most, if not all 4 ohm nominal speakers will have dips to around 3.2 ohm, may be +/- 0.2 ohm I would reasonably assume, based on quite a few speakers measured right here on ASR, Erin's corner and Stereophile. It would be rare for the reviewers to say such speakers should be paired with amplifiers rated for 2 ohm loads, just because there are a couple of low dips in the audio band.


In this specific case, we are responding to @Mort who is going to use an amp to drive his BMR bookshelf speakers that Stereophile's measurements show that the speaker has 2.9 ohms between 152Hz and 190Hz dips, also a 2.5 ohm dip that occurred at 1220 Hz.

The measured values are not that far off from 3.2 ohm, and there are quite a few speakers measured on ASR and Erin's corners that showed dips to below 3 ohms too; that does not mean one has to use 2 ohm rated amplifiers for such speakers. The A7 se should have no issue handling such dips when use only for music listening, but no one is saying the se versions can be used for 2 ohm nominal speakers, that should be pair with amplifiers that are rated for 2 ohm nominal impedance. In reality, there aren't that many power amps rated for 2 ohm (nominal impedance) speakers. There also that many 2 ohm nominal speakers, in fact for hifi, HT use I am not aware of such speakers either, though I am sure they exist.

In my opinion, as I have said so earlier, Mort should go for the A7, not the A7 se, and I even recommended he goes for the 10 A brick, though the 5 A brick can do the job too depending on his listening habit, distance etc.

 

[peng]

Let's take a step back here. A narrow band dip in impedance to 2ohm, does not turn a 4ohm impedance speaker into a 2ohm one.

Current limitations on impedance dips are only going to start to become an issue:
1 - When trying to output full power from the amp
2 - When a high proportion of that power is at the specific frequency of the dip.

This will certainly be a problem for single-tone test signals testing for full power, but it is unlikely to be a significant problem for real music which spreads its spectral power over the whole audio bandwidth, and more often than not is played at levels well within the capability of the amp.

I would certainly go for one of the PBTL models myself - but if I were already an owner of an SE, then I'd fail to lose sleep over it - even if I had speakers dipping below three ohms. This is especially the case for one rated for 230W into 4 Ohm. Which - even if current-limited at that point, will still be able to output 115W into 2 ohm without breaking a sweat.

Sorry for repeated some of what you are saying, I wrote mine after read Roland68's but before reading yours.
Anyway, Mort has plenty of inputs by now, probably enough for him to pull the trigger lol......

 

[Mort]

enough for him to pull the trigger lol....

Yes, which I did. $335 before tax for the A7 and the 48v/10a.

Decided against the ncx252, which I'm sure is a darling performer. And I hate separate power bricks but I think for a $2k bookshelf speaker that isn't my main set, the A7 is perfect.

 

[peng]

Yes, which I did. $335 before tax for the A7 and the 48v/10a.

Decided against the ncx252, which I'm sure is a darling performer. And I hate separate power bricks but I think for a $2k bookshelf speaker that isn't my main set, the A7 is perfect.

I just checked with REW, level matching was almost perfect, not by my own effort, purely based on the fact that both amps have about the same gain.

The mic does hear a difference, though practically insignificant at least not by my ears or probably most ears older than 40, 50?

Amp A is A7 Mono, Amp B is NC502MP, Amp A has the shorter speaker cables, AWG 12 but about half the length of the pair for the Amp B, NC502MP:

Amp A is still A7 Mono, Amp B NC502MP, but I swapped the speaker cables, now the A7 Mono has the longer cable:

That's pink noise sweep, I have not tried using music file to sweep, yet.

 

[Mort]

I just checked with REW, level matching was almost perfect, not by my own effort, purely based on the fact that both amps have about the same gain.

The mic does hear a difference, though practically insignificant at least not by my ears or probably most ears older than 40, 50?

View attachment 503866

View attachment 503871

That's pink noise sweep, I have not tried using music file to sweep, yet.

Haha. This is awesome. ASR always delivers.

 

[Alannn]

...In this specific case, we are responding to @Mort who is going to use an amp to drive his BMR bookshelf speakers that Stereophile's measurements show that the speaker has 2.9 ohms between 152Hz and 190Hz dips, also a 2.5 ohm dip that occurred at 1220 Hz.

The measured values are not that far off from 3.2 ohm...

Although I agree with the rest of your post, I'll disagree on the above quote.
3.2 ohms is about 28% higher than 2.5 ohms. In this frame of reference, the 0.7 ohm difference is "far off," IMO. To clarify, using a different terminology, a 28% higher measurement is significant.

Let's take a step back here. A narrow band dip in impedance to 2ohm, does not turn a 4ohm impedance speaker into a 2ohm one...

Correct. A narrow band dip in impedance to 2 ohm, turns a 4 ohm impedance speaker into a 2.5 ohm one (IEC 60268-5 and EIA/RS-299-A).

 

[peng]

Although I agree with the rest of your post, I'll disagree on the above quote.
3.2 ohms is about 28% higher than 2.5 ohms. In this frame of reference, the 0.7 ohm difference is "far off," IMO. To clarify, using a different terminology, a 28% higher measurement is significant.

You might have missed the point I made earlier, I was not too concerned about the 2.5 ohm because it was at 1220 Hz, so it will be handled by the one 2.5" Balanced Mode Radiator. There are a few versions for that radiator but being that it is a round one, based on the spec sheets, the power handling spec is in the range of 10-30 W, that's a lot lower than that for the 6 inch woofer. Since the A7 can do at least 200 W into 4 ohms according to 3 e Audio's spec sheet, it should be able to do 100 W into 2 ohms and should be able to do more if the 2.5 ohms is at around 1220 Hz or just between 3 ohms in the range 850-1700 Hz, not a narrow dip, but still only about an octave, far from being continuous.

Of course you can say that is significant based on IEC's 0.8 (i.e. 3.2 ohms in this case) guideline, but significant or not could be a subjective thing so I wouldn't disagree.. I still standby my belief that while as Stereophile commented, that this BMR version is difficult to drive, the A7 SE that is rated for 4 ohm loads can handle such dips because the impedance of the speaker is specified as 4 ohm nominal by a reputable designer. I trust Dennis gave it the 4 ohm nominal for good enough reason.

For the OP it is now a moot point because he ordered (in my opinion, wisely) the A7 anyway, it saves us from keep debating.

 

[peng]

Is it worth paying for a better power adapter for the A7? On us Amazon there are only third party options. No 3e model in 10A.

I would say the gaN (Gallium Nitride) types are good, such as the Aiyima one I linked before, there is one by Fosi as well, but they have different version, the gaN one does cost more than the Ayima one. The ones I got from 3 eAudio for the Mono are also the gaN type.

 

[monsterlag]

I would say the gaN (Gallium Nitride) types are good, such as the Aiyima one I linked before, there is one by Fosi as well, but they have different version, the gaN one does cost more than the Ayima one. The ones I got from 3 eAudio for the Mono are also the gaN type.

Same here, I also got the 48V 10A GAN charger. It’s still a massive brick.

 

[peng]

@Mort , below are what I posted when I received the A7 Mono:

The one on the left was from Fosi that I bought way back with the V3 stereo, they didn't offer me choices, so it was their default supply at the time I guess. It is not the gaN type and it is gigantic, compared to the GaN adaptor from 3 e Audio. Your 10 A ones will be much larger than the 5 A one shown in the right, so I hope for a few more $, you did get the gaN, unless size and efficiency won't bother you.

 

[NDA357]

AVR - Pioneer sclx79. 3eA7 stereo. 1. Front speakers are connected via RCA, auto-tuning sets them to L_0, R_0. 2. XLR is connected, auto-tuning sets them to L_+5, R_+5. Why is there such a difference?

 

[harkpabst]

AVR - Pioneer sclx79. 3eA7 stereo. 1. Front speakers are connected via RCA, auto-tuning sets them to L_0, R_0. 2. XLR is connected, auto-tuning sets them to L_+5, R_+5. Why is there such a difference?

Which gain setting did you use for RCA?

I don't see any XLR outputs on your AVR, so obviously you must have used some kind of adapter (cable). In this case the output voltage is simply the same, but the XLR input's gain is designed for twice the RCA voltage.

 

[Alannn]

You might have missed the point I made earlier, I was not too concerned about the 2.5 ohm because it was at 1220 Hz, so it will be handled by the one 2.5" Balanced Mode Radiator. There are a few versions for that radiator but being that it is a round one, based on the spec sheets, the power handling spec is in the range of 10-30 W, that's a lot lower than that for the 6 inch woofer. Since the A7 can do at least 200 W into 4 ohms according to 3 e Audio's spec sheet, it should be able to do 100 W into 2 ohms and should be able to do more if the 2.5 ohms is at around 1220 Hz or just between 3 ohms in the range 850-1700 Hz, not a narrow dip, but still only about an octave, far from being continuous.

Of course you can say that is significant based on IEC's 0.8 (i.e. 3.2 ohms in this case) guideline, but significant or not could be a subjective thing so I wouldn't disagree.. I still standby my belief that while as Stereophile commented, that this BMR version is difficult to drive, the A7 SE that is rated for 4 ohm loads can handle such dips because the impedance of the speaker is specified as 4 ohm nominal by a reputable designer. I trust Dennis gave it the 4 ohm nominal for good enough reason.

For the OP it is now a moot point because he ordered (in my opinion, wisely) the A7 anyway, it saves us from keep debating.

Nope, I said I agreed with your post because I didn't miss your point. The SE version amp would have worked fine for the reasons you mention.

On "significance" possibly being subjective, you remind me that an amp with significantly better specs than another, may have no audible difference. No audible difference brings up the question of the meaning of significance. It is a fact of life that some here chase inaudible, but clearly better specs. That significance! That's why we buy the 3e amps with their impressive SINAD measurements.

 

[NDA357]

Which gain setting did you use for RCA?

I don't see any XLR outputs on your AVR, so obviously you must have used some kind of adapter (cable). In this case the output voltage is simply the same, but the XLR input's gain is designed for twice the RCA voltage.

I connected a Wiim Ultra to the RCA input to avoid adapters. I connected an AVR to the XLR input using an XLR adapter. The A7's gain switch is set to RCA. What do I need to do to make the AVR set my edges to zero?

 

[antcollinet]

I connected a Wiim Ultra to the RCA input to avoid adapters. I connected an AVR to the XLR input using an XLR adapter. The A7's gain switch is set to RCA. What do I need to do to make the AVR set my edges to zero?

Why do you need to. The AVR is just compensating the lower gain of the XLR input by putting it back in the level settings.

Alternatively use the RCA inputs. If you are not experiencing ground noise, there is no benefit to XLR.