Argentum 05
Member
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3e audio A7/A7 Mono Amplifier Review
- Thread starter amirm
- Start date
it's just my double vision (caused by TBI) this time
Just for fun I thought I'd try to figure out what the SPL would be if I were to get a 3e Audio A7 amp to clip when playing through my La Scala speakers.
Situation
- My tests with the A7 showed that --- with the RCA Gain set to Low (i.e., 25 dB) -- the amp would clip at 46W into a 16 ohm load.
- I have La Scala speakers. Klipsch rates the La Scala as delivering approximately 105 dB SPL @ 2.83V @ 1m (i.e., 1 W at 1m when going into an 8 ohm load).
- Although my speakers are tri-amped , an unmolested La Scala presents an 8 ohm load.
- All of the drivers in the system are also rated at roughly 105 dB SPL @ 2.83V @ 1m
- I am listening to 2 speakers
- My listening positions are about 3m (10 feet) from the speakers.
- I seldom listen at much more than 90 dB SPL.
Recall:
- while dB power is calculated as 10log(P2/P1), dB amplitude (such as SPL) is calculated as 20log(A2/A1).
- adding a second speaker increases SPL between +3 dB (for incoherent/out-of-phase sources) and +6 dB SPL (for coherent/in-phase sources)
+ 3 dB SPL --- additional SPL from second speaker (worst case, assumes speakers are incoherent)
108 dB SPL --- total SPL from both speakers
- 9.5 dB SPL --- SPL reduction at 3m distance (i.e., 20log(3/1) = -9.5 dB SPL)
98.5 dB SPL --- SPL at 3m when both speakers are driven with 1 watt
From information provided by Crown alongside one of their calculators, we find two formulae that can help us:
1) dBW = Lreq - Lsens + 20 * Log (D2/Dref) + HR
2) W = 10 to the power of (dBW / 10)
Where:
Lreq = required SPL at listener
Lsens = loudspeaker sensitivity (1W/1M)
D2 = loudspeaker-to-listener distance
Dref = reference distance
HR = desired amplifier headroom
dBW = ratio of power referenced to 1 watt
W = power required
Let's start by working backwards from 46W (the power level above which the amp starts to clip when driving 16 ohms)
W = 10 to the power of (dBW / 10)
46 = 10^(dBW/10)
dBW = 16.63
Recall that dBW was calculated with a 16 ohm load. The power into 8 ohms should be nearly double that.
Therefore,
dBW = 16.63 x 2
= 33.26
With that we can approximate the SPL using
dBW = Lreq - Lsens + 20 * Log (D2/Dref) + HR
33.26 = Lreq - 105 + 20log(3/1)+0 (since we are not interested in amplifier headroom at this time, HR can be ignored)
33.26 = Lreq -105 + 9.5
33.26 = Lreq -95.5
Lreq = 128.76 dB SPL
Of course, very few speakers could deliver that sort of output. The drivers in my La Scala would all have blown up before getting to those levels. And that's from one speaker! Adding a second speaker would add another 3 to 6 dB SPL, taking the volume above 130 dB (in theory). That’s extremely loud.
According Decibel Pro 130 dB SPL would be equivalent to:
- a jet take-off
- the loudest rock concert ever recorded
- a gunshot at close range
Let's repeat the calculation for @Argentum 05 's speakers.
First, let's need to calculate (well, approximate) the A7's clipping point into 6 ohms when the RCA Gain is set to Low (i.e., 25 dB).
If the amp clips at 46 watts into 16 ohms, it should clip at roughly
- 92 watts into 8 ohms
- 184 watts into 4 ohms
Now let's calculate dBW
138 = 10^(dBW/10)
dBW = 21.4
With that we can approximate the SPL using
dBW = Lreq - Lsens + 20 * Log (D2/Dref) + HR
21.4 = Lreq - 92 + 20log(2.5/1)+0 (since we are not interested in amplifier headroom at this time, HR can be ignored)
21.4 = Lreq -92 + 8
21.4 = Lreq -84
Lreq = 105.4 dB SPL
The second speaker should increase the volume at the listening position by between 3 and 6 dB SPL.
At roughly 108 - 110 dB SPL, the noise level would be similar to that at a concert or when using a jack hammer. Listening at that volume can cause permanent hearing damage in just minutes. Your neighbours would be right to arm themselves and come after you.
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Roland68
Master Contributor
You should simply refrain from performing clipping tests with such a powerful amplifier as the A7.
The likelihood of damaging your hearing and/or the speakers is far greater than the chance of seeing clipping indicators.
This kind of testing is done with load resistors or extremely inefficient speakers, which hardly anyone owns.
Suitable load resistors should be rated for at least 300 watts at 4 ohms.
Argentum 05
Member
Thank you very much for the calculations you did for me!At roughly 108 - 110 dB SPL, the noise level would be similar to that at a concert or when using a jack hammer. Listening at that volume can cause permanent hearing damage in just minutes. Your neighbours would be right to arm themselves and come after you.
Am I correct in assuming that the CLIP indicator should turn on when my speakers reach 105 dB SPL?
If so, that's too loud for home use. And my speakers probably won't handle it.
+1 on what @Roland68 said.
For the A7 tests that I did I used a 16 ohm/200W power resistor as a dummy load. Even though I wasn't pumping more than 46 watts into it, it got hot!
I have 4 ohm/400watt and 8 ohm/200 watt resistors on order. If I were to order them again, I'd get ones with even higher wattage.
Argentum 05
Member
Thank you. I understand. I'm not the enemy of my ears and speakers)))
@Argentum 05 that should be the threshold just before the clipping indicator on each channel comes on. Anything above that should cause clipping.
Roland68
Master Contributor
I work in industry, so I'm referring to resistors that can withstand 300 watts continuously without being damaged. Of course, they can get hot. Some of them get over 1000°C, but unfortunately, they aren't induction-free.
Bear in mind though, the phone measurement will be an average - or short medium term reading. Transient peaks can be 10db (10xpower) or more higher. Also a 6 ohm 92dB sensitive speaker needs 1.5W for 95dB (Sensitivity is to a voltage, not a power - and the lower impedance needs more power for that voltage), so under those conditions (2.5m), peak power is going to be around 180W to 190W (According to the crown amp power calculator)
Right on the ragged edge of clippping with this amp on a 6ohm speaker.
VU meters? SPL meter?
TurtlePaul
Major Contributor
Yes, but on the other hand, OP wants to see the clipping light and that may not come on until 3-5% THD. That can be several dB above where voltage clipping flattens the waveform. I am not sure the exact level needed to reach clipping because my A7 has never been close.
The latter, with blinky lights warning my teens or their the guests to turn it down.
Ideally can trigger external devices e.g. via a relay
The clipping indicator from the TPA chip is self clearing, and lasts only as long as the signal is over the clipping threshold. The clipping indicator pulse can be as short as 0.5 ms. Without some extra circuitry to keep the indicator light on for a significantly longer period of time after a clipping event is detected, chances are that the light will be unnoticible because of the insufficient clipping time for the brightness to build up.
"Mono speakers"... Speakers?
SoundAlert - Lights Up When Noise Levels are High
The SoundAlert shows the sound levels in dB and clearly indicates when the noise is high. An external sign gives a clear indication to anybody nearby.
www.noisemeters.co.uk
not cheap though.
Argentum 05
Member
These are most likely the quirks of online translation. Google Translate constantly confuses words and meanings. When translating from Russian to English and back, it also often replaces "amplifier" with "speaker." Reading many posts here, I understand the meaning of what's written based on context, not literally.
@3eaudio
EDIT: I have made substantial changes to my original post. Further testing revealed that the autosense on capability does not always work when dealing with the amp that powers the tweeters.
I wanted to provide an update on the 3e Audio A7s that I purchased to use with my tri-amped La Scala speakers.
TLDR, they are excellent devices. They meet almost all of my goals. My only concern is that they may be too powerful for my use case; I have only about 6 volume steps between silent and deafeningly loud.
My setup
I run tri-amped La Scalas in a 2.2 system with two Bill Fitzmaurice designed (but home built) THTLP subwoofers. My source is a Bluesound Node streamer which connects to a MiniDSP Flex Eight DSP/active crossover. The 8 outputs from the DSP are connected as per this diagram:
I have been using Aiyima A07 amps with the La Scala drivers. One amp drives the woofers, another drives the midranges (aka "squawkers"), and the third drives the tweeters. The three 3e Audio A7 amps would replace the Aiyima amps.
Why replace amps that worked perfectly well?
The Aiyima A07 amps performed perfectly well and I was happy with how they sounded. I purchased them because they provided an inexpensive way to experiment with tri-amping. Having convinced myself that tri-amping is the best way to go, I thought that I might upgrade the amps.
I was hoping that by upgrading the amps I could:
one two of those goals: I still have the clutter associated with 3 separate amps and 3 separate power supplies, and the autosense capability will not always power on the amp serving the tweeters. Although I had been concerned about the autosense on/off on the A7 (particularly since some drivers --- like the tweeters --- seldom see more than a few mW), the autosense has worked fine.
I had been concerned that the tweeters would require so little power (single-digit to double-digit mW) that the voltage sent to the amp powering them would be insufficient for the autosense to recognize that they needed to be turned on. It appears that concern has been borne out: the amp does not always turn on via the autosense. This is easily remedied by turning the amp on manually. The autosense has worked fine for the amp powering the midrange drivers and the amp powering the woofers.
However, even when music is playing, the amp sometimes seems to think that there is no activity at the tweeter and turns itself off automatically.
Integrating the new amps into my system
In my first post in this thread (post #1394), I reported that "the amps didn't sound great when I plugged them into my system". At that time I had not done anything to integrate them into my system, so that it was likely an unfair comment.
All that was necessary to get them to sound great in my system was to set the gain per driver. The A7 amps are more powerful than the Aiyima A07 amps they were replacing so that it was necessary to change the gain setting for each driver in the DSP.
I took two sets of 1m on-axis readings of each driver using a UMIK-1 calibrated microphone and REW. One set of measurements was of the existing setup (with A07 amps). I then replaced the A07 amps with the 3e Audio A7 amps and repeated the measurements. It was important that the microphone stay in exactly the same place for the two sets of measurements.
This chart shows what the gain settings needed to be:
With those gain settings applied in the DSP and no other changes, the Frequency/SPL graphs of the 3e Audio A7 and Aiyima A07 match almost perfectly:
I'll refrain from making any subjective observations, apart from that I think that the system sounds really good with the 3e Audio amps. (But it did with the Aiyima A07 amps too).
Conclusions
The 3e Audio A7 is a fine amp; sonically it cannot be faulted. The A7 delivered on almost all of the objectives I had for the upgrade.
There are onlytwo three things that keep the A7 amps from being ideal for me:
The biggest issue is that the autosense functionality doesn't work with my configuration. Specifically, at low listening levels my tweeters draw so little power that the autosense to know to turn the amp on (or to keep from shutting the amp off).
Only users that have highly efficient HF drivers and are powering them with a separate amp would be likely to run into these problems with the autosense on functionality.
The A7 may be too powerful for my system. I have only about 6 positions on my volume control between silent and deafening. Although it's hard to measure, each volume position is about 2 or 3 dB from the next. Finer volume control would be desirable. But I don't know if going to a lower-powered amp would give me more granularity with the volume control, or if it would just reduce the "headroom".
The 3e Audio A7 is a fine amplifier. But, much to my regret, I fear it's not for me.
I'm reflecting on @Roland68 's suggestion that the lower-powered 3e Audio A5 might be a better match for my system. However, since the autosense problem would likely be present with the A5, it is a non-starter.
However, the 3e Audio/ALSOZONE PAM156, which uses the same amp modules as the A5 might be an option. It should address the 3 issues (clutter, on/off convenience, and insufficient volume granularity) that I identified:
EDIT: I have made substantial changes to my original post. Further testing revealed that the autosense on capability does not always work when dealing with the amp that powers the tweeters.
I wanted to provide an update on the 3e Audio A7s that I purchased to use with my tri-amped La Scala speakers.
TLDR, they are excellent devices. They meet almost all of my goals. My only concern is that they may be too powerful for my use case; I have only about 6 volume steps between silent and deafeningly loud.
My setup
I run tri-amped La Scalas in a 2.2 system with two Bill Fitzmaurice designed (but home built) THTLP subwoofers. My source is a Bluesound Node streamer which connects to a MiniDSP Flex Eight DSP/active crossover. The 8 outputs from the DSP are connected as per this diagram:
I have been using Aiyima A07 amps with the La Scala drivers. One amp drives the woofers, another drives the midranges (aka "squawkers"), and the third drives the tweeters. The three 3e Audio A7 amps would replace the Aiyima amps.
Why replace amps that worked perfectly well?
The Aiyima A07 amps performed perfectly well and I was happy with how they sounded. I purchased them because they provided an inexpensive way to experiment with tri-amping. Having convinced myself that tri-amping is the best way to go, I thought that I might upgrade the amps.
I was hoping that by upgrading the amps I could:
- address some of the deficiencies of the current amps (imbalance between channels in each amp, inconsistency between amps)
- make usage more convenient with auto on/off (preferably via a 12V trigger)
- provide an ability to use XLR connections (not needed now, but maybe in the future)
- see what difference PFFB makes
- have more "headroom"
- reduce clutter (fewer chassis and power supplies)
I had been concerned that the tweeters would require so little power (single-digit to double-digit mW) that the voltage sent to the amp powering them would be insufficient for the autosense to recognize that they needed to be turned on. It appears that concern has been borne out: the amp does not always turn on via the autosense. This is easily remedied by turning the amp on manually. The autosense has worked fine for the amp powering the midrange drivers and the amp powering the woofers.
However, even when music is playing, the amp sometimes seems to think that there is no activity at the tweeter and turns itself off automatically.
Integrating the new amps into my system
In my first post in this thread (post #1394), I reported that "the amps didn't sound great when I plugged them into my system". At that time I had not done anything to integrate them into my system, so that it was likely an unfair comment.
All that was necessary to get them to sound great in my system was to set the gain per driver. The A7 amps are more powerful than the Aiyima A07 amps they were replacing so that it was necessary to change the gain setting for each driver in the DSP.
I took two sets of 1m on-axis readings of each driver using a UMIK-1 calibrated microphone and REW. One set of measurements was of the existing setup (with A07 amps). I then replaced the A07 amps with the 3e Audio A7 amps and repeated the measurements. It was important that the microphone stay in exactly the same place for the two sets of measurements.
This chart shows what the gain settings needed to be:
With those gain settings applied in the DSP and no other changes, the Frequency/SPL graphs of the 3e Audio A7 and Aiyima A07 match almost perfectly:
I'll refrain from making any subjective observations, apart from that I think that the system sounds really good with the 3e Audio amps. (But it did with the Aiyima A07 amps too).
Conclusions
The 3e Audio A7 is a fine amp; sonically it cannot be faulted. The A7 delivered on almost all of the objectives I had for the upgrade.
There are only
- Clutter
- Auto on/off
- Is it too powerful?
The biggest issue is that the autosense functionality doesn't work with my configuration. Specifically, at low listening levels my tweeters draw so little power that the autosense to know to turn the amp on (or to keep from shutting the amp off).
- Depending on volume settings and source material, the signal is not always sufficient to trigger the autosense to turn on. This has been noticed only with the amp that serves the tweeters.
- As mentioned above, even when music is playing the amp sometimes seems to think that there is no activity at the tweeter and turns itself off automatically. That is a deal breaker for me.
Only users that have highly efficient HF drivers and are powering them with a separate amp would be likely to run into these problems with the autosense on functionality.
The A7 may be too powerful for my system. I have only about 6 positions on my volume control between silent and deafening. Although it's hard to measure, each volume position is about 2 or 3 dB from the next. Finer volume control would be desirable. But I don't know if going to a lower-powered amp would give me more granularity with the volume control, or if it would just reduce the "headroom".
The 3e Audio A7 is a fine amplifier. But, much to my regret, I fear it's not for me.
I'm reflecting on @Roland68 's suggestion that the lower-powered 3e Audio A5 might be a better match for my system. However, since the autosense problem would likely be present with the A5, it is a non-starter.
However, the 3e Audio/ALSOZONE PAM156, which uses the same amp modules as the A5 might be an option. It should address the 3 issues (clutter, on/off convenience, and insufficient volume granularity) that I identified:
- The PAM156 essentially houses several (mono) A5s in a single chassis with an integrated power supply.
- The PAM156 uses a 12V trigger for auto on/off.
- Each channel in a PAM156 is rated at 150W into 4 ohms @ 1% THD (versus 250W for the 3e Audio A7). However, I don't know if lower power would provide more granularity with the volume.
Last edited:
Wow, exactly what I was imagining. Maybe useful as an A/B SPL comparator too for testingSoundAlert - Lights Up When Noise Levels are High
The SoundAlert shows the sound levels in dB and clearly indicates when the noise is high. An external sign gives a clear indication to anybody nearby.
not cheap though.
At that price one would think it is accurate, or at least well repeatable.
Thanks!
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