I will try those suggestions. I do have have some DIY skills but im wondering if its worth the effort. I'm completely fine with running the setup with RCA cables. Like i said in my first post, when running with RCA, i only hear noise when i put my ear close to the tweeter. I wanted to make sure this wasn't something that i was causing or due to faulty components. Thanks for the help!
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3e audio A7/A7 Mono Amplifier Review
- Thread starter amirm
- Start date
Hello, have you tried reversing the polarity of the power plug? For example, when using S3, if only S3 and A7 are connected, try reversing the polarity on one of them. Also try all 4 combinations of polarity combinations.
I will try that suggestion as well.
Over the weekend, I tried S3 -> Optical -> Topping E70V. It was completely silent with either RCA or XLR regardless of volume bypass setting. I did try the S3 + A7 combo at a friends house as suggested and there was no noise with either RCA OR XLR. He has different speakers but it seems the problem is with my place and can be eliminated with an external DAC. Thanks for the help everyone.
Over the weekend, I tried S3 -> Optical -> Topping E70V. It was completely silent with either RCA or XLR regardless of volume bypass setting. I did try the S3 + A7 combo at a friends house as suggested and there was no noise with either RCA OR XLR. He has different speakers but it seems the problem is with my place and can be eliminated with an external DAC. Thanks for the help everyone.
Hi there,
Wanted to ask about 3E Audio A7 10A - can you connect L+ and R- to single woofer driver terminal as mono output? I would feed in only one signal channel (left or right). I've got stereo but now intend to use as mono, is this viable? THX
Wanted to ask about 3E Audio A7 10A - can you connect L+ and R- to single woofer driver terminal as mono output? I would feed in only one signal channel (left or right). I've got stereo but now intend to use as mono, is this viable? THX
Roland68
Major Contributor
No, that's not possible, as each channel is already configured as PBTL.
Even with TPA3251/55-based devices that are only configured as BTL, this wouldn't be possible without major technical modifications, unless the manufacturer has explicitly planned for it.
The A7, however, already has the highest power output per channel achievable with a TPA3255 chip.
Thanks. So I would be better buying mono, cheaper and "stronger". Too late to think when I have it...
Guddu
Major Contributor
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If you are planning to buy then mono is your best option.
If you already have A7 stereo version then just use L or R (any channel).
Op amp swapping can do one of two things:
1 - If the circuit remains stable - no audible difference. Sound quality is determined primarily by the circuit around the op amp chip.
2 - If the circuit becomes unstable - possible zero audible difference, ranging up to dramatic detriment to sound quality.
Without measuring the result you can't know which of these is happening - unless the sound goes wacky.
In either case - if you compare sighted (and it is difficult to compare blind especially if one chip is shared between the channels), then your perceptive biases will likely tell you there is an audible difference that doesn't actually exist.
Bottom line - don't waste your time, effort, or money.
I don't know how regional sales on these are.
But amazon has them at 23% off coming to $314 Canadian.
There also was a $47 off coupon that I got (but does not seem to still be available when I looked today)
So I ordered one for $267.25CAD pre tax and $299.32 CAD total.
Not sure if that is a great price for it these days. But I felt it was too good to pass on and a buy now, think later situation.
I was going to use this to power my front L+R in my theatre but if people have better recommendations let me know!
Here is my new house setup plan if people have other recommendations:
'Moving to a new house - Re-vamping all my listening spaces and need amp (and other) recommendations!' https://www.audiosciencereview.com/...and-need-amp-and-other-recommendations.70287/
But amazon has them at 23% off coming to $314 Canadian.
3e Audio A7 TPA3255 2x250W PBTL Next-Gen Hi-Fi Stereo Amplifier | Enhanced PFFB | for Home Theatre & Bookshelf Passive Speakers | 48V 5A Power Supply Included : Amazon.ca: Electronics
3e Audio A7 TPA3255 2x250W PBTL Next-Gen Hi-Fi Stereo Amplifier | Enhanced PFFB | for Home Theatre & Bookshelf Passive Speakers | 48V 5A Power Supply Included : Amazon.ca: Electronics
www.amazon.ca
There also was a $47 off coupon that I got (but does not seem to still be available when I looked today)
So I ordered one for $267.25CAD pre tax and $299.32 CAD total.
Not sure if that is a great price for it these days. But I felt it was too good to pass on and a buy now, think later situation.
I was going to use this to power my front L+R in my theatre but if people have better recommendations let me know!
Here is my new house setup plan if people have other recommendations:
'Moving to a new house - Re-vamping all my listening spaces and need amp (and other) recommendations!' https://www.audiosciencereview.com/...and-need-amp-and-other-recommendations.70287/
@3eaudio , @johnp98
I, too, noticed that the 3e Audio A7 was on sale on Amazon.ca. The $47 off coupon was limited to one per customer. I bought three to use with my tri-amped La Scala speakers.
The amps didn't sound great when I plugged them into my system so I thought I'd better characterize them so that I could integrate them optimally.
I've spent the past couple of days measuring the amps. I've been limited to using making measurements with my 16 ohm/200W dummy load. Higher wattage 4 ohm and 8 ohm resistors have been ordered, but won't arrive until near the end of the month.
I've been able to determine that input sensitivity of the A7 is much lower than the published specs. Input sensitivity tells us how large the input signal must be to drive the amplifier to its maximum output without causing distortion (clipping). I also found that setting the RCA gain to H (high) is counterproductive.
Testing
I sent a 1 kHz sine wave into the amps and measured the output signal. In all cases, providing a input at 1.75 VRMS (as per 3e Audio's specs) caused significant clipping when the amp was set to VOL BYPASS (i.e., maximum gain).
This slide deals with RCA input, with the RCA gain set to L:
This slide deals with RCA input, with the RCA gain set to H:
This table shows the measurement results for all 3 amps:
This table summarizes the results for all three amps. It shows the actual input sensitivity (the lowest of each amp's 2 channels) and the power delivered into 16 ohms at maximum gain (i.e., VOL BYPASS set).
Summary
The A7's input sensitivity is not 1.75 VRMS. It is less than 1.5 VRMS when the RCA gain is set to L, and less than 1 VRMS when the RCA gain is set to H. Those wishing to use the A7 as a power amp (i.e., with VOL BYPASS enabled) may need to attenuate the signal being sent to the amp.
Also, setting the RCA Gain to H provides a maximum of 42W/channel. It's higher --- 47W/channel --- when the RCA Gain is set to L.
Roland68
Major Contributor
Which power supply did you use for the measurements? 48V 5A or 10A?
When the amplifier is in bypass mode, the signal is attenuated almost to zero by the external volume control anyway, and can then be adjusted as desired. Unless there's a severe impedance mismatch, no additional attenuation is necessary.
@Roland68 That's a very good observation.
On Amazon.ca, the 3e Audio A7 was only offered with a 48V/5A power supply; there wasn't an option for a 48V10A PS.
I wondered if my conclusions might have been due to the PS being unable to provide sufficient current. However, I don't think that was the case. All of my measurements (into a 16.3 ohm load) showed clipping occurring when the amp's output was at less than 30 VRMS. Using Ohm's law (I=V/R) it's clear that the A7s were never drawing more than 2A, well below the 5A that the PS is capable of delivering.
I don't understand your statement about how the signal is attenuated "almost to zero" when in bypass mode. Would you please clarify and expand on that?
I was thinking that I'd need to attenuate the input to the amp by about -2.5 dB (from my streamer's 2 VRMS output, so that it wouldn't deliver more than 1.5 VRMS to the amp).
harkpabst
Addicted to Fun and Learning
Just for the records, a lower voltage (like 1,49 V instead of 1,75 V) doesn't indicate a lower, but a higher input sensitivity. The definition is a bit unintuitive and not as helpful as one might think, as it depends on how you measure the "undistorted" output power.
It's much more helpful to think in terms of gain to get an impression of where the unexpected results migh stem from. In your case (input voltage 1.49 Vrms, output voltage 27.4 Vrms) the amplifier's gain is 18.39 or 25.3 dB. I think that this is within the margin of error of the specified 26 dB.
Consequently, according to your measurements, there's not really a problem with sensitivity but with available output power (undistorted voltage swing). Did the clipping LED light up when you saw clipping on your scope?
I also noticed a slight mismatch between peak-to-peak and RMS voltage values. For a pure sine wave 27.4 Vrms should equal 77.5 Vpp or 81.6 Vpp should equal 28.85 Vrms.
The TPA3255 data sheet doesn't contain any specs for a 16 Ω load, but it also doesn't specify a maximum load impedance (just a minimum load). We should expect the maximum output voltage to be the same as with 8 Ω. You already explained how the maximum PSU current cannot be a problem with the higher than usual load impedance, but let's not forget that Amir did his testing with a 52 V PSU.
You started all this because you were disappointed with the sound of your amplifiers. So far I don't see how the results you obtained would translate into audibly bad sound. There could be something else ... or just not.
Great work on the testing.
Just to clarify @harkpabst statement - the lower sensitivity voltage is defined as a higher sensitivity, because the amp is "more sensitive" to the input voltage.
Something in your results that doesn't make sense though. I can't come up with a mechanism that would cause a higher gain to result in a lower output voltage at clipping. (unless the input stage clips, which seems unlikely). Amir's measurements also show his amp is able to output
How were you determining the clipping point? If visually looking for a flat top on the scope waveform, I would think this is not accurate enough. You would need to measure THD and set a specific THD threshold (eg 1%) to indicate clipping. If this is what you were doing, what were you using as the THD threshold.
Oh, and how to you filter the output to prevent the switching frequency from disturbing the measurement?
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Sorry, I don't understand how you're saying that MUCH lower from 1.5 to 1.75V and without getting the exact 1%THDN point.
You are free to measure it if you have a tool running more similar to Ap.
Roland68
Major Contributor
I didn't even notice what kind of speakers you have at first.
Which La Scala speakers do you have?
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