Important to note... I think we're done here for now.
The two pics I have posted here are pretty close to being tone matched. Or at least reasonably similar.
The red knobs are from my active system. This is the tone control settings for my headphones and ultimately the speakers. It's a Schiit Loki Mini+. This chain has an A07 with 2 SparkosLabs SS3602's driving the speakers.
The tone controls shown with black knobs are the A07 pro. The two are pretty close to being tone matched as you can see.
When I switch the Loki to flat/neutral with what is an effective tone defeat, the system, for the most part, sounds the same as when the A07 pro has its tone controls at the 12 position, which is effectively no added tone/flat as well.
My observations are that the A07 Pro's Bluetooth output, is artificially tweaked to have a sound that is a bit more punchy and dynamic due to the raised highs and lows. A slight V shape if you will.
When I first posted the picture with the A07 tone controls with this setting, I stated that this was where we tuned it so the RCA input/output matched as close as it could the sound of the Bluetooth output with the knobs at 12/flat.
So these amplifiers, both the A07 and the A07 pro, when compared, sound pretty much the same. The A07 though has a better posted SNR and THD+n than this "Pro" unit. So it isn't really a "Pro" unit after all.
You can effectively introduce tone controls without adding this much noise to the system.
The Loki Mini, which costs $149 USD has an SNR of greater than 114db and a THD less than 0.0008%
You get a nice range of frequencies to play with in the 4 knobs the Loki Mini+ gives you. Based on my system. All the components have very close SNR and THD numbers. Things are quiet.
Loki Mini+
THD: Less than 0.0008%, 20Hz-20KHz, at 2V RMS in/out, pots centered, active stage enabled, less than 0.005% at any potentiometer setting
SNR: Greater than 114db, unweighted, referenced to 2V RMS
My Magni+ Heretic measurements as posted on the product spec page are:
THD+N:
High Gain: Less than 0.0002% (-112dB) ref 2V RMS at 300 ohms
Low Gain: Less than 0.0001% (-119dB) ref 2V RMS at 300 ohms
SNR:
High Gain: Greater than 115dB, unweighted, ref 2V RMS
Low Gain: Greater than 123dB, unweighted, ref 2V RMS
The A07 amplifier with stock op-amps
THD+N:0.008%
SNR:110db
The A3001 subwoofer amplifier
THD: 0.03%. - not great!
SNR: ≥106dB
And now you have the A07 pro.
THD: 0.002%
SNR: 90dB. <- Seriously?!?!
A correction - so to speak
The A07 pro overall is not dull... And I really shouldn't have said that. Because dull as compared to the sound through Bluetooth is not a statement about poor sound quality with the RCA sound.. But moreover a confirmation as to who Aiyima really wanted to sell this "Pro" unit to.
The A07 and the A07 Pro essentially sound the same.
It is my opinion that while they upgraded a few parts and added all those op-amp slots.. It really wasn't designed to be a true A07 upgrade..
An A07 owner has no need to purchase the "pro" unit because it is not an upgrade to that unit. It is just another product for them to sell... One with objectively worse specs than it's predecessor. But catered to the mobile crowd for sure.
A "Pro" version of anything should not be measurably worse than the preceeding non-pro model.
Why they did this is somewhat confusing because they essentially already gave us a TPA3255 unit with Bluetooth and tone controls in the A08 pro. With a different shape and that VU meter.
The A08 pro also supports LDAC! Why doesn't the A07 Pro support LDAC?
The A08 pro has tone controls and a posted SNR of ≥104db. They however do not post the THD+n measurements.
(
Aiyima at one point also produced and released an A07 with Bluetooth with what appears to be an overseas market test of sorts. You can find it on AliExpress.)
The Aiyima A08 pro was reviewed by Amir -
Here
So for me it is clear... The amps are all very similar and Aiyima does a good job for the most part with their TPA3255 implementation.
That being said, with the ability to add Bluetooth to any part of your chain with components such as the DAC, headphone amp, Pre or speaker amp, etc. You can inject that as you see fit. I have Bluetooth capability with my Aune X8 XVIII DAC and it does not artificially Amp up the frequencies like the A07 Pro does.
Aiyima just wants to have a product that can be marketed and sold to the most people. Which makes sense from a business point of view.
However, that said... This A07 Pro basically has no need to exist. None at all. They did not specifically design it to be a straight and true successor to the A07.
Right now... There are folks who have already put sagami inductors and better capacitors into their A07 and swapped out the op-amps. Some have even modified the case for convective cooling.
All the things I posted in my thread of what the current A07 needed.
We didn't need tone controls or Bluetooth. Although there is an audience for both. These things can be in your chain though with much better performance without adding to the noise floor.
Aiyima already make units with these features and the often suggest these other units be chained in front of the A07.
So while it is a good amplifier, the A07 Pro as it exists now... Doesn't need to exist. It doesn't do anything for the A07 user in regards to being a "Pro" version.
Not when you can modify your A07 to be a Pro unit for far less money by buying a few capacitors, a few inductors, some op-amps if desired and a better power supply.
I am very disappointed.. But not dissatisfied per se. Vote with your dollars and just buy the A07 if you are looking for a component to add to a simple stack.
But if you really are on a budget and just need a simple 2.0 system to drive speakers via Bluetooth... Then the A07 pro is all you need. You will like it.
Is the A08 pro better? Or the T9? Only a massive review thread with all the items measured, listened to and compared can we truly know...
My take..
Dump the Bluetooth, the tone controls... Make sure the SNR & THD is equal to or better than the A07... Then maybe you could call it an upgraded A07. But you have no business calling this a "Pro" anything.
I look forward to hearing more experiences with the A07 "Pro" from this fine community of audio enthusiasts.
It takes a village... Am I right?