Foremost, if you are aware of the highly reviewed Aiyima Amps such as the A07 and A08, you would be delighted to realize that the A300 also has interchangeable op amps which will make a huge difference in output.
The firsts thing I did with the A300 is to change out the 5 op-amp slots in that unit. If you don't want to spend much money at all, get the Texas Instruments model LME49720NA ops amp, which you can get it at (do NOTE: This amp requires a dual channel model, which these are):
https://www.digikey.com/en/products/detail/texas-instruments/LME49720NA-NOPB/1647708
It lists for only $3.41 each or $30.63 for a pack of 10. I was so surprised what a difference this op amp made in terms of linearity, dynamics, and overall smoothness.
The next op amp I tried - and far more expensive, is the Sparkos Labs SS3602 discrete op amp. This is the type of op amp often touted by audiophiles to really improve things, and it most certainly did. Yes, I had 5 of them on hand (they are rather expensive), and linearity-wise, they made things even smoother with great 3D effects, imaging, and depth. Discrete versions of op amps tend to be larger and more expensive, and generally acknowledged to be some of the best-sounding versions you can get. You can get the Sparkos Labs SS3602 (if you are inclined to spend the money) at:
https://sparkoslabs.com/product/dual-discrete-op-amp-ss3602/;
Do keep in mind, Sparkos Labs offer a discount right off the bat and if you are a repeat customer - which I tend to be - they give you a 20% return customer discount (RETURN20). One tends to enjoy doing business with this small operation, and you can pepper them with questions and the owner typically responds within 24 hours with a wealth of information.
Now to to make this A300 sing, and sound more like an amp that costs anywhere from 3-5 times as much, switch out the op amps as mentioned above, there are a few things you need to do. First off, do be careful to install them properly. These things are easy to install - the key is to line them up and not insert them backwards which will fry the op amp immediately. There is an excellent video that Sparkos Labs puts out with regard to installing them, and it's here:
Then leave your amp on - don't keep turning it off and on. In general, Audiophiles tend to keep their gear on all the time because as time passes, things warm up/break-in, and the sound tends to improve (there are exceptions of course). In each instance, adding new op amps in the likes of the A07, A08 and the A300, have improved the quality of the audio output substantially - in the areas of improved linearity, imaging, sound-staging, depth perception, and instrument timbre. And I don't make these claims lightly. I've been an audiophile for over 55 years now. However, now my audiophile efforts are confined to a desktop, near-field scenario.
The gear I used to evaluate the A300 (and other amps) are:
Speakers: KEF Q150's and Wharfedale D340's
DAC's: Various Schiit models, iFi ZenDAC V2, JDS Labs Atom DAC X, and the Topping D10S
Speaker cables: By Audioquest and Blue Jeans Cables
USB cables: By Audioquest and Monprice
RCA cables: By World's Best Cables (WBC) and Blue Jeans Cables.
Hey look gang, all we can do is observe, experiment, and then make suggestions - which I'm doing here. The Aiyima amps are a bargain and can be made to sound like some of the "big boys" out there by changing out a few things. Good luck...
