Holy hell! The Topping A30 is a very nice sounding little headphone amp stock. It’s very neutral to slightly warm. But the upper registers can sound a little veiled. I read some reviews and several mentioned Opamp rolling with the Burson V5i opamps. Being a newbie to headphones, but not audio, I researched and decided to pull the trigger. To be honest I wasn’t expecting much. I mean, I knew the Topping sounded a little veiled but holy hell, what a difference. Right out of the box. It’s amazing. Flight of the Cosmic Hippos hit with punchiness that the original amp just didn’t have. Highs are more detailed but at the same time less harsh. How the hell did you guys do that? Topping should be really proud to offer such a good amp at the $100 price point but they should seriously talk to you about offering a version of the A30 with these amps already installed. It’s a night and day difference. Seriously I’m in disbelief. I was just wanting to get an acceptable level of fidelity out of a headphone setup at my desk. After trying different headphones and amps I was starting to worry I was going to have to pay thousands to get a sound as pleasing as I have with just a Sprout 100 and some Elac UniFi UB5’s in my living room. This may not sound the same but it’s definitely pleasing to listen to now. I’m listening to the music and not trying to troubleshoot what the weak component is anymore. It’s pretty clear that 2 of the weak links in the chain were the OPA2134 opamps. Topping touted that those opamps had .00008%THD. I don’t know if the V5i’s compare on that front. To be fair, they didn’t sound bad. But they didn’t sound like these either. This simple mod made my little amp sound great! Really, really great! Thanks! Now I can get back to listening to the music.