The Triangle Bro 3 responds well to both class D and class AB. There are alot of class D amps coming out of China under $500 and some match up with their respective dacs. For class AB, buying used, an NAD or the Rega IO are also choices.
When I was looking for a small form factor class AB amp I came across the Keces E40 which was reviewed by Soundnews, so you can look up his take. I concur with his findings. The Keces E40 is slightly more powerful, has the same connections as the IO and adds a usb dac (not that important to me) but also a pre out for a sub or amp connection.
Compared to other amps I have tried, including an Emotiva A400z, it hands down sounded better. The emotiva added more wispy highs but the lows, mids and highs of the Keces are full bodied , and well fleshed out, and has better depth and separation. Bass and mid bass are tight. Made in Taiwan, not the ROC if that’s important. And has great looks. Unfortunately, it is a bit over your $500 budget at $630.
I havn’t heard the IO but it is also well regarded for $600.
But, the Triangle Bros will sound great on class D amps as well. I have the Focal 807w and Triangle Zetas. My cheaper class D didn’t bring the best in the Focals but the Keces sounds as good on the Focals as my Hegel. In fact it sounds alot like it at low to moderate volumes which is where I listen.
Class D and class AB sound great on the Triangles. But the Keces makes them sound better for me but I could easily go with class D on them. Not so with the Focals, they need the punch of a solid class D.Anyone else hear the Keces e40?... let us know your thoughts.
