We almost want to say: what sound? Because the first thing you notice about the Pass Labs INT-25 is that it comes across as incredibly neutral. How is class A warm sounding? Yes: the amplifier gets warm, but this Pass does not sound warm at all. Just extremely fast and open. Airy.
Now some readers will think: huh? Isn’t this Pass ‘musical‘? It certainly is! Don’t confuse a warm sound with musical. A warm sounding amplifier colors. And coloration is not something your editor likes. Coloration is an interpretation of the manufacturer. And that is by definition not good. What we want to hear is the interpretation of the musician…. That’s HiFi… This Pass Labs INT-25 gives space to the music. Nelson neatly steps out of the signal path from source to speaker.
If we have to compare to the XP-12 with Bryston 4B SST3, the Pass Labs XP-12 plays a little bigger. And it manages to place in depth and height a little more precisely, but okay: it is also a class above the INT-25.
The Bryston is a bit more “clunky” than the INT-25. It gives more bass-kick and a bit more foundation, but we sacrifice resolution and speed. This is really audible in vocal work, where we simply hear that the Pass gives it more refinement. That will be both the purist circuitry of the INT-25 and the fact that the INT-25 is single ended class A and the Bryston 4B is a class AB circuit. Crossover distortion is and remains an issue with a class AB amplifier. And then when you compare directly it is audible.
Open up that power!
Very quickly we get the urge to turn open that volume. This is because there is just no sharpness in the Pass Labs INT-25. The Focals really love this amp. Eric Clapton with Layla is in our playlist and finds its way to our streamer…. The acoustic music glides into the room. No fray, every string is easy to follow, Eric is in the room. What a performance. It’s on the same level as the Pass XP-12 with the Bryston, in a way. We sacrifice something in scale, but advance in smoothness and resolution.
Time for some Infected Mushroom. That, too, is fine. The volume goes towards 50, which is almost maximum (63, weird number by the way). We hear no compression. Nothing. It just keeps going. We hit about 75 dBa on the couch with our Focals. Loud enough for many a living room. It won’t get much more than 80 dB we estimate. But believe us: 80 dBa after an hour of listening is really substantial. We do not recommend this on a daily basis.
Adele picks up where Infected Mushroom left off. Love Song is a familiar track in our test list. A small and intimate song in a way that in our opinion should also sound small and intimate. It does. Adele is projected rock solid between the speakers. The guitar on the left and right. And sometimes projected in the middle. The beginning sounds fluid and coherent. Not every system manages that by a long shot. When the warmth comes in, it complements beautifully without getting in Adele’s way. Every part gets its space… every instrument gets its place.
Gazpacho gets the stage. Just 20 minutes of spectacle. Guitars, opera… wonderful. This track is in a way all over the place. And that makes it quite a tricky song to put down well for a system. It must be able to reproduce voice flawlessly, but also ‘grande’ work. Not to mention the sudden changes of tempo and volume. The INT-25 faithfully does its job. Nice is that the layering remains intact in both the bombastic work and the small passages. We can even hear the ‘vinyl ticks’ under the ‘opera work’ that rises in the background. A detail that often gets lost. But not now.