Power Amplifiers

PrimaLuna DiaLogue Seven Tube Monoblock Power Amplifier

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I tested the two DiaLogue Seven monoblocks with an OPPO BDP-83 Special Edition universal player, Lamm L2 Reference tube preamplifier, and Paradigm Studio 20 v3 bookshelf speakers. Cables were Emotiva.

The Paradigm Studio 20's are 8 ohms nominal, have a sensitivity of 90 dB, and are made for amplifiers in the range of 15 to 180 watts output, so I felt they were ideal for the DiaLogue Sevens.

Notwithstanding the speaker's reasonable sensitivity, I had no illusions that 70 watts per channel, let alone 40 watts, would deal with the Jurrasic Park soundtrack. So, I chose music that I would realistically listen to with an amplifier of this modest power output. I used the 8 ohm taps exclusively for the listening tests.

In fact, that was no problem for me, as most of the music I listen to is classical chamber music and choir.

Mozart's Piano Sonatas (Virgin Classics 5-099969-947322) was a good choice to start out with, because I love classical piano, and piano is a dificult instrument to reproduce.

Although in ultra-linear mode, there was more power (authority?) and snap to the sound, I preferred the triode mode. The more limited 40 watt output was still sufficient to give me a nice listening level, and the sound was richer. It seemed to have more softness rather than hard edged. This is typical of triodes, which have more low-ordered harmonic distortion. The highs as well as the deep lows (the lowest note on a piano is 28 Hz) seemed a bit rolled off, but that is no surprise, as it is just one of those things that tube amplifier output transformers tend to do (the tubes themselves are flat from DC to several megahertz). Not all tube amplifiers do this, as different design parameters (e.g., the amount of negative feedback employed) can flatten the response. Also, there are tube amplifiers that don't use output transformers at all (called OTL, or Output TransformerLess).

But, the DiaLogue Seven was rolled off. The solution for me would be to add a subwoofer to handle frequencies below 50 Hz or so. I don't like up front highs anyway, so the rolled off high frequencies suit me just fine. Realists would say this is not high fidelity, but the idea is to have a pleasant listening experience, and the DiaLogue Sevens delivered that to my satisfaction.

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Classical choir is another of my favorite types of music, such as this SACD, entitled Solvguttene (2L42SACD). I reviewed the DiaLogue Sevens during the December holidays, and this recording is a Christmas album. Voices in particular, sound terrific with triodes, and the DiaLogue Sevens were no exception. Although the sound could "reach" farther in ultra-linear mode, I still preferred the triode mode, for its sweetness.

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