Axiom Home Page Forums General Discussion Advice from Axiom Owners Hybrid amps with Axiom M60v2s

Alan, is it true that once your reach the point of distortion (for whatever reason) that a tube amp's distortion is a different type of distortion (or different harmonic frequency) than SS amps? From light reading I thought that was one "scientific" means for the tube fans to id a real difference is amp sounds.

Just curios, I have no desire for a tube amp - too damn pretty for my set up.

Yup. Tube distortion typically generates even-order harmonics, which are far more pleasing to the ear then the odd-order harmonics generated by a clipping solid-state amp.

Think of even-order harmonics as a pleasing musical chord in a major key, and odd-order harmonics as a kid practicing violin for the first time.

Charles, it would depend on the specific design of the tube amplifier involved. A push-pull tube design which tends to cancel even order harmonics wouldn't exhibit a different spectrum of distortion components than would a similarly designed solid state unit. Amplifier tests done by SoundStage frequently demonstrate this similarity. So, the bottom line is that there doesn't necessarily have to be a "tube sound" if well-known design principles for amplification with high fidelity are followed.

I've used both types of amps for many years and while its tough to generalize there are certain attributes of both that I enjoy. As others have mentioned the even order harmonics can result in a more pleasant sound. Much of that sound comes about from the larger amounts of even order THD generated by the "soft" clipping of tube electronics. With SS amps when clipping occurs even instantaneously there are large amounts of objectionable intermodulation distortion created from the ensuing square wave. It sounds harsher than a "soft" clipping tube amp. The upshot is that for brass, strings, piano or voices tube amps can sound more natural. For these reasons some recording engineers still use tube electronics or microphones. What is accurate and what is not is debatable but not relevant if the objective is to reproduce the most pleasant realistic sound.

The downside of tube amps is they require more maintenance from worn out tubes. And from an energy efficiency point of view they act like small heaters. Also while strings and brass sound more natural, the greater harmonics can sometimes make bass sound "fat" and undefined.

I still go back and forth between tube and ss amps. These days its between a tube McIntosh MC2102 and the Axiom A-1400-2. Both are great amps which do sound different. For a while I actually bi-amped both amps with an external crossover, using the tube amp for the mid and high drivers and the SS amp for the woofers, though such rigs are tricky to setup owing to the amps different phase and gain characteristics.

As far as hybrid amps go I haven't had much luck with them. Mixing tubes and transistors under one hood must pose some difficult design compromises and challenges. Usually they are designed so that above a certain power draw transistors kick in. They offer the advantage of more power than tubes but can be finicky. If you are thinking of tube amps it may be more satisfying to listen to a tube only amp first and compare it with a capable SS amp at different volumes.