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

Hello all, been a while since I've posted here but I'm thinking about changing my system and wanted to see if I could get any feedback from the forum members.

I currently have the Axiom M60v2s for FL and FR. I use an Emotiva RPA-2 (200W @ 8 Ohms) to drive them while using my Denon 3808 to drive center and 2 surround channels. This system sounds very good to me but I'm one of those people that always wonders "what if".

I've been reading about tube amplifiers and everything I see talks about how warm and wonderful they sound. One reviewer was using a Primaluna Prologue 5, which is all tube stereo with 36W/channel and he states that when he removed his 200W amp he thought "no way could this 36W tube amp work in his system" but says that it plays much louder than he would actually listen to and sounded better than his solid state amp.

I've become somewhat interested in some hybrid amps and in particular the Vincent SV-236 MKII which has a combo of solid state and tubes and is rated at 150W/channel @ 8 Ohms.

I guess to make a short story long I need to know if anyone uses tube amps or hybrid amps or has at least listened to one or the other with the Axiom speakers and if so what are your impressions. On some but not much music my M60s sound a little bright and I was wondering if a hybrid or tube amp would avoid that.

Also would it be possible to biamp the M60s using the Emotiva RPA-2 to drive the woofers and the tube or hybrid to drive the mids and tweeters?

Any and all responses appreciated

I would send a PM to 2x6spds he uses/prefers tube amps or just wait, he should be along sometime.

Bobby, if any amplifier, tube or otherwise, sounds more "warm" than the source material, it's either not well-designed for sonic accuracy or is defective. The very essence of high fidelity is to not add a sonic coloration to the material, and the technology is well-known for designing both solid state and tube amplifiers to meet that standard.

I think everyone will agree that tubes sound different than solid state. Who is to say which is more accurate? Because tubes sound more warm does that mean that solid state is more accurate? Maybe the ss is coloring the music by not reproducing it correctly. I mean who says the ss reproduction is actually the correct reproduction. Maybe the tube reproduction is what is closest to what the original sounds like. Why is it assumed that the ss is the correct sound but the tube actually sounds better when listening to the source. Personally I think I would like the one that is more pleasant to listen to.

Now I might be wrong on this but I seem to rememeber some studies which stated that when a signal is sent through a tube amp and then looked at on the output side, there is some minor distortion and the signal is not exactly the same as it was when it went in to the amp; unlike a good solid state amp which outputs the signal just as it went in. This would mean the SS amp is the correct reproduction of the signal once amplified.

Which is more pleasing is up to the individeual listener but which is more accurate is measurable.

I really like my solid state setup but haven't had a chance to really listen to any modern day tube amps. It's a little confusing when most of the magazine and online reviews seem to be so positive about the tube amps and even the hybrid amps, about how they sound warm and the soundstage if engulfing and huge. SS fans say that the tubes put a little coloration on the music so you aren't hearing exactly what is coming from the recording.

Does one really want to always hear what is exactly recorded? I kind of look at it like this, sometimes I have food on my plate and it is exactly the way it came off the grill or whatever. If I add a little salt it's now not exactly the way it came off the grill but it tastes better to me than the original.

I was hoping an Axiom owner that uses and has used a tube or hybrid amp would be able to tell us of their experience.

I appreciate you guys throwing in your 2¢ worth.

Keep in mind that Axiom's design philosophy of striving for accuracy is based on a lot of research -- especially double blind listening tests -- that points to the conclusion that pretty much everyone finds accurate sound to be the most pleasing.

Just to play devil's advocate, the only problem I have with that research is that they coach people on what constitutes good sound quality. I'm just wondering how different the results would be without instructing people on what to listen for.

I am thinking like you. When I see reviewers replacing 200W ss amps with 36 to 40 W tube amps and talk about how much better the soundstage, etc. is, it pushes my curiosity into high gear. Since I don't have any high end audio shops around here that actually carry tube amps I look for input from my fellow forum members

In a true double blind test there would be no information given to participants nor there would be any interaction between the experimenter and participants. The goal is to create an unbiased testing environment as possible to ensure accurate results/minimize error/bias or any other anomalies.

From Axiom's page About the Research:

Training is important, otherwise they could have classified good speakers "bad" and bad speakers "good"... Hm... how was first determined which of the speakers were supposed to be the good ones and which the bad ones?

I understand CV point now. Both are valid IMO . Say one study with 10 random joes/jills as participants vs 10 industry professionals in the other for example. What would the results show then?

I suppose, as with many audio tests, one needs a reference point of some kind. Some people prefer bass heavy music and therefore say a "fat" sounding speaker is "normal" or perhaps someone who prefers classical type music might prefer hearing a more "forward" or detailed sound ect. I guess if the test is done with enough participants, either way there should be an overall census on what sounds "right".
I tend to discount any review or opinion that is too over-the-top or one that is very underwhelming.

but most people measure straight up frequency response into a machine load and THD without any understanding of why this doesn't translate 100% into what we hear when it's driving a real speaker.

I can tell you that I preferred my brother-in-laws Jolida 302 tube amp with my Axiom M60s to my Denon 1804 solid state. I borrowed the tube amp for about three months. I rarely listen to music louder than about 85-90 decibels, so it is not a matter of pushing either amp to the point of clipping. The Jolida seemed to give the music more depth and fullness. I did not do any double blind tests so discredit my findings if you wish. Upon going back to the solid state amp, I found that preferred the tube sound. The only way that you will know whether you like the tube sound is to listen to one yourself.

Hi CV, Edmondwolfman, and all,

Interesting discussion, and I think a few comments are appropriate. Until recently, there has been very little controlled double-blind testing of trained versus untrained listeners in loudspeaker listening tests. As many regulars on the forums know, I participated for years doing double-blind listening tests of various speakers (for magazines I was editor of) at the National Research Council in Ottawa, Canada. Indeed there was a training period for all regular members of the listening panel so we could quickly zero in on such speaker colorations as "fat" bass and other anomalies.

In recent years, however, acoustical scientist Sean Olive (who was finishing his graduate work at the NRC under Floyd Toole when I was on various listening panels) conducted an elaborate study using 300 untrained and trained listeners at the Harman acoustical facility, which is a more elaborate setup than the NRC's listening room. What's fascinating about the results is that essentially the untrained listeners' ratings of good and bad (accurate and non-linear or inaccurate speakers) nicely tracked the ratings of the trained listeners. The major difference was that the trained listeners gave lower scores overall than the untrained listeners.

You can read the study in greater detail at Sean Olive's blogspot and download the study for free here:

http://www.aes.org/e-lib/download.cfm?ID=12206&name=harman

I'd also point out that tube amplifiers do not necessarily sound different from solid-state amplifiers (except when pushed beyond their output limits into distortion). Tube amplifiers can be well designed for linear smooth frequency response and low distortion. In one double-blind test of amplifiers at the NRC in which I participated, there was a large tube MacIntosh amplifier that measured flat and had low distortion. No-one on the panel was able to distinguish it from a number of other solid-state amplifiers during the tests.

Regards,

Alan

Thanks for that info Alan, that is a very interesting study.

Thanks, Alan! I'll have to read it later, but I look forward to it.

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.