Tubes in Hi-End Preamps

I’m confused. If some of you engineer types could pipe in on this subject, it would be greatly appreciated. I know a little, but not a lot about electricity. I’ve been in the battery industry for 20 years and have taken two semesters of college electronics, so I know just enough to be dangerous.

For 15 years, I’ve been sans preamp. The idea being that I don’t want anything messing up the source signal. That limits me to one source only though, and I’ve finally caved in to the need to be able to access multiple sources with the turn of a knob.

It’ll be nice to finally have hifi sound when I watch DVDs, and I would like to spin vinyl again after 20 years away from analog. To that end, I have an Audio Illusions Modulus 3A unit on its way now.

OK, here’s my question:

Why is it that many higher end preamps, Audio Research for example, that are said to be “neutral” and “transparent” sounding use tubes in their designs? Wouldn’t it be a lot easier and less expensive to build a solid state circuit that produces clean, neutral, and transparent sound? Aren’t tubes supposed to “color” the sound?

I've noticed the presence of a lot more equipment out there (the latest generation of some designs) with tube output sections that are described as not sounding "tubey." What's the point then of having tubes?

I hope I haven’t opened a can of worms here.
I think there's been a lot of work done in the last few years by both tube and solid state builders to eliminate or at least ameliorate those pejorative characteristics of either discipline. Tube-based builders have succeeded in becoming less tubey (warm, lush, euphonic, mushy), while solid state mfrs have likewise become less solid state (clinical, brittle, etched, etc.).

I personally own both tube and solid state gear from B.A.T. It seems evident that their philosophy is either can be done well, and that there should be little gross difference between them. They build both tube and solid state designs for both pre- and power amps, and have achieved acclaim in the press and satisfaction from buyers.

To be sure, some tube-based designs deliberately deliver the traditional tube sound and there are buyers for whom this is the satisfying choice. I would likewise assert that some solid state gear displays a certain 'sound' that is pleasing to others. In each case, system dependency is frequently a major factor.

I don't believe either is intrinsically incapable of delivering neutrality and/or musicality. . .but I could be wrong, and it wouldn't be a a first.
In theory you are right, the less in the signal path the better. But in practice this is not always the case. My CD player sounds much better running through my preamp than straight into my amp. With a different amp or CD player it might sound better. I think one of the most important things is system synergy. You can have two very expensive and great sounding pieces that just don't sound good together.

No audio equipment sounds perfect, no matter how high end. There is always a bit of a compromise. Some tube equipment can sound tubey and euphoric. Some SS can sound very detailed but thin and lifeless. The best stuff is somewhere near the middle of these two extremes. It is a matter of what you prefer and what sounds best to you. I own a Audio Research LS25 and I am very happy with it. It is very detailed but does not sound thin and lifeless to me. It is one of the most musical preamps I have heard. My advice would be to listen to everything you possibly can, both tube and SS and see what sounds best to you with the rest of your system.

I really like Kjweisners take on things. Another tidbit, fwiw, is that the solid state route typically is more prone to higher frequency harmonic distortion than tubes. A popular school of thought is that our ears and brains find this type of distortion more unpleasant than the higher magnitude/lower frequency distortion that has to be dealt with in tube designs. It may be that our ears interpret lower order harmonic distortion the same way they interpret delayed reflection of sound from building surfaces, and so the distortion can come across as pleasant and natural sounding, or at least not very offensive. Or maybe not. Hope you like the new pre-amp!
Is your Audible Illusions the latest production? If so, it will require a LOT of break-in. I was talking to Art Ferris at Audible Illusions last week. He says the caps he's using are specially made for him, and include lead wound into the cap. they are especially immune to stray interference and vibration, he says. However, they take forever to break in. I got a new one this month and I've been playing it for about 3 weeks. Only now is it starting to open up and reach its potential.

Going back to your question... the previous answers are sound, I think. The tube guys are getting very good at designing circuits that take into account the actual tube behavior at different loads, and in different parts of their response curves. So they're less coloured in sound and more linear in response. And the comment about even-order harmonics being psychoacoustically more benign is a tube advantage. But most of my engineering buddies believe that it's possible to design solid state circuits that will match or exceed the performance of any tube-based preamp, with better objective performance, and greater long-term reliability. Of course, they're the kind of people who see the glass partially full of water as simply being over-designed...

My previous Audible Illusions preamp had a sort-of "holographic" quality that made musicians almost real in my listening room. I liked it, even if it WAS based on artifacts of the design. As a previous poster said, my CD-player sounded much richer and more "real" through the preamp. Of course, since most of my listening is vinyl, I don't really have a choice. But I think you'll like what the Modulus does for you after it finally breaks in!

Hope this helps!
I own a tube and a couple of SS pre amps aswell as tube and SS power amps. Believe me when I tell you that the small voltage gain the tubes provide yield a cleaner sounding pre than the SS preamps. I have an ultramodified ARC SP6B (6 tubes) which has had every extraneous circuit disabled and it is astonishing in its purity. I have been able to change the sound to a limited degree but not its fundamental character by using different exceptional NOS tubes in tube rolling experimentation.
However as far as "tubey" goes which to me means slow and syrupy when used as a perjorative, this pre maintains a "Wire with Gain" sound. In fact I have noticed that small signal tubes actually do the opposite of that rather trite conventional wisdom. If you add tubes to a CD output stage for instance, it makes the sound generally brighter and cleaner,they actually seem to add sparkle and liveliness. This probably accounts for all the modders who know that audiophiles desire detail and purity and add small signal tubes in a previously pure SS circuit.
I think that the so called Tubey coloration you speak of occurs only with the big output tubes when used to provide big voltage gains on your power amps for instance. Even then the aforementioned expected distortion may really provide a rather extended clean sound until you push the tube to its limit then the distortion becomes quite unpleasant. This is very easy to do if you are using one of the smaller tube amps.
Therefore I can only conclude it is the circuitry that really colors the sound. I can only suggst that you rid yourself of any prejudice and see for yourself. See if you can get a couple of preamps together from the same maker one with tubes and one without and draw your own honest conclusion. I didn't want to believe it either but via extensive exposure to both types of equipment (I am part of a very active Audiophile group) and I could only draw this conclusion. Trelja was the first to point this out to me. He was right as he usually is.
All active and passive devices add distortions; we simply pick the ones that are most consonant with our inner paradigm of what music sounds like. We then label them with fictions like "neutrality" and "musicality".
04-30-06: Viridian
All active and passive devices add distortions; we simply pick the ones that are most consonant with our inner paradigm of what music sounds like.
I find Viridian's statement to be refreshlingly insightful, and it helps to explain why I favor the sound of tube gear over the sound of digital gear. Digital gear has far less distortion and noise, yet I find tube gear reproduces audio that "sounds more like real music". That's my personal paradigm, and it won't apply to those whose paradigms are different.
Thanks for all the great input.

Question for Dfhaleycko:

My AI pre that’s in route now is a used one. It’s supposed to be about two years old. After reading more threads on this device, I understand that they eat tubes for breakfast, lunch, and dinner. Any recommendations on what the best replacements would be. Do you think I should listen to the unit first and then decide if I should try retubing or install new tubes right away so that I know I’m getting the best performance from them without guessing?

Also, I understand the AI pre is constantly evolving. Is there any difference between the units being made now from ones just a couple years ago?
"All active and passive devices add distortions; we simply pick the ones that are most consonant with our inner paradigm of what music sounds like." ... "most of my engineering buddies believe that it's possible to design solid state circuits that will match or exceed the performance of any tube-based preamp"... Which makes you wonder if any of the solid state designers are tinkering with adding a bit of even harmonic disortion to voice for what is percieved as neutrality or as depth in midrange.
neutrality does not exist. it is unattainable. all components are colored. choose your favorite coloration.

unfortunately many allegedly "neutral" components have a character which is evident after extensive listening.
Mr Tennis,

"Neutrality does not exist. It is unobtainable"

Please explain how you know this to be so. Have you heard all the equipment available? Or, as I suspect, are you just making a provocative statement based on a huge surmise, without any factual basis to support it.

Perhaps I'm not familar with your definition of 'neutrality', let alone how I would know if I were in its presence.
I might have to agree with MrTennise. Event the most neutral of components have a sonic signature. Of course, our ability to hear it is another matter altogether.
I believe neutrality to be a fiction because, to be neutral, a device would have to be absent of distortion. All passive and active parts add measurable distortions, be they dynamic, harmonic or enharmonic. Certainly, some devices add less distortion, but the problem becomes guaging the effect that this has on the fabric of the music. Is .1% second harmonic distortion worse than .005% seventh order distortion? Harmonic distortions are musically related to the signal, distortions like IM and power line hum are not. Dynamic distortions mimic the compression used in most modern recordings. I would posit that this is where preference comes in.
Veridan, The key in this part of the discussion is not, IMHO, the presence or absence of distortions in the electrical signal but whether or not neutrality is an aural experience or a just a difference in the electrical signal itself which may not be audible.

When you take a strict approach by saying that neutrality cannot exist in the presence of distortion as measured by an electronic devise I would agree. However, if a premise is based on the surmise that the product of a distortion in the signal must be audible when heard to be meaningful, a different conclusion can be reached.

Personally, I do not believe we can hear the effect of all that we can measure if for no other reason than we have not the means (our equipment) or ability (our ears) to do so.

That is why it becomes necessary to define 'neutrality' before we can conclude whether or not it can exist.
Newbee, I completely agree with your position, though you are making a distinction between neutrality and audible neutrality and I will still go back to which would sound more neutral 10% second harmonic distortion or 2% IM? It just might be nice if you would spell my user name correctly when you make your point.

Sorry 'bout the name - I think my mis-spelling is the result of my mis-pronouncing it and not looking back. I'll be more careful - wasn't meant to be personal, just laziness on my part. :-)

As to elections of distortions, I'm a tube guy - I'll take a bit of 2d order harmonic distorion every time. Makes those sources sound more natural (neutral?) to me. And, at 10% and 2% I could well imagine that both should easily be audible.
Newbee, yes I picked the example because, in my experience, both are clearly audible, but which would be more audibly neutral? For me, there is the rub. The former, while an order of magnatude greater, is related to the signal, the latter is not. You said that the former is more neutral, to you, but doesn't that imply that neutrality is a subjective judgement? My definition of neutrality would make it an objective quality with both examples equally failing to be neutral. I think that is what makes the concept of audible neutrality a fiction to me.

What I said was that 2d order harmonics sound more 'natural' to me. I parenthesized 'neutral'with a ? mark only to emphasize that I didn't think the my use of the term natural necessarily encompassed neutrality, but some might think these terms were identical in this context. That is, to be natural demands neutrality.

If I may digress a bit - I think many, myself included, are convinced that the best result in home audio is brought about by a careful matching of the speakers to room acoustics, the amps to the electrical requirements of the speakers, the pre-amps to the needs of the amps and sources, and lastly the sources to please the ears of the listeners.

None of these components need to be neutral to succeed in their function, in fact bending of the tonal balance by selection of certain components is often what makes a meaningful difference to the user because they need to compensate for other tonal imbalances brought about by compromises in the choice of room, speakers, amps, etc. They should all be highly resolving as pratical but tonally accurate (read neutral) is, for me at least, not necessary.

Some bend the tone with cable, IC's, tubes, PC's and even tweeks. But bend the tone they do and in the final analysis they have the tone that they feel is most natural, not which is not necessarily more neutral.

On a purist level, I will be very impressed when some one can prove to me, not just speculate, that they have been successful in actually replicating, or even coming close for that matter, to the sound that was recorded on the source. For those who might, I might ask if they were present when the recording was made and why they have such confidence in their long term aural memory.

Being a 'hair shirt' audiophile is no walk in the park! :-)
Newbee, yours is as cogent an illumination of our constant tweaking and upgrading as I have ever read. I would not hold my breath waiting for someone to come forward with any "proof" of accuracy.
This is an interesting thread. But has anyone yet answered the question, "What's the point then of having tubes?"

I won't talk much about neutrality and/or transparency or the issues of distortion, etc., as much of this can be rather subjective. But what tubes do for me is simply recreate the portrayal of space, the harmonic textures and decays. It's been a few years since I have heard some solid-state-based "audiophile" systems, and these were not even close to much lower cost tube based systems in the context of these sonic attributes. I have to believe this is inherent with solid state devices.

I have done a lot of experimenting with Mullard and Telefunken 12ax7 and 6DJ8/6922 tubes in Aesthetix Io and Callisto models. When these models started with Sovtek tubes, and immediately changed to a mixture of Tele/Mullard, the overall character of the sound was very similar. I can relate to what Mechans says about his highly modified SP6B. But what the tube changes did was take these models from a very good level to a stellar level. For $1000 or so, I made improvements here that would have cost 10x as much on a similar scale with solid state designs.....and still, the SS design would not come close to the attributes noted. SS diehards would claim I added all sorts of distortions to the system. But when I go upstairs and hit a piano key, the end result indicates to me something is very "right" with the change.

The nice thing about tubes is tuning a system to one's preferences. I do not think of this as synergy as this implies a perfect match. Rather, it is all about achieving a balance of many sonic attributes most important to each of us.

If I want more energy and dynamics on the top with a 6922 tube, I choose the Mullard. But the side-effect is a fatter midrange. A change to the Tele and I have greater tonal coherency, a little less life on the top but more extended low-end. Which is more accurate or neutral or transparent? Who knows as I am judging the result based on the rest of the system which is also loaded with tubes. And the same with the 12ax7. The Tele 12ax7 brings out magical bloom in the Io but with the Callisto, for me anyway, the Mullard 12ax7 brings on an authoritative and dynamic presentation that is wonderful.

I can put all these tubes in a CAT Ultimate preamp's line and phono stages and hear these same differences between tube brands. The fundamental sonic signature and strengths/weaknesses of each preamp design carries on as I change from one tube brand to the other. I simply get greater refinements and a little more emphasis in one direction (dynamics/warmth) or another (coherency) when I try these differening tube models. This is something I can not do with a SS product nor a product that uses the 6H30 "super" tube.

The key for me has been to find a product (in stock form) that really caught my attention. The CAT and Aesthetix models are about as different as any two I have heard and I owned ARC and BAT preamps for a combined 17 years until going with Aesthetix. Choose the model that feels right and then play with tubes to perhaps bring out a little more magic or alter the tonality to your own liking. This to me is the point of owning tube gear.

Here's an answer for the tube question:

Our ears have evolved a certain way over literally millions of years. We cannot change that. Tubes and transistors have distortions that are unique to those devices. It just so happens that tubes have distortions that are innocuous to the human ear, IOW they more closely observe the rules that the ear has evolved to. Transistors are less observant of those same rules and so while they have less *measurable* distortion, the distortions that they do have are far more irritating and audible than those of tubes.

In short, if we can reduce the distortions that tubes have then we will be really getting somewhere. Fortunately that is happening in the world of high end audio.