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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.
blumusician
viridian's avatar
viridian
4,184 posts
 
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.
newbee
4,093 posts
 
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.
viridian's avatar
viridian
4,184 posts
 
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.
newbee
4,093 posts
 
Viridian,

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.
viridian's avatar
viridian
4,184 posts
 
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.
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