Adding to the brief tube perspective of this thread...

Although my profession is in live theater and am frequently a sound technician,I do not have a technical background in sound engineering or electronics. Regarding the 990, I can only add my transformative experience especially concerning the "dry, cool, analytical, and fatiguing" sound. Personally I do not find the 990 to be fatiguing.

My young childhood was spent witnessing my father's hi-fi habit, with 2,000 vinyls, Audio Research pre/amp, and IMF transmission line speakers (talk about warm and full sound). Fortunately and unfortunately, my ear was tuned to fidelity very early on.

After I left home and paralleled with the growing technology of SS in the 80s/90s, all I could afford and easily available was SS.

Last year, I finally was able to move into the separates realm. I had a Sony STR-DA3000ES HT receiver which has an internal digital amp. Supposedly, a SS way of providing a warmer sound. To me the receiver sound was too laid back, flat, and with no midrange life.

When I changed to the 990/7125 combo, I immediately notice an improvement of the sound. Better presence, and as you state bensqsun "more resolution, more air and openness."

However, there was still something lacking when listening to music. I was enjoying what I was hearing but I was not immersed in it. This I refer to as the emotional connection. Technical jargon is not my specialty.

Pondering back to my tubular roots, I decided to research tube possibilities and came across tube buffers as a fairly inexpensive alternative to an amp. I purchased a Grant Fidelity tube buffer as an experiment.

I started with the buffer between the CDP and 990. I immediately noticed a difference. The sound was a more forward midrange, liquid highs, slightly tighter bass, and more warmth. Above all, there was an emotional connection to the sound. Whether this is correlated to "warmth" I don't know, probably a bit subjective. I do not qualify sonic characteristics like audio or wine critics. Simply, it was the first time in the evolution of my system, I really wanted to listen my entire music collection all at once. Finally sonic satisfaction.

Maybe Altec can shed some light on the descriptive sonic differences between tubes and SS.

Thus, my long winded suggestion would be to try a tube processor or buffer. If there is a local hi-fi store, try a tube cd player. The added benefit to tubes is the "rolling" to customize for your enjoyment.

BTW--In my system, I do not hear any distortion with the buffer in line. Quite the contrary, the sound is just as clean as with out the buffer.

So, this may be an inexpensive alternative to try. Switching out for another SS pre/pro is not the only alternative.

Really bang for the buck, the 990 is a solid unit. I'm sure there is tweaking that is needed in a lot of systems to find the ideal synergy. I am pretty content without having upgraded the firmware yet.

Good luck bensqsun. Keep us informed on your progress.

AK

BQ,

Ideally, it would be best if you could audition them all and keep the one you like best; I wouldn't rush to part with the 990, I'd wait until you had a listen to the other two. The 990 is incredibly versatile and great bang for the buck. It's all a matter of compromise, it seems. And, these systems are all in a state of flux, I think and so if you could be patient, you might find a greater number of choices in the future (at least that's what I'm hoping for and, so for me, the 990's a practical holdover).

My Anthem amp is notably bright and so this also contributes to the analytical side of my listening experience. The B4 is certainly not that way, is very warm and powerful (ideal for the DQ10's), but obviously not an option for surround sound. I'd like an Anthem D2, pre/pro, but I understand the setup is more complex (required to get the best from it) and also very pricey, by comparison.

Again, I hope this helps.

Good luck and keep us posted.

John

That is a great suggestion John.

AK

Much of the reason tubes sound better is the spectral distribution of the distortion components which every audio component produces. Solid state amplifiers produce lower (by an order of magnitude or more) static distortion numbers, but the quantity of the distortion is not nearly as important to the ear as the spectral distribution.

Tube amplifiers produce a nearly "ideal" spectral distribution of distortion components with a strong 2nd harmonic, which masks the presence of the offensive higher-order distortion components, with the 3rd, 4th and 5th desending in level quite rapidly.

This can be seen in this photo of the distortion produced by a 1kHz signal in a single ended triode amplifier. A tube buffer would have a very similar distortion spectra.



By contrast, here is the distrotion spectra of a 1kHz tone in a high quality solid state amplifier.



Notice that the 2nd harmonic at 2kHz is almost totally missing, as are all of the musically-related even order components (the 4th, 6th, 8th harmonic etc). The presence of the 2nd harmonic is very important for good listening quality because it masks the presence of all other distortion components. Now look at the other parts of the spectrum - there is high-harmonic-order distortion all the way past 10kHz, and this is completely unmasked by the lack of a 2nd order component!

Tubes are also highly linear devices themselves and in amplifiers can be run with little, or no, global negative feedback. By contrast, solid state gear must make use of high levels of global negative feedback, otherwise the distortion would be intolerable.

There are other advantages of tubes, but these are the most important ones.

Akdrama,

Thank you!

And, Altec, WOW, what a difference! Isn't one of the great advantages of SS, over tube amplifiers, the fact that it can produce more, pure power, more efficiently? Isn’t this partly responsible for the birth of hybrids or tube pres with SS amps (best of both worlds)?

BQ, I think I was also trying to say that these new pre/pro's are more complex systems and as such, are mostly imperfect, with both positive and negative traits; hence the notion of "compromise."

Ok, here's a somewhat funny story. When I was a young man, an apprentice at GM, the old journeymen would lecture me on finding a wife. "John," one fellow said, "in all women, you're going to find things you like and dislike about them. What you need to do is find a woman with faults that you can tolerate, that you can live with and the rest will take care of itself." I think he makes a good point; these pre/pro's are all the same way, complicated creatures, exhibiting both strengths and weaknesses and so in choosing, perhaps it’s best to focus on finding an example where you can tolerate its shortcomings. A one trick pony is yet somewhere down the road, I think

My new setup often surprises me in ways I’ve never experienced before. As I’ve come to better understand and play with the 990’s features, I’ve certainly come to enjoy the HT experience (something I couldn’t do before); an example of one of the 990’s strengths. Unfortunately, for pure musicality, even in two channel, bypass mode, it doesn’t compare with the old Bryston setup. To be fair, however, my old system also had a quality and expensive cd player, Dual turntable and a separate tuner, by comparison to my current sources: a relatively inexpensive Oppo 990 and the 990’s built-in tuner, with a weak signal.

In your case, you’ve swapped out one component and so you can attribute the changes directly to the 990. I wouldn’t rush to judgment, however, not without first spending more time with it and playing with its features. Once you have a better feel for it, then compare it to the others.

Again, good luck, keep us posted!

John

Certainly solid state is more efficient than tube, but that doesn't have anything to do with sound quality, does it? Digital amps are even more efficient than typical class A/B linear amplifiers, but you pay dearly for that efficiency in degraded sound quality with high amounts of out-of-band garbage being fed to your tweeters, thus causing distortion in the audio band as a result.

I'll take inefficiency, thank you.

At any rate, my own system uses horn loaded drivers in an actively bi-amped arrangement. The power amp for the woofers is only 60 watts, and the amp for the tweeter horn is only 5 watts !, yet with 106dB efficiency for 1 watt, I can produce way, way more output than anybody could stand.

I don't care for hybrid solutions since there is still a solid state output stage, still producing the solid state distortion signature, though not so much as an all-solid state amplifier.

However the main reason I don't like solid state output stages is because of crossover distortion, which is especially bad when using efficient speakers. Typical solid state class A/B power amps only run in class A for perhaps a watt or so before switching to class B - that transisition is smack dab in the power level where most listening takes place, and where all the subtle details of music reproduction resides.

Crossover distortion is especially nasty sounding.

By contrast, a class A/B tube amp will remain in pure class A for about 1/3rd of it's total power output before switching to class B. With my 60 watt tube amp, that is 20 watts before switching to class B. Single ended triode tube amps such as the 5 watt one I use for my tweeter horns don't exhibit crossover distortion at all since they are always running in pure class A.

Great discussion.

For some of this, I am going to have to reference my Yamaha sound bible.

To make sure I understand correctly. The important element is the amplifier.

I understand the power to speaker sensitivity aspect.

If we look at the two graphs Altec provided...
the tube signal after 10khz, it flattens out. As compared to the SS after 10khz, there are a lot more peaks (distortion peaks?). In regards to the tube signal, would this account for the "liquid highs" characteristics of tubes? Tubes are often characterized as having sparkle? How would that show when analyzing the graph?

And with the distortion of the solid state after 10khz, would it be safe to say this is the "brightness" aspects of SS?

My next question concerns hybrid systems. What defines hybrid? One component SS and the other tube? Or one component that uses both transistor and tubes? If I remember correctly, my dad made the transition to solid state in the mid 80's, when (correct me if I am wrong) tubes were still not effecient. He bought a Audio Research SP-10 preamp that if my memory serves me correctly (please cut me some slack for a conversation over 20 years ago) was a hybrid component, both SS and tube. But I am saying this without researching the component.

If you have one component SS and one tube...I am assuming ideally you want the pre amp to be SS and the amp to be tube. Yes? This is especially relevant regarding HT, since there doesn't seem to be a plutheria of tube HT processors.

However, maybe the tube relevancy is only when considering 2 channel audio. I find that I do not have any sonic quality issues with the 990. In this realm, with multi-channel decoding the signal processing seems to be more important. There is a lot more information for the processor to decypher.

What has more effect on the sound quality, pre/pro or the amp? I would assume it is the amp, even the preamp is processing the signal to analog considering Altec's reference to the output stage.

At this point, I may need a little sound 101 before I thoroughly confuse myself.

This may not be making BQ's decision any easier (chuckle).

AK

Distortion components ideally should not extend beyond the 5th harmonic, and they should decrease linearly in level as the harmonic number increases.

The 2nd harmonic component is essentially harmless because it is fundamentally musically related, being an octave above the original frequency, and in fact has the beneficial effect of masking the presence of the other, higher order distortion components. This effect is one reason tube buffers smooth out the sound of an otherwise solid state system.

The 3rd harmonic is a musical 5th, and is still not overly objectionable, but it should never be higher in level than the 2nd harmonic.

The 4th harmonic is just a double-frequency replica of the 2nd, and is likewise musically related and relatively harmless. It should be at a lower level than the 3rd.

The 5th harmonic is the first harmonic which can start to sound harsh if it is not lower in level than the 2nd, 3rd and 4th.

The 6th and above start to have really negative impact on sound quality, no matter how low their absolute measured level is. The structure of these higher harmonics is one of the main reasons different pieces of audio gear sound different from one another, albiet in subtle ways.

The distortion components I showed of the solid state amplifier photo go all the way up to the 20th harmonic and above! This will color the sound, causing sound quality differences between it and other amplifiers, especially tube ones, which have a virtual absence of distortion components beyond the 5th.

In subjective terms, tube amplifiers, because of their benign distortion signature, "get out of the way" of the reproduction of music. That goes a long way toward explaining the "liquidity" and "sparkle" in the high end.

The presence in solid state amplifiers of high-order and non-musically related distortion components will contribute to their sounding "hard" or "sterile".

From a sonic importance standpoint, the earliest components in the full audio chain have the most influence. In my recording work, this means a tube microphone preamplifier. In home audio, the same thing applies, with the preamp having more influence than the power amp.

However, all components in the chain will together influence the ultimate sound quality, so that is why as an ideal I always recommend a totally vacuum tube setup for music reproduction if at all possible. Short of that, a tube preamp (or tube buffer) at the low level audio stages can be greatly beneficial.

Altec, your amazing.
That is the first rational explaination I've ever heard of why tubes sound better.
Bless You.

All,
I am a little taken away by so many replies/advice from you outlaws. What a community!
Last night, with a disappointed mind, I scanned my collections of music and DVDs and decided to try a Diana Krall live concert DVD.
Holy Mama! Could this be that same Diana with the NAD? Within minutes, I got up and rushed upstairs and brought my wife into the room. After a few minutes into the concert, both my wife and I looked at each other, mouth wide open, in total disbelief! Diana comes to life, and for the first time! We listened and listened that night, feeling for the first time that our music enjoyment went to the next level. (I have never really cared about Diana's performance since I tried them with the NAD, either as a receiver or as a pre/pro. I just felt all the raves about her are overrated. But my perception changed totally last night)
Could it be that my music gears are meant for playing Diana and the likes only? Or, could it be that the way how recordings are made makes a difference? I am going to spend this weekend trying to this out, if I could.
Thanks all and have a great weekend.