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For tube sound, which is more important: preamp or power amp?

I have always loved the “tube sound” - warmth, midrange, soundstage. Through the years (since about 1975), I have owned many tube and solid state amps and preamps, in various combinations. Presently, I have a tube amp and a solid state preamp. But like most of you, I am thinking of making changes, again.  Not to cloud the discussion, the specific brands are not important.  I also listen to acoustic music, females vocals, love mini monitors, EL34s, NOS tubes, and don’t care that much about bass.  So you can see that my taste fits the tube sound very well. But I have had systems that are too warm, not enough dynamics or details, and fat in the low end, too.

okay, now to the discussion.  To produce the tube sound, which is more important: the preamp or the power amp?  Let’s talk in general, and (if possible? May not be) not tied to one specific piece/brand/model of equipment.  I know there are exceptions to any general rule.  Not sure if it makes a difference to your comments, but I have no phono and am running line stage only.

As an attempt to prevent the conversation as going in a big tangent, let’s assume equality of price/quality. i.e. not comparing a $10k power amps contribution to a system to that of a $1k preamp.  Let’s also assume that the amp (tube or solid state) can drive the speakers just fine, such that compatibility does not limit the decision. And ignore mono blocks versus stereo amp differences.  

two follow ons: I have  the perception that preamps give you more bang for the buck - meaning that it takes less money to get a great tube preamp compared to a great tube amp.  Agree/disagree? And second, I have never owned a tube dac or CD player, and will assume that tubes in either of these is less critical than in a preamp or power amp. Agree/disagree?

i am interested in your thoughts.

Bill
meiatflask
kalali's avatar
kalali
1,977 posts
 

dpac996, you start your post with asking what is a "tube" sound and end it by making the statement "If you are after "tube sound" cut to the chase; buy a tube amp and relax!" Makes a little sense.

People buy what sounds good to their ears. Tube sound or SS sound are just labels.


charles1dad's avatar
charles1dad
10,249 posts
 
"The other way around can be just as rewarding"
Hifiman5 thanks for sharing this personal revelation. Different types of components can be combined with success. 
Charles 
wolf_garcia
6,683 posts
 
Also it’s another fact (!) that tubes are more fun…you can swap ’em out, hold them and look at them, collect them, watch and listen to them die (macabre, but part of the tube deal), bewilder friends. People ranging from my age group to my kid’s friends (mid 20’s) often have no idea what tubes are, which means I get to have fun trying to explain the damn things (guaranteed to bore the crap outta anybody). Interestingly, once explained to "normal" people, they still don’t care. At friend’s houses they’re often just yelling at Alexa to play something from a 1" speaker. I actually took a foam block and stuck some of my spare tubes in it just to look at them (that's called Art)…fun...stick a bunch of transistors in something so you can look at them…not so much fun. You can use a SS amp anywhere, preamp or amp, and although it may sound fabulous, I KNOW I’m having more fun. I rest my case.
mulveling's avatar
mulveling
1,855 posts
 
Either combination can give you a great dose of "tube sound". Of course power tubes need more maintenance, and the NOS flavors of large power tubes quickly approach $$$$/unobtanium territory. BUT there are really excellent Russian power tubes made today (KT120, KT150), and tube amps will often have at least a few crucial small-signal tube slots for you to get your NOS on.

On the preamp side, higher gain tube preamps are more likely to cause noise issues your system (i.e. tube rush and/or microphonics excited during playback) than SS preamps or tube power amps. That bears consideration. Also, with a tube preamp feeding into a SS power amp it’s a bit more common to experience an impedance mismatch (i.e. high output impedance into a low input impedance, which throws away gain and caused significant FR aberrations), than with SS pre into tube power. Research potential pairings before proceeding, just as you have to research any power amp’s ability to drive your speakers.
dc_bruce's avatar
dc_bruce
11 posts
 
What do you mean by "tube sound?"  I think tube preamps are great because small signal tubes don't "age" much, so they're sound does not change.  I think, done right, tube preamps provide a greater sense of "articulation" or "naturalness" (i.e. absence of glare) to the sound . . . and I'm not talking 12ax7 tube euphony.  Tube power amps, with output transformers, inevitably interact with the speaker in ways that are not entirely predictable, changing the speaker's frequency response.  The combination could be synergistic, or not . . .  And, it's hard to get accurate bass from a tube amp, unless you're driving a fairly high efficiency loudspeaker.   
In any event, tube power amps that generate much over 75 watts per channel have lots of tubes, generate lots of heat and suck down lots of power.  And, in my experience, even in a simple amp like a Dyna Stereo 70, the sound quality changes as the output tubes age.  More elaborate and quality amps (Audio Research) have been known to self destruct in expensive ways when an output tube fails.

Obviously, there are, at a price, tube power amps that do all things very well, but these tend to be both high maintenance and seriously expensive in the first instance.
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