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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
charles1dad's avatar
charles1dad
10,250 posts
 
Iscm,
As the level of negative feedback (NFB) is increased the output impedance decreases and damping factor (DF) is increased. Depending on the speakers involved the additional NFB can be beneficial up to a certain point. Generally speaking I believe that the less NFB utilized he more natural and open the sound quality becomes so I understand your listening observations. Some speakers are intentionally designed to work very well with low and even zero NFB amplifiers.

I use a DAC, line stage and power amplifier and all 3 of them are zero NFB designs. The result is a very organic, lively and emotionally engaging sonic character.
Charles
lloydc's avatar
lloydc
753 posts
 
I went all tube- pre, amp, phono - more than 30 years ago, when SS amps were harsh and consequently, I had lost interest in recorded music.  Solved that problem!  Amps and preamps are equally important.
As many above have noted, there are many ways to skin a cat.
   I think tube maintenance issues are exagerated. Yes you have to change them every few years, and they cost a bit.  It’s trivial compared to what most here have spent on gear.  We all have had to nurture some trouble shooting skills, and occasionally, soldering. No big deal.
   You can make an argument for ss amps based on less heat and power useage, and sometimes these can be controlling factors; I live in Houston, there are times I am not inclined to run all those tubes - but I’m not convinced that class D amps will compare.  the electric bill (power and a/c costs) is a relatively minor consideration when you’ve spent tens of thousands on gear and content.
  Tubes are more musical.  I really see no reason to use a SS pre. 
   
   
iscm
40 posts
 
Regarding tube maintainance, one can select a power amp that is not so high powered and uses output tubes such as EL34 or el86.
These sound good and do not break the bank when they need replacing.
Of course the amp still needs to be well designed and have good output transformers.

I am amazed just how powerful some low output valve amps can sound.

If I could only chose to have a valve pre or power I would still chose a good valve pre first with the intention to change the power to tube later.

iscm
40 posts
 
charles1dad,
I now find that even though I have Triode and feedback switching on my power amp, I nearly always keep the amp in triode mode with minimal feedback.

The maker of the amplifier said that these days most of his amps are fixed in triode mode with low feedback.
He suggested that if I ever wanted to upgrade that I should try one of his single ended pure triode models.
He thought that triode amps can often drive speakers better than ultra linear anyway if they have well designed output transformers.

For now, even thought I rarely use it, I still like the option the switch modes and change feedback.

atmasphere's avatar
atmasphere
11,864 posts
 
Is it possible that one of the reasons that Valve amps sound so good is that they tend to use much lower amounts of feedback that most transistor amps?
I have noticed that the sound seems to open out as I select lower amounts of feedback.
You can either run high amounts of feedback or very low amounts; in between (about 6db up to about 15db) its application can be really detrimental.

Feedback, while suppressing distortion, also adds some of its own, and the type it adds (harmonics 5th and up) is pretty audible. Even though its a very small amount, its audible because the ear uses those harmonics to sense sound pressure, so it has to have a 130db range!

Tubes (triodes in particular) are very linear so it is possible to build zero feedback tube amps much easier than it is to do so with solid state.

So, quite often, yes, this is one reason tubes can sound better than transistors.
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