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

The amp just provides a higher voltage to drive the speakers.

As well as vastly more current and power, of course.

If the preamp distorts the output signal, the amp can’t fix that.

However, if the amp distorts its output signal the preamp can’t fix that either :-)

Regards,
-- Al

Regarding the statement by Mr. Carver about the 50+ year longevity of the power tubes in his amplifier, I would point out that in general there are statistical approaches that are commonly used in deriving published MTBF (mean time between failure) specifications which produce misleading results.

For example, many of the mechanical (non-SSD) hard drives used in computers have published MTBFs of 1,000,000 hours.  Or in the case of some Western Digital Gold Drives I recently purchased, 2,000,000 hours.  2,000,000 hours corresponds to 228 years of continuous operation.  Does that mean these drives can be expected to last anywhere close to that amount of time?  Of course not.  What it means (and I'm choosing the following figures for purposes of illustration) is that if say 100 drives are operated simultaneously one of them can be expected to fail after slightly more than 2 years.

Similarly, **if** Mr. Carver's 50 year figure is based on similar statistical methodology, and given that there are 12 power tubes in a stereo pair of these amplifiers, it would mean that one tube can expected to fail after a bit more than 4 years.

On the other hand, though, if we assume an average of say 1 hour of use of Mr. Carver's amplifier per day his 50 year figure would correspond to 18,250 hours.  I suppose that if the tubes are driven very lightly, and his design includes good soft start provisions, numbers approaching that figure might not be totally unreasonable.  For example, I recall reading that the Western Electric version of the 300B power tube, when used under recommended conditions, can last for 40,000 hours.  (I'm not sure, though, if that applies to the original 1930s version, or to the relatively recent reissue, or to both).

In any event, personally I would consider Mr. Carver's claim as simply indicating that the KT120 and KT150 tubes that are offered with the amplifier will last considerably longer than in most other applications.

Regards,
-- Al
 

Inna 11-13-2017
...so stop talking nonsense.

Inna, I'll follow up on my earlier response to your contention by speaking with uncharacteristic bluntness. In my opinion, your contention is nonsense.

Regards,
-- Al
 

Charles, thank you for your characteristically sage commentary.

Inna 11-13-2017
What is the rationale to have solid state phono or/and line preamp and tube amp ?

... I can't think of any top amp designer who would do this BS. Not many roads lead to Rome, just a few, don't fool yourselves.

Inna, obviously there are countless audiophiles who use tube power amps with fine results, and obviously there are countless audiophiles who use solid state preamps with fine results.  And typically a solid state preamp will have no problems driving a tube power amp.  So it seems to me that the question should not be what is the rationale for combining the two, it should be what is the rationale for describing such a pairing as "BS."

Regards,
-- Al
 

Analogluvr 11-12-2017
Good tube sound is not lush and warm. In my experience good tube sound just tends to have slightly more realism, palpability, and is better at Soundstaging.

+1. Excellent comment, IMO.

My experience, though, has been consistent with the comments by Keith, Charles, and Hk_fan, with tube power amps having tended to contribute more to those three qualities than tube preamps. I should add, though, that my experience with tube preamps has not been particularly extensive, and for the most part has involved well regarded vintage units (e.g., Marantz 7, Marantz 1’s). Also, to provide context, most of the speakers I have owned over the years have had benign impedance characteristics, and medium to high sensitivities.

Regarding your ground rule of...

... equality of price/quality. i.e. not comparing a $10k power amps contribution to a system to that of a $1k preamp.

... and your statement that...

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?

...I agree, at least in the case of medium to high powered tube amps. Tube watts tend to be expensive, for a given level of quality. So if highish power capability is needed in a given application, comparable quality between a tube power amp and a tube preamp might be hard to find at comparable prices. Which may tip the balance in favor of a tube preamp/solid state amp combination.

Regards,
-- Al