I wanted to know in particular what are the advantages of the tube amp besides the warmth.
1.Is this warmth increase of detail and resolution as in the vinyl sound or is it loss of detail as in smoothening?
In my experience, there can be a slight softening of the highest frequencies and lowest frequencies depending on the type of tubes and the circuit design. But in exchange for this I find that the tube preamplifiers and tube integrated amplifiers and receivers I have used do a much better job of passing ambient information that is part of the original recording through to the listener than most solid state gear.
2.What else does a tube amp do that solid state doesn't.
Run hotter, except for Class A solid state amplifiers that can run hot too.
Have a lower damping factor (see my response to #4)
Not sound obviously bad when driven into moderate clipping
Pass recorded ambient detail from the original recording session through the amplifier circuits and to the speakers or headphones, an ultimately to your ears.
Reproduce the sound of string instruments and woodwinds, and the human voice in a way that very few solid state amplifiers can match.
3.And which one is better for what kind of music according to your opinion? Is a tube good for rock?
If your are using headphones, and they sound good when listening to rock music, their sound can be maximized with the right amplifier. Sometimes this is a solid state amp, sometimes tube. Tube amplifiers tend to work well with high impedance headphones like the Senn HD-580/600. But you really need to audition, or if you can't do that at least get another reviewer's opinion, to determine whether a particular amplifier will work well with a given model of headphone.
4.And also how much sensitive speakers do you need to have in order to use a tube amp of low wattage and get the same volume as in a normal SS amp?
A watt is a watt and a decibel is a decibel. If you normally use a 100 watt amplifier with a particular model of speaker that has a rated sensitivity of 87db, in your listening room, then only another amplifier of close to the same power rating will play the speakers at the same level as before. However, increasing the sensitivity of your speakers by 3db, by switching to a different model or type of speaker, will reduce the power requirement by 1/2, for the same acoustic output level. So a 50 watt amplifier will play as loud with speakers with a 90db rated sensitivity as with the less efficient speakers in the same room.
Another factor is clipping distortion in the amplifier. Both tube and solid state amplifiers clip the output signal when their output stages can no longer amplify the signal to a higher level. When a solid state design clips, unless the clipping is very brief, the sound will begin to sound distorted and quickly become unlistenable. When a tube amplifier clips, the output signal starts to become compressed, but without the odd-order harmonic distortion products that are typical of a solid state design. So when you push a solid state amplifier beyond its rated output, it quickly begins to sound bad even to an untrained ear. When you push a tube amplifier hard, it is not as obvious that the amplifier is clipping the output unless you are monitoring things on an oscilloscope. Depending on the circumstances, you can push a tube amp 3db, 6db, or even more beyond its rated output and not hear anything amiss. In this way, a 50 watt tube amplifier can appear to play as loud or louder than a 100 watt solid state design. When an amplifier is clipping the peak music signal levels, the average output level is usually 10-12db below this level. So a 100 watt amplifier driven into clipping is really only delivering an average of less than 10 watts on music. With test tone signals, this example would not apply.
5.How much can a DIY kit for a tube amp cost besides this that someone brought up lately tha is about 140 dollars incl. a multimeter and screwdrivers.
How much or how little? A used tube amplifier or receiver can be a good way to start. The Dynaco SCA-35 is a small tube integrated design that is rated at 17 watts per channel. It has a phono preamplifier and uses 12AX7 tubes for the phono preamp circuit, and (2) 7199 driver tubes and (4) EL84 output power tubes These amplifiers were originally sold as kits as well as factory assembled. If you watch eBay, these come along fairly often and rarely cost more than $175 for a nice working example.
One advantage of the SCA-35 is that it is very compact for a tube amplifier. There is a mounting location on the rear of this amplifier for a heaphone jack to be installed.
Another good choice is the Fisher 400 receiver. Much larger than the Dynaco, it features a FM stereo tuner and a phono preamp and inputs for a tape deck and a spare auxilliary high level input. These usually sell for slightly more than $200, and will usually require some parts to be replaced, but the Fisher 400 is great sounding headphone amplifier as well as a tube receiver. The Fisher 400 has a headphone jack.
6.Some people mention the combo of tube preamp to get warm midrange and solid state amp to drive normal speakers and get rich bass. At the preamplification stage where tube is used shouldnt the deep rich bass be already "cut off" ? What's the point of this combination. The tube amp alters the sound information in its own way. Then what does the SS amp add? Is there a good explanation for this?
The motion of a speaker driver, especially the woofer driver, needs to be controlled by the amplifier due to the energy generated by the voice coil as it moves inside the magnet structure, and the mass of the moving speaker. The property of an amplifier that works to control this back EMF is called damping factor. Tube power amplifiers have lower damping factors than solid state power amplifiers. A typical tube amplifier damping factor could be as low as 10-15, while damping factors for solid state amplifiers are typically several times higher. If an amplifier does not have a high enough damping factor, the motion of the bass driver will be poorly controlled and the bass will not sound clean, but muddy. Some speakers don't work particularly well with tube amplifiers for this reason.
One work around is to use a solid state amplifier, to get higher power and also the needed damping factor to control the woofer, and use a tube preamp because of the way that some people believe the tube preamplifier can bring out the subtle tonal qualities of the music, especially in the all important midrange. Many times, singers sound more natural when the music is passed through a tube preamplifier or amplifier. Also, in my experience string instruments (violin, viola, bass) and woodwind instruments ( oboe, clarinet) sound much more natural when heard though a good tube system than with most solid state gear.
One potential problem with pairing a tube preamplifier with a solid state amplifier is that depending on the circuit design of the tube preamplifier, the output impedance of the preamplifier can be much higher than the input impedance of the typical modern solid state amplifier. So a preamp with an output impedance of 500,000 ohms (the vintage Dynaco PAS preamplifier for example) is not going to mate well with a power amplifier unless the amplifier has an input impedance in the same range as the output impedance of the preamplifier. Even 100,000 ohms is really too low to be a good match with the 500,000 ohm preamp and most modern solid state amplifiers have input impedances of under 50,000 ohms. This potential for impedance mismatch between the amplifier and preamplifier are eliminated if you use an integrated amplifier or receiver.
7.This last question is about preamplification in general. Pre amplification for phono is a neccessity to hear sound. What else is pre amplification for and what are the advantages and disadvantages.
Like a lot if things it depends. Except for a true low level signal as from a moving coil or moving magnet phono cartridge, a preamplifier is unnecessary to drive a power amplifier. (Note:the phono stage preamplifier is also applying the inverse of the RIAA phono response curve that was used when the LP record was mastered. Without this inverse filter, the sound would be shrill and with hardly any bass.)
I have a CD player than has variable outputs as well as fixed outputs. I have tried various listening experiments to see if the CD player could drive my power amplifier directly. In this case, the resulting sound was a bit cleaner than when the signal was passed through my preamplifer, but at the expense of losing the balance control, tone controls, and being able to switch to another source such as LP radio. Some amplifiers have their own input level controls, so you can directly connect a component such as CD to the amplifier even if the CD does not have variable outputs. Depending on how far you place your source from the amplifier(s), the signal level may not be able to be run through a long cable without dropping off or picking up noise in the cable.
A better name for a preamplifier would be control amplifier, since most of the function and benefit is in switching and patching the signals between the various sources and the main amplifier.
