Richard, here is what I have gleaned from investigating tube amplification and solid state amplification. Simple triode tubes have a cathode coated with a substance that will release free electrons when the cathode is heated. The a plate with a positive charge that will draw those electrons. a grid that will control the flow of those electrons. when working if a sine wave input to the grid forms a flow of electrons to the plate matching the input sine wave but now with much more energy due to the high voltage. Thus voltage amplification. That is converted back to a high current flow thru an output xfmr. The sine wave is in tact matching the input. Hearing specialists and sound engineers have found that this type of tube amplification tends to exemplify the even harmonics of the fundamental frequency which are accepted well by our ear to brain function thus sounding louder than the db meters indicate.
In solid state devices are solid materials with positive to negative junctions. When a sine wave is entered the solid state material has to give up electrons thus becoming a positive charge or give up protons thus becoming a negative charge. What happens then is positive and negative current flow occurs in two directions. One is called electron flow the other called hole flow or positive flow. This constant interchange causes two sine waves of the original to flow in opposite directions. not only can this cause distortion but causes an emphasis on odd harmonics of the original frequency. This has been found to be irritating to the ear to brain interpretation, thus our brain tends to shut down the level. The musicians have indicated that their solid state amps sound like someone threw a blanket over them. This started a hard long investigation of sound reproduction be sound engineers, electronic engineers, ear specialists to find out the difference. This has led to our great SET low poured tube amps.
I use only vinyl because I have printouts of oscilloscope graphs showing all of the original sine wave missing due to the sampling rate of the digital sampling. I do realize that there is a great difference in the way different sound engineers and recording engineers do their vinyl recordings. Some over emphasize the highs which are very irritating. Some over emphasize the lows and out comes boom, boom, which is also very irritating. With my preamp I can get some control on this with my tone controls.
With a passive preamp how do you deal with this?
My preamp is an EICO ST84. It uses 12AX7's thru out except for the rectifier. It was a kit when In bought it in 1967. It was a steal at that time because kit building had gone out of interest. I went thru it last year. Most of the carbon resisters were out of specs. replaced the resister, caps and tubes. The EICO ST84 is a highly sought after preamp now. I saw three of them sell on EBAY for over $900.00 last year.