Are passive preamps better?

Pubul57,
I have used three different tube preamps with my Pass X250.5: ARC LS15, Cary SLP-05, BAT Vk5i. I have used these with my two digital sources, Marantz SA11S1, and a Squeezebox 3 (with overkill linear PS). I have also used a TVC for a few months as well.
I recently discovered that plugging my Squeezebox 3 directly into the Pass (single ended, with jumper shorting plugs installed in xlr's) results in a very liquid and great smooth sound with well defined images and appropriate size. I thought I was hearing things (no pun intended) and that surely there was no way this combo could sound so warm and relaxing...more relaxing than the recent tube preamp I just had in there. So I gave it a few days and it still sounds really really nice. What does all this mean? Who knows. What is tube sound after all? Does it mean layers upon layers of image density? Does it mean a natural organic utterly non irritating midrange? I really don't care, but if it sounds good, IT IS GOOD no matter what anyone else thinks.

This recent test clearly illustrates that an all solid state chain can yield a nice easy on the ears midrange with vocal heft and texture (not grain). Granted the SB3 is more limited in its resolution and I have no way to hear the SA11 direct, but when the SB3 was going through the tube jobs, the sound was more in your face, more forward, as if the midband was pushed further forward in the speaker plane. I said to a friend that I really feel like i'm hearing the fundamental characteristics of the Pass amp (to the resolution of the SB3, of course) and this result has had a huge positive effect on me (the amp is amazing: rich, detailed, powerful, great sense of depth), and has really pushed me to try a really nice solid state preamp. Perhaps it's just that i'm now realizing that I really like a laid back midrange (as in depth). Perhaps due to the emphasis on the midband that tubes seem to manifest that its too much and not needed with my amp (and speakers of course). Also the bass was off the charts with the SB3 direct, definitely better than through any tube preamp I had in the system. So all of this threw me for a loop and that's why I said what I did about the "warm tube sound" being a mystery to me. Maybe all the pre's I tried with the Pass were just not matching up correctly, but I just bought a Pass X2.5 preamp, and though it's not here yet I look forward to hearing it's effect, or lack there of (I hope) in my system. Pubul57, as you said nothing sounds like tubes but tubes and maybe i'm simply tired of that "sound". That being said next month I will probably look for an LS26 -lol

I'm not saying this happened, but my experience with Pass Amps is that they tend to be less than ideal matches for most tube preamps because of their typically low input impedance. This would tend to lessen the output at the bass and treble regions, which is the same thing as saying that it might tend to push the midrange forward, which seems to be what you heard. You SB3 experience seems really interesting, that might be a good next experiment. The hard drive storage "transport" idea is starting to intrigue me. I bet you like the LS26, alot.

Thanks, Pipedream, for info. It probably is the hard drive, but my sister and brother have the latest H/K 75W AVR's, and that sound is also amazing as Dpac996 describes. I don't know if I'm upgrading to stay ahead of them or just to keep up. The latest stuff is sounding awfully good. Lynne

I found that I had an IC about a ft shorter than I was using. So I tried going direct to amp again. With shorter IC I lost the distrtion components that were present with the longer IC. I also discovered that the CD player's volume control is motorized for remote. I cite a very small knob and poor lighting to diminish my embarrassment and proclaim the volume control to be a high quality pot--better than the one on the Celeste. This set-up is significantly better than with preamp, I can tell even though the IC needs some break-in time.
Pubul57, Why does an amp with a low imput impedence affect the frequency response by increasing the mid's? Why doesn't it simply drive the pre into distortion?
I infer from John's comments that age is not such an issue with tubes as with SS. You can simply upgrade tubes and capacitors.
Endler has my money but haven't heard a word.
Lynne

Low input impedance with high output impedance from the pramplifier reduces the output in the base and trebles, they roll off. As a result the mids seem to be pushed forward since the balance of the sound is altered from top to bottom. Typically, as a rule of thumb, the input impedance should be at least 10x the output impedance. With the AI3, I think you would need at least a 20kohm input impedance for balanced sound across the spectrum.