Ever perform a preamp bypass comparision test?

Drubin, what I've noticed in my tests is more of a subtraction from the sound than an adding to it, which I guess is good sign in theory. For instance, piano can lose a little of its sparkle and percussive incisiveness, rendering it just a little veiled in comparsion. Stand-up bass loses some heft and definition, becoming less pitch-precise and more rubbery. On the other hand, some sounds do seem to gain unwanted artifacts; a half-opened hi-hat cymbal sounds more like two pieces of metal clashing against one another when listening to the DAC straight, but when the preamp is inserted, the sound becomes more akin to indiscriminate white noise - could this be the result of added intermodulation?

That's my SS preamp, though; with my tube preamp, there are losses to be sure, but you do notice right away a certain subtle tonal quality (which I like to characterize as 'sunny') is lent to the whole presentation. It can be attractive once you get used to it, but that is certainly something which is added, probably low-order harmonic distortion, and I don't know how it can be considered to make the result sound 'more like music'. This preamp definitely sounded more like music than my older cheap SS preamp that departed long ago, which was grainy, shrill, and flat in comparision, but it doesn't IMO improve on the straight feed from a quality DAC.

Zaikesman, I was thinking of my own personal dilemma with my two preamps. The (active but no gain) Placette, which is very, very close to adding or subtracting nothing at all, and the First Sound, which can sound glorious and more musically convincing in some respects, yet sounds entirely different from the Placette.

You say you don't want to introduce specific preamps into this equation. I find that frustrating since that can make all the difference in the world as to how this test turns out.
You bias your test in the beginning by stating that if you don't recognize the benfits of running direct you must have one whizbang of a pre amp.
I have done comparisons with customers who were using Tenors without a pre, Audio Aero straight into their amps and passive devices using nothing more than naked Vishay resistors on their amps. All who have heard a benefit when switching to transformer coupled pre. I have attached one such thread from a die hard passive fan.
It seems to me your test is not real world because your trying to make a case that direct is better when comparing it to your solid state pre-amp or some one's pre which may or may not be that great of a pre. In that case a dircet feed is going to sound better. I have always agreed with that. My argument is that you can't make a generalization of which is better based on this kind of a test.
The impedance mismatch alone of the driving device and amp is reason enough for active gain stage. Comparing to a capacitor coupled preamp is still a compromise.
I have owned many!!!!!! players with direct outputs, passive devices including the Placette, First Sound (when he made them) EVS, Reference line etc. So I have had much experience with these devices. I know I have been down this path before. I have issued challenges regarding this. So far every person who has taken me up on the challenge has gotten away from their passive or direct devices.

"The system is so much more visceral with the M-5. Everything got better. I don't know how anyone could think running the AA capitole atright to the tenor would be better than this"

Why do the Audio Note preamps sound so much better
I took Joe over at JC Audio up on the offer of a shoot out. Actually it was the second time. About nine months ago I went over and had a shoot out between my EVS Nude Attenuators and the Kora triode preamp. I have to give Joe credit he agreed if you could live with the inconvenience and lack of flexibility that the EVS attenuators sounded as good.

But I made a bad mistake today. I went over and did the same shoot out with the Audio Note M5. I should have never done this. The M5 made the attenuators sound dry and lifeless. The M5 sounded prettier with much more top in extension without ever sounding bright. It was more transparent and fuller bodied at the same time. And the layering and the soundstageing was just beautiful. This is disturbing to me for I have been a big proponent of passive, especially the attenuators since you even eliminate a set of interconnects and a power cord. Why does this line stage sound so much better.
bilbondo@hotmail.com

08-02-02
08-15-02: ralph@atma-sphere.com
The Audio Note, EAR (E11??), the big Jadis and Atma-Sphere (P-2) preamps are the only high-end audio transformer-coupled units out there to my knowledge.

Transformer-coupling is common in professional tube gear, particularly from the 50s and 60s. This is because the equipment had to match to the 600 ohm balanced line standard (which is still very much around today). Tubes coupled by output coupling capacitors would never be able to play any bass driving a 600 ohm load!

We built the P-2 (discontinued when it was replaced by the MP-3) so it could drive the 600 ohm standard as well. The nice thing about the 600 ohm standard is that it ameleorates the role that interconnect cables play in the sound of the system, which is why the standard has been used for the last 5 decades by the professional recording and broadcast arts. Its always been a puzzle to my why audiophiles are so slow to embrace the same standards, despite having the same concern about cable qualities. This has spawned the high-end audio multi-million dollar/year cable industry.

We're an OTL manufacturer, but we've been a major supporter of balanced line technology for the last 14 years (mostly due to prolonged exposure to the recording studio); our preamps support the standard using direct-coupled ouptuts, which is the only other way to do it as capacitors won't work (since no-one would take a tube preamp with an electrolytic output coupling cap seriously...). IMO, its a shame that more manufacturer's aren't wise to what's happening here (sorry for the hype blast).
ralph@atma-sphere.com

I meant to say "sources that would seem good candidates for a passive, such as the theta's", but I should add "also from output voltage and what I have read". The theta seems to benifit less from going passive, while my phono, seems to benifit more from going passive. My findings so far are opposite from what I have read would be the case.
In the quicksilver line stage, the volume is before the line stage curcuitry. The path is fron inputs, to the rotary switch, then to the other swicthes (mono, ect.) then to the attenuater, then to the active curcuitry. I have added two leads going to output jacks from the attenuater, so the active and passive are in parrallel coming from the attenuater each with it's own set of output jacks. It is actually what seems to me a good quality passive, given the stepped attenuater and quality of jacks. The only inconvenience is that the active reverses polarity, so I have to reverse the speaker cables whenever I go from one to another, or else I would put in a switch.
You bring up interesting point about the bass frequencies, I have not payed that much attention to it insofar as a mismatch, perhaps I should. I have looked only at rolling of highs as a mismatch that just would'nt work well (sound quality is the main thing, but I am refering to situations where it is not possible due to the interfaces to evan consider).
I wish I knew a way to invert polarity on a single ended signal.

JC, I appreciate your input, but I think you may have read some things into my post that I did not intend. I am not trying to make a case for running direct, and I do realize that my preamps (list prices about $1,800 to $3,000) are not SOA. Neither are most folks' preamps, and neither do most folks want to run direct or passive. I am also not trying to solicit advise concerning my own preamp situation in particular with this thread, which is why I'm leaving out the make and model info, since I don't want my comments taken out of context.

My post is just intended to explore the notion of employing a bypass test to look at preamp performance, and to see if other members have had experience with this kind of procedure and what their results may have been. In my own case, where I feel confindent that my DAC, at least, is just as capable of driving my amps' inputs as my preamps, I admit I am skeptical of the notion that a preamp could not only fail to cause *some* signal degradation, but could actually make the sound 'better'. I acknowledge that I don't have epxerience with the best preamps, but rest assured that I have no intention of removing the preamp function from my system. I just want to know exactly what it's doing.