Ever perform a preamp bypass comparision test?

We're still on slightly different pages here Sean, so maybe it is me who's not being clear. What I am suggesting is to stay with one set of outputs from the DAC (could be either one - the variable ones could be useful for achieving an overall volume that doesn't blast away the subtle differences, but once it's set, leave it there and treat it as fixed), or to use any other source. The idea is to focus on what *the preamp* is doing to any line-level signal it gets. To do this, you have to maintain the same interconnects and I/O jacks, and just swap the output leads on the preamp from the active, normal ones to passive, direct ones like processor bypass. That way, you can compare the sound with and without the effects of the preamp's gain and attenuation stages, while keeping the connections and cables constant. To do this, you must set the volume control on the preamp to unity gain, wherever that may be. What you are describing is comparing the sound of your DAC's attenuation to that of your preamp's, which is a different comparision, and one that only matters for that particular source component (it does tend to confirm that your preamp must have a quite transparent gain stage and jack complement, as well as your interconnects being very fine, since you're losing one set when you go to the DAC's internal volume control, and as we theorized above, it could mean that the two attenuators behave very similarly, but your test does not isolate the preamp or maintain all the other variables as constants - it's a legitimate and useful test, but a different test nonetheless).

Basement, I'm not completely sure about this, but I think most preamps place the volume attentuator after a gain stage, so it might be that taking an output straight from the attenuator bypasses the output stage, but is not totally passive. The loss of bass when you run in this mode could very well be due to the interaction of the volume pot's output impedance with the load presented to it by the amp and interconnects when the normal output impedance-lowering buffer stage is not present.

I'm a little confused by your fifth paragraph, but maybe you put 'passive' in some spots where you meant to write 'active' (also, your phonostage is actually going to possess the highest voltage gain of any of your source components, although not probably the highest output voltage). In the next paragraph, I'm sure the input impedances you refer to on your amps must be K-ohms, not ohms, but again, it would be bass frequencies which would be rolled off if the input impedances were too low, not the highs (it's cable capacitance which can roll off the highs.) Help me out here Sean if I've screwed up any of this!

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