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REVIEW: Seamless Interface Electro Acoustiques Big Dog Preamplifier (HT)

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Model: Big Dog
Category: Preamplifier (HT)
Suggested Retail Price: $2700
Description: Transformer-based passive preamp
Manufacturer URL: Not Available
Manufacturer URL: Not Available

Review by DavidZ ( A ) on July 01, 2002 at 18:17:14
IP Address: 24.91.12.48
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for the Big Dog


“Don’t it always seem to go that you don’t know what you’ve got til it’s gone.”

Joni Mitchell wrote those words to lament the steamroller of progress, as in “they paved paradise and put up a parking lot.” But when it comes to building an audio system, getting rid of things can really represent progress. For many audiophiles, that’s the true allure of a passive preamp. By definition, a passive pre only attenuates (and sometimes provides source selection). If your system is suitable for a passive, you can get rid of a gain stage and all the attendant circuitry that inevitably add “personality” to the signal, good, bad or indifferent.

My search for a passive led me to try the Big Dog, by Seamless Interface Electro Acoustiques, a new company in Houston started by Carlos Lozano and Riley Norman. Let me give some system context, pre-Big Dog. I was using the Accuphase DP-90 transport feeding a Chord DAC64, driving a Berning Siegfried 300 B connected to Avantgarde Duos. The Berning already is a passive of sorts – it has a level control in the form of a Noble potentiometer. It’s designed to be used as a stand alone stereo amp (with volume pot wide open) or as an integrated, using the volume pot. With the volume control wide open, and the resistance almost nil, any effect of the pot on the sound is substantially eliminated.

I had tried using the Berning with an excellent active tube preamp, but it was sort of like putting mayonnaise on corned beef – both components produce a different sound. There was no synergy. The personality of the tube amp just sounded colored and constricted dynamically compared to the Berning by itself. Since the Berning sounded fantastic by itself, I resorted to the cardinal rule of audiophiles: never leave well enough alone. (If that logic isn’t apparent to you, you probably have surfed over to Audio Asylum by mistake.)

Deep in the recesses of my mind, I remembered bad things about potentiometers. When I heard about the Big Dog on AA, I was intrigued. Rather than resistive elements, as with a pot or stepped attenuator, it uses a 1:1 step-down transformer to lower the voltage. There are 24 (I think) different taps on the secondary winding that are fed to a switch with a comparable number of positions (the feel is just like a stepped attenuator in that regard). In the tradition of passives, the Big Dog has no power supply. One of the claimed advantages of a transformer volume control is that the output impedance changes very little with the volume setting. With resistors, the output impedance gets larger as the resistance increase, i.e., on lower volume settings. (I mention this not as an endorsement of the transformer approach, but for informational purposes; evaluating the technical merits of either approach is beyond me.)

To cut right to the chase, the Big Dog made a Big Difference. As near as these ears could tell, the benefits were all subtractive, in the very best “less is more” sense of the word. To paraphrase Joni, I could tell what the Noble pot was doing to the sound once it was gone. Layers of grit and fuzz seemed to disappear, and the soundstage seemed to widen and deepen by about a foot, depending on the recording. The difference was impressive and immediately apparent. As I A/B’d some tracks, it became clear that the Noble had been distorting different parts of the tonal spectrum. On “Groove Yard” by the Montgomery Brothers (an excellent JVC XRCD release 0018-2) the first cut begins with a brief solo stand-up bass riff by Monk Montgomery. Big, round, fat luscious acoustic bass notes. But much more so on the Big Dog. Going back to the Noble pot, deformations in the wave were all too obvious, and it sounded as if the artist had less control of his instrument than he really did.

Another fave of mine is Trumpet and Organ of the Baroque on Water Lily Acoustics (WLA WS 13 CD). This is an analog recording that Kavi Alexander lovingly transfered to CD. There’s a Scarlatti cut in which Emma Lou Dieter repeats a theme right on up the scales to where the positivs of the organ get a work out. Through the Big Dog, there was a sweet dimensionality that maintained itself throughout, right up to the high pitched tones that held me captivated. By comparison, the Noble volume control flattened and coarsened the sound. These are just a couple of examples, but the Big Dog consistently opened a window on the sound that was big, clear, refreshing and sonically habit forming. The knock on passives (of the resistive variety) is that they can have weak dynamics (I’ve no prior experience to have an opinion). In this case, however, the Big Dog’s dynamics mirrored that of the source – there was no diminution in small or large scale dynamics, and the musical flow was effortless. I’m convinced the Chord DAC64 can pack a punch and whisper with the best of DACs, and that came through fully with the Big Dog, at every volume level. The requisite Mahler and Wagner auditions passed the spine tingle test, and made me want to listen to more.

It’s amazing when you think about it. A volume control all by its lonesome is pretty passive and minimalist. The Big Dog showed, however, just how much coloration and distortion the pot was injecting. Now imagine all the stuff inside an active preamp. I’m not saying your system can’t sound better with an active preamp – there’s an awful lot of incredibly good equipment out there. But there’s something very appealing about well-thought-out, well-engineered simplicity. If your source components, amp and speakers work well together, it’s hard to imagine not being thrilled with the Big Dog. (I haven’t gone into all the caveats about building a passive system, but there are many posts on AA and the audiophile press about things such as amp sensitivity, cable length and capacitance, and impedance matching. Be sure to do your homework if the passive approach appeals to you.)

Before finishing, I have to mention one of the spookiest (in the good sense) qualities about the Big Dog’s volume controls. All of us who have flipped volume controls on electronic things since toddlerhood have become acclimated to the shifting tonal balance that takes place as they get louder. That doesn’t happen on the Big Dog. The effect is hard to describe –when you turn it up, you notice that there’s greater sound pressure, for sure, but the normal physiological (and unconscious) cues for “increasing loudness” aren’t there. The closest analogy I can come up with (and not a great one) is when you quietly watch the light of dawn gradually illuminate the objects in a quiet suburban street, not in direct sunlight. The light intensity increases by a comparable amount, slowly and subtly on everything, not favoring the fire hydrant or a windshield, or the neighbor’s lawn. Twisting a knob happens faster, but the effect is similar – a bit of a paradox, but I leave that for you to grapple with.


Product Weakness: Requires the careful system matching that all passives need.
Product Strengths: Purity and faithfulness to the input signal.


Associated Equipment for this Review:
Amplifier: Berning Siegfried 300 B
Preamplifier (or None if Integrated): Berning Volume pot / Big Dog
Sources (CDP/Turntable): Accuphase DP-90 transport / Chord DAC64
Speakers: Avantgarde Duos
Cables/Interconnects: Nirvana SL all arouund
Music Used (Genre/Selections): various
Room Size (LxWxH): 18 x 15 x 8
Time Period/Length of Audition: 1 month
Other (Power Conditioner etc.): Sound Application CF-X
Type of Audition/Review: Dealer Demo




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Topic - REVIEW: Seamless Interface Electro Acoustiques Big Dog Preamplifier (HT) - DavidZ 18:17:14 07/1/02 ( 5)