TEO Audio Liquid Pre preamplifier Review

The obligatory tour

The TEO Audio Liquid Pre certainly looks harmless enough; a tidy, smallish brushed aluminum chassis with a couple of big fat dials on the front, the left with five detents for selection of SOURCE and the right with about 24 detents for VOLUME, neither labeled. While appearing weighty, it is disarmingly light, able to be carried with one hand like a large book, and is sealed under pressure. Opening it may result in death – no, I’m kidding, but if you do mess with it, you may never get it put back together again, so it’s best not to. Remember, also, the cables…

The rear is Spartan, with the corresponding four sets of RCA inputs, a single pair of RCA outputs, and twin toggle switches. The irony that I was demoing a pair of TEO Audio Balanced interconnects, but the Liquid Pre does not accept balanced connections did not escape me. Alas, I had no TEO single ended wires, so the two never graced each other. One toggle switch corresponds to an unusual feature for a product sold in North America, a dedicated ground wire to be run from the third leg of a grounded outlet to the GROUND input.

Taras gave specific directions in regard to use of the grounding wire supplied:

The preamp should be grounded to a power bar or power access point that is central to the system. The specific included ground wire is essential to the sound of the unit. It is very, very much better with only its own included original ground cable in use, no add-ons, no extras (extension wires, etc.); original ground cable only. It is to be attached to the binding post on the back of the unit, via the Delton/banana plug on the one end of the cable, and to a ground point of a 120V electrical jack, one that is central to the system.

The GROUND lift switch allows for either the grounding of the signal to the chassis, or for separation of the chassis from the signal ground. According to Teo Audio the unit sounds best when the switch is in the up position, when the grounds are connected.

The other toggle switch operates a 47pf high frequency HF FILTER that shunts to ground on the outputs. It addresses possible HF oscillation, as, according to Taras, “the passive preamp is capable of unlimited HF response.” It is recommended that the owner start out by using the HF switch in the up, or ON, position. Then the switch can be turned off and assessment made as to the sound quality. Taras states the best sound quality is with the supplied ground cable, the GROUND switch on (Up), and the HF FILTER off (Down).

Compared to active and passive preamps

I have been blessed to use a wide variety of active preamplifiers over the years, and while the ability to add gain to the signal is a very pleasant sounding experience, I have grown to appreciate the purity of the passive preamplifier. When it comes to ultra pure listening I place the passive preamp technology slightly ahead of the active preamp. It depends upon the goal for the system; if the goal is “jump factor” and bass presence, then active preamps deliver superbly. However, if a performance is desired, “beyond a shadow of a doubt,” that is, one which seems utterly believable, quite a bit more indistinguishable to the ear from live sound, then I prefer a passive preamp at this point in my reviewing career.

One variation on the passive preamp is the TVC, or the Transformer Volume Control, a sample of which I wrote about in the Music First Audio Baby Reference Preamp. At the time I reviewed it the Baby Reference was the cleanest preamp I had used. Now, with the TEO Audio Liquid Pre, I am forced to revise my hierarchy of preamps again, for in the Liquid Pre an even simpler, yet more profoundly perfect method has been discovered. Using the same speakers, the same cables, the same source and DAC as in use for the Baby Reference I am made systems with greater precision and breathtaking realism. In a word, the TEO Audio Liquid Pre vivifies the performance of whatever it touches, be it a source or amp.

What is the big difference? Basically, the wire. Whereas the Baby Reference utilized hundreds of feet of copper (or silver in the upgraded version), the TEO Audio Liquid Pre uses short segments of the liquid cable. The stepped attenuator operates similarly, though they are different makes; consequently, I cannot say definitively that the cable is the greatest difference. However, in practicality it makes no difference; the components are what they are, and sell not piecemeal but entirely. The TVC was outclassed by a liquid cable/stepped attenuator setup, period.

Playing the game simply

Before I discuss the question of use of an integrated DAC with a preamp function along with the TEO Audio Liquid Pre, I will share about the components and speakers used in this review. I used one headphone system, the KingSound M-20 Headphone Amplifier and KS-H3 Headphones under review. Speakers included the Daedalus Audio Ulysses, the BMC PureVOX, and the Vapor Audio Nimbus White. The source was consistently the Mac Mini with iTunes or Amarra, and routed through DACs as discussed below. Amplification was typically the Wells Audio Innamorata stereo amplifier. Cabling was primarily Silnote Audio, upon occasions along with Clarity Cable.

When it comes to system setup for a digital source, one might think that the obviously superior solution is to utilize the on board preamp function increasingly found in USB DACs with DSD capability in lieu of an outboard preamp. Not so. While an individual can build a terrifically pleasing system with a stripped down chain of source/DAC (with pre) and amp serving speakers, the preamp as a separate component should not be unceremoniously dumped. I would agree that it may very well be the case that a most favorable result might be found by opting to bypass an active preamp. Bypassing a TVC is a more questionable proposition, as it is in my experience categorically cleaner sounding. Its use to enhance the soundstage and macrodynamics is justifiable in many cases. It likely would causes less degradation than the active pre, in general, and expands the soundstage as most integrated preamps in DACs cannot.

The TEO Audio Liquid Pre is another creature altogether, and I simply state that among the DACs I have used to date with it, including the BMC PureDAC, iFi iDAC Micro, iFi iDSD Micro, Eastern Electric Minimax Solid State DAC Junior and Minimax Tube DAC Supreme, as well as the exaSound Audio Design e22, all 32-bit DSD capable units, all have been invigorated by the influence of the Liquid Pre. Not a single one of them sounded better through their own preamp function as opposed to use with the TEO Audio preamp. I struggle to think of a time when categorically all DACs were benefitted by the presence of a preamp. Usually it takes quite a bit of system magic, a lot of shuffling of cables and amps, to get a DAC to reach an ineffable state, but not when the Liquid Pre was employed! The simplest way to explain the effect of the TEO Audio Liquid Pre upon these devices is to say they were made better. How? In every aspect, better holistically, not partially. Better, as in seeming like I was hearing a DAC two models above, better as in it sounded like a $5K upgrade to the DAC had been done.

Alternative to QOL

A while back I had an in-home demo of the much discussed QOL, which has been well received by the press and treated in forums as having a sort of Holy Grail efficacy. As I used it in my system, I wasn’t convinced of its seemingly unassailable merits due to the significant level of degradation encountered simply by its presence in the system. In short, it couldn’t get out of its own way. Ultimately, I was unwilling to accept the sense of expansiveness to the sound and fullness of instruments and voices at the expense of diminished purity.

The TEO Audio Liquid Pre more perfectly accomplishes what QOL attempts to do. The Liquid Pre does not merely expand the soundstage, it does so with no sonically perceptible degradation. It does not simply place the musicians in front of me, it precisely locates them and scales them properly. Beyond getting tonality correct, it gets the structure of the instrument making the tone correct. The best part is that it doesn’t compromise the sound by adding electronic haze because it has the advantage of being a passive component.