The IRD LLC-P Preamplifier

Product: LLC-P "Purist" preamplifier
Manufacturer: Integrity Research and Development Company, Ltd. (IRD) - Thailand
Approx. price: $665 USD, includes shipping to the US ($25 credit shipped elsewhere)
Reviewer: Richard George - TNT USA
Reviewed: June, 2003

The audio press pays a great deal of attention to various components and configurations in home audio equipment. There is a large and diverse selection of articles available in print and on-line about digital and analog sources, whether to use valve or solid state power amplifiers, monobloc or stereo, what types of speakers work well with which amplifiers, how to tweak the system to optimize performance, what works, what doesn't, what's in fashion, and what is last year's news. The list is endless. In all the reviews, dialogues, monologues, dissertations, and diatribes about audio components, preamplifiers seem to receive relatively little attention. They are often somewhat neglected, sometimes outright ignored, or perhaps referred to as a 'necessary evil' by people believing that any preamp is a bad preamp.

Having listened to and admired many stereo preamplifiers ranging from my first serious preamp, a Dynaco PAS-3X a few decades ago, to, much more recently, a Halcro DM-10, and disliking many more, it has always been apparent that preamps cover a huge range in price and quality. It is generally accepted that higher quality is usually accompanied by much higher price, though such is not always the case.

Preamplifiers, which are more accurately known as audio control amplifiers or line-level controllers, are a necessary but sometimes undervalued component in the audio chain. When shopping for a new preamp, people often ask the wrong questions, such as: Does it have enough inputs? Does it have a low-level output for a subwoofer and an HT pass-through? Does it have balance, tone, equalizer controls, and remote? Many people shop with a laundry list of desired features, but they often forget a critical question: how does it sound? Most manufacturers cater to this attitude with designs that compromise preamp sound quality in favor of attractive convenience features, which is especially true in the sub-$1000 category. There are, however, some audio equipment manufacturers that place sonic performance first, then add convenience features later.

Integrity Research and Development Company, Ltd. (IRD), an established though relatively young audio company based in Thailand, is rapidly building a reputation for providing excellent quality components with surprisingly good value. While IRD initially operated largely as an OEM supplier for several companies, Curt Wishman, the company president and chief electronics engineer, is now working to improve IRD brand name recognition. In addition to founding a new audio company, Curt is bringing fresh ideas on circuit design to the market.

IRD has been selling its MB-100 (a.k.a., nOrh Le Amp), solid state, monobloc power amplifier for about a year and a half, both as an OEM product and under the IRD name. Having sampled a pair of very affordable MB-100s, which had excellent build quality and very good performance, I waited with little patience but much anticipation as IRD issued statements and reports with tantalizing details on development of their new preamp, the LLC-P, or the "Line Level Controller - Purist".

However, IRD is not stopping with the MB-100 and the LLC-P. Indeed, their new product development is only accelerating. New products slated for introduction within the next few months include the MB-250, a 250-watt monobloc amplifier, and two active, line-level, crossover networks. In addition, the LLC-P "Purist", is only the first of three preamps that IRD soon will be unveiling. The second will be the LLC-A, "Audiophile", which will incorporate built-in, 24 dB/Octave, 2-way active crossover filters. The third, the LLC-S "Sabai", will be a more all-around preamplifier and will include an IR remote control and a moving magnet (MM) phono stage.

What is the IRD LLC-P Purist?

The Purist is the most elemental of the new IRD series of preamps - its mission, as stated by IRD, is to be a "no nonsense, ultra precision, low THD+Noise, line-level controller." It is a very well-made, solid state, dual-mono preamplifier with an elegantly simple circuit that outwardly appears to follow convention in design and construction. When looking more closely, it becomes clear that, despite outward appearances, the LLC-P Purist manages to break a few established design rules, not for the sake of breaking rules, but to provide superior performance. Opening the case, one is reminded that IRD does not like flimsy construction - like the MB-100, the LLC-P is built to last. Weighing 10.5kg (23 lbs), the Purist is no lightweight. Twelve allen head screws must be removed to open the top cover. Inside, the LLC-P is very cleanly built and very neat, with its sparse wiring tied out of the way with cable ties. This preamp looks like it was designed by a serious engineer with an eye for details, rather than by someone that is merely a circuit designer.

The back panel of the LLC-P has four RCA source input pairs, two RCA output pairs, and an IEC power connector socket. As with other aspects of the LLC-P, low noise is a priority - the IEC connector has a built-in, EMI/RF filter. The power transformer, which is located on the opposite side of the chassis from the signal gain and control circuitry, is a large, toroidal unit that clearly is under-stressed for the job. This is a departure from many solid state preamps that seem to use just enough power transformer to get the job done, and not one bit more. Power consumption of the Purist is listed as less than 20 watts.

The IRD preamplifier design departs from conventional designs in another interesting way. In most preamps, the volume control pot attenuates the incoming signal level prior to the gain stages. This is the way it was originally done by most manufacturers and has become convention. IRD has turned things around. In the LLC-P, the signal goes through the single, IC gain stage before it reaches the volume control. This allows the entire signal to be amplified by the gain stage, then the output is controlled by the volume control. This design was utilized to minimize noise added by the preamp. Output impedance is 100 ohms; input impedance is 33.2k ohms.

The LLC-P provides up to +12dB of gain with maximum output signal level of 9v, but that isn't the end of the story. Gain is selectable through a knob on the front panel. In standard configuration, gain is adjustable in three steps, +6dB, +9.5dB, and +12dB. This allows users to customize the LLC-P for use with individual systems by selecting the proper gain that will provide optimal control range of the volume level with different sensitivity systems or in different rooms. The IRD website recommends using as little gain as necessary to minimize the signal-to-noise ratio.

In addition, IRD has listed on their website, the "Factory Approved, LLC-P Mod #1". This modification entails clipping the leads of two conveniently placed resistors, one per channel. These can be clipped by IRD prior to shipping or by the end user. By clipping these resistors, selectable gain will shift to 0dB, +6dB, and +9.5dB - in essence, this provides the end user with the ability to use the LLC-P as a passive preamp with interconnect drivers, active buffers, and proper impedance matching, while still being able to switch in up to +9.5dB gain when using lower output sources.

The volume control is another element that is well thought out, designed, and beautifully constructed. It is a custom-designed, Swiss-made, ladder-step attenuator that provides only two resistors in the signal path at any volume setting, one per channel. It uses 96, low-noise, metal film resistors. In addition, the lowest volume setting does not silence the output - even at the lowest volume setting, it has a very low volume output. This design was deliberate, as it allows users to turn the volume knob all the way down, cue a source, and still be able to hear what is happening. If total silence is needed while a source is providing an input signal, the preamp can be switched to the mute position.

Another view of the interior, showing the stepped attenuator on the right.

The mute position is one of two additional, very interesting features are found on the LLC-P. Mute is selected by the 'mute' position on the input knob. Unlike most preamps that simply mute the output, the LLC-P switches to a separate input that has no outside connectors. It is tied to ground with a 32k resistor, the same as the remaining inputs, which simply acts as a short circuit that follows all the same traces a standard input would. This unusual mute design provides absolute silence, as there is no signal at all going into the circuit. It also allows for system noise diagnostics by letting the user completely isolate the input from any source, while still providing stable impedance. The value of this feature was proved during evaluation when a bad interconnect in the reference system was quickly located using the mute feature. The second feature is also diagnostic - the LLC-P contains a pink-noise generator selectable by the input selector knob. This feature will help end users isolate sonic problems in listening rooms.

Aesthetically, the LLC-P is quite simple and attractive. Most of the case is finished with crinkle black paint. The three control knobs are made from polished, machined, stainless steel and stand out against the silver-colored, brushed finish of the thick, aluminum face plate. Knob functions are identified with black, silkscreened lettering. The simple and tasteful IRD logo, finished in white with the superimposed word 'Purist' in black, is located on the front panel. On the sample unit, the gain selector knob has the three positions identified by +6dB, +9.5dB, and +12dB - future versions will be identified only by position numbers 1, 2, and 3 to remain accurate no matter which gain-shift option has been selected. A single blue LED lights when the black rocker switch is turned to the 'on' position. While the sample unit had a silver faceplate, the LLC-P is also available with a black anodized, brushed aluminum front panel. Attention to detail even carries over to the underside of this preamp: the Purist stands on four machined, stainless steel feet with rubber inserts.

How Does It Sound?

How should a preamp sound? In truth, a preamp shouldn't have a distinct sound; it should only provide signal gain and user control of volume and inputs. The LLC-P aims at the difficult-to-hit target of an 'amplified wire', and it comes as close to that target as any preamp I've ever evaluated. It sounds almost completely neutral. It simply doesn't seem to add much of anything to the signal - no warmth, as tube preamps often add, no grit or harshness, additional sound that solid state preamps often contribute. As a result, the sound is clean, clear, and as detailed as the rest of the system will allow. In addition, the LLC-P Purist is quiet, not just 'relatively' quiet, but absolutely quiet. The website lists the noise floor at -130dB, but hearing is believing. Using the mute position, turning the gain to +12dB, then turning the volume all the way up was the only way to hear any noise at all from the Purist, and one has to place an ear against the driver to hear it. If you have extraneous noise in your system, this preamp will not be the source of it.

Comparing a digital source to an analog source showed just how detailed and revealing the LLC-P can be. The usual digital source was a nOrh CD-1 with RCA 5751 output tubes. A Pioneer DV-525 with an ART DI/O DAC was used for a few DVD discs. The analog source was a Music Hall MMF-5 turntable using a Dynavector DV20XH cartridge into a Channel Islands Audio VPP-1 phono preamp. Despite the generally smooth and musical nature of the CD-1, there was never any doubt that the digital source was being used. Switching between LPs and CDs of the same material, the CD always had blacker background, but it sounded brighter, harsher, and with distinct grain, while the LP was smoother, cleaner, grain-free, and more natural sounding. The LLC-P was at its best with an analog source. Whenever an observation of 'grain' in the output sound of the LLC-P was noted, it was always with a digital source. Popping and scratches were reserved for the analog source ...

When using the LLC-P with power amplifiers that have their own volume controls, comparisons were made between the sound of the system with the amplifiers directly connected to the source, and the sound of the system when using the LLC-P. Using a Decware SE84-C Select, a very low-powered (1.8 wpc), but very smooth, detailed, and accurate single-ended triode amplifier, with a pair of Omega TS-1 speakers (96dB efficiency), some additional, high frequency grain could be heard, but the effect was slight and was only noticeable when using a CD-player as the source. In fact, the effect was so slight, that before switching between 'no preamp' and using the IRD preamp, the added grain was not apparent. Generally, using the LLC-P seemed to result in slightly more bass detail and better controlled bass than without the preamp in place. Mid-frequencies sounded slightly more natural and realistic without the LLC-P.

Musical detail is excellent with the IRD preamp. The little Decware amp is famous among its fans for its ability to separate instruments and singers into three-dimensional, holographic space. To this end, using the LLC-P as a preamp in front of the Decware did not reduce the detail or blur instrument separation. Oddly, despite the fact that detail seemed unaffected, the depth of the soundstage seemed to be flattened when using the LLC-P. This might result because, while listening to music, there was a change in how different frequencies were presented. It seemed as though vocals, or other sounds in the mid-frequency range, were a bit more forward with the LLC-P than without. This seemed to alter the perceived soundstage depth information. Some experimentation with speaker placement and toe-in minimized this effect. In all, the sound of the Decware by itself seemed slightly more musical and less 'hi-fi' than the system sound when using the LLC-P preamp with +6dB gain.

After doing the factory approved, gain-shift modification allowing 0dB gain, several things changed. Highs had less grain than before with the digital source, and bass still was a bit more controlled than using the Decware by itself, but the LLC-P no longer seemed to push the mid-range forward. This change was unanticipated, but welcome. After spending some time with the 0dB Purist, it seems that the less gain you use, the better the sound quality. Of course, when switching to a phono input, more gain was required to get the most out of the analog input.

The second amplifier was a Sophia Baby Amplifier, a Class A, push-pull stereo valve amp with 10 wpc. The Sophia has nearly the detail and mid-range smoothness of the Decware, but delivers much more power. As with the Decware, highs were a bit sharper, and a touch harsher with the digital source, and bass, though not appreciably extended, sounded cleaner and better controlled when using the LLC-P. In this case, the system actually sounded slightly cleaner with fuller, better overall sound quality using the IRD preamp in place than it did without it, despite the fact that the LLC-P was used with the Sophia before the gain shift mod was done.

Conventional wisdom says that if tube and solid state components are mixed, the preamp should be tube, and power amp should be solid state, but never the reverse. Despite conventional wisdom, the IRD Purist performed extremely well with tube power amplifiers including both of the previously mentioned amps, and a Fi X 2A3 stereo amplifier. Still, when comparing the overall system sound using my reference preamp, a Decware ZTPre tube preamp, synergy seemed somewhat better as all three tube power amps delivered music with slightly richer sound, a little more realistic and musical in presentation, and a little more life than did the LLC-P.

But the ZTPre is no ordinary preamplifier. It is my reference preamp because of its sonic quality and high fidelity. Comparing the LLC-P to a more ordinary tube preamp, a Conrad Johnson PV2a, was no contest. The Conrad Johnson was noisy and very colored, it was quite warm and soft sounding, compared to the Purist (or compared to the ZTPre). Any amplifier, tube or solid state, sounded much better with the Purist than with the Conrad Johnson. Unfortunately, no suitable solid state preamps were available for comparison at the time of the evaluation.

In another comparison, the Purist was used with a Decware SE84B Zen amplifier to drive a pair of very high-efficiency speakers (105dB), designed and built by "John Smith", a trusted and golden-eared fellow member of the exclusive and secret organisation, Audioholics Anonymous. Similar results were observed with this system. That is, the LLC-P was supremely quiet, surprisingly neutral, and the quality of output was excellent, though the SE84B had a bit more life to the sound without the LLC-P. There was some 'grain' noticed in some music, but it was slight. However, switching in a McIntosh MC-240 tube amplifier brought some startling results. Mr. Smith believes the synergy between the Purist and the Mac was the best he has heard, and that it was clearly superior to using the McIntosh by itself with its own volume control. Musical detail, micro- and macrodynamics were substantially better with the LLC-P than without it.

However, most power amplifiers that will be controlled by the LLC-P will be solid state. Using the Purist with a solid state power amplifier revealed yet another level to its performance. A pair of IRD MB-100 monoblocs was used to drive a pair of Reynaud Twin loudspeakers. The result was the best performance I have yet heard from the MB-100s. Besides the power, which is substantial for a 90dB speaker, the clean, clear, dynamic sound was superior to any combination I had yet tried with the MB-100s. From sparkling clear highs to deep, but clean bass, and everything in between, this combination delivered output that was moving and musical with sufficient power and dynamic range necessary for most classical music, even when played a bit too loudly. Synergy between system components is crucial, and synergy between the Purist and the MB-100s was excellent.

Other speakers were tried, and results confirmed that the LLC-P drove the MB-100s to new heights of performance. When using this combination to drive a pair of nOrh SM6.9s, the result was very satisfying. The SM6.9s have a great deal of low bass, down to, or just below 40Hz, and the LLC-P delivered bass so cleanly that bass details that were never audible with these speakers in other combinations became very clear. Listening to Ray Brown on bass and Monty Alexander on piano from the excellent Hi-Res Music DVD, "Trio", details at the lower end of the audio spectrum stood out better than I have ever heard with these speakers.

The LLC-P seemed to work equally well with John's Hafler DH-500 and a pair of Acoustat Spectra 11 loudspeakers, delivering smooth, clean, and detailed performance - while the Hafler is very powerful, John notes that it is grainy with most everything, but less so with the electrostatics, and the LLC-P did not seem to contribute any grain or other sonic artifacts to the presentation.

Positive Impressions

The sound quality of the Purist is excellent, its nearly absolute neutrality is one of its greatest attributes. In addition, the utter silence of the Purist is, quite simply, the way all active preamps should perform. The clarity of sound, and the clean, pure details allow stereo imaging and instrument separation that is as good as it gets, especially at 0dB gain. Unlike most preamplifiers, the LLC-P doesn't seem to damage the signal.

While the Purist was designed to provide clear, clean, high-fidelity audio performance, it is not completely spartan and has an interesting set of features to enhance that design goal. The adjustable gain is an excellent feature that is especially handy when switching between two sources of greatly differing signal strength, and the removable resistor that allows the use of the LLC-P as a buffered, passive preamp (0dB gain) only enhances its flexibility. The mute and the pink noise generator can be used as diagnostic tools, unusual features that are very useful.

Simply put, the build quality of the sample LLC-P was flawless. Everything worked, nothing broke, nothing needed adjustment, and, since the Purist seems to be overbuilt, it should continue to perform at its best for many years. You can buy a fancier looking preamp, but you will have great difficulty finding one that is better made. Aesthetically, the Purist has an elegant and simple appearance, which is much appreciated in these days of overindulgent cosmetic designs.

Much could be written about the price of the LLC-P, and, what would be most written is that the price is amazingly low considering the quality of the component. Up to this point, I have referred to the excellent performance of the Purist, its superb build quality, its aesthetically pleasing and well-finished appearance, and its rich features designed specifically for the enthusiast. Not once have the words, "in its price range" or "for the price" been used. The reason is that the IRD Purist performs superbly as a preamplifier, disregarding price as a qualifier. For the price, it isn't superb, it is amazing - the LLC-P costs $665 USD, including shipping to the US ($25 shipping credit if shipped elsewhere). Will a Halcro DM-10 perform sonically better than the LLC-P? Yes, but then again, for fifteen times the price, it better! There are, certainly, other preamps that will deliver better sonic performance than the LLC-P, but it is doubtful they will be found anywhere near the price IRD has set for this unit.

Negative Observations

The LLC-P is an unusual product in that very few negative observations were made during the course of this evaluation. One minor complaint dealt with the control knobs - in low light, the subtle position markings on the knobs were difficult to see. Yes, this observation is quite petty...

Using the LLC-P with some tube amp/speaker combinations resulted in a slight loss of 'liveliness' in some music when compared to using a CD-player directly attached to the power amp or using a high quality tube preamp. Proper synergy with the entire system is crucial, and, while the LLC-P didn't work perfectly with everything, it must be remembered that at its worst, it sounded better than many preamps sound at their best. In equipment combinations in which synergy was better between components, the performance of the LLC-P was simply excellent.

With CDs played on my CD-player, there was slight grain that was evident when using the LLC-P and was not as noticeable with my reference preamp. With speakers that are very revealing of minute detail, the grain was rather easily heard 'surrounding' pure tones or notes. After switching to an analog front end, no trace of grain remained. While it would be easy to blame the slight grain on the preamp, the fact remains that since grain vanished when using an analog front end, then the cause of the grain was, in fact, the digital source. The sound quality of a system can only be as good as the source, and the LLC-P will, for better or worse, identify substandard sources and other components.

Conclusions

Curt Wishman's goal in designing the LLC-P was to create a preamplifier with uncompromised sound quality without having to charge stratospherically high prices. He has succeeded. The sonic performance of this preamp with improperly matched components was very good, and with well-matched components it was excellent. The nearly absolute neutrality of the LLC-P is very pleasing. While expected of a multi-thousand dollar preamp, such neutrality and fidelity of sound is surprising in this price range. Many far more expensive preamps 'brand' the sound output with their own signature - not so, the LLC-P. It strikes very near the mark of an 'amplified wire.'

Integrity Research and Development Company, Ltd. is one of a small number of audio companies that is quietly helping to fuel a revolution in the audio industry. No longer will audiophiles have to mortgage their homes in order to have equipment that will suit their needs - although extremely expensive audio jewelry will always be available for those who desire such things, or need them to assuage their egos. For many years, the term 'mid-fi' has been sneeringly applied to components that cost less than a certain threshold. Audio snobbery simply wouldn't accept as 'high-fidelity' components that were not prohibitively expensive. However, the LLC-P helps discredit that concept by combining truly high-fidelity performance with modest price. If the LLC series of preamps is as successful as it deserves to be, Curt will then be free to turn his engineering talents to producing new and groundbreaking phono preamps, or DACs, or...?

Many thanks to Curt Wishman, president and chief audio engineer of IRD, for providing background information and the sample used in this review.