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Positive Feedback ISSUE 78
march/april 2015


Trilogy 925 - Integrated Amplifier
text and images by Wojciech Pacuła


trilogy 925 integrated

As I already mentioned once (in the review of Wow Audio Lab L1/M1 amplifier), Audio Show in Warsaw is a place for me to collect information. Not necessarily about the sound but rather about brands, products and people. But I always welcome a nice surprise, I mean a really good sounding system. Such a system, such a presentation is usually awarded by us by Best Sound Audio Show. Such an award in 2014 was given to a system that included a product of a British company Trilogy Audio, and one can find it mentioned next to their hybrid integrated amplifier 925 on company's website. To be clear—this system, with this amplifier delivered truly delightful presentation during Show, so the Award was no coincident.

Trilogy was founded in 1992 by Nic Poulson and from the very beginning power supplies of their devices received special attention from designers. This might be obvious today, but at the time power supplies were rarely at the center of interest of audio equipment designers. Nic knew what he was doing – his professional background (working for BBC, designing runway lighting systems and others) gave him enough knowledge and experience to ensure that. Since power supplies were that important for him it was a natural move to start another company that would focus its activity on designing devices and accessories improving a quality of a current fed to audio systems. And so he was a co-founder of a company called Isotek. Little is known about reasons but Nic left Isotek in 2001 to start his own company ISOL-8. It's a sister company to Trilogy Audio.

If you take a look on Trilogy's webpage you'll surely notice that there seems to be a few blank years in company's history between 2001 and 2008. It seems that it was a period of hibernation for this company. Before that Trilogy offered tubes based devices. And then, in 2008, they came up with the first hybrid design, and integrated amplifier called 990. After that new products were launched but it seems that it never has been done in hurry. A phonostage, 907, was launched in 2010, a headphone amplifier, 933, in 2012. 2013 was a year when a new hybrid integrated came to life—the 925.

trilogy 925 integrated

It is a fully balanced design, with a preamplifier section based on two double triodes 6H6Π. As one can read on manufacturer's webpage, these particular Russian tubes were chosen for their "high transconductance and very high linearity". A carefully optimized servo ensures the tubes operate perfectly symmetrically.

The output stage works with no negative feedback loop and it's based on two types of transistors – MOSFETs and bipolar ones. The former operate only within the first watt, in class A. The latter operate up to few watts also in class A and then they start to work in class AB, in push-pull mode.

The device looks really solid. Operating it is something nerds will love. After turning the amplifier on one has to input a unique PIN before one can start to listen to the music. The amplifier has a sophisticated monitoring system to maintain safe operation at all times. Temperatures and critical voltages report to a dedicated microcontroller. Proprietary formulated algorithms monitor output current against time and frequency with great accuracy. This enables reliable discrimination between DC faults or demanding musical conditions, providing excellent protection but avoiding unwanted shutdowns.

Despite the fact that it is a classic integrated amplifier it is also a user-friendly one. User can label inputs and set a sensitivity of each of them separately to equalize different signal levels from different sources. Settings of volume and channel balance are stored in device's memory so the next time device starts it uses the same settings.

Remote control allows user to change phase, but it can be set also in amplifier's menu. A proprietary external communication interface, TAS link, allows 925 to communicate with outside world and other Trilogy devices.

A real time clock provides multi event, seven day system that allows user to pre-programm an activity of the amplifier: it can turn on or off the device at set time on any day of the week using TASlink. User might use this system to turn the amplifier on some time before listening session, thus allowing a warm-up time.

trilogy 925 integrated

A sleep function provides power down after a selected period of user's choice. Other Trilogy products can be "Named" via TAS link for status monitoring and remote control. Any intelligent features will then be available for use or monitoring via the 925. A wide range of user programmable defaults are possible, including setting the home page display and PIN protected control menu locking.

This amplifier was used as a part of my reference system, and additionally with the Compact Disc CEC CD5 Player, that was used also as a DAC receiving signal from a PC. As a power cable I decided to use the Crystal Cable Absolute Dream.

Along the amplifier user receives a small, plastic, not particularly nice looking remote. If one wants something better it's an optional purchase – a very good looking, user friendly Personal Remote Control (PRC). I believe that it is an integral part of the 925 experience so one should simply add it to the bill—one shouldn't regret it.

A few simple words…


Trilogy, ISOL-8 | CEO

From a designers point of view an integrated amplifier has a lot of advantages from a sonic point of view. You can keep the signal path really short and the current loops nice and tight. You can often miss out an extra stage of amplification compared with a pre-power combination too. The only area where you have more restrictions is the physical size, you have to package everything in one chassis. That gives you a ceiling for output power because you need to shift the heat of the output stage and you have a size limit on the power supply. I didn’t want this restriction to limit the every day performance of the amplifier at all, so we made the 925 as good as it could possibly be within its power envelope.

I wanted the amplifier to be fully balanced, even right through the output stages and drive to the loudspeaker. Some amplifiers claim to be balanced, but they get converted to single ended somewhere along the signal path. The signal positive and signal negative are never tied to ground in the 925. This keeps big currents out of the vital ground reference and the whole signal path is fully symmetrical. The gains in small signal resolution and dynamic composure are worth the extra complication of doing everything twice; once for the positive phase and once for the negative phase. It also means we could do absolute phase inversion as a feature.

I observed long ago, that if everything else is equal, zero feedback amplifiers have better musical flow and less listening fatigue because the harmonic structure of the amplifier varies less under the different drive conditions the music demands as it plays. The input stage uses a pair of 6H6П triodes for Class A voltage gain and the output stages use our unique MOSFET and bipolar topology for current gain, so the amplifier has no overall feedback.


Recordings used during test (a selection)

Filia Praeclara, perf. Ensemble Peregrina, Divox CDX-70603, CD (2008).

Legend of St Nicholas, perf. Anonymous 4, Harmonia Mundi France HMU 907713, CD (1999).

Miracula. Medieval Music for Saint Nicholas, perf. Ensemble Peregrina, Agnieszka Budzińska-Bennet, Tacet 213, CD (2014).

Western Electric 300B Vacuum Tube Sound, ABC Records HF1043, "HD Mastering", CD (2012).

• Bemibem, Bemowe Frazy, Polskie Nagrania MUZA/Polskie Nagrania PNCD 1096, "Polish Jazz DeLuxe", CD (1974/2007).

• Blood, Sweat & Tears, Child Is Father To The Man, Columbia Records/Audio Fidelity AFZ5 195, "Limited Edition No. 0115", SACD/CD (1968/2014).

• Bud Powell, Jazz Giant, Norgran/Verve Records/Universal Music Japan UCCU-5062, "Jazz The Best No. 62", CD (1956/2003).

• Count Basie, Count Basie Live at the Sands (before Frank), Warner Bros. Records/Mobile Fidelity MOFI UDSACD 2113, "Special Limited Edition No. 0197" SACD/CD (1998/2013).

• Cream, Disraeli Gears, Polydor/Universal Music LLC UICY-40023, Platinum SHM-CD (1967/2013).

• Eric Clapton, Pilgrim, Warner Bros. records Inc/Audio Fidelity AFZ 188, "Limited Edition No. 0115", SACD/CD (1998/2014).

• Leonard Cohen, Popular Problems, Sony Music Labels SICP-4329, CD (2014); review HERE.

• Miles Davis Quintet, Relaxin’ With The Miles Davis Quintet, Prestige/Universal Music LLC (Japan) UCCO-40005, Platinum SHM-CD, (1958/2013)

Some reviews are more difficult than others as they bear even more responsibility. Like this time. Trilogy 925 is a "statement" product of Nic Poulson, he dedicated his entire life to get to this very moment, to create this product. So writing about it means a lot of responsibility. For such a review to have a proper "weight" for Readers and Manufacturer it has to be informative to give a proper sense about what this product is and what it offers, but it also has to include, subjective obviously, assessment. An assessment based on knowledge and experience of the reviewer. At least that's my approach to reviewing based on what I expect, as a reader, form other reviewers. Yes, every month I read a lot of reviews from different magazines—just as I did 20 years ago when I heard the word "audiophile" for the first time.

trilogy 925 integrated

In fact in this particular case review was that hard to conduct, as Trilogy amplifier is a remarkable device. It is quite pricey but if you're not ready to spent 5 times more money on another system, then ‘925’ is a no-brainer. Obviously one needs to realize what one gets in this "package". There are other great choices available—fully solid-state amps like Mark Levinson No.585, or Accuphase E-560, or some great tube amplifiers. These are also fantastic designs offering top performance that might appeal to a particular person more than what Trilogy has to offer. But the whole audio "art" is about matching – all the element of the system has to match, and the system as a whole has to match its owner's expectations, needs and so on. Once one find the ONE device that offers an amazing experience of listening to the music, that brings incredible amount of enjoyment, then one can't help but thinking – how could have I lived without it before?

It was very clear to me at the very beginning of the first listening session with Trilogy what kind of system one could build with this amplifier. Later all I had to do was to clarify some details. This is one of these cases where it is an amplifier that can be the most expensive element of the whole system. When it comes to building an audio system I tend to be an agnostic, I guess. Although I'm a pragmatic person too—when something works, it means it's good. One could build a system around a source of choice, or around speakers, or amplifier. In ma particular case amplification (power amp and preamplifier) cost 5 times more than speakers and source altogether. It wasn't planned, it just happened while I was developing a system for a particular person, for myself.

Trilogy opens for its owner a similar path of development. It is a device with a soul, with a beautiful soul. All that is left to do for its owner it to choose other elements of the system offering similar set of sonic features. In this case, so when it comes to particularly sophisticated performance adding on even more sophistication will never hurt. It will only intensify the best features of the performance.

One of the key elements of this performance is an outstanding differentiation this amplifier delivers. It is this type of differentiation the "supports" understanding of played music. It is not about bringing more details to the surface. Surely they are all there, nothing's lots or hidden. What you get is an impression that all these details serve a purpose of emphasizing interactions between sounds, instruments and planes. Lots of details presented as a way of making distinction between different elements of the music doesn't work well, it separates elements of music. Trilogy delivers plenty of details, lots of information, but they all are there to serve the "bigger picture", to serve the music.

Tonal balance is very accurate so it's not really a "warm", neither a "cold" sound. If you put a gun against my head to make me choose I'd probably say: slightly "warm" rather than "cold". But one gets this impression not because the leading edge is soften, or roll-off of treble, but because of how rich and dense the sound is.

trilogy 925 integrated

That's probably what makes most recording sound so well with this amplifier. At least as long as they make some "musical sense", if there is something more to them than just a "surface sound", if there is some depth in them. That is why I enjoyed so much Bemowe frazy by Bemibem. This record was originally released in 1974 and recently it was remastered by Ms Karolina Gleinert. It's a fantastic recording, also because Tomasz Jaśkiewicz, who had left Niemen's band three years earlier, played a guitar there. I knew that this recording offered a very interesting sound but with Trilogy it was only a second time (the first was with my own system) that I could fully realize how great it was despite recording's own limitations. Next to amazing richness and wonderful treble, British amplifier correctly presented not that rich bass, and slightly "rustling" midrange.

But listening, right after that, to new Audio Fidelity remasters of Blood, Sweat & Tears and Eric Clapton, I couldn't help but admire the quality of Polish producers. Especially considering the quality of equipment they had to work with. Both American recordings offered slightly smothered attack and decay phase, but also deeper sounding vocals.

Sounds delivered by this amplifier (assuming it's supported by well-matched system) materialize in front of the listener with a wonderful, black background. Such a performance recreates all aspects of the recording including instruments' acoustics, room's acoustics, tonality, and non-musical effects caught on the recording, making it sound amazingly real.

So what would be a well-matched system? There are several options. If the budget is limited and you can't spend a 50.000 PLN per system's element, I would recommend spending most of your budget on Trilogy 925. Next step—speakers. I have to "first choices" here - Harbeth M30.1, or Graham Audio LS5/9. Or some other similar design. As for power supply—the choice is obvious: 925 for designed to work best with ISOL-8 products and that's the best recommendation. Other cables could also come from UK—I'm thinking—Tellurium Q should do a great job here.

If you're vinyl fans I can see two options. The basic one would be Kuzma Stabi + Stogi S. That's a beautiful, wonderfully sounding turntable. If the design is too modern for you another choice would be the Funk Little Super Deck, a deck that was a part of a system awarded by us during Audio Show 2014. But if you could spend more than Avid Acutus SP should be a great choice.

If digital source is your choice that a natural partner for Trilogy could be (coming from the same distributor) Lumin T1 or (more expensive) S1 music server. If you are, like me, CD aficionados, than the CEC CD5 might do a trick—don't be fulled by its price! Later you could always purchase the Aurender X100L  music server and hook it up using USB input in CEC.


Considering its price I can't really see anything that could still be improved. Even with double the price tag I'd still have to think really hard to point out some space for improvement. It's easier for me to define Trilogy's sound by comparing it to my, costing over 300.000 PLN, reference amplification. When compared head-to-head they delivered similar performance in terms of tonality and impressive, TNT-like dynamics. My Austrian-Swiss tandem, that I am so proud of, creates deeper, more palpable images, and is able to differentiate textures even better than 925. But switching from my system to Trilogy clearly shows that there is no huge gap between their performances—my system is simply slightly better. The only obvious advantage of my system is its ability to create significantly deeper, more natural soundstage. Trilogy builds a wonderful soundstage too, but it is more focused on whatever is going on in the front of the stage.

Model 925, a pinnacle of Mr Poulsen's professional life is an outstanding device. It's a fabulous design, one of the best I've ever seen, and it delivers glorious performance too. As for and integrated amplifier it's not particularly big, looks good and is user-friendly. I gave you a recipe to build a top performance system around it. If you can afford it you could also build a much more expensive system around 925, with other elements even from a 100.000 PLN price range, or even more. It seems as the sky is the limit for this remarkable integrated. It is pure high-end, an amplifier for a life-time…


Trilogy 925 is a device created by an experienced designer for people, who want to feel special and require a certain level of convenience when using their special devices. So 925 is not another "big box" that user has to fight all the time to get it working. It is a rich-feature, customizable, user-friendly integrated amplifier.

trilogy 925 integrated

Let's start with colors of its casing. It is made of high grade aluminum and offered in one of five colors: "Sunburst Yellow", "8C Red", "Mediterraneo Blue", "Nero Carbonio" and "Iron Grey". These fancy color names try to describe a particular color in the best possible way and, you have to admit it, they also sound cool. There is another British manufacturer who uses similar strategy—Roksan (also from London). Their K3 series devices are offered in colors like: "Opium" (dark brown), "Anthracite" (silver) and "Charcoal" (black).

Casing is build up with aluminum elements—thick slabs and extra-thick radiators. Front panel seems minimalist so it is hard to believe that a manual for this device has a form of a thick book. It is so because the device is highly customizable. Also all safety guard are very elaborate.

Apart from many commonly used customizable settings like changing inputs' label, changing phase, or display deeming, Nic Poulsen thought about many other useful features. Amplifier is equipped with a "real time" clock that allows scheduling certain activities of the amplifier so each day of a week. Amplifier, or the whole system (when using TASlink), can automatically turn on or off according to pre-programmed schedule. One can program the amplifier to turn on some time before planned listening session, so that when time for session comes amplifier/system is already warmed up.

An access point to the whole menu is a large volume control knob, that is also used to operate menu in conjunction with three small buttons. The large, red, readable display is very helpful too.

trilogy 925 integrated

The back panel sports an abundance of sockets. There is a clear division between right and left channel. There are three balanced inputs—there are Neutrik XLR sockets. The whole amplifier is a balanced device. The output stages are arranged in a bridge configuration and large currents are kept out of the system ground. There are also three single ended inputs with very solid sockets that look as they might be coming from Mundorf. Same manufacturer (most likely) delivered solid speakers posts. 925 sports also a pre-out (RCA). Next to it there is an Ethernet (RJ45) port, used for communication between Trilogy devices using TASLink protocol. You can always try connecting 925 with devices from other manufacturers—there is still a chance that they will be able to communicate despite different brands. Amplifier is delivered with ISOL-8 power cord and it was used during this test.

Inside one will find even more elements from Mundorf, like polypropylene capacitors coupling preamplifier section with output stage. 925 is a hybrid design with tube input stage, and solid-state output.

trilogy 925 integrated

Tubes in the preamplifier section are Russian 6H6Π (6N6Pi), at the first glance quite similar to popular 6H30 Π (6N30Pi), used, among many other devices, also in my Ancient Audio CD Player. There are two NOS triodes working per channel, manufactured in Soviet Union in Nowosybirsk.

trilogy 925 integrated

Output stage is a Nic Poulson's proprietary design. It combines advantages of MOSFET and bipolar transistors. The output devices are configured to operate in a high bias state, giving a generous envelope of Class A operation. The relatively high dissipation, in conjunction with the high thermal inertia of the heatsink, keeps the devices in their optimum operating condition and improves sound quality. The fast, agile FET only operates within the critical first watt region. The bipolar transistors then seamlessly contribute high current when music conditions demand. It reminded me of the Devialet that sports a small, analogue amplifier operating in class A, combined with a powerful class D amp. Trilogy uses two analogue amplifiers though.

Signal's path is very short. Three fully balanced and three single ended rear panel inputs are switched via instrumentation grade ruthenium plated relays within millimeters of the rear panel connectors. A separately selectable auxiliary loop is provided. In addition, a 3.5mm jack on the front panel allows portable sources to be connected quickly and easily. A carefully selected audio grade digitally controlled potentiometer provides volume control and balance in 1.0dB steps. Conventional extruded heatsinks display strong resonant signatures and have been rejected in favor of custom, machined solid billets of aluminum. Each weighs in excess of 5kg. Their high mass and irregular form provide outstanding mechanical and thermal stability for the output devices.

Trilogy 925sports three power transformers. One supplies output stage, one preamplifier, and third logic circuits. The power transformers are mounted on a thick machined plate of K-material (same one is used inside ISOL-8 power conditioners). This high metal, low resin content composite has excellent mechanical properties and superior self damping to metal. It provides additional damping and stiffening of the non magnetic chassis too. K-material is also used for the feet, providing the optimum interface between the 925 and the equipment support. Custom (Mundorf?) Trilogy reservoir capacitors smooth each channel of the output stage DC and valve HT supplies.

This is an outstanding piece of engineering. All aspects of the design were carefully thought through. While the signal's path is extremely short the rest of the circuit is very complex, just like in my Soulution 710 power amplifier.

Specifications (according to manufacturer)

Rated power (@ 8 Ω): 2 x 135 W

Input impedance (single ended): > 42 kΩ

Input impedance (balanced): > 84 kΩ

Distortion: Less than 1% A weighted at rated output

Frequency response: 10 Hz-50 kHz (+/- 0,5 dB)

Input sensitivity: 600 mV RMS (for rated output)

Dimensions: 445 x 430 x 127 (WxDxH) mm

Weight: 20,5 kg

Price (at the time of the test): 51 900 PLN

PO Box 56402
London | SE3 7WQ
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