Conrad-Johnson MF2550SE

Solid-state power amplifiers
Conrad Johnson MF2550SE
Conrad-Johnson MF2550SE

Most people associate conrad-johnson with amplification, specifically valve (tube) amplification. But the company has a long history of also producing good solid-state electronics; it just doesn’t do it that often. In fact, the last solid-state power amp from the brand was the Premier 350SA, from 2003, and that one stayed in at least one UK reviewer’s system until very recently. Can the new MF2550SE live up to the reputation of its older brother?

Essentially, c-j holds to the idea that what works, works universally. The core ideas of its amplifiers adhere to the basic tenets of the company’s design brief: a sort of electronic version of Occam’s Razor. The circuits should be simple, linear circuits designed without recourse to significant amounts of loop feedback, and fewer parts in a circuit mean every component counts. So, there’s no scrimping or saving in the parts bin at c-j. It also means, for any given budget, the component quality of a c-j amp is typically very high, and that’s certainly the case here.

The 250W per channel power amp itself combines discrete solid-state technologies, with FETs in the input stage and bi-polar devices in the output stages. This layout, the company suggests, supports an extremely linear input at the first voltage gain stage, while bi-polar transistors are there for their ability to deliver current into a reactive loudspeaker load. As befits a company used to valve amplifier design, the power supply is given special attention, with discrete DC regulation on the voltage gain stage and fully isolated transformer wiring for different stages of the amplifier itself. 

The circuit is then packed with the best components c-j has to offer; custom film and big 30µF polypropylene caps and metal film and Vishay foil resistors throughout.  It even includes 16 of c-j’s own Teflon caps in key circuit locations. Everything down to the wire (literally, it’s high-grade case wire) is accounted for and improved, exemplifying Michaelangelo’s familiar adage, which holds that ‘trifles make perfection, and perfection is no trifle’, although how an Italian Renaissance painter and sculptor would know anything about the classic English ‘jelly and sherry’ dessert escapes me. Regardless, unlike c-j’s valve amplifiers, this is non-inverting at output, so you don’t need to swap absolute phase at the speaker terminals; positive stays positive throughout.

This could not be a simpler amplifier, from the outside. The front panel is finished in c-j’s distinctive gold livery, while the rest is matt black powder-coat. There’s a big power-on switch on the front that glows orange when powered up,  and there’s a pair of gold-plated RCA connectors and a matching pair of gold-plated multi-way loudspeaker terminals out back, plus an IEC socket. Aside from feet, some grilles on the top and bottom, and uniform heatsinks on the side, that’s it. By the hernia-inducing standards of modern audiophilia, it’s a comparatively light 23.6kg and is evenly weighted, with only a slight balance toward the front panel. 

If the appearance is understated and subtle, the power cycle is remarkably uneventful by high-end standards. You turn it on, wait a few seconds, and play music. In fact, the nearest it gets to ‘eventful’ is the gentle pop of the caps discharging a few seconds after turning the MF2550SE off. The music does get better after about 20 minutes of playing and those Teflon caps take dozens of hours to condition themselves, but as ever it sounds good from the outset and does its fine wine impression; this is something to savour and something to take time to enjoy. 

Otherwise in terms of operating idiosyncrasies and observations, nada; no buzzing transformers, no humming, no rattling, no need to turn it on with a stick, no hoping for the best and preparing for the worst. It’s load tolerant, and just does what a power amp is supposed to do, and the fact this is impressive in its own right doesn’t necessarily say good things about some other members of the audio amp club. It’s equally happy with long interconnects and short speaker cables, or short interconnects and long speaker cables, and any point in between. 

However, it is best when it’s given the best. I used it with the excellent Townshend Allegri passive preamplifier into Wilson Duette II, connected with a whole lot of Nordost V2, and it sang. I also used it with an old ECA Vista preamplifier and a whole lot of Cardas Clear into the same speakers and it sang a slightly different tune, but it still sang clearly. OK, so the pot on the ECA Vista is on its last legs and turning the volume now sounds like someone’s letting off fireworks nearby, but when the volume was set, it sounded magical.

Ultimately, the MF2550SE is detailed enough to show what good equipment, good ancillaries, and good installation can do for a system, but not so twitchy that it demands these things before it begins to reveal what it can do. And what it can do is not sound like you would expect solid-state to sound, especially if you are the kind of person who likes the typical c-j sound. However, it’s not a solid-state amplifier doing an impression of a tube amp. It’s just got that sense of absolute rightness of performance and texture that is so hard to find these days, and so satisfying when you hear it.

Although good audio is supposed to get the listener closer to the sound in the studio, in reality we appear to have made some trade-offs along the way. This is perhaps inevitable, but it seems there comes a point where high-end audio goes for texture and tone, or detail and imagery. A few manage to get past this divergence and produce a sound that combines all four of these attributes, and the MF2550SE is one such product.

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