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Conrad Johnson ET250S Amplifier Review

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Introduction

Prior to purchasing a McCormack UDP-1 that was specially updated by Conrad Johnson, badged the “deluxe”, Conrad Johnson’s products had been well outside of my scope of interests in all things audio. Then last year, solely on the basis of verbal recommendations from some close friends and on the strengths of the qualities of the analog-like sound of the UDP-1 Deluxe, I decided to replace my aging Melos 333Reference-v.6 preamplifier with the Conrad Johnson CT-5 Composite Triode linestage. To this day, the sonic performance of this powerfully synergistic pairing of the UDP-1 Deluxe and the CT-5 leaves me shaking my head in disbelief. Given the rather modest cost, it simply should not be as spectacular as it is! However, I am very grateful that it is. Given this recent personal history I immediately jumped at the chance to review the Conrad Johnson ET-250S stereo power amplifier when the opportunity presented itself.

The ET-250S is esthetically representative of the new direction Conrad Johnson has embarked with respect to their electronics. The handsome chassis and gold colored aluminum faceplate with the now-familiar vented semi-circular plates of plexiglas that house the 6922 vacuum tubes. It’s physically taller than my CT-5 preamplifier, but otherwise a dead ringer in looks. The ET-250S tips the scales at over 65 pounds while managing to keep a rather compact footprint of 16 x 19 inches.

The ‘ET’ nomenclature is short for “Enhanced Triode”. The ET-250 is the only two-channel stereo amplifier currently offered by Conrad Johnson that is classified as such. The Enhanced Triode Conrad Johnson ET-250S is considered a hybrid amplifier, while the CT-5 preamp is all tube in circuitry. It employs high-current solid-state output devices in the output buffer stage. The use of these devices allows the amplifier to maintain a high damping factor and this is said to make it therefore very flexible for use with a wide variety of speakers. A pair of 6922 vacuum tubes provides gain to the input voltage. According to the manufacturer, these two input voltage tubes are what provide the ET-250S’ tube-like character. Conrad Johnson specifies that the ET-250S will deliver 250 watts per channel into an 8 ohm load and 400 watts per channel into a 4 ohm load. This makes the ET-250S the most powerful amplifier next to the ART amplifier currently offered in Conrad Johnson’s line.

The Break-in

Having already experienced breaking in the CT-5 linestage, I had ample warning that the break-in period for the ET-250S would be long and involved due to the extensive use of the CJD Teflon coupling capacitors. I figured on 200 hours or so. I pretty much let it play my break-in disc for about 2 weeks. During that period of time, I witnessed the amplifier change dramatically in sound, particularly in dynamic expression, midrange liquidity, and in low frequency authority. During my first planned extended listening session, it did not take very long to note that the amplifier was evidently going into what I can only describe as “stress” on peaks and highly dense music.

Also, there was very definitely a seeming hard limit to dynamics and low frequency extension. At that point, my presumption was that the very difficult load my full-range electrostatics were presenting to the amplifier, nominally 4 ohms descending to 1.5 ohms at 20 kHz, was causing it to act up. So the question remained, was the amplifier still going through break-in issues or was there some other compatibility issue at work here? A quick exchange of emails with the manufacturer confirmed that the amplifier still had a ways to go in terms of break-in. Lew Johnson himself intimated that the play time period required for the Teflon capacitors to fully form was on the order of 300+ hours. I complied with the suggestion and played the amplifier non-stop for another 10 days using my trusted “break-in” CD. I know this sounds a bit extreme, but if you have never had to break-in a piece of electronics that utilize these CJD Teflon caps and/or large polypropylene caps, you have been sheltered from this rather painful process.

Music at Last!

So then after weeks of anticipation, by all counts the ET-250S should absolutely be ready for prime time. Once the stylus dropped on Neil Young’s Prairie Wind, I knew that indeed, things had markedly improved. For instance, one of the features of the song “The Painter” is the wonderful stage presence of the drummer and back-up harmony singers. Indeed, the ET-250S did a very credible job of capturing the live quality of this recording as well as the reverberation off the back wall of the studio each time the drummer slams the bass drum pedal. In the song, “Here for You”, I had a distinctly different impression. The tonality of the harmonica was not as I am accustomed, instead of being rich in tone, it seemed a bit thin and dry. In “It’s a Dream”, once again the dryness and lack of tonal structure was clearly evident in the reproduction of piano and the string section.

Switching to the digital source, I listened to the superbly recorded Trio Jeepy by Branford Marsalis. With this recording once again that same dryness and lack of tonal development was clearly evident in the way Branford’s tenor sax was being reproduced. On a positive note, the sound was very well-defined; the soundstage was well lit and clearly delineated. In fact, the ET-250S was very, very quiet and it delivered a superbly “black” background. The bass was very well extended, fairly well-defined although not as clean as I would have expected.

Moving back to analog, I listened to Brand X’s Do they hurt? Once again, on this record, everything was there, an abundance of detail, clean and sharp transients, very well-extended and clean highs, wide, tall, and deep, image; however I just wasn’t feeling the groove. Somehow, my system had been robbed to certain extent of the riches and organic splendor, and pace and timing that the Conrad Johnson CT-5 preamplifier had contributed to my system in such abundance. In addition to the aforementioned sonic setbacks, I also noted that the amplifier was still limiting dynamic swings and exhibiting some signs of stress in the form compression.

Lessons in System Compatibility….a bit of the Jekyll and Hyde emerges

Knowing full well that this type of performance is completely out of character for an amplifier with the richest of audiophile histories behind it, I went on a quest to identify any incompatibilities that may be causing the conditions I have detailed thus far. The most obvious, of course, being the complex difficult load presented by my reference Martin Logan CLS IIz Anniversary electrostatic speakers. A quick check using two different vintage mini monitor speakers I have on hand, handily demonstrated that indeed the CLS could in fact be the source of the issue.

As luck would have it, I happened to also have on hand a review pair of the PMC OB1i speakers. These speakers are steeped in the most British of traditions in terms of their sound. Not only were they an ideal load for the Conrad Johnson ET-250S, but they handily provided insight as to the true nature of this rather complex amplifier. The Conrad Johnson ET-250S was finally able to strut its stuff when playing the PMC OB1i speakers. Gone was the edginess and tentative nature of its sonic signature. Also gone was the dynamic compression. In fact, the ET-250S came through as an ideal match to my Conrad Johnson CT-5 preamplifier.

The amplifier’s low-end heft and punchiness worked quite well with the somewhat lacking extreme low-end of the CT-5 preamplifier. The voicing of the midrange is noteworthy in its smooth and silken quality that provided a certain richness and lushness to both male and female vocals as well as acoustic guitar. The soundstage also proved to be broad, black, and deep. Yes, indeed as is the case with the CT-5 preamplifier, the ET-250S may be a tube-hybrid, but it most definitely carries the rich tradition of the Conrad Johnson house sound.

I found myself easily immersed in the musical performance and completely forgetting about the ET-250S’ scenario on my full-range electrostatics. Running through my current play list of vinyl and CD’s proved that the ET-250S faithfully reproduced the signals fed from both my vintage Accuphase moving coil phono cartridge and my McCormack/Conrad Johnson UDP-1Deluxe with that ever-so-slight burnished and romantic quality that makes it unmistakably a Conrad Johnson. Indeed, the ET-250S delivered generous helpings of dynamics, detail, and slam from some fine recordings in my 1970’s Classical Rock catalog to the most recent of acoustic recordings from the likes of Katie Melua and Rickie Lee Jones.

Summing it all up

In summarizing my experiences with this amplifier, it was clearly evident that the sonic signature of the Conrad Johnson ET-250S I was hearing while powering the full-range electrostatic speakers tended to the classic “old school” solid-state sound and not the tube-like character that I was expecting to hear. In other words, it was not very Conrad Johnson-like.

On the other hand, the ET-250S became a completely different sort of animal when mated with the rather easy and benign load of the PMC OB1i’s, as well as my vintage British mini monitors. Take this as a lesson learned. System compatibility is of utmost importance and this experience certainly drives that point home. The ET-250S is capable of delivering an excellent performance as the amplification anchor in most systems. For us 1%’ers that have full-range electrostatic speakers or speakers with difficult loads, it is most important to audition the amplifier in your home under your own conditions prior to making your choice. Ideally, you should be doing this anyway prior to any major change in components.

I wish to express my thanks to my editor, Constantine Soo, and Mr. Lew Johnson for their support and patience in this rather lengthy process of getting to know and fully understanding the true nature of the ET-250S. It was quite the learning experience.

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