Well, ten days after receiving the “mystery amplifier” I finally took a break from stand building after dropping off a new batch of stands at our powder coaters. I drove over to where I do all of my prototyping and tuning- about a 50 mile ride one way and finally plugged in and listened to the unit on my LRS.
I purchased a used Conrad Johnson Sonographe SA 250. It is rated at 125 watts a channel and about double that into 4 ohms and is a high current design. The unit is well built and moderately heavy for an entry/mid-level amplifier. Sonographes were solid state and designed to incorporate the tube like presentation of the companies more upscale tube offerings.
I purchased the amp to see how well it powered a vintage set of electrostatics I own but always value being able to switch between multiple amplifiers when prototyping new stand designs.
Having only listened to the Sonographe for a little over 4 hours- these impressions are only preliminary. After warming up for an hour the amplifier one can definitely sense musically engaging tube like character- it is open and dynamic and almost tactile at times. Image focus is good with a deep and wide soundstage when called upon. The Sonographe has a vividness that makes many other (even more expensive) amplifiers sound less involving and certainly less organic.
Subtle details and dynamic shadings and instrument sustains and decays are well rendered. In many ways there is a bit of the EL 34 tube midrange sound inherent in the 250.
The Sonographe drives the LRS and MMG to very loud levels while retaining a coherency and the ability of the speakers to hold together without sounding bright or strained in ways you normally only hear with more expensive amplifiers and speakers. Driving the 250 at loud levels the amplifier remains basically cool to the touch. The High current designation seems well suited for the LRS and with the MMG the amp seems to be loafing. Part of the holding together character is also something owners hear with the addition of their Magna Risers.
The high frequencies are refined and natural sounding and even a bit delicately rendered with quality recordings. The Sonographe does very well in combination with the LRS and even MMG in offering musically authentic high frequencies- no brightness or splash- just musically natural.
A tale of two amps.
The bass of the Sonographe is enigmatic. The 250 has a two prong power cord which is reversible. The amp has two distinct sonic signatures in the bass depending on the orientation of the plug. In one direction the bass is tube like- reminiscent of the early Dyna 70 with a more rounded slightly less articulate character. With the plug reversed the bass has added snap and sounds more precise and solid state like. For the bass players out there it is a bit like the difference of using a Fender Bass Man tube amp and an Ampeg solid state bass head.
The dichotomy also applies a bit to the midrange and highs where a harmonically leaner character accompanies the more articulate bass wall plug orientation. You also lose a bit of the sweet refined high characteristics in the highs and midrange palpability found in voices and in wood bodied instruments using the more articulate bass plug orientation but may gain a little bit of electrostatic etched clarity.
So in some ways owning the 250 is a little like owning two amplifiers. The more articulate bass plug orientation still offers musically enjoyable sound. The alternate plug setting does provide glimpses of an even more vivid, bold and three dimensional musical world. I will also note that placing the LRS and MMG on Magna Risers significantly improves the speakers’ bass resolution and imaging capabilities and none of my listening was done using the stock factory fee.
For the investment of 300-500 dollars on the used market this amp may be a worthwhile alternative to the Adcom and Hafler and other used amplifier offerings. I own an Adcom GFA 545 and the difference in performance of the Sonographe is instantly recognizable with a sense of added vividness, detailing and dynamic swings and shadings and vivid sound staging all much more evident. The Sonographe simply offers a sense of refinement in comparison to the Adcom. If you want a musical amplifier at an affordable price the Sonographe may keep you happily listening for quite some time. For those using fully active bi-amplification with subwoofers on their LRS or MMG the Sonographe may be a choice you will celebrate in many hours of great listening-times when it is just the music and not the equipment. For those in search of a musically engaging amplifier and for those who have struggled with harmonically thread bare and more two dimensional sound stages provided by many entry level amplifiers the Sonographe may open new musical worlds.