New Rowland Criterion 2-chassis battery pre

Claude, I do not have complete information, but it is apparently correct that JRDG has unwrapped a new preamplifier at CES. The device is called Corus (that is correct--Latin spelling). It seems it is very similar to Criterion, except that it lacks DC batteries power operations. The AC power supply is likely the same as that of Criterion, but housed in a machined Aluminum box to fit behind the main chassis or on the floor. . . perhaps similar in shape to the PC-1 rectifier. Most other internals I believe may be the same as criterion, or extremely close to it. I'll know more in the next couple of weeks. US price might be just below $10K.

Mike and Guido:

I just saw your October posts about the "zeel" 50 Ohm connections and want to pass along the following -

I have a Coherence II preamp, which I note has a stated 50 Ohm output impedance. When I bought my darTZeel amp, Jonathan suggested that I try the 50 Ohm connection in view of the output impedance of the Coherence II. Peter Ledermann (a/k/a Soundsmith), bearing in mind the special PIN arrangement for Rowland XLR connections, reterminated a 50 ohm cable for me with a female XLR on the preamp end, of course retaining the BNC connection for the darT end. I believe it is a 30 ft. run, but it might be 25 ft. The preamp drove the amp, but I thought I might be hearing some distortion. In A/B tests with a 25 ft. run of Jena Symphony, I preferred the Jena and left it in, where it has remained ever since. There was some speculation that the XLR termination may have spoiled the party, but I was told by others that this does not make "electrical sense". It could also be the case that the stated 50 Ohm output impedance of the Coherence II is nominal (no bandwidth is specified), and that variations at other frequencies screwed things up. In any event, it didn't sound obviously wrong, but there was something subtle that was awry, which I perceived as distortion.

Conventional wisdom challenges the very idea of 50 Ohm connections, but Herve swears by it and I have heard a top-flight PD --> darT preamp --> darT amp set-up with 50 Ohm connections and it sounded great (the owner greatly preferred it to his Jena Symphony, incidentally). I do not question that 50 Ohm connections work - it just didn't work given the particulars of my Rowland experiment.

It's hard to say whether modding the preamp to include an actual BNC output would have made a difference, but given the annoyance I experience with such experiments (my preamp to amp cable run traverses an inhospitable crawl space, the area behind my equipment shelves is tight and requires a lot of contorting to make preamp connections, not to mention what would be involved in sending the preamp back to JRDG for modding), I didn't take it any further.

Raquel, Is your Coherence an II or an I series II? Guido

It's a II (manufactured February 1999). For those curious about the differences, Rowland's website states:

"Q. What is the difference between Coherence Series I and Series II?

A. The Coherence Series II was released April 1997. The Coherence Series II upgrade involves the redesign of the attenuator amp circuitry. The actual circuit topology is similar; however, all of the circuit components were improved, taking advantage of recently available modern surface mount technology. The output amplifier is a newly developed, dual high-current transimpedance amplifier which handles both phases of the output circuit on one isothermic, copper lead frame power device. This output amplifier and all associated surface mount circuitry allow significant reductions in circuit loop area and path length yielding wider bandwidth, faster setting time, reduced dielectric absorption and greater thermal tracking stability. The overall sonic result is greater clarity during complex music passages and increased resolution of intertransient silence."

Thank you Raquel, one difference in the output stage between Coherence I and II appears to be--according to the copies of the manuals I have--that the older varsion had an output impedance of 300Ohms unbalanced and 600Ohms balanced, while verion II seems to have 50Ohms regardless. Manuals also say that Coherence outputs are direct coupled. I suspect this may mean that there isn't the transformer-coupling present in later designs, whose function, among other things, is to maintain impedance invariance. Whether this has had any bearing on your results with the coax2XLR adapter experiments, is of course, anyone's guess.