First sounds. Those came upstairs fronted by a Soundaware D100Pro SD card transport, again with no noise of any kind. Whilst I had a companion CanEver ZeroUno digital preamplifier on hand, to limit changes to one item meant starting with our COS Engineering D1. That's a premium fully balanced Burr Brown DAC with precision analog volume control. It fed the Venetian whose power supply supported the D100Pro beneath the foot stool. Speakers were our Acelec Model One monitors with Mundorf AMT, ScanSpeak mid/woofer, rubber-bonded aluminium enclosure and compound 1st-order filter.
140w/4Ω in class A is a lot, especially from quite compact a chassis without, apparently*, the usual array of radiator fins. Our Bakoon AMP-13 here does 50wpc/4Ω in class A/B. Now I had essentially thrice. Creative marketeers exploiting expectations might promise seriously more authoritative and decisive control. Isn't that synonymous with bigger power? My very first impressions instead were of a gentler power. Class D with very high NFB might exert an iron-fisted grip over one's drivers but often has them sound energetically pinched. Olimpico didn't exert that type of pinched control. Using no feedback, that even made sense. Its sound clearly had power, earthiness and intensity but was of a softer less domineering not rigid kind.
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* As we'll still see a few photos down, the real radiating surface is much bigger than what's external and visible. Below the daisy chimneys sit liquid-cooled chromed copper thinly finned radiators, one per Mosfet. Each of those is capable of dissipating 130 watts for a total of 520 watts. What's more, the daisy radiators mount to two big aluminium plates which become part of the dissipation system. "The total radiating capacity is probably as large as big monster amps with enormous fins on either side – over 650 watts in our case. We simply distribute the radiating surface in unusual ways. For heat sink efficiency, it's not the amount of material one uses but the total radiating area. Our thin fins maximize the latter and being copper, we have 70% higher thermal conductivity than the usual aluminium. Finally we add liquid-cooled heat pipes to assist the copper."
For a first A/B, I meant to hook up our SMPS-powered Crayon CFA-1.2 to the RCA outputs of the COS to shuffle between it and the XLR-connected Olimpico by simply swapping speaker leads. Because most transformer-coupled SET amps aren't happily driven without a load, I asked Mario whether his was. "Olimpico can run without a load forever and with zero risk. This isn't about transformer-coupled outputs. It's about how the active output stage is configured. I don't work with any global feedback so having no load can't compromise stability. The output stage only amplifies current. No load equals no current. That puts the output stage in standby. The output stage input impedance loads the push/pull triode drivers. That remains present and active.
Olimpico's entire signal path. All the rest is power supply.
"Finally, I use lateral Mosfets. Their self-protective makeup means that as temperatures rise, their middle channel conducts less current and temperatures decrease. This form of 'natural' not electronic feedback protects the device against overload. It responds to temperature not voltage swings. It's a process at the quiescent device level, not the dynamic music signal level."
That was convenient. I'd incur no thermal variables from repeat on/off switching. Both amps would receive simultaneous signal and stay on. I simply hit 'pause' whilst reseating Chris Sommovigo speaker cables. To spice things up, I'd roll in Node Audio's Hylixa for another sample of the upscale monitor art that's most appropriate for our smaller upstairs room.
To kick off Hylixa, I cued up the title track from Antonino Rey's Dos partes de mí album. I wanted to hear first-rate flamenco guitar plus solo and chorus vocals on the intricate beat patterns of a bulerías. The Italian amp did things a bit different than the Austrian. On the overriding rhythmic swagger which permeates the piece, it was the more decisive and propulsive. As a performance element, I'd call it something like beat urgency or rhythmic tension. Here the Crayon exhibited less. Related to it where those micro-distance dynamic spurts. Certain parts of a melody or arpeggio lash forward then fall back. Likely abetted by its enormous power supply, Olimpico had a more coiled sense of contained force. It just waited to flick out whenever performer emphasis released it. As such the reading felt more active in the dynamic domain. The Crayon presented it more relaxed and contained.
On the tonal axis of transient/bloom-sustain/fade, the Crayon was slightly more vigorous on the leading edge. With the CanEver, the bloom portion developed more. To stay with a flamenco idiom, envision a Spanish dancer's heel stomps. One hears not just their hits but, immediately after, how they propagate through usually suspended wood flooring to amplify such foot percussion. Applying that to guitar and bass, the Crayon had more focus on the initial heel impact. The CanEver better tracked its continuation and bloom through the floor.
As "Dos partes de mí" gets denser toward the end and dual chorus lines intersect the instrumental action, the Crayon's sense of separation and sorting was slightly higher. Most audiophiles would call that higher transparency. The CanEver felt a bit more materially robust/substantial. That didn't separate as down to the bone.
The insert shows what happens right beneath the daisy radiators: liquid-filled heat pipes and very fine fins below which the fan sucks up air from the ventilated air cushion beneath the enclosure.
This small shift (edge of seat, weight on the front foot, leading edge) from the Crayon to the CanEver (touching the seat's back, weight equally on both feet, bloom) segued back to soft power. By not over-accentuating the attacks but putting more weight on what happens right after, Mario's circuit with its heavy magnetics started gentler but followed up heavier. Voila, soft power. Inherent to greater post-attack bloom was more tonal fullness as a typical class A signature; and the aforementioned greater dynamic ripples. Combined, it notched up musical energy or vitality. We might call it juicier. But it wasn't the wetness of low-power triodes nor their particular fragility. The CanEver sounded warm yet drier than SET so non-humid. And rather than fragile, wispy and airy, it was substantial, chunky and weighty. Back on our Model One, it was time to replace the COS with Mario's ZeroUno and report on interactions between stablemates.
