A couple of issues ago, we looked at the latest in the Classic line from conrad-johnson’s power amplifier range. At that time, we focused on the SE versions of the Classic Sixty-Two and Classic One-Twenty. These feature hot-rodded versions of the standard models, with KT120 power valves in place of the stock EL34s. We almost skipped over the standard versions, little knowing that decision would come back quickly in the shape of the CAV-45 control amplifier.
The standard version of the Classic Sixty or Sixty-Two power amplifier forms the basis of the CAV-45, to the point where the CAV-45 could be considered one of those stereo power amplifiers with a three-input line stage attached. This isn’t exactly the case because where the power amplifiers push their power tubes to deliver a healthy 60 watts per channel, the CAV-45 delivers – as the name suggests – just 45 watts per channel from the same basic tube layout. If you compare the casework of the control amplifier with the similar power amplifier, you notice less substantial power transformers, which leads to a less substantial weight and more even weight distribution.
The CAV-45 is perhaps the ultimate in minimalist integrated (sorry, ‘control’) amplifiers, in that it has a power amplifier with a volume pot and a three input rotary selector where the power on LED usually sits. These ’preamp’ stages are entirely gain-free, making this a power amp with built in passive stage. Balance control? No way. Remote control? Try using a stick. In fact, rather than a power amp with a passive preamp, think of the CAV-45 as a power amplifier with three switchable inputs in place of the single preamp input, and a potentiometer in between that input and the triode-based voltage gain. This means you can run longish interconnect cables, but overall output is relatively low.
The other great advantage to this arrangement is it’s incredibly low noise, up (should that be ‘down’?) there with high-performance standalone passives like the Townshend and MFA designs. This fits well with the conrad-johnson’s ethos that rejects the idea of an ‘integrated’ in favour of a ‘control’ amplifier. While for most people, a control amplifier is an archaic way of describing a preamplifier, conrad-johnson like to place some distance between a device like the CAV-45 and most integrated amplifiers. The company feels most integrated amps throw the baby out with the bathwater, eliminating key features and better quality components (in the process sacrificing good sound) just to make a cheaper product, or to have fewer models in the line. Rather than paring down the quality too far, the CAV-45 eliminates the need for potentially sonically deleterious long interconnect cables between preamp and power amplifier. Although, in going down the passive route, long cables are off the radar anyway. In fairness, the unique construction of attenuator after the input of the power amp means there can be longer cables between source and amplifier than if there were a passive preamp in the system. You need a device of sufficient gain and output impedance in order to use cables of 1m or longer, however. Eliminating the line stage – especially a c-j tube line stage – also has a direct benefit in that the output at the loudspeaker terminals is in absolute phase (c-j preamps typically invert phase).