conrad-johnson ET6SE preamplifier

Tubed preamplifiers
Conrad Johnson ET6SE
conrad-johnson ET6SE preamplifier

There has been something of a rationalisation in the conrad-johnson line-up of late. While the brand has never been guilty of having a vast range of electronics, the current line-up of three preamps, three power amps, two phono stages, and an integrated amplifier must be one of the most streamlined the c-j brand has offered in years. However, far from paring back too far, this has a sense of right-sizing the brand for the current audio world. Yes there are gaps – no personal or digital audio products being the most notable – meaning this is a range without flab. And that’s good. 

That being said, depending on how you look at it, those three preamplifiers could be considered as many as six preamplifers. There are three basic models; ET6 occupying the ‘good’ slot, ET7-S2 in the ‘better’ position, and GAT-S2 as ‘best’. The specifications for the top two are fixed in place and there are no mix-ins or add-ons. Not so the ET6, which comes in standard and supercharger ‘SE’ guise, and there is an optional (and retrofittable) phono stage. And let’s get this out of the noggin right away; just because the ET6 is the most affordable of c-j’s current line-up of products, doesn’t make it the ‘entry-level’ or ‘starter’ preamp. This is through and through a c-j preamplifier, stripped to the bone in the ET6 and then built back up to fighting weight in the SE version, but this is not austerity audio and the ET6 is no pared-back preamp. If anything, it draws so much from past masters both above and below the price of the ET6 it’s like the distillation of all c-j preamps from the last few years, delivering – as they often do – far more of the performance of the mighty GAT-S2 than you might expect.

As ever, that ‘ET’ prefix to the name means ‘Enhanced Triode’, in that the circuit uses a single 6922 double triode tube, acting as a single-ended triode for each channel. This provides voltage gain, and sends the signal to a similarly minimal high-current MOSFET buffer, which helps provide a very low output impedance. This makes the single-ended only ET6 extremely flexible in terms of interconnect cable design and length. DC voltage is provided by a discrete voltage regulator that isolates the audio circuit from the power line by maintaining negligible impedance across the audio frequency band. In addition, infra-sonic noise is minimised by operating the tube heaters on a DC voltage supplied by a separate regulated power supply. Power up puts the ET6 into soft-start heat-up mode, and the blinking mute switch is a reminder of that.

The ET6 also retains the microprocessor-controlled relay system and network of metal-foil resistors as gain control, allowing one hundred 0.7dB steps in volume and balance, as seen in the ET7-S2 and GAT-S2. All that’s missing here is a balance control on the front panel; although it has two yellow volume displays, so you might expect to be able to adjust one at a time or even alter them individually. Visually too, the ET6 shares much with the ET7-S2, although the chassis is a centimetre or so thinner in this model. Both, however, retain a sort of Art Deco styling to the front. Even the number of inputs on offer are similar, with the ET6/SE having five single-ended line inputs and two external processor loop input/outputs, the second of which puts the preamp into ‘Theater’ mode and automatically switches the ET6 to unity gain. 

These are more than relatives, they are siblings; GAT-S2, ‘mini GAT’ (the ET7-S2), and now ‘baby GAT’ in the ET6/ET6SE. The ET6 isn’t the first preamp to receive that ‘baby GAT’ title, as it was bestowed on the ET3 preamp, which we tested a little under a decade ago. That classic preamplifier came with an optional phono stage, too, itself based on the circuit of the then-current version of the TEA-1 equaliser, the ET6 sporting a circuit based on the TEA-1-S3 that is today’s example. The phono stage itself offers enough gain and low enough noise to be good for moving coil cartridges of 1mV and below. The resistance loading of the phono module is adjustable thanks to two DIP switch arrays. Factory default is 47kOhms, but the ET6 board can cope with 9.6kOhm, 1.9kOhm, 200, and 500 Ohm loads. It uses a trio of 12AX7 double triodes.

blog comments powered by Disqus

Featured Articles