I’ve always been very agnostic about audio. In our world there are so many claims made about hardware and software that don’t hold up to scrutiny and I learned long ago that many differences some people claim to be significant can’t be reliably identified in a blind test. There are however some things which definitely do make a big difference. One of them is the humble valve.

It’s no secret that valves do lovely things to audio. I think most people are aware that the way they distort and compress does great things for guitars. Twenty years ago I hadn't heard them anywhere else apart from in guitar amps (and in my grandmother's radiogram). I had been unconvinced of the benefit of valves outside of guitar use because I hadn't heard it. Just to be clear, even back then I wasn’t under the impression that valves didn’t help, just that I thought they probably helped a bit but not that dramatically.

That all changed when a friend, who had an good quality 60’s stereo valve HiFi amp, brought it round and we AB’d it against a modern solid state amp. The experience was one of the most significant audio moments in my life. We listened to the solid state amp first, it sounded good. It was clear, clean, everything I expected. We put on the valve amp. Immediately there were the things I expected - a little fur on the bass, the top sounded softer and sweeter, all due to the distortion and non-linearities valves are known for. But there was more. The imaging was wider. The reverb seemed to wrap around the dry signal. Most of all it seemed “alive” (OK, I know this is starting to sound a bit like a HiFi review). But this wasn’t the dramatic bit which made the impression on me. That only happened when we switched back to the solid state amp. It still sounded clear and clean. I described it as having “nothing wrong with it” but it bored me. It didn’t interact with and entertain me in the way the valve amp did. I remember I said something along the lines of “it sounds fine but boring, turn it off”.

So, proper valves are amazing, but not all valve equipment has that “thing”. I have heard lots of plug-ins which claim to have the valve thing. The best sound really good, they soften, round and sweeten in an appealing way but I’m yet to hear something which adds as much interest as real valves. The plug-ins I’ve heard which come closest so far are from UAD. The one which has my full attention at the moment is the Culture Vulture...

Thermionic Culture are a company who are doing valves right. A small UK company who make hand-made valve equipment and nothing else. The Culture Vulture is a distortion box and as such is dedicated to the sound of the valves themselves as opposed to compressors or equalisers which use valves to create another process. Its well known that as valves distort they create pleasing harmonics, the Culture Vulture offers comprehensive control over the harmonic distortion created by the valve, from almost nothing to totally destroyed.

Of the three distortion modes available, my personal favourite is the cleanest. Triode mode runs the modelled 6AS6 pentode distortion valve as a triode. In this mode it is sweet and rich with even order harmonics added and with the bias backed off slightly from the default it is very clean indeed but still adding some of that elusive valve “thing”. P1 and P2 offer progressively more aggressive distortion. P1 runs the 6AS6 as a pentode and is louder and more aggressive, with odd harmonics adding an edge of obvious distortion. P2 models an alternative wiring of the pentode 6AS6 and encourages extreme effects and breakup.

I didn’t really understand how to use the Culture Vulture until I understood the structure of the hardware on which it is modelled. The 6AS6 acts as an electrical bottleneck through which the signal has to pass. The Drive control uses an EF86 input stage valve to overdrive the 6AS6. The choice of distortion mode and the bias control dictates how much headroom is available (or in this case isn’t available) to the incoming signal level as dictated by the drive control. The Bias control supplies the cathode and the effect of under and over-biasing can be seen in the screenshots. The effect in the two pentode modes is clearer, with the destructive effects of P2 mode clearly visible. P2 appears to fold the waveform over on itself and give rise to frequency doubling effects. Some really destroyed sounds can be found! Over biasing generally results in added weight, whereas under-biasing results in a thinning of the sound, particularly at extreme settings.

As distortion adds harmonics, the addition of an LPF is welcome. The two well-chosen frequencies of 6 and 9KHz tame the fizz, though I would be tempted to use a dedicated LPF like McDSP's F202 or UAD’s excellent Moog filter as very distorted, heavily filtered sounds offer many creative options. With this much distortion on offer, judicious use of filters and the mix control can make the previously unusable, very musical indeed.

There are quirks about this plug-in. The controls are very interactive, with changes on one affecting the results to be found with another. It is quite resource heavy using nearly 30% of my Twin Duo. Some of the controls appear to be backwards. This is accurate to the hardware original but is worth being aware of. If you think there is more to valves than guitar amps then you will enjoy this processor. It does extreme very well but my favourite thing about it is that it also does subtle brilliantly. I've been setting it up just a little over-biased in triode mode and just listening to music through it - I've never done that with a plug-in before!