Thermionic Culture Vulture

Valve distortion unit

Thermionic Culture Vulture Valve distortion unit

Review by George Shilling

When I reviewed the TL Audio Indigo Valve Distortion Unit I predicted that we would see further expansion in this area of outboard equipment, and, belatedly, here it is. Whilst not an essential in every studio, a distortion box is something for the enthusiast recording engineer to really get his teeth into. Many engineers have spent frustrating hours struggling to connect guitarists' stomp-boxes with inappropriate impedances. There are few studio multi-effects boxes that include distortion effects, and these are often an afterthought, possessing all the character of a microwave oven.

So, hot on the heels of Thermionic's groundbreaking Phoenix compressor comes the Culture Vulture, which looks similarly out-of-this-world. The black 2U front panel includes a host of vintage style knobs and toggle switches. The unusually ugly meters aren't VUs, but ammeters, measuring current flow through the valves. The unit's construction is similar to the Phoenix, with a sealed metal base section containing smaller components, on top of which are mounted the larger parts. These include a large old-fashioned bobbin mains transformer and an array of obscure valves, almost conceivably from the designer's attic. This top section is covered with a metal mesh casing. The unit is surprisingly lighter than it looks, especially as this is an all-valve unit. There are no ICs in sight, and not even any printed circuit boards.

Thermionic Culture Vulture Valve distortion unit

The front panel layout is irritatingly messy. The two channels' controls are arranged side-by-side, but as a mirror image of each other, which can be confusing. The two meters are vulnerable to breakage, as their glass casing protrudes from the front panel. Each channel has controls for Bias and Drive, scaled 1 to 11. A three-position switch selects Triode or one of two Pentode modes. However, all these controls' labels are below the large knobs, and are therefore invisible if one's eye level is above the top of the unit. At either end of the panel are Overdrive toggle switches for each channel. These appear to be something of an afterthought, mounted extremely close to the Drive knobs and without proper legending, just a stuck-on label. Between the meters is a large On/Off toggle with accompanying light, which is a torch bulb behind a green cover that takes a few seconds to brighten at switch-on.

Below the meters are chunky Output level knobs, also legended 1 to 11. Also on the front panel are unbalanced jack sockets for inputs and outputs of each channel, their layout following the mirror imaging of the controls. On the back of the base section are duplicate connectors: both sets of outputs can be used simultaneously, but the front input jacks override the rear ones.

Thermionic Culture Vulture Valve distortion unit

'Drive' behaves like you would expect, working similarly to a preamp gain control on a guitar amplifier. 'Bias' is a little more esoteric. As you turn it up it 'starves' the valve, and the level drops. A brightening tonal change takes place, depending on the mode selected, and a gating effect starts to take place, with only the peaks getting through and sounding fairly nasty. The meter displays the bias current: and as you increase the Bias knob, the current decreases. As signal is passed, the meter waggles slightly, upwards if you are starving the valve, or downwards if the valve is 'over-fed'. The latter setting (with Bias knob at a low position) gives a warmer, more even distortion. In use, one finds that the Output knobs have to be constantly adjusted in conjunction with the Drive and Bias knobs. The Triode distortion mode (even harmonics) and Pentode 1 mode (odd harmonics) can vary from gentle warming to raucous, with the latter mode seemingly slightly richer and creamier. P2 mode provides an even more drastic distortion, with a really horrible thin sound at high bias settings. In any mode, flipping the Overdrive toggle gives a boost to the Drive and Bias for more radical distortion effects.

I found the Culture Vulture most useful for distorting guitar parts that were lacking a bit of sparkle, and warming up plain-sounding electronic keyboard D/Is. I tried the manual's suggestion of putting the whole mix through it and after some experimentation it was possible to add some subtle warmth in Triode mode with a low Bias setting. However, without any onboard bypass switches it was difficult to set up and assess. Also, the unusual mirror-image layout takes some getting used to. It is easy to find yourself adjusting the wrong knob, particularly when you cannot see its label.

At extreme settings, there is a remarkable lack of self-induced noise. Any buzzes or hums I came across were generated by the source plugged into the inputs. This is thanks to the use of a very high-quality military-spec valve (CV4010) which gives plenty of gain with very low noise.

The Culture Vulture is a peculiar piece of equipment, a luxury rather than a necessity. It does what it sets out to do, but is a little awkward in operation, and comes across as slightly unrefined in terms of usability. However, its quirks will probably endear it to potential owners, and Thermionic Culture should be applauded for their unique approach.

Reproduced with kind permission from Copyright ©

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