Home » Recording Resources » Featured Reviews » Thermionic Culture Vulture 20A and the Universal Audio Culture Vulture plug-in for UAD-2 and Apollo

Reviews by Paul Vnuk Jr.

UK-based Thermionic Culture was formed twenty years ago by Vic Keary and Jon Bailes. As implied by its name (a thermionic valve is the proper UK term for a vacuum tube), the company’s speciality is the creation of tube-based audio recording devices.

To celebrate its twentieth year, Thermionic Culture has crafted a limited run of 120 special anniversary editions of the legendary Culture Vulture dual-channel tube saturation processor. I had a chance to work with the 20A and compare it to Universal Audio’s plug-in Culture Vulture, made in cooperation with Thermionic Culture for the UAD-2 DSP engine and Apollo interfaces.


The refined cathartidae

The Culture Vulture is an all-tube dual-channel “valve enhancement” processor, housed in a 2U 19″ rack enclosure. The original is dressed in black, while the CV20A is purple. Each channel contains a matched set of mirrored controls with three large vintage-style chickenhead knobs for Drive, Bias, and Character. Further controls on each channel include a coarse input/overdrive switch, a lowpass filter (yes, lowpass), output pots, bypass switches, and a master power switch. In the center of the unit are a pair of large meters that look like VU meters, but are actually milliammeters that show bias current for the tubes.

All connections on the Culture Vulture are of the 1/4” variety, unbalanced on the original and gold-plated TRS balanced on the CV20A. Note that in addition to the line-level ins and outs, there are front-panel instrument inputs and lower-level rear-panel outs (–20 dB) for use when connecting the Culture Vulture to an amplifier.


Valves of the Vulture

The Culture Vulture has a minimal point-to-point hand-wired circuit design. Each channel gets an EF86 tube for the input stage, a 6AS6 tube for the distortion (“enhancement”) stage, and then both channels share a single 5963 (12AU7/ECC82) tube in dual triode mode for the output.

In the CV20A, the tubes are upgraded to rare Mullard and Phillips tubes with an M8100 (5654, CV 4010, EF95) on the input stage. The CV20A’s ins and outs are balanced using Sowter transformers, and it boasts a 10 dB lower noise floor than the basic Vulture.


Further alterations

Almost every control on the 20th Anniversary edition is altered in some way, big or small. All of the controls are detented for accuracy and recall, and the Drive and Output controls are now numbered 0 to 15 rather than the original’s 0–11 (it’s just a number with no units).

A 3-position input stage switch adds a +10 dB Drive choice between normal line level and full-on overdrive, and there is an added –10 dB pad available for the output stage. The original offers a choice of 6 or 9 kHz on its lowpass filter, where the CV20A offers a single fixed choice, –6 dB at 5 kHz.

On the original Culture Vulture there is a choice of three Character modes, determining how the distortion tube is driven—Triode (T1) and two Pentode choices (P1 and P2). On the CV20A there is a third Pentode mode between the original settings (the old P2 is now P3).

I found Triode mode to be the gentlest setting, best used for tube warming and thickening. Pentode 1 introduces a greater level of harmonic distortion; it can still be set on the clean side but is overall more punchy. P2 is similar to P1 in punch, but as signal spikes hit its ceiling its distortion clamps down with the sound of hard circuit compression. P3 quickly gets unpredictable, grungy, nasty, and intense in delicious and evil ways!


The Vulture in flight

True and embarrassing story: when I first encountered the Culture Vulture years ago, I thought it was broken. I knew nothing about the gentleness and patience needed when setting the controls, and the fact that the Bias dials make an unearthly static-filled scraping sound when adjusted caught me off guard.

Of course all the fault was mine, as I was expecting instant gratification with no learning curve. Years later, when Universal Audio released the Culture Vulture plug-in, I took another crack at it (starting with their suggested presets) and took time to learn to drive this beast.

Setting each channel’s Drive dials the same might not result in the same signal levels. You need to watch the meters more than the Bias dial settings, and the transients, tonality, and input levels of different source signals will react quite differently even when the front-panel settings aren’t changed.

While it sounds like I am picking the Vulture’s bones clean, it is actually these tube-induced nuances that make this box sing. This is a delicate set-by-ear/feel device. Once you learn its fantastic quirks, it can warm up a signal with a gentle tube tone with a mere 0.02% THD… or it can decimate a sound or beyond recognition, something akin to a broken or circuit-bent device.

This behavior can all be distilled down to how hard you drive the inputs and compensate the outputs, which tube character you choose, and whether you push or starve the tube with the Bias control. Every control always affects the others, all at the same time!

Knowing that tubes are finicky animals, each Anniversary model—and presumably each regular model—comes with a test sheet to let you know the best Bias settings for a literal clean reference point. From there you can treat the Bias controls as volume/saturation knobs. Counterclockwise adjustments push the tube for more standard tube-style saturation and overdrive, while clockwise turns starve the tube to introduce more of a clipping effect than a distortion (along with lower levels, unpredictable dropouts, grungy thumps, and more).

In use

The CV20A can add grit, sizzle, and life to the drum bus, or flat-out destroy room mics or snare or kick. On prerecorded electric guitar tracks, a gentle dose of overdriven Culture Vulture can help gel and glue the guitars together.

I have been doing a fair bit of string recording lately, and the Culture Vulture—at low gentle settings with the lowpass engaged—helps even out the strident nature of the bow on the strings, while the gentle harmonic drive keeps them lively rather than dull.

On vocals, the Culture Vulture 20A is great for everything from subtle roughing up to trashed industrial vocals. With overdrive, starved bias, and the P3 setting pushed, lyrical intelligibility may vary. Badly.

My favorite home for the CV20A is on the master bus. Triode setting is best here, with the output at full and then moving the Bias counterclockwise to taste as a thickening de-digital-izer, especially on in-the-box mixes.

But mixing’s not all—this is one heck of a great DI. Using the direct input on electric guitars, bass, and Rhodes piano, it can yield instant tube-console overdrive and beyond. For distorted guitars, overdrive plus P2 with a pushed bias and liberal drive settings equals a broken-up late-’60s British sound.

On DI bass the CV20A is even more forgiving and versatile. In Triode mode there is such a huge throw of sonic possibilities from clean and solid to growling and driven, it makes this unit an easy choice as a permanent studio bass DI. Unlike many bass overdrive boxes, you can set it so the punch and distinction of the bass notes remain with just the right amount of top-end string growl. It also makes a nice Rhodes DI for similar reasons.

Universal Audio Thermionic Culture Vulture Plug-In

The Universal Audio Thermionic Culture Vulture Plug-In

The Universal Audio Culture Vulture plug-in for UAD-2 and Apollo is an input-to-output painstaking circuit model of this all-tube behemoth. The plug-in is modeled on the stock Culture Vulture, with every switch, knob, dial, and the all-important milliammeters represented.

There are also two additional features not found on the hardware. The first is stereo linking, and the second is a Mix control for blending and parallel processing of the dry signal alongside the effected one. I really wish the hardware offered this feature, as it really expands the versatility of the unit and becomes hard to live without!


Vulture in the box

As mentioned above, I learned how to get the hang of this bird thanks to Universal Audio’s library of presets, which contain starting points for drums, guitars, bass, vocals, and the 2-bus. I also found that recreating these presets on the hardware proved the best way to do side-by-side comparisons, including direct bass tracking with the plug-in printed in real time on my Apollo Twin MKII. For these comparisons, I ignored the anniversary edition features when I could.

Usually the biggest discrepancy when comparing hardware and plug-in models is the variation of input and output levels, as well as saturation and ballistic response. Comparing the Culture Vulture hardware to the plug-in is no different, but here it’s more the hardware’s fault. Since tubes are temperamental beasts, it can be hard to match two different Culture Vultures—even the two channels within one Vulture will vary a bit. To tackle this, I fine-tuned each by using some test tones for input and output, and more importantly relied on the milliammeters for bias matching. Even so, I couldn’t compensate for the fact that the plug-in, like the original, is transformerless, while the 20A is transformer-balanced.

Despite the above caveats, I was impressed by how well UA really nailed the hardware’s characteristics. Not only did UA pull a great-sounding analog triode warmth from mere computer code, the developers also captured the extreme breakup and black-hole sound sucking when starving the tubes in the highest pentode setting. The plug-in even simulates the low-harmonic unpredictable punchy thump that the hardware has! I am not sure I’ve heard any other in-the-box distortion do it so realistically before.

The plug-in even adds the gentle harmonic widening that the Culture Vulture can add to a mix. I would be lying if I didn’t wish that the hardware could be as quickly linked and matched for stereo mode as the plug-in, but the one thing I do miss when using the plug-in is the tactile feel of working with the controls for subtle changes.

Oh, and the plug-in does have one other downside: of all the plug-ins UA makes, it’s in the top five for processor load. It uses 63.1% of a chip in mono and 71.2% in stereo, which means you can only use one instance of Culture Vulture per SHARC chip and even an OCTO card will only yield eight instances. Yikes.



Once you use and get to know the Culture Vulture in your studio, hardware or software, it’s a hard piece to not become addicted to. Not only is it one of the best sonic manglers ever invented, as a gentle mix warmer it’s simple, effective, and second to none.

The plug-in will continue making regular appearances on my mixes, and thanks to the transformer-balanced mastering-grade quality of the 20A edition, well… I’ll be right back, I have to talk to my wife about our credit card balance…


Prices: Culture Vulture 20A, $2699; standard Culture Vulture, $1999; Culture
Vulture plug-in, $299

More from: Thermionic Culture, www.thermionicculture.com; Universal Audio,



2018 Reviews