Up Close Helio 5011 Equalizer

I often wondered why a lot of the albums recorded in England in the late '60s and early '70s had a wonderfully different sound compared to the recordings coming from the US at the same time. After all, studios had (for the most part) the same microphones, same analog tape recorders, same instrumentation but not usually the same consoles as in the US. English-made Neve and Trident boards were well-known around the world, but it turns out that a smaller company, Helios Electronics, made a console that greatly contributed to the sound and magical vibe of those records.

First of al a bit of history: Helios Electronics was started by Dick Swettenham in the 1950s when he was a maintenance engineer at Abbey Road Studios. A contemporary of Rupert Neve, Swettenham moved on to work at Olympic Studios and started to offer his own line of console designs under the name of Helios Electronics. Swettenham's console designs were based on the idea that the studio console is like a musical instrument and could impart a distinctive character rather than be more transparent like the Neve and Trident desks.

In early 1967, Olympic Studios started to become a spot for many nascent British Invasion groups and producers. All or parts of four albums by Led Zeppelin including "When the Levee Breaks" (using the Rolling Stones' mobile which had its own Helios console) were track there. Traffic, Joe Cocker, and Black Sabbath as well as producers George Martin (The Beatles), Chas Chandler (Jimi Hendrix), Jimmy Page (Led Zeppelin), Paul McCartney, and many others, all sat behind the Helios at Olympic.

The 0011 Helios Channel Strip

Fast-Forward to the present day: H2 Audio--a collaboration between Grammy winning producer Al Sutton, Q2 Audio pro audio product designer Tim Mead and recording artist/engineer/songwriter Perry Tell--has reissued the Helios 0011 Channel Amplifier. The design goal from the start was to stay as close as possible to the original the original channel module from the Helios console, although there was one mod: to remedy the original's lack of headroom, an output transformer was added for maximum output level of 25 dBu.

Under The Hood

The 0011 uses a Helios 2128 mic pre-amp with 70dB of gain, -20dB pad, polarity flip, phantom power on/off, and a high-pass filter with 0, 40, and 80 Hz selections. It adds an output fader with a range of off to +10 dB. The 2128 uses a custom-designed mic input transformer that duplicates the original's Lustraphone transformer's performance and character. (Lustraphone was a venerable British ribbon microphone company at the time.)

Inside The Helio 5011 Equalizer Module

H2 Audio used an electron microscope to examine the core laminations of a Lustraphone M10 transformer so as to reproduce it accurately. Fine ribbon microphone maker Deni Mesanovic of Mesanovic Magnetics makes 2128's input transformer and also the output transformers for both it and the 0011 EQ.

The 0011 Channel continues with a three-band EQ module with a fixed, 10 kHz shelf and inductor-based low frequency and mid-frequency sections. These taller channel strip modules measure 7-inches in height (4U), 7-inches deep, and 1.7-inches wide and are exactly like the console modules. H2 offers the 002 Helios outboard rack to hold two 0011 Helios Channels or the 008 rack that holds up to eight.

500 Rack

To accommodate 500 Series racks, the 2128 mic pre-amp and 0011 EQ are offered as two separate, single-slot 500 Series modules. They have the same circuit, same specifications and same Elma switches and Bi Tech conductive pots as the 0011 Channel Amplifier. The 500 version of the 2128 mic pre uses a Mesanovic mic input transformer adapted to fit the module's size. Both the 5011 EQ and 2128 modules use the same output transformers as the 0011.

The 5011 equalizer owes its unique sound to Swettenham's take on what an analog equalizer could be--more musical, with an attractive character and sound that separated it from all other console equalizers at the time.

The 5011's three-bands start with a fixed-frequency, 10 kHz shelving equalizer control knob with ten 2dB detent positions between -10dB and +10dB, with a 0dB (or flat) is when the knob is straight up--center position.

Reminiscent of a hi-fi's tone control, the high-frequency EQ section has an extremely broad operating range covering from 2kHz to around 96kHz! The Audio Precision showed shelf boosts of up to 14dB and cuts up to 20dB. I liked the way this section opened up the top end for more "air" around any source using moderate to large boosts. Vocal tracks got a beautiful "shine" without exacerbating hard fricatives or sibilance.

The Mid-Range section has selectable frequencies of 700Hz, 1k, 1.4k, 2k, 2.8k, 3.5k, 4k, and 5kHz. Unlike the RC-based high frequency shelf, this section uses an inductor-based circuit for a bell-shaped, broad boosts and also very narrow cuts. The Q changes drastically between peaking and cutting; a small toggle switch changes between a broad peak (PK) and very narrow cuts or trough (TR). Cutting in the mid-range frequency is ideal for "slicing out" an annoying peak or resonant buildup without dulling the rest of the sound.

I liked the larger knobs on the 5011 for selecting the frequencies of the mid-range band and low frequencies. Smaller knobs are used for the Mid-Gain and LF boost. There is no mistaking these controls when quickly hunting for the exact sweet spot while listening and not necessarily looking at the 5011.

The Low Frequency section is also an inductor-based circuit with its own Boost (only) control. Frequencies available for boosting are: 60, 100, 200, and 300Hz. There is a center 0 (flat) position; turning the switch further clockwise changes this section into a fixed-frequency, 50 Hz high-pass filter with 3, 6, 9, 12, and 15dB positions. Key to the sound of the LF section is that the Q of the boost is proportional; it progressively narrows with higher and higher frequencies.

In the Studio

On bass guitar, the 5011 changed the instrument's "footprint" by enlarging its girth. Large boosts at 60Hz will compress slightly in a warm and colorful way. Its LC equalizer works like a Pultec but with a sharper Q. For me this is a familiar and distinctive bass tone I remember from records back in the day.

Boosting with the Mid-Range EQ, with its low Q, is very smooth. Boosting 1 kHz will bring out the front edge and attack of a bass guitar that's played with fingers. I also used the 10 kHz boost for pulling out the sound of the fretted strings (and occasionally some noise). I followed this process with an API compressor/limiter.

On the same song, I used the 5011 on the female lead vocal. The 10kHz nearly max boost opened up the air around her voice with not much sibilance increase! I set a small trough at 1.4 kHz to lessen the singer's reedy tone but without losing much clarity. I used the LF's 50Hz HPF to lessen proximity just a bit.

Electric Guitars

This is a good equalizer for multiple guitar tracks to get them to blend better within the track. Pushing midrange frequencies drives the output harder yet retains most of the clarity--that is noticeable when bypassing. I liked scooping different mid-range frequencies on each guitar track usually between 700 Hz to 2.8 kHz. Thinning one guitar track (part) allowed another to speak better. This technique, used in a more subtle way is also great for large backing vocal stacks to differentiate the harmony tracks/parts better.

The Helios 5011 is the British EQ sound in a 500 module, and I think it is an essential must-have, alternate tone shaper useful for both recording and mixing.