Field Test: A Designs HM2EQ Hammer Tube Equalizer

Mar 1, 2008 12:00 PM, By Michael Cooper



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The A Designs HM2EQ Hammer 3-band equalizer ($2,695) takes a different approach to equalization as compared to most other EQs. One look at the supplied filter-response graphs in the owner's manual tells the story: The bandwidth of each channel's three bell-curve filters spans more than seven octaves at full boost/cut! But don't be fooled into thinking that such far-reaching effect can only deliver pile-driver action; while the Hammer is certainly capable of powerful tonal shaping, it also produces far more subtle effects.


The Hammer's jet-black, two-rackspace metal chassis and milled-aluminum faceplate are offset by the highly visible white titling for control functions and settings. Each of the two channels sports a separate frequency selector and boost/cut gain control for its low, mid- and high-frequency bands. Also included are a hard-wired channel bypass and separate high- and low-cut filter switches per channel.

Each band offers six switched center frequencies and bell-curve response. The low-band frequencies range between 30 and 400 Hz. Six mid-band choices range from 250 to 2k Hz, while the high-band selections are between 2.5 and 15 kHz. The boost/cut control for each band provides ±13dB continuously variable adjustment with no detents. All control knobs are large and made from milled-aluminum, and exhibit very smooth and deliberate action. There are no Q controls or individual bypass switches for each band.

The Hammer's high-cut (LPF) and low-cut (HPF) filters' cut-off frequencies are fixed at 8 kHz and 84 Hz, respectively. A large, blue-jewel lamp (indicating power status) and heavy-duty Carling toggle power switch finish off the unit's front panel. The spartan rear panel is home to balanced XLR I/O connectors for each channel and an IEC receptacle for the detachable AC cord provided with the unit.

The Hammer uses both tubes and solid-state components; inputs are passive. Each channel has one AT7 tube in its audio path. Special filters before the tube stage cull noise from the audio signal but pass desirable even-order harmonics. (The noise floor is specified to be -94 dBm across a 30kHz bandwidth.) The outputs are driven by ICs and are transformerless.

The Hammer provides no global input or output gain controls, but the lack of additional amplification stages is intentional, because it keeps the signal path sounding more pristine and free of noise. The 3dB down points for frequency response are at 5 Hz and 40 kHz.


My first test using the Hammer involved mastering a stereo mix that had a lot of midrange and severely lacked both bottom and top end. Boosting 30 Hz/12 dB and 15 kHz/9 dB lent more fullness, punch and detail to the mix, without adding any perceptible noise. Considering the broad range of the Hammer's filters, the extreme amount of boost I had to employ necessitated choosing center frequencies at far ends of the audio spectrum to lessen the degree to which the midrange would also be boosted. Even so, I needed to apply 1 dB of cut at 2 kHz to bring the midrange back into proper balance. The overall sound was very open, pristine and sweet.

Next up was an acoustic piano beautifully recorded with a spaced pair of AKG C-414 microphones. This track needed no EQ, but I ran it through the Hammer anyway with all gain controls nulled, and high- and low-cut filters bypassed. In bypassing both channels, I heard no change in timbre or stereo image, confirming that the Hammer's pristine audio path has no audible effect when in-circuit but “idle.”

On a stereo acoustic guitar track recorded with a spaced pair of Neumann KM184 mics, I set the Hammer to cut 1 dB at 100 Hz and boost 4 dB at 10 kHz. The recording's silvery high end was beautifully enhanced while low-end mud was removed. When I activated the channels' low-cut filters, the sound cut through the mix even better and kick drum bleed on the track was reduced.

I next used the Hammer on an electric guitar track that had too much bass and brittle highs. I kicked in the Hammer's high- and low-cut filters, cut several dB both at 10 kHz and 200 Hz, and boosted mildly at 1.2 kHz to accentuate the midrange frequencies. That helped the track a lot, but I still ended up using a more surgical equalizer — one with Q controls and adjustable HPF and LPF corner frequencies — to sculpt the track to sound the way I wanted it to.

The Hammer EQ sounded awesome on dull, pre-recorded kick and snare tracks. Boosting 9 dB at 50 Hz and 6 dB at 3.5 kHz gave the kick way more slap and punch. A 9dB boost at 5 kHz gave the snare track a wonderful crack.


My main quibble with the Hammer is that it omits independent band bypasses and output gain controls, making A/B comparisons to unprocessed material difficult at best. The unit is also fairly pricey.

If you're looking for an equalizer with a vintage-tube sound or the ability to tweak narrow frequency bands, the Hammer isn't for you. This box delivers a sweet, smooth, pristine sound in very broad strokes. Its effect is quite subtle until you use large amounts of boost. Then the magic begins.

A Designs Audio,, 818/716-4153.

Mix contributing editor Michael Cooper is the owner of Michael Cooper Recording in Sisters, Ore. Visit him at

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