Presonus ADL 600

Dual channel mic, line, instrument pre

Presonus ADL 600 Dual channel mic, line, instrument pre

Review by George Shilling

The story of Italian-American designer of boutique outboard Antony DeMaria meeting up with PreSonus president Jim Odom at the New York AES Show will be familiar to some readers from press releases. Odom noticed a prototype mic preamp at the back of the ADL booth, and was intrigued, and upon hearing it, mightily impressed. Convinced this was a match made in sonic nirvana, the ADL 600 was eventually born.

DeMaria’s ADL brand is known for expensive all-valve outboard, especially vintage-inspired compressors (the ADL 1500 was reviewed in Resolution last year). PreSonus, on the other hand, is known for modern designs at a lower price point, but with a reputation for reliability, clean sound and excellent build quality.

The ADL 600 is a dual channel mic, line and instrument preamplifier, built in the USA to apparently exacting standards, and featuring three tubes per channel. Out of the box, it is a mightily impressive piece of kit, a deep 2U box with a contoured charcoal front panel, large chrome toggle switches, unusual matt-finished knobs, with both VU and LED meters. The two channels are similarly, but not identically laid out.

Presonus ADL 600 Dual channel mic, line, instrument pre

The Instrument input jack for each channel is on the outer extremes, whilst the toggles and knobs run left to right on both sides, meaning the physical relationship between toggles and knobs is different on each channel. You therefore have to look carefully before flipping the similar looking toggles – their indicator LEDs are lusciously but unhelpfully all blue! The toggles are high quality components and not overly stiff. All functions are accompanied by a reassuring relay click. Interior construction is equally impressive, with a dividing metal wall around the power supply.

The VU METER -6dB switch usefully pads the meters, allowing higher output indication with less needle bending. Additionally, these “VU”s are legended to +5dB and the needle stop is just past that. Although the meters are deeply recessed, a warm backlight helps visibility. Furthermore, between the VU meters are a pair of 8-segment LED bargraphs, ranging from -18 to +24, with all LEDs blue except the top one red, this one around the maximum output level.

All knobs are click-switched, except the Trim knob which is virtually undamped, providing a smooth -10dB to +10dB adjustment with no détente – perfect for riding dynamic vocalists up the verses and down in the choruses, or just setting as appropriate. Coarse Gain goes up in 5dB steps from 30dB to 65dB, so with the Trim at full tilt, there is an indicated 75dB of gain, and certainly plenty enough clean, quiet amplification for anything I could throw at it. And for loud signals a -20dB pad is available. The HP Filter is selectable at 40Hz, 80Hz or 120Hz, but the knob to select this is placed away from the enabling toggle. And looking from above when mounted in a rack, it’s slightly hard to read the legending with toggles down and off. But this is really a very small niggle, and any other arrangement would spoil the beauty of the front panel!

Presonus ADL 600 Dual channel mic, line, instrument pre

On there rear are clearly labelled Neutrik XLR sockets, with separate mic and line inputs. A large heatsink is bolted on between these and the IEC mains socket. Mains voltage is factory preset. There is also a Chassis Ground Link strapped across two tag screw binding posts.

In use, one is immediately struck by the silkiness and smoothness of character. This unit has a distinct character which sets it apart from the competition, and seems to bring the best out of any microphone in terms of depth and clarity. The exceptionally low noise floor undoubtedly helps the detail shine through. It sounds decidedly posh, and especially suits female lead vocals and stringed instruments. But that’s not to say it lacks guts. This is a modern designs that does not set itself up as a vintage copy, but instead claims – and achieves – a genuine improvement over its predecessors.

Presonus ADL 600 Dual channel mic, line, instrument pre

There are four different mic impedance settings, from 1500 down to 150 ohms. With a trusty large condenser, differences between adjacent settings are subtle, but a more open sound is produced at higher settings, as expected. The lower impedance settings tend to sound clogged. With a cheap dynamic mic an exceptional level of high frequency detail is extracted, giving the mic something leaning towards a condenser’s character, but again, lower impedance settings tend to be less appealing for vocals. With a ribbon mic, again an enhancement was evident, with a sparkle and clarity not normally expected, although there was none of the slightly exaggerated ‘air’ found on Focusrite Blue models, for example. I was expecting the ribbon to perhaps do something interesting with the lowest impedance settings, but at 150 ohms the level was significantly lower than at other settings, with no obvious benefit to the tone.

The Instrument inputs are a bonus feature, they sound great, and provide plenty of gain for low output guitars. However, on higher output instruments like bass and Les Paul, I found my Phoenix DRS-2 Neve imitator sounded a little livelier.

Line inputs are provided for mix processing. I was expecting this to be subtle, but cranking the Gains and lowering the Trims really gelled a rock track in an instantly gratifying manner. The effect was akin to mixing through a big analogue desk as opposed to in-the-box, the ADL took away a little digital nastiness, and added pleasing analogue glue – it really was like hearing great vinyl versus lacklustre CD!

Oddly, approximately half the manual is taken up with a basic guide to mic techniques for various instruments, and even more oddly there is a small Allen key taped to the cover, apparently for knob removal. However, all functions and features are adequately explained, and the ADL 600 is a joy to use, and looks and feels a million dollars.


Silky smooth mic pre with exceptional performance; Line inputs warm up your mix; beautiful design and impeccable build


Poor pointer on Trim knob; Lower impedance settings rarely useful

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Reproduced with kind permission from George Shilling. Copyright George Shilling.