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A Designs MP-1 Tube Mic Pre/DI

A welcome addition to the ranks of top-quality mic pres for less than $1,000 By Dan Richards
The MP-1 microphone preamplifier is a new single-channel version of the successful MP-2 by A Designs of California, USA headed by Peter Montessi. With a list price of $1,150 and a street price seen as low as $899, the MP-1 is a welcome addition to the ranks of excellent, top-quality mic pres available for less than $1,000.

There's been lots of discussion of tubes and using them to warm the signal path, but if you didn't have a thick wallet, a true tube microphone preamplifier was probably out of reach. Getting into tubes for under $1,000 has meant hybrid-tube designs or even units that claim to have tubes, while in actuality the tube had little or nothing to do with the sound of the unit and more to do with marketing.

Out of the Box
The MP-1 arrived for review and I was immediately struck by its large two-rackspace size and its vintage appearance. While many designers are coming out with small half- and third-rack sized units, the design of the MP-1 is a return to everything that was cool about quality vintage tube gear: elegant simplicity, solid construction and warm sound from even-order harmonics.

The black front panel of the MP-1 is simple and to-the-point: featuring a variable input gain knob, backlit analog VU meter, switches for polarity, phantom power and output between 600 ohm and 10K ohm as well as on/off power switch and lamp. The back panel is minimalist and contains an IEC socket with 100/120/230 VAC rated at 42 watts, XLR output connector and a Neutrik Combo XLR 1/4" Input Connector for microphones and instrument DI.

In Use
At Sea Note Recording, we're currently using and testing around 30 microphone preamplifiers and ever since the MP-1 arrived it has been standing out for its ease of use, impressive but minimalist design, superb sound and, of course, price. I really appreciate the inclusion of the the variable input gain, and although the MP-1 wouldn't be considered a high-gain mic pre, there was more than enough gain for any of 30+ different microphones that have been used with the unit, including many FET and tube large condensers, dynamics and older ribbon mics. The 600 ohm and 10K ohm switch allows the user to operate the MP-1 between balanced pro studios and unbalanced project-studio systems. Toggling the ohm switch also results in a change in volume and sonics ? so it can be considered as additional "colors" in the sonic palette of the MP-1.

Input Impedance 1.4k Ohm
Gain Range 46 dB

Noise (EIN)
-120 dB

Mic Phantom Switchable 48 Volt Power Source

Mic Input Phase Switchable 0-180
Instrument Jack Input 1/4 phono combo XLR

Input Impedance
Min > 100k Ohm

Frequency Response
20 Hz - 60k Hz
Balanced XLR Output:
Output Impedance 600 Ohm Switchable to 10k
Maximum Level +22 dBu

Low-Z, transformer-balanced

THD: > .08 @ 1 Khz
Power Requirements: 100/120/230 VAC - 42 Watts

(W x H x D) 19" x 3.5" x 10"

15 lbs. (Shipping weight 17 lbs.)
The MP-1 runs 6NI-P and EF86 tubes with a Jensen input transformer on the front-end and a custom-wound output transformer, which yields stunning sound quality with serious bass response and a warm, airy top end typical of great tube mic pres. I don't find the MP-1 to be overly colored. In tracking sessions, any source that sounded too thin has gotten the MP-1 treatment. The introduction of a good tube design adds even-order harmonics mostly in the area of seconds and fourths. This occurs in nature and is what makes ours ears define a sound as "pleasing."

In DI listening sessions with a Lakland Bass through over 20 pres, the MP-1 rose to the top of the pack and was among the favorite of several engineers and was chosen as the best pre by the bass player. On syth/workstation sessions, the MP-1 was used to thicken otherwise thin piano and pad sounds. The MP-1 has also become a first choice for vocals. I'd really like to try an MP-2 version on drum overheads.

The only shortcoming of the MP-1 I tested was that the 1/4" DI jack was on the back panel rather than on the front panel. A Designs Peter Montessi told me that a front panel 1/4" jack is in the works for the next production run of the MP-1. Other than that, I simply can't find anything wrong with this unit. Everything is right.

After being so impressed with the MP-1, I asked Peter Montessi of A Designs to fill me in a little about the origns of his mic pres and the design philosophy of the company. Peter said, "The idea for the mic pre came out of desperation and simple economics. I know that there are thousands of mic pres out there ? some good, some bad ? some expensive and some very low cost. But, no one seemed to be providing the best of both worlds. High quality with affordability. The high quality mic pres are primarily tube ? but very costly. The lower-quality mic pres are primarily made up of IC's and resistors, which are very inexpensive. The mid-cost micpres are hybrid or "discreet" ? a combination of tubes and IC's ? cluttered with compressors, effects and EQ's. No one seemed to be focusing on the fact that anyone could produce a high-quality mic pre at an affordable price. I determined that would be our niche. So, in keeping with the overall philosphy of A Designs, 'Making Pro Audio Affordable,' the MP-2 was the first product with that in mind and the MP-1 followed."

If you've been wanting to add a real all-tube microphone preamplifier/DI to the front-end of your recording system, I urge you to pick up an MP-1. At a street price of $899, this unit is within reach of even budget-minded recordists and yields a sound only obtained from quality and an all-tube mic pre. I have seen no other all-tube mic pre that compares with the MP-1 in its price range. Having used many mic pres, I place the MP-1 as one of the top mic pres under $1000 and flat out the best tube mic pre under $1,000. For project studio owners, the MP-1 is, in my opinion, a no-brainer and a must-have unit.

Audio soundclips of the A Designs MP-1 as well as other mic pres can be auditioned at The Listening Sessions. For more information on the MP-1 and A Designs, visit their website at

Dan Richards is a Contributing Editor for Digital Pro Sound and is currently producing The Listening Sessions.

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Related Keywords:A Designs, MP-1, Tube, Mic Pre, DI


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