First of all, for using this mic preamp you'll need a rack that powers the modules (API, Purple Audio and BAE manufacture these racks among other companies).
The MA5 is very well made, only quality parts are used, every component from the potentiometers to the capacitors, the pcb, the knobs and of course the input and output transformers are only the best you could find in the business.
Panasonic caps, input transformer from Carnhill, output transformer from Jensen, custom made for this preamp, and a real Marconi knob (you could choose a red one or a black one) complete the module build.
On the faceplate you'll find a gain knob that goes 'til 70db in steps of 5 db, a 28k button, a phase reverse button, a 48v phantom power button and an output knob to fine trim the output, since the gain have 5db increments.
If you're here I don't have to explain for what you need the 48v and the phase (polarity) reverse button, right?

But maybe is a good thing to spend few words about the 28k button.. Basically it's a boost of 6db peaking at 28k.. It's very nice and musical, it's not harsh nor aggressive, and helps to add that special air that might be looked for when do you want to add some detail or sparkle on some vocals, ac guitars, etc...
The sound:
It's NOT a clone of a Neve preamp even if it shares the circuit topology..and of course falls in that category of sound.
It has a big bottom, it's huge but at the same time it's not muddy or flabby, it's very tight, this might be thanks to the custom ouput xformer made by Jensen. Bass drum, Bass and vocals might benefit from this, since it gave a nice coloration to the sound without making it muddy or unfocused.
The mids and the top are relatively clean, slightly colored in a nice way, especially the top is still detailed even if it's very sweet, not bright and not harsh at all.
The overall sound is very lushy, fullbodied and sweet at the same time..it will give that finished tone.. (I try to avoid warm as a term).
Drums, bass, ac guitars and of course vocals are his forte' IMO.
It also stacks very well..
It's an high end preamp so the price is not cheap per se, but if you consider all the quality parts and the time that are needed for building one, the fact that is hand made in the USA by Avedis himself, and that NO corners are cut at all and at what price the competitors sell their 500 series preamps..Well then I'd say that is cheap for what you get, honestly you can't find a better deal in terms of quality outthere.
The MA5 was also thought to be serviceable with ease in the years to come.. It will be easy to service even in 20 years from now, and afaik there was not an MA5 failing because of a part went bad yet (despite some output knob pulled too hard when taking out the unit from the rack).
Of course as every piece of gear made, it will have his uses and you might prefer another module/preamp for an intended application or reaching a certain sound, but this is another story.
I like people/companies who are truly passionate about their products, something that nowadays is rare.. In a world where the profit is what counts most and marketing will do the rest... So I like to support people like Avedis, very knowleadgeble and without any ego, that really care about the stuff they make.
As always the best thing to do is trying it in your place, so that you could have your own opinion, even I'm sure you'll like it...and in the case you don't (really??) you could always return it to your dealer..
To me this preamp is a no brainer that everybody who has a 500 series rack should own..
Cheu