Just to clarify: you have an Mbox or Mbox2 with S/PDIF inputs, so you want a 2-channel pre-amp with S/PDIF outputs, right?

To make any useful recommendations, you need to tell us a bit more:

What type of acoustic material are you recording (e.g. male vocals, acoustic guitar)?
Which type of microphones or other sources do you want to use with this pre-amp?
Do you need a DI input?
Do you need the extra features found in a channel strip (EQ, dynamics etc)?
Is this for live or studio use?

I own a Mico and have also used the DBX. I have not used the 5001. I tried a TwinTrak but rejected it as unusable.

hi, yes I have the Mbox2 with spdif inputs, I record acoustic guitars especially but often voices and other eletrical instruments.
I record ac guitars with 2 Neumann km 184 with different positions due to what level and if it is a solo guitar or part of a song ecc..
classical guit with a Neumann tlm 103 and di input. voices with tlm 103, and sennheiser 416 for other use not music
not live, EQs of the DAW are ok for the moment
so as you see I have pretty good mics but not a pre..
what I need is color presence harmonics deepness and better AD

thanks for answering

The Mico is not going to give you "color presence harmonics deepness" - it's a very clean pre-amp. I use it for acoustic guitar with the DI taking the pickup output and the second channel handling an instrument microphone (usually dynamic on stage, condenser in the studio). I set up an X-Y oscilloscope driven from the output of channel 2 (mic) and a delayed version of channel 1 (pickup). I set the delay to account for the distance from the mic to the guitar sound hole (usually around 0.8 to 1.2 ms), and then alter the phase control on channel 2 of the Mico to get the best diagonal distribution on the X-Y display. Get this right, and the mic and pickup channels blend perfectly.

If the Mico is too clean for you, you may get more character from the DBX unit. If you are serious about getting one, a reputable dealer should be happy to lend you one to try. As I mentioned, I have not used a TL audio 5001, but it has had some good recommendations in this forum. I would steer you off the Focusrite Twintrak for the usage you stated, as the sound quality is not in the same league as the Audient or the DBX.

Art MPA II

If you want more color, harmonics, etc. go for a transformer coupled microphone preamp. API 312 series which include 3124 & 512 series. Almost any NEVE, Sphere, Electrodyne, Auditronics 501/110. Most of these offer a great quality transformer along with discrete transistor circuitry although the Auditronics relies upon IC chip amplifiers. You could even have more fun with a DIY project building up your own.

Dave made a good suggestion. Those are popular too.
Mx. Remy Ann David