Audible Illusions L-1 vs. Marsh P2000T preamps?

The L-1 is dual mono but uses two gain controls(one for each channel) and a single volume control that uses twin wipers(instead of using two actual volume controls but performs the same function.) Actually, the L-1 is easier to control the volume than the M3A and a better setup in my opinion.
It is basically the the M3A without the phono board. It does have an excellent headphone amp also.
Tube quality effects the overall sound of the AI products more than most. You can add sparkle or midrange bloom by trying different tubes as in most tube preamps.
The L-1 is just a hair softer sounding than the M3A. However, that isn't really a bad thing. It is an excellent overall preamp and hard to beat. It certainly is more neutral than some tube pre's out there.
If you end up with one, the best input for CD is the Aux. input and the best output is output #1. These do not have resistors in the circuit as output #2 and CD in do. It gives you a more neutral signal path.

In response to Bigtee's proven expertise in AI pre-amps, let me opine that, to my ears, the best input on the L1 is to use the tape input for your most favored line source.

Also, a belated thanks to Bigtee for informing me where the dip switches were on my L1. Thanks!

Theduke, you might be right. I used my L-2 with the tape in jacks at times. My thinking was hopefully to bypass the source switch and just go through a single set of contacts on the tape in switch. I never could decide which was actual better but I will take your word for it.