There is not a lot you can do about the MPX 1 but you might consider picking up an MPX G2 which is basically an upgraded MPX 1 with an analog overdrive circuit added. The G2 has 24 bit converters compared to the MPX 1's 16 (may be 18 on the outputs) and includes stereo IN via the aux inputs.  The G2 also includes 20 seconds of delay memory and some new effects including compressors and loopers. The only real negative that I know of with the G2 is that it doesn't have S/PDIF IO. Analog only.  Otherwise an excellent MPX 1 upgrade.

Hi Bob,
sorry, I actually meant just the audio memory of the delay times, nothing else, because they are soo short 
I've taken a look to the Service manual of the MPX-1 and I've supposed that only by changing the resident DRAMs with more capable ones, I could increase the audio memory for the delay times
but, after contacting the Lexicon staff, they said me that it would be useless to change the resident DRAMs, because the DSP can't reads the memory upgrade.
I would invest in a project to upgrade the MPX-1's DSP with a new frimware, so that it will be able to achieve much more delay times..
who knows if there is someone which could help me to do that.

I don't think there are going to be any updates for the MPX 1 since it is discontinued but what exactly do you need the delay to do? 

You definitely want to press the Options button when on one of the delay fields. You can select delay time as meters, feet, ms and a ratio of the current tempo which can be tapped or locked to external MIDI clock.

One of the biggest limitations was the amount of audio memory so longer delay times are not possible without hardware and software changes.

Hi guys,
It would be a dream for me to have the possibility to rewrite a new firmware version for the MPX 1 to achieve more delay times to fit in.. who knows if it would be possible, I would pay for it, of course..

best greetings