Mismatched pre/power amps

Hi I'm new to the forum so hope this is the right place.

I still have my cherished lecson AC1 preamp which I used with my AC3 power amp before it died. I also have an Audiolab 8000S - with pre/integrated/pre power/pre power.av - connected to an 8000P power amp which are bi-wired to my Epos ES12 speakers. CD is an Audiolab 8000CD.

Out of curiosity - and really nothing more than nostalgia - I wanted to see what the Lecson preamp would sound like with the Audiolabs, but I think there must be a voltage mismatch - with the volume on the Lecson turned to maximum the sound output is very low and totally unusable. I have a lead made up by Lecson many years ago to allow the AC1 to be used with other power amps and one of the phono pickups altered to allow for a CD player. Unfortunately, I no longer have the output and sensitivity values.

I have tried all combinations of settings and the only one which gave me the output was to connect the AC1 main output to the Power IN socket on the 8000S and use the Pre Power AV switch to allow the AC1 to drive the power amp in the 8000S. I also had this scenario with an old Yamaha cassette player. I tried connecting directly to the 8000P power amp but no results. Having said this, I suppose if the output is so low, other connections may be working but just inaudible.

I'm getting to the limit of my working knowledge, but is it possible to boost the output from the Lecson in some way or perhaps go about this differently? Or am I just dreaming of a bygone era.......?

Any thoughts/suggestions would be gratefully appreciated. Many thanks.