I owned a stock refurbished 81 in the 70's 80's.
The can caps were replaced and something feeding the rectifier tube was changed.
The coupling caps were also replaced with Yellow Illinois brand caps which I was told would sound similar to the originals.
Sources were various Thorens TT's, Nakamichi cassette decks and believe it or not Beta and VCR video decks used to record LP's and to record/mix live music.
The only thing I found lacking was the 81's phono section.
I patched in the phono section of an Advent 300 receiver which easily bested the stock Eico phono section.
So maybe just try an outboard phono preamp for starters.
Though I haven't used it for years I now own a Pilot 240 integrated amp and the same thing goes.
The line inputs sound great, but the phono section is lacking.
During the time I owned/used the 81 I also used Mac 30's and various modified Dynaco Stereo 70's (in mono block and stereo versions).
The 30's were stock/refurbished and the 70 mono blocks had a tiny transformer and other parts added to the power supply (maybe used as a choke).
The above were used with the preamp section of an Advent 300 and sometimes a Dynaco PAS 3X preamp.
The 81 held it's own against the Mac and Dynaco gear.
I sold them all in 1986 and didn't own another decent rig until the late 1990's.
DeKay
The can caps were replaced and something feeding the rectifier tube was changed.
The coupling caps were also replaced with Yellow Illinois brand caps which I was told would sound similar to the originals.
Sources were various Thorens TT's, Nakamichi cassette decks and believe it or not Beta and VCR video decks used to record LP's and to record/mix live music.
The only thing I found lacking was the 81's phono section.
I patched in the phono section of an Advent 300 receiver which easily bested the stock Eico phono section.
So maybe just try an outboard phono preamp for starters.
Though I haven't used it for years I now own a Pilot 240 integrated amp and the same thing goes.
The line inputs sound great, but the phono section is lacking.
During the time I owned/used the 81 I also used Mac 30's and various modified Dynaco Stereo 70's (in mono block and stereo versions).
The 30's were stock/refurbished and the 70 mono blocks had a tiny transformer and other parts added to the power supply (maybe used as a choke).
The above were used with the preamp section of an Advent 300 and sometimes a Dynaco PAS 3X preamp.
The 81 held it's own against the Mac and Dynaco gear.
I sold them all in 1986 and didn't own another decent rig until the late 1990's.
DeKay