[Gvt1911]

Have an old (1995) Sonic Frontiers SFL-1 preamp using one 12AT7 and one LF353N chip. I upgraded caps and sound and clarity improved. Was reading about guys upgrading the LF353N chip to another type in headphone amps and wanted to know if I can swap out the 353 for a Burr Brown OPA2604AP I have lying around ? 
Any input would be appreciated ! 

[Occam]

Yes, the LF353 is a fet input dual opamp like the OPA2604. Its should be a straight swap. It should also be a significant improvement. My personal recommendation would be for an OPA2107AP which IMO is a significant step up from the OPA2604AP, available from States based sellers on EBay.

FWIW,
Paul