12 volt ac power adaptor inplace of 18v?

[allsavy]

I've missplaced my 18v/14w (1300ma?) AC wallwart power adaptor for my Alto tube dual mic pre. Have a few 12v adaptors laying around... Could one be used in place of the 18v?

[Rockn]

Substitute

It would probably not work and you would need to be more concerned about the amperage you are getting off of the wall wart.