In this paper, we have investigated into JFA used for speaker recognition. First, we performed systematic comparison of full JFA with its simplified variants and confirmed superior performance of the full JFA with both eigenchannels and eigenvoices. We investigated into sensitivity of JFA on the number of eigenvoices both for the full one and simplified variants. We studied the importance of normalization and found that gender-dependent zt-norm was crucial. The results are reported on NIST 2006 and 2008 SRE evaluation data.