My experience with pre-amps has been rather limited. I have a V-Amp, and Line 6 pod which I have used with various power amps with ok results but the SVP is what I have been looking for! I bought it used and have not changed the tubes. I have had noise 60hz hum and sizzle at various clubs but not at others.
Ampeg SVP Pro
The Ampeg SVP-Pro Series Bass Preamp uses 5 - 12AX7 tubes to provide the true, rich, tubular tone only a genuine multivalve signal path can generate