Tube Preamp with PS Audio P300

The PS Audio P300 is not a transformer type conditioner, it is an ac regenerator. It converts the AC from the outlet to DC and then back to AC.

If your AC power is clean with no fluctuations in voltage and with little noise, than a power conditioner or power regenerator will have less of an effect than if the power is poor. In my case, the P600 made a tremendous difference on my TV (blacker blacks and less noise) and my stereo (more soundstage depth), even without using any of the multiwave settings. But again, every situation is different.

Tube equipment is inefficient and thus the P300 would be unlikely to provide enough current over time, regardless of the make or brand of tube amplifier. The p300 is best for front-end components.

I think PS Audio offers a 30 day no questions asked return policy, so it might make sense to try the unit

I thought I saw on AudioAsylum that Victor K__ said the 5i drew 450W peak, and it won't work with P300.

There seem`s to be alot of diferent thought`s on this one. I have a p600 and have my whole system pluged into it at 60 hz sine wave. Keep in mind it`s a AC generator not a line conditioner ,it`s better takeing your line AC changing it to DC then generating back to AC this time all cleaned up. But the big advantage is you can run it form 50hz to 90hz sine wave in 5hz levels. In muli wave settings 50 to 120hz. Tubes don`t like anything but 60hz sine wave it make`s the transformer`s buzz or hum.
Back to my system In my anolog I have a BAT vkp-5 and tried running at a multiwave setting it hummed so I called Victor at BAT and asked if it would hurt it HE SAID NO it would only cause a humm in the transformer. I have to admit it did really open the soundstage, but I did not like the hum so I`m running at 60hz sine wave again.
Now the important part that many touched on the start voltage it will double on the starts Victor said just make sure it does not excede the generator`s capacity. In my case with my system powered up then I turn on the vkp-5 it jumps to 244 watts then back to 158 watts at a idel. You got 300 watts to play with on your starts with the vk-5i I don`t know what the voltage will go to with just that pluged into but I cant imagine it will excede 300 watts give it a try and see what it reads. If it stays under 300 watts your good to go. David