Double the grid voltage?

[STURMJ]

Someone on the old board was going to try doubling the amount of 9v batteries in his quickie.  I was hoping to hear the results of that experiment.  It looks like the the 3s4 is rated 90-100V (plate) depending what you read.  Would this increase the overall gain? I'm still getting good comfortable volume at maximum, but would like just a bit more. 

[Paul Joppa]

It won't affect the gain, but it will increase the maximum available power - if you have enough drive voltage.

The 3S4 is rated maximum 67.5v on the screen grid, which is tied to the plate in the Quickie. It's reasonable to use a maximum of 72v (eight 9-v batteries) but not more. Note that the current will more than double, cutting battery life to less than half. It also makes the voltage a bit more risky - for example, you'd probably want to put the top four batteries below the plate with only the lower-voltage ones on top.

[Len]

Someone on the old board was going to try doubling the amount of 9v batteries in his quickie.  I was hoping to hear the results of that experiment.  It looks like the the 3s4 is rated 90-100V (plate) depending what you read.  Would this increase the overall gain? I'm still getting good comfortable volume at maximum, but would like just a bit more. 

I think that was me. I haven't done it yet. I built the low pass filter Quickie, and now I'm shoehorning in the Hammond chokes. Then I'll build the headphone Quickie for 300 ohm and 32 ohm headphones with a selector switch. If I have trouble driving the 32 ohm phones, I'll double the up the batteries.