Double the grid voltage?

STURMJ · 11416

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Offline STURMJ

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on: November 03, 2009, 06:59:47 PM
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. 



Offline Paul Joppa

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Reply #1 on: November 03, 2009, 07:33:14 PM
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.

Paul Joppa


Offline Len

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Reply #2 on: November 04, 2009, 12:11:53 AM
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.

Paramours
Paraglows
Excites
Heavily modded Soul Sister and Groove Thang
Quickie modded to active low pass filter
Quickie modded to headphone amp
Lots of Bottlehead parts used for building other stuff