Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Electron Tornado on April 19, 2019, 10:08:24 am
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Ref this schematic again: http://www.muzique.com/news/images/Epi1.gif (http://www.muzique.com/news/images/Epi1.gif)
Looking at R1 and R2 at the input - Some amps have R1 connected as seen in this Valve Jr schematic, while I've seen others with R1 connected at the input jack to ground. Is there a reason behind either configuration, or any pros or cons?
This would lead to a similar question about R5 and whether it matters if it is connected as shown or connected between R15 and the grid of the output tube.
Still a third question would be why there is no grid stopper between the volume control and the grid of V1B.
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To be most effect, a grid stopper should be mounted directly to the tube socket. This means R2 would move to the right and R1 would move to the left, even mounted directly on the input jack.
R5 and R15 are already shown in the more optimum position.
Many famous manufacturers don't use a grid stopper between the volume control and following grid. That's something you are more likely to see in a high gain amp.
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First stage, 1Meg and 68k-- no real difference either way.
Second stage: the grid looks into a clump of 1Meg resistors. Any position except Vol dead-zero, it's got lots of stopper.