One for the amp gurus - 5e3 question

MtB

I'm always looking to improve my 5e3 self build, and have seen a "new" cap location that I've not seen before on this amp model. See the image below. 

What is the purpose of the yellow cap on the pre-amp valve number 2? I looks as though it's on the 12AX7 assuming a 12AY7 is in position1. Is it just to quieten the hiss / noise from the circuit?

https://i.imgur.com/P6z4iCM.jpg  ;

RiftAmps

That's not a standard 5E3 layout...the whole PI section in that amp is the same as a Princeton Reverb (although both cathodyne, they're slightly different).

Without a detailed shot of V2 socket, it will be difficult to guess what pins that cap is connected across.

martinw

That looks like the coupling cap to the PI grid. Normally on the board, but as Chris says, that's a non standard layout.

MtB

Thanks for your comments gents.

springhead

It's the 5E3 circuit but just different slightly layout on the board around the post vol/tone gain stage and PI.  That cap is the coupler between those two stages which you can also sit directly across the valve base when using the standard 5E3 layout.  Saves having V2B's grid effectively presented right across the board on 4" of wire, hence possibly a little less hum/noise.

Pre-amp B+ dropping resistor looks non standard - 15K?

Who's amp is it?

MtB

Don't know - I just did a g@@gle search on 5e3 to have a look at how folks wire their amps up, how tidy they are, etc and saw the image.  

RiftAmps

springhead said:

It's the 5E3 circuit but just different slightly layout on the board around the post vol/tone gain stage and PI.  That cap is the coupler between those two stages which you can also sit directly across the valve base when using the standard 5E3 layout.  Saves having V2B's grid effectively presented right across the board on 4" of wire, hence possibly a little less hum/noise.

Pre-amp B+ dropping resistor looks non standard - 15K?

Who's amp is it?

It's a Gartone Bluesman