DC on Presence Pot?

[s2]

Howdy all! Been a while since I posted, but I finally got around to building my Wreck clone.

Everything seems to be great with this amp except that I have some DC on the presence pot, which makes it scratchy. Is this normal? As I look at the schematic it seems like there should be some DC there, but I'm not familiar with its behavior so I thought I would ask.

Thoughts?

Pic:

http://www.websitetoolbox.com/tool/view ... &id=159898

[mlp-mx6]

Yes, it is normal. The Presence is a ground path for the phase inverter, according to the schematic. The current through the PI tube is flowing through the presence pot, so there is DC. You only hear it when you turn the pot, right?

[Elcabong]

I have the same behavior with mine. I literally "hear" the pot when I use it.

Nice work S2! I notice that you distributed the filtering on the board; I first planned to do that but I had some problem to fit everything on a 12" board.

What are you first impressions about how it sounds?

[s2]

Yeah. I couldn't fit the ginormous Atoms in the space between the board and xformer bolts, so I had to get creative and distribute them along the boards.

I also put a 250K trim pot in series with a 10K resistor in place of the 150K bleeder so I can adjust it. It is pretty cool this way. I'm thinking this belongs on the front panel cuz it allows me to adjust it from spanky clean to extreme gnarl.

This is a really nice amp and I'm very pleased with it.

On the presence pot thing, it obviously shows the pot as the path to ground for the PI, so there absolutely should be some DC on it, but I've never noticed a scratchy presence pot on other amps before, so I just thought I would ask if it is normal. It is only noisy when I turn it, so I'm not worried about it. Just thought I would ask some other Wreckies.


Thanks!

[mlp-mx6]

The "distributed power" is recommended by some as being better/quieter, especially if you ground the power and cathodes together that belong together. Beautiful circuit work.

[Elcabong]

I also put a 250K trim pot in series with a 10K resistor in place of the 150K bleeder so I can adjust it. It is pretty cool this way. I'm thinking this belongs on the front panel cuz it allows me to adjust it from spanky clean to extreme gnarl.

I like the way you describe how it sounds. I did something similar but was more conservative using a 50K resistor and a 100K pot. I cannot get extremely gnarly but pretty clean, though!

I like my amp but to really appreciate it, it has to be quite loud. When I play it with an attenuator, the sound becomes dull.

[PaisleyTube]

Hi

I really like the range of the "scratchy presence pot" too. You can also use a 4k7 resistor and a 25k lin pot in series with the cap but the "scratchy pot" rules regarding the range imho.

Chris