Presence control?

Artie

Artie

Peaveyologist
I need to replace the Master Volume pot in my Spider Valve. While looking at the schematic, I notice that the "presence" control is nothing more than a passive tone control, (just like in a guitar), in the NFB loop of the amp. The owners manual confirms this.

For some reason, I thought the presence control on my tube amps were a little more . . . substantial. Some kind of reactive tube magic. I'm bummed.

Is this typical?

Presence_pot.png Presence_pot_manual.png
 
Artie said:
I need to replace the Master Volume pot in my Spider Valve. While looking at the schematic, I notice that the "presence" control is nothing more than a passive tone control, (just like in a guitar), in the NFB loop of the amp. The owners manual confirms this.

For some reason, I thought the presence control on my tube amps were a little more . . . substantial. Some kind of reactive tube magic. I'm bummed.

Is this typical?

Click to expand...
NFB presence controls are pretty simple and can be added to most amplifiers. There are some variations https://robrobinette.com/Voicing_an_Amp.htm#Presence_Control .
 
That's typical. There's some amps that do things more complex (Diezel comes to mind, as do some Bogners), but on most amps, the presence knob is a simple LPF in the NFL.
 
Cynical said:
That's typical. There's some amps that do things more complex (Diezel comes to mind, as do some Bogners), but on most amps, the presence knob is a simple LPF in the NFL.
Click to expand...

That's one of the things that surprised me. This is a Bogner amp. (Or at least, "Bogner designed.") The Spider Valve is a Line 6 front end, going into a Bogner designed all tube amp, into a Celestion G12 Vintage 30 speaker. I mainly use just the "power amp in" with one of my other front ends.

Block-Diagram.png
 
Like I said, "some Bogners". Not all. The ones that are based more on Marshalls just have the simple LPF. The Uberschalls and some of the oddball amps have more complicated circuits featuring custom inductors.
 
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