Adding Presence Control to Deluxe Reverb

[ChrisM]

Would this be the correct way to add a presence control to a Deluxe Reverb? I think it is right, I am not sure about the NFB resistor though (R48), thinking it might need to change...

[IMG:639:512]http://img.photobucket.com/albums/v610/ ... esence.jpg[/img]

Thanks...

[Structo]

Yes it is.
The feedback resistor (820R) can be from 820 to 100K depending on the amount of clean you want.

[jaysg]

You really want a smaller pot value like 500 ohms. The capacitor will either be relatively large film type or electrolytic Non-Polar. You should put the 47 ohm resistor back in.

[ChrisM]

Cool, so the presence setup is correct then?

820R is kinda low isn't it? I kinda wish I had a tiny bit more headroom, might have to play with that value.

[ChrisM]

You really want a smaller pot value like 500 ohms. The capacitor will either be relatively large film type or electrolytic Non-Polar.

Why would I want a smaller pot value? Most schems I look at have the presence setup in a similar fashion as this with either a 5K or 1K pot.

[jaysg]

The feedback ratio is set by the 820 ohm and the 47 ohm missing from your schematic. It's a matter of scaling. I've done it before, but I don't have my notes with me. I used 820/100 with a 500 ohm pot and I believe a 17uF non-polar I cobbled together. 10uF is the target.

[Cygnus X1]

My question is why?

I stuck a NFB defeat switch where the ground switch was, and end up right where it was designed-with the NFB in place.
Maybe I'm missing something.
I think a mid control would be more useful.

[ChrisM]

I wanted to be able to tame excess highs. Was going to mount the control on the back in the ground switch hole.

So if I install this 5K pot that would throw off the NFB ratio wouldn't it? That would mean I would have to increase the NFB resistor.

Stock it is a 1:17 ratio

[Jana]

adding a presence control isn't going to tame excess highs, it is going to add highs.

[Structo]

I have the same NFB circuit on an amp.

I used a 5K and a .1uf with a 100K feedback resistor.

That is a pretty common design.

Also which tap you come off of will change it a bit too.

IF you want to bring the overall treble down maybe try a smaller slope resistor on your tone stack or your bypass caps.

Here are a couple examples.

[billyz]

If you want to tame the highs then maybe you really want a " CUT " control.

Also, I like to increase the middle resistor to balance out the tone of the Deluxe reverb, princeton reverb too. Gives them a little more juice too.

You can also lift the 47pf cap around the volume control, that will tame the highs.

[briane]

I wanted to be able to tame excess highs.

What you want is the treble bleed control. do a search for 'treble bleed'. I ended up liking 250k/.0047 off master 3.

[moj067]

I think Guitar Player offered a NFB mod tutorial in the late nineties. What was cool was that it was reversable if you didn't like it. You use the Reverb and Vibrato footswitch rca outs as the holes for your pots. I tried and didn't like it, so went back to stock,but was glad I didn't change the chassis by drilling more holes in it.

[robrob]

Here's one way to add a presence control to a blackface/silverface amp. It uses the 5F6A Bassman presence control and the amp's NFB & PI Tail resistors are adjusted to compensate for the presence circuit's added resistance.

https://robrobinette.com/AB763_Modifica ... ce_Control

[martin manning]

Why post a random addition to a 10-year old thread?