Does the Fender BF Vibrato Suck Gain or Tone

[dumbassbob]

Hi..I have seen in a 1994 Guitar Player 2 mods you can do,that won't mess up a BF Fender..One is a Off On switch you put on where the intensity pot is,And the other is a NFB pot that you put where the EX jack is..Would doing either of these be worth while..Does the Vibrato always put some signal to ground,and what does a NFB pot do,is it like a presence

[Leo_Gnardo]

Hi dab & it's good to see you back. How's things in Dana Point?

1994, a bunch of my blues playing customers saw that GP article and began clamoring for the intensity pot mod. Well it is true that removing the intensity pot - that's what the switch does - pops up the gain and brightness noticeably. As if we don't already have enough in a Fender, but I digress. Here's the drawback: the intensity pot is a reverse audio taper 50K pot. This allows the vibrato to start to be heard with the pot around 5, and full strength at 10. Not much action below 5, that's the nature of the beast, and the reason why Fender used a reverse taper in an attempt to spread the control area. Problem is, where do we find a reverse taper 50K pot with a switch attached? There ain't no such thing, or if there is it's mighty rare. I've never seen one. With a linear pot, it has to be dialed up near full to hear the vibrato. But many players twist the vibrato up all the way, anyway. For those guys, who cares what the pot taper is, heck they could leave out the pot and just have a switch, vib on or off as you please. So... that's the story on that one. After the first flush of interest maybe one or two customers carried through with the mod, everybody else forgot about it and went their merry way.

Variable feedback. Well, presence is essentially a variable feedback that concentrates on high frequencies. Variable feedback works over the whole frequency range. Minimize or eliminate the feedback, you get a noticeable bump in gain. It's easy enough to experiment to see if that's the direction you want to go, just lift one end of the wire carrying speaker signal to the feedback resistor usually 820 ohms. If that floats your boat, and you would like to be able to pick a spot somewhere between stock and no feedback, you could install a pot to vary the feedback value say 10K in series with that 820 resistor. And a handy place to park that pot is in the hole where the ext speaker jack resides, if you're not in the habit of using it.

There are some other effects noted with removal or reduction of feedback. I'm sure we have some MEFsters who can sound off on this. What's been claimed, is a "wilder" or less refined tone, like amps used to have before feedback in the power amp became the norm.

Hope this helps!

[Justin Thomas]

My Bassman came with an NFB switch. It lasted all of 5 minutes when I got it home. With no NFB it was just an out-of-control noise-fest, buzz, hum, bad artifacts...

I don't know the details of the mod itself, but I would keep the pot value to as small a range as needed for the effect you want. Personally I think it's another one of those "I found a spot & never adjust it" so a pot can just be used as a test to find a different value you like.

On my third build I was messing around with an NFB loop & added so much my 50W amp turned into a .5W amp... Way too much NFB. I think I took it out entirely.

I also think the need or use of an NFB loop can be drastically affected by the layput of the amp, especially in amps that are very picky anout their layout. Also in my Bassman, a few nudged wires on the tone controls gave me all kinds of ick, until I returned it to the layout diagram.

Good luck, and never change more than one thing at a time in your experiments!

Justin

[dumbassbob]

Thanks guys...