good info on bright caps

[DonPetersen]

"The little capacitor that is soldered to the hot lug and wiper lug of your amp’s volume control is called a “bright cap” or treble bypass capacitor. That little capacitor helps your amp retain its bright clear treble response when the amp is played at a lower volume. The human ear is not as sensitive to treble frequencies at lower volumes and the bright cap allows treble frequencies to flow through the cap. As you turn up the volume control the bright cap has less and less effect and with the volume control on “10″ it has no effect at all.

(...)The smaller values will have less effect than larger values. Small values are in the 47pF range and have little effect. Larger values in the 100pf-180pF range will affect the upper treble frequencies. And even larger values in the 250pF-500pF range will affect a wider band of frequencies making the amp sound louder and have the lower treble/upper mids pronounced.

(...)The advantage of tweaking these bright cap values comes in when you own a wide variety of guitars. For example you may not need a bright cap at all with a Strat or Tele but may need a larger value to brighten up your Les Paul or SG with full size humbuckers. Having the bright cap on a switch or a second channel of an amp with a bright cap as on many Fender tweed amps like the 5F6-A Bassman can accommodate different guitars."
http://www.300guitars.com/articles/diy-how-to-tweak-bright-caps-in-your-guitar-amplifier/

p.s.
1nF (nanofarad) = 1000pF (picofarad)

edit
from HRI:

"plexi dudes... bright cap??
by samtheman » Sat Jan 08, 2011 10:44 pm
It depends how loud u play, my fav is 120pf but thats me"

works fine!
dammit, I can't stop playing Plexis now...

 

[Patzag]

Thanks Don,
This is very good information and pretty much solves a question I was asking myself on how to make a quick X/Y to switch from my single-coil guitar to my Humbucker equipped guitar while leaving the presets otherwise identical. Much appreciated.
P

 

[DonPetersen]

Thanks Don,
This is very good information and pretty much solves a question I was asking myself on how to make a quick X/Y to switch from my single-coil guitar to my Humbucker equipped guitar while leaving the presets otherwise identical. Much appreciated.
P

after reading the article I was immediately able to dial in a better Plexi/JCM800 patch then (in the year) before!
I never thought the effect of the bright cap would be so huge.

 

[nikki-k]

Cool article!
This is one reason I have been going on and on about the underpinnings in the Axe-Fx II Amp Block, and why I suggested playing with those values (Bright Cap), especially while tweaking other values, and also desiring different cap materials. The Axe is, essentially, behaving as a tube amplifier... albeit with a seeming "universal chassis and control set" being available to the end user. IMO, understanding tube amp theory and operation enables deeper understanding of the Axe. It is really cool to see this getting attention

BTW- one of the items on my wish list.. if I were playing in clubs... would be a something like a CC addressable SP3T (rocker) for the Bright Switch. Being able to toggle between values would be sweet!

 

[DonPetersen]

BTW- one of the items on my wish list.. if I were playing in clubs... would be a something like a CC addressable SP3T (rocker) for the Bright Switch. Being able to toggle between values would be sweet!

oh, I can see the benefit of that!
have a nice rounded crunch tone for the rhythm work and then switch to the same sound but with way more bright cap bite for the solo. (or the other way 'round)

shouldn't the x/y feature be able to pull that off?

 

[Patzag]

Sure does

 

[nikki-k]

Yeah, about 5-10 minutes after writing that bit about a virtual rocker switch, I realized, "Doh! Even with a more complex chain, there are ways to accomplish this easily." I am still thinking in physical amp *terms* while getting up to speed in the virtual amp realm; I imagine this will swap at some point (soon?).