Express Amp - Alternate Brite Cap Values

[RJ Guitars]

I did a search and didn't come up with much but I am confident this topic has been worked over before... I just finished up an Express that someone before had started and I used the original spec brite caps, but I didn't really care for that combo much.

I did find a little bit of discussion that was useful - http://ampgarage.com/forum/viewtopic.php?t=8849

It does seem to me that the 500pF brite cap makes this awful treblish grating sorta boost, while the 100pF seems to be more reasonable. That seems counter intuitive to me but I already had the amp packed up and shipped before I thought to look and make sure I had the right one in the right place. However, as I read about this topic it seems that other folks have the same experience... so a couple questions:

1 - Is the express more trebly with the 500pF brite cap than the 100pF

2 - Has anyone settled on a couple good alternate values?

I was sorta thinking that I'd try a 100pF and a 250 pF.

Any thoughts?


3) - As the bonus question - has anyone looked into this further - http://ampgarage.com/forum/viewtopic.php?t=5422 this sounds like a win win situation?

rj

[Colossal]

RJ,

Right now I have 100pF and 250pF in my Liver-mule. Most of the time however I run it with the bright switch off (Glen's suggestion). Thickens the tone slightly but still plenty of treble on tap. When I switch in either cap, the effect is noticeable but pleasant. The 250pF cap has a bit more added shimmer, maybe sheen is the better word.

Dave

[JamesHealey]

I've found moving the tonestack treble and bass leads further apart tends to effect the amp as does the two wires to the power tube control grids from the back end of the long tail pair.

I'd suggest playing with the spacing of these wires before giving up on the 500pF.

I really dig the 500pF with the express when it's dialed in right.

[hbamp]

I made a few express clones and always end up between 150-370 pF.
I like to combine silver mica with styroflex.

[redshark]

I agree with jamesHealy that playing with wires in the tone stack can help with the voicing of the amp to make it not as bright.
I think the values of 100pF and 500pF is what the express needs for the bright switch if the amp is played as Ken voiced it. Than means with a 4x12 cabinet. Also the 500pF value is used only with guitars that have high output humbuckers and lower value pots like Gibson 300k volume pots. That setting balances for the mudiness that can be heard playing that types of guitars.

[rooster]

I think, given the particular amp volume, the particular guitar and speaker cab, the stock values could work.

Fender used 120pf on the larger BF amps, 47pf on the BFDR, and Marshall used 500pf for a brief time. The Marshall was definitely connected to a 4/12, the Fenders were open back. It could well be that Ken was thinking: 100pf/open back cab, 500pf/closed back cab. Dunno for certain, just speculating.

All of this said, I use 50 and 100pf values and typically I leave it off.

[M Fowler]

I have no comments on this subject

[guitarsnguns04]

I use the stock values but what I've found is that the 500 is unusable when the amp is new...as they break in it seems to get darker and now I use the 500pf setting almost all the time.

[Roe]

This works for me:

100pf with vol around 3
500pf with vol around 5-6

[RJ Guitars]

I ended up using a 100pF and a 250pF - in both cases they are still a bit brite for me. I am curious if I'll see some of the edge come off after they have a chance to burn in for a while. I must admit that I see the potential for this to be an audible illusion that is caused by the loss of my high frequency hear as I play the amp more and more - it's pretty loud.

I also wanted to share the layout I employed in an attempt to minimize the lead lengths between the brite caps and the volume pot.

rj