500pf Treble Cap

[mcrracer]

There is another thread where one guy says going down to 250pf darkens the tone and another guy says it brightens the tone. Which is it? I am in the middle of a build and want to get it right. I want the amp to be LESS bright than with the 500pf. Thanks

[rooster]

Man, this might get interesting...

The short of it is that the 250pf cap mod should have stripped some upper mids out of the signal and made the modified amp BRIGHTER, not darker as reported.

So you need to build your version and see what you end up with. 500pf is the fattest treble cap used in any tone stack I know of. Which is to say that the Express tone stack is very mid-heavy by design. The amps that people have - that are reported to be 'bright' - well, I don't have that issue with my builds. I suspect that there is a lack of bass in these amps, which leaves the impression that they have too much treble. But I am not here to speculate on that really. What I am saying is that the stock tone stack value of 500pf is not what is making the amps bright. I hope this is clear.

I have played a friend's Epress that is lacking bass but I, as yet, have not seen it to trouble shoot it. But it must be what the others are experiencing so it doesn't seem to be unique. Build your amp stock, then consider some parts changes if you think you need it, that's my advice.

[leleduke]

My express has more bass than my D'lite.

[mcrracer]

My express has more bass than my D'lite.

Which cap did you use? Did you change your coupling caps from the schematic values? Thanks

[leleduke]

My express has more bass than my D'lite.

Which cap did you use? Did you change your coupling caps from the schematic values? Thanks

Everything is stock other than the VVR. The amp is breaking in real nice.

MD

[jjman]

Using Express values, the top line is using a 500pf, the bottom a 250pf. Both with all tone controls on 50%.

[M Fowler]

I am building another Express head right now and using stock components. With my Express combo I used stock components and had no problems.

But the Ceriatone built by Nik was a different animal and needed many adjustments.

Mark

[Jana]

When you are talking about tone stacks it is not a matter of simply swapping one cap for another to get "brighter" or "darker." The post by jjman is an excellent example. At first glance it would appear that the 250pf cuts more highs. But, do you see the shift in notch frequency? The 250pf moved it up, as would be expected. So, the lesson is, chose the cap values/slope resistor to set the frequencies that you want. Then, adjust the tone controls to give you the amount of those frequencies you want. The tone controls are adjustable potentiometers for a reason.

This would also explain why choosing a larger value treble cap would appear to make the amp darker, not brighter. The larger value shifted the band that the treble control is affecting down, hence more meat, more substance to it.

[Buschman]

The 250pf will give you a more of a Fender sounding edge. The 500pf will have a bit more bark or authority to it. You are letting more frequencies through the treble control. It is an easy change once the amp is built.