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Author Topic: 2204 - reinserting the bright cap  (Read 1792 times)

gwEm

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2204 - reinserting the bright cap
« on: October 27, 2010, 05:00:55 PM »
i removed the 1nF bright cap across the volume control some time ago. But its try that the amp loses top end when I reduce the volume control.

Was thinking of putting it back, with a slightly more sensible value (1nF is clearly too bright).

Has anyone experimented with this? Was thinking of trying 100pF.


EDIT: I also noticed a while ago theres a couple of 10uF electrolytics in the power amp. Is it worth replacing these with a higher quality type?
« Last Edit: October 27, 2010, 05:09:44 PM by gwEm »
Quote from: AndyR
you wouldn't use the meat knife on crusty bread but, equally, the serrated knife and straight edge knife aren't going to go through raw meat as quickly

jpfamps

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Re: 2204 - reinserting the bright cap
« Reply #1 on: October 27, 2010, 06:09:41 PM »
This is a very sensible course of action. You will see values down to 47 pF (eg Brown Tolex Deluxe) in amps, so 120 pf would be a good starting point.

I've succesfully used values of 47 - 270 pf in amps.

The effect is akin to the loss of treble when you turn down your guitars volume control (if you ever do thsi), and is caused by the increased source impedance forming a low pass filter with the input capacitance of the next valve (made worse by the Miller effect).


HTH AMPS

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Re: 2204 - reinserting the bright cap
« Reply #2 on: October 27, 2010, 07:24:29 PM »
with the 2204 (or any amp really), I find it depends on what you want out of the amp.

if you're the type of guy who wants to set the gain almost full and cause structural damage at their typical gig, then use a 4700pF bright cap - you'll get REALLY snarly high mids if you have the gain on around 7-8.

if you want a usage range of gains all the way through the rotation of the gain pot, 100pF is perfect and doesn't get too ice-picky when the gain is turned down.  500pF is the most you'd want to use here, imo.


gwEm

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Re: 2204 - reinserting the bright cap
« Reply #3 on: December 29, 2010, 06:15:39 PM »
finally got around to doing this, should have done it sooner really, only took 15mins.

anyway, its a great mod, far better than just removing the thing. Thanks HTH and JPF.

having played around with it for a while, i think 100pf in this spot will be hard to beat for linearity in tone as you roll it. i tried it with a strat, just to be sure.
Quote from: AndyR
you wouldn't use the meat knife on crusty bread but, equally, the serrated knife and straight edge knife aren't going to go through raw meat as quickly