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Old August 5th, 2011, 10:25 AM   #1 (permalink)
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"Clipping the bright cap" on DRRI

I have a '65 DRRI Limited Edition - different speaker from the standard model and wine red / wheat color scheme. I love the amp and I'm not super anxious to mod it, HOWEVER....

I keep reading references to "clipping the bright cap" on these amps and my searches turn up lots of references, but no explanations, for what this is. Can anyone help me out with a simple, lightly-technical explanation for what this mod is, what it does and how it affects the tone and/or responsiveness? Does it affect both the regular and rev/vibrato channels?

Thanks in advance for cluing me in....

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Old August 5th, 2011, 10:35 AM   #2 (permalink)
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The DR uses a cap on the Vibrato channel's volume control to increase the brightness at lower volumes, just like the "bright" or "instrument" channels of the tweed amps. This effect can be mitigated by plugging into the #2 input or turning down the treble control, but some people dislike the effect so much that they chop out the cap entirely. Does the amp sound good to you? Leave it alone if it does.

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Old August 5th, 2011, 11:11 AM   #3 (permalink)
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The cap is a 47 pf disc cap. You could experiment with smaller values like 10 pf or 22 pf to reduce the "brightness". I think the cap is a good thing and adds some edge and definition. I wouldn't just cut it.

You could also try a silver mica cap. You might hear a more pleasing tone.
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Old August 5th, 2011, 11:16 AM   #4 (permalink)
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Here's a chassis layout for a vintage Deluxe Reverb. Look at the volume control of the vibrato channel and you'll see a 47 pf capacitor wired across the input lug and output lug of the volume control. That's the bright cap.

There is no bright cap on the normal channel volume control.


Another part to experiment with: if you look at the bass control there is a 6800 resistor mounted on the back of the pot. That's a fixed midrange control. If you replace it with a 10K resistor it would be like having a standard Fender midrange control set to "10".

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Old August 5th, 2011, 11:27 AM   #5 (permalink)
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Quote:
Originally Posted by telefan62 View Post
I have a '65 DRRI Limited Edition - different speaker from the standard model and wine red / wheat color scheme. I love the amp and I'm not super anxious to mod it, HOWEVER....

I keep reading references to "clipping the bright cap" on these amps and my searches turn up lots of references, but no explanations, for what this is. Can anyone help me out with a simple, lightly-technical explanation for what this mod is, what it does and how it affects the tone and/or responsiveness? Does it affect both the regular and rev/vibrato channels?

Thanks in advance for cluing me in....
One more thing to just consider (BTW I did do the "bright cap clip" to my '68 DR): The bright cap I believe is functional only when the amp is at a lower volume (say under 4) right? So if you crank the amp (I don't, 3-4 is plenty so I did the "clip") the Volume pot sweeps past the operating range of the cap....Am I correct on this?
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Old August 5th, 2011, 11:37 AM   #6 (permalink)
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Originally Posted by Chiogtr4x View Post
One more thing to just consider (BTW I did do the "bright cap clip" to my '68 DR): The bright cap I believe is functional only when the amp is at a lower volume (say under 4) right? So if you crank the amp (I don't, 3-4 is plenty so I did the "clip") the Volume pot sweeps past the operating range of the cap....Am I correct on this?
The bright cap is like running only the high treble frequencies through a volume control set on "10", regardless of where the actual volume control is set.

If you turn your volume control to "10" then, in theory, the bright cap has no effect.
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Old August 5th, 2011, 11:45 AM   #7 (permalink)
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Originally Posted by Gypsyblue View Post
The bright cap is like running only the high treble frequencies through a volume control set on "10", regardless of where the actual volume control is set.

If you turn your volume control to "10" then, in theory, the bright cap has no effect.
OK so the volume has to be all the way up... That will never happen with me! I love my amp, but besides the volume issue, I don't think my DR sounds good all the way up
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Old August 5th, 2011, 11:46 AM   #8 (permalink)
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You don't have to remove it, just lift on the legs off the lug so its out of the signal path. I had to do with my DRRI because it just made my fuzz/distortion pedals too fizzy sounding. Afterwords they had some girth.
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Old August 5th, 2011, 12:01 PM   #9 (permalink)
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+1 Do it.
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Old August 5th, 2011, 12:39 PM   #10 (permalink)
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Mine didn't need to be clipped. Love the sound as is. (I did replace the filter caps and put in a decent set of tubes.)
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Old August 5th, 2011, 04:54 PM   #11 (permalink)
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I hate linking to that "other" Fender related forum, so google "DRRI Fritz mods" and you will discover a detailed description with pics on how to clip the bright cap. It's easy. Be careful inside the amp and drain the filter caps first! Or take it to a tech. Fritz lists other cool DRRI mods also.

My DRRI needed the bright cap removed in order to be pedal friendly. Overdrives sounded like crap at low volume with the bright cap and I never use the Normal channel.
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Old August 5th, 2011, 05:30 PM   #12 (permalink)
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I replaced the volume control on my old '65 DR with one that has "pull pot" switch so I can elect to use the bright cap by pulling the control out. On my DRRI I left the cap in, and at very low volumes at home it is too bright. However at gigs the volume goes up to 4 or more and the effect becomes subtle and very nice - a touch of shimmer on top of the sound. I'm leaving it for now.
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Old August 6th, 2011, 09:25 PM   #13 (permalink)
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Wow, thanks much for all of the info and explanations! I really love the sound of my amp as is - no plan to mod it. I just wanted to know what people were talking about when they talked about this particular mod. Thanks again.
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Old August 7th, 2011, 05:04 PM   #14 (permalink)
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Quick question regarding the brite cap and tone.....does turning the treble down at a given setting accomplish the same thing?
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Old August 7th, 2011, 05:19 PM   #15 (permalink)
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Originally Posted by mikiedreb View Post
Quick question regarding the brite cap and tone.....does turning the treble down at a given setting accomplish the same thing?
No. But if your amp sounds to bright to you by all means turn the treble control down. I mean, that's what it's there for!
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Old August 7th, 2011, 11:22 PM   #16 (permalink)
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I got a mint used 2010 DRRI. I put in JJ 6V6s (more like a 6L6 tube with more headroom and rounder sound); a tungsol 12ax7 in V1 and a EH 12AY7 in V2. Also did the bright cap 'clip' this weekend (needed if you use dirt pedals in channel 2). Used a low wattage solder iron and toothpicks etc to push one end of the capacitor lead through (did not have to remove the circuit board but you need to be quick so as not to lift the pad). Much better without the bright cap. Can't make up my mind which channel I like more 1 or 2 asthey are both similar and have a lot to offer. They both take dirt pedals much better. The reason I put in a 12AY7 in V1 is I find that often lower gain tubes help dirt pedals sound better.

I sweated over 'removing' the cap but now that I have done it, it was the right choice by leaps and bounds since I use dirt pedals.
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Old August 8th, 2011, 02:42 AM   #17 (permalink)
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It is an easy mod and it is reversible.
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Old January 8th, 2012, 07:30 PM   #18 (permalink)
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Easy way to clip C10 = bright cap.

Hey,

I was helping a friend work on a DRRI - just a retube and rebias -
and I noticed that the bright cap mod ( on the vib channel) could be
done without taking the green control board off (I think).

If you look just on the normal-channel side of the
vibe-channel vol knob there's a trace that runs from
the bright cap to the pot lead.

Why not just cut that trace and put the usual switch across that
(now interrupted) trace? Back to stock is just putting a jumper
over that same trace.

Is this a better way than taking off that entire board or am I missing
something?

Regards
p
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Old January 8th, 2012, 07:40 PM   #19 (permalink)
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Very easy to make this mod. Just unsolder one leg of the cap and pull it away from the pot slightly. Try it in any variety of settings and see how you like it. Most folks like it removed, but you may not. Easy to put back if that's the case.

I did one for a guy who was using a reverb pedal through the normal channel he hated that cap so much.
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Old January 20th, 2012, 04:51 AM   #20 (permalink)
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I understand how to do it if you lift the pot board. My question is whether anyone
has either noticed (almost certainly) or objects (for good technical reson) to just
clipping the trace under the cap on the other side ( i.e. the visible side) of the pot board without having to uncrew 50 gazillon knobs and pot nuts.

If you do it this way there's no lifting a cap leg at all...

If I'm unclear on what I'm suggesting I'd be glad to try again.

Thanks
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