If you want to add the bass cut capaciter you may want to use a toggle switch to access or wire your tone control bass cut instead of treble cut ... or you can add a jazz bass pickup in the mute cavity ...
or ... just turn up the treble and turn down the bass ...
What's "wrong" with a new 4003?
Moderators: rickenbrother, ajish4
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jwr2
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prague
On my 4003 I had unwound the pickups from about 12k ohms to 7.5k ohms and added the .0047 cap to get that '60s-'70s tone. After a while though, I took the cap out because I started to miss the lower-mid growl the bridge pickup had. I'm really happy I unwound the pickups though; they sound so much clearer now, like someone took the cotton out of my ears. Another modification I did: I replaced the 250k volume pots with 500k ones (the tone pots were already 500k.) That brightened up the tone a bit as well. (As you can probably tell, I like a bright, clear tone. Once in a while I'll roll off some treble if needed for the music, but most of the time I like it wide open.)
The tone caps just bleed the treble to ground, the more you turn the pots down the more treble goes to ground, the treble pass cap from the pickup is wired directly in the path of the output of the treble pickup to the amp (series) and blocks all the bass and a lot of the low mid. They are wired differently. you could get different sounds experimenting with different caps if you wanted to, from sharp treble to almost no bass cut. The less capacitance the higher the cutoff point (I think). Caps are also used as crossovers in many hifi speakers, wired in series they are treble pass for tweeters, wired in parallel across a woofer (cheap speakers only) they act as treble cut caps. Don't touch the 2 identical tone control caps, only the third cap going from the treble volume pot to the 3 way switch.
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prague
Thanks for those links. Ric sure does wire things oddly. Typically, the wiper of a pot (see the Volume pots) isn't used as an input, since the resistance seen by the source (pickup) changes. It would be interesting to hear why this was done.
The Volume pots are wired as rheostats, or like a T-pad. At an even setting (125k/125k) half of the pickup voltage is developed across 125k to ground, while the other 125k is in series with the input impedance of your amplifier. Plus, the 4.7nF figures into the cutoff frequency. The behaviour is all easy enough to calculate, but it's just a bit odd as to why. Could be it just sounded cool, which is 100% valid.
As you turn up the volume on the bridge/treble pickup you also change the slope of the RC "filter" (the volume path is a filter). The cutoff frequency at full volume is about 135Hz, but at half resistance (125K) it is about 290Hz. This is when not plugged into an amp.
Interesting.
The Volume pots are wired as rheostats, or like a T-pad. At an even setting (125k/125k) half of the pickup voltage is developed across 125k to ground, while the other 125k is in series with the input impedance of your amplifier. Plus, the 4.7nF figures into the cutoff frequency. The behaviour is all easy enough to calculate, but it's just a bit odd as to why. Could be it just sounded cool, which is 100% valid.
As you turn up the volume on the bridge/treble pickup you also change the slope of the RC "filter" (the volume path is a filter). The cutoff frequency at full volume is about 135Hz, but at half resistance (125K) it is about 290Hz. This is when not plugged into an amp.
Interesting.
I believe the reason they are wired that way is because if one volume control is turned down all the way this doesn't cut off the output as it would if the wipers were connected to the output jack, which would be shorting the jack to ground. This is how a lot of two pickup instruments are wired, for example, Jazz Basses are wired this way for this very reason. On single pickup instruments it is best to wire the wiper to the output jack so when the volume control is turned down there is no load on the input of the amp as it is in effect shorting the input of the amp to ground.
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prague
Right you are, Jeffrey. The two pots are a quasi T-pad. I might even experiment with my Jazz and wire a passive blend knob. It is helpful when playing live.
A dual pot with reverse log tapers would be "ideal" but these aren't as common and do add to the expense. They also don't allow the two pickups to be at maximum.
Great info, everyone. Thanks.
A dual pot with reverse log tapers would be "ideal" but these aren't as common and do add to the expense. They also don't allow the two pickups to be at maximum.
Great info, everyone. Thanks.
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mortivan