Cap bypass surgery

morrow · Post by **morrow** » Wed Mar 16, 2005 12:20 pm

I am a newbie here and have been trying some searches on a topic that I am sure has been covered a million times but I am looking for simple instruction on how to do the cap bypass mod.

I will have a tech friend do the operation and although he has a Ric ( an old checkerbound mapleglow) he has never done the op.

I apologise for asking about something that has been hashed out time and time again but I just haven't been able to get the fine details.

jaymi · Post by **jaymi** » Wed Mar 16, 2005 12:33 pm

welcome...the cap can be removed and a wire put in it's place and voila!! MORE back pickup..

johnhall · Post by **johnhall** » Wed Mar 16, 2005 12:43 pm

Better yet, leave the cap in place and solder a wire across it. No damage during unsoldering that way, easy to remove it later, or just give the wire a cut to quickly disable it. Use a switch instead then you can have your cake and eat it too.

rictified · Post by **rictified** » Wed Mar 16, 2005 1:01 pm

That's what most of us do here, just soldier a wire over it like JH says. I figured out a way to use one of the tone controls like a variable cap control also and it's completely reversable electrically and cosmetically. The only down side is that if you significantly turn down either volume it cuts the treble, it gets noticable at around 60% or more cut on the volume control.

jps · Post by **jps** » Wed Mar 16, 2005 3:23 pm

I used to have a pickguard with a VVT control setup and a switch to select a piece of wire or the cap on my '73 4001

Now I have the original PG back on with the cap bypassed and a V63 horseshoe in her!

jwr2 · Post by **jwr2** » Wed Mar 16, 2005 5:19 pm

take out the cap and put some balls is your bass!!!

rickenbrother · Post by **rickenbrother** » Wed Mar 16, 2005 6:28 pm

Like Mr. Hall suggested:

Wire a SPDT switch in parallel to the .0047 cap like I have here and you can have both sounds. It's a very simple mod.

rictified · Post by **rictified** » Thu Mar 17, 2005 7:13 pm

with my mod you can have it all the way in or out like a toggle switch plus anywhere in between and you don't have to make a hole in your pickguard, it's a continous cap control like a volume or tone. It's easy to do also, although some other people here seemed to have a hard time because I could never get a big enough schematic uploaded.

rickinroma · Post by **rickinroma** » Thu Mar 17, 2005 10:02 pm

what's the exact use of this "cap bypass surgery"? I mean will the pickup sound more trebly or warmer, or will you have more volume or what?

paul_yan · Post by **paul_yan** » Fri Mar 18, 2005 6:09 am

Francesco,
Yes, more volume and fatter. The .0047 mfd cap is a "high-pass/low-cut" filter cap that cuts everything below about 400 Hz which is pratically the "main body" of a bass' sound. Only high and high-mid "clank" is let through. With the cap bypassed, you get a full bass sound which is almost two times louder than the capped one. '70s 4001 basses came with the cap.

rictified · Post by **rictified** » Fri Mar 18, 2005 6:21 am

The net effect is more warmth and more volume, and less apparent treble even though it is not changed, the cap filters out bass and mids, the lower the frequency the more the cut. When I use my treble tone to add more cap into the circuit (the bass tone controls both tones, and the treble tone is like a variable switch) I get more and more of a scooped sound and less presence. It's kind of nice because sometimes if you cut the bass volume you get a lot of low mids as the treble pickup predominates and you can control that with the cap control, with the switch it is either on or off.

rictified · Post by **rictified** » Fri Mar 18, 2005 6:23 am

Yeah, even the early 4003's had it, I think JH eliminated the cap when he took over sometime in late 84.

morrow · Post by **morrow** » Fri Mar 18, 2005 6:31 am

Thank you one and all....I think we will be doing the mod Sat or Sun.

I play in the house band for a jam every Sunday and it will be nice to hear her at stage levels. ( not excessive ).One guest that generally comes every Sunday for the jam is one of the local jazz monsters and teachers so I will also get a chance to hear it played ( very well I might add) out front.

I have put a lot of time on this bass at home and I must say that I am really thrilled with it. I have a fair number of others so that is saying something. ( I had bought a new G&L five string about six weeks ago and I haven't touched it since the Ric came in )

I can't wait untill Sunday night.