Both pickups on, bass rolloff capacitor question...

[brensabre79]

So I recently aquired a lovely Lakland Decade. thing is, the old Jazz Bass V-V-T controls never worked for me. On all my Jazz basses I have replaced with a 5 position pickup selector switch, then volume and tone controls.

This bass is a little different though. For one, the pickups are Humbuckers (and very nice they are), but secondly, they are spaced very far apart - a bit like a certain type of bass that shall remain nameless (although this one is certainly not a copy of any other bass). The result is that with both pickups on full volume, there is a tremendous loss of level due to the comb-filtering effect of running the two pickups in parallel. Most of may basses are also active so this isn't really a problem, but I'd like to keep this one passive and the volume drop is a huge problem for me. the whole point of the pre-set switch is to quickly dial in the sound I want in between songs.

Now, I've heard that on a certain make of bass (where the pickups are placed in a similar position), they add a capacitor in line with the bridge pickup to roll off the lower frequencies when both pickups are on full. the idea being to get the just mid & high frequencies from the bridge pickup, with the full range of the neck to avoid the volume drop. So I'm interested to try this out. But I have no clue what value capacitor to use. I do realise it might be a bit of trial and error, but I was wondering if anyone had tried a similar thing and could give me a good starting point?

My proposed diagram is below, the capacitor in question marked in [color=#ee82ee]pink[/color]

Thanks for looking! Any advice welcome



[color=#000000]P.S I know the pickups look like they are out of phase on here[/color], but they are not reverse wound on the BPU so need to be.

[ikay]

This thread says it's a .0047 [size=3][color=#000000][font=verdana, arial, sans-serif]uF cap (see 7th post down by Teleharmonium) - [/font][/color][/size][url="http://www.thegearpage.net/board/archive/index.php/t-689218.html"]http://www.thegearpa...p/t-689218.html[/url]
[size=3][color=#000000][font=verdana, arial, sans-serif]This other thread says the same thing so probably right (also 7th post down) - [/font][/color][/size][url="http://www.rickenbacker.com/forum/viewtopic.php?f=5&t=12786"]http://www.rickenbac...php?f=5&t=12786[/url]

I like your 5 way switch BTW, very neat. I take it the 500k preset pots are used to back one pup off slightly when both pups are on to get the sweet spot?

Edited April 28, 2014 by ikay

[brensabre79]

Brilliant. Thanks iKay (again!)

Yep pre-sets are basically to have, say, 100% NPU with 60% BPU but as a switch position instead of having to dial in each time. When I've done this on my other basses I will have it open while I set the pre-set pots to get just the right sound.

For the centre position I wanted both pickups 100%, but this results in a huge loss of mids (and volume) so thought I'd experiment with the capacitor trick. Although i suppose ideally a mid boost would probably do the trick, I don't want to go active though.

Edited April 29, 2014 by brensabre79

[Beer of the Bass]

I have a bass-cut capacitor on my bridge pickup on a push-pull pot, otherwise the bass is wired like a Jazz. I can't remember what value I used, but I think I copied the Rick value. I like the effect, but I tend to use it in conjunction with the two volume controls, with the neck on full and the high end of the bridge pickup dialled in to taste.

[brensabre79]

Thanks beer, interesting... I might try that in conjunction with the preset pot then. Or maybe put a switch for the cap mod on the tone control. For me the switching is essential as I rarely get to audition a tone setting between songs, so I need to just pick a setting and go with it knowing exactly what it will sound like

[dannybuoy]

Would flipping the phase of one of the pickups help? Just desolder and swap the wires around on one of them. I had the same problem on a Jazz once, made a world of difference.

[brensabre79]

Thanks Danny.
Wouldn't that mean the two pickups are just out of phase though? i.e. thin and nasal sounding... with no bass?
My Sabre had an "out of phase" switch for the two pickups. Has to be the single most useless switch on a bass ever, including one that's not wired up! I swapped it for Series/Parallel switching instead.
Maybe your Jazz was out of phase to begin with Danny?

Interestingly, I spoke to Lakland via email - very nice people. According to what they say, the humbucker circuit should have 250k pots, and the single coil circuit 500k pots. I'm not convinced this isn't a mis-print though to be honest. But the wiring diagram confirms that the above diagram is correct - i.e. pickups seem out of phase. Probably because they don't do a neck and bridge version, just a universal one...

[dannybuoy]

My T40 had that switch also, it's only use was being able to select which of the coil of the bridge humbucker was in use when set to single coil mode!

The pickups in my old Jazz had both black wires going to earth and white going to the pots - but they were out of phase and flipping them sorted out.

Makes sense to me that if you sum two pickups and the result is less volume, there must be some cancellation going on, so flipping one of them should produce the opposite result, i.e. louder than one pickup soloed?

[brensabre79]

[quote name='dannybuoy' timestamp='1398761202' post='2437233']
Makes sense to me that if you sum two pickups and the result is less volume, there must be some cancellation going on, so flipping one of them should produce the opposite result, i.e. louder than one pickup soloed?
[/quote]

Ahhh if only it were that simple

Yes, you're right that if the pickups are out of phase you will get a significant loss of both volume and low frequencies, resulting in a rather nasal middly sound.

However, if the pickups are in phase, turning them both on 100% will usually result in a slight loss of volume as well as some low mids. The reason for this I think is partly to do with the combined impedance of the two pickups (a bit like speakers in parallel), but also to do with the [url="http://www.soundonsound.com/sos/jun13/articles/qanda-0613-3.htm"]comb-filtering effect [/url]where certain frequencies will cancel out. This will differ depending on the distance between the pickups. on a Jazz bass it's not too bad as basically the pickups are not that far apart. The effect is more prominent on my 70s spacing Jazz bass, but not that bad.

On this particular bass, one pickup is right on the end of the neck, the other is roughly where the MusicMan Stingray Bridge pickup goes - so there is a larger distance between the pickups, and a larger amount of the combing effect when both are on full... Meaning that if I select both pickups full up there is an unacceptable loss - so either I turn down until selecting both pickups then turn up for that setting to compensate, or find another solution...

It's accepted on any 2 pickup passive bass that a certain amount of percieved volume drop happens when both pickups are on. however, I'm trying to overcome this with circuitry the best way i can find The shocker is that Mr Hall's company seems to have used two solutions that work. The other being running in Stereo and letting two amps fight it out.

[iiipopes]

Gentlemen, Time. If the bridge pickup is in the same place as a Rickenbacker 4001/4003, then the .0047 capacitor works well. But if the bridge pickup is in the vicinity of a Jazz bass bridge pickup, or even closer to the bridge, there is so little string excursion comparatively that the .0047 capacitor is too low in value, and not enough signal will be passed. The value to try is the .01 microfarad. I use this on all of my basses, and even Rickenbacker uses a .01 inline on the bridge pickup of the 4002, since that bass is a 2-humbucker bass with the bridge pickup in the Jazz Bass bridge position.

Now, there is no cure-all. This will still drop the level of the bridge pickup slightly. But it leaves the fundamental frequencies intact so they are not affected by either the impedance drop or the comb filtering, and that is the primary goal.

Edited April 29, 2014 by iiipopes

[brensabre79]

Thanks iiipopes.

I'd say it's a little further back than a R'backer 4001 yes, not as far as the 4002 though.
I shall try the .01 microfarad as well as the .0047 suggested earlier and see what works best. This gives me a pretty good range to experiment with.

[brensabre79]

Quick update on this. I tried the .0047 (as it arrived in the post yesterday). I popped it on a DPDT on the tone control and went out to my gig. Well it made a huge difference. I was really pleased with the result too. After i'd wired in the above circuit, with the pre-sets and started using a compressor, alot of the volume issues of both pickups disappeared anyway. Adding the capacitor mod basically gave me another tone to work with.

In short (no pun intended), with the capacitor in place it sounds like that classic Ric tone. lots of bass and some quite pronounced mid/treble from the bridge pickup thrown in. Switch it out and its scooped like a Jazz on both pickups. Another interesting sound is with 50% BPU, 100% NPU and the capacitor in place. So I have about 7 quite distinct tones as presets on the bass now. 14 if you include the coil tap!

I'm chuffed to bits with the mod, so thanks for your help guys

[ikay]

Good to know that it worked. I'm keeping a note of your nifty 5-way switch for future reference!

[brensabre79]

Ah no worries. There's a version I did for my Jazz bass a while ago on here somewhere too. That had a Series/Parallel switch on it instead of coil tap