I sold my yamaha active 5 string a few months ago as id sort of given up playing bass on a regular basis but within days was asked to cover as gig. I picked up a budget Tanglewood Rebl 4k just for the one gig and tinkering at home.

It has 2 vol pots, 1 for neck and one for bridge with a global tone pot.

The neck pickup is fine but the bridge is quit weak in comparison. If i dial the kneck flat out then add some bridge there is no difference until about 95% then the vol drops back as if the bridge pickup is working on its own

in reverse if i dial the bridge flat out and add some kneck there is no difference until the last 5% when the sound deepens, again its at a lower level until i back off my bridge pickup.

does that make sense.

I know its a cheap bass but it plays ok for me , has a small translucent purple body so it looks nice hanging on my office wall.

So is there a fix, are the pots/pickups possibly phasing or something or just a faulty pickup. Would a pickup switch be of any use?

Bit hard to diagnose over a forum but its a start

cheers

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I eat kebabs when i'm sober!

Sounds like there is a huge difference in the quality control from the factory and probably a bad pickup slipped by. If it is under warranty you could ask them to ship you a new pickup. If not - I'd suggest you get something over the counter. Cheap but decent pickups are Select by EMG.
http://www.emgpickups.com/products/category/20/1

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www.descentintomadness.com

Sorry 4TrackMadman, but I think you are leaping to assumptions and then making a further leap to a false conclusion. Although, admittedly, the pick-ups on a such a budget instrument are never going to be great.

Dave, in all probability what you are experiencing here are two fairly common issues that are generally easily resolved but are working together to make things seem even worse than they really are. The first is a simple set-up problem, and the second is a flaw with the standard way of connecting up multiple pick-ups with individual volume controls.

The difference in volume between the neck and middle pick-ups is the basic set-up issue. But don't be too hard on Tanglewood quality control or the distributor/dealer because this is something that a lot of otherwise very qualified and experienced guitar techs often ignore. They make sure that the action, intonation, and mechanical set-up is fine. They also test the pick-ups and the wiring to make sure everything is working properly. But what they fail to do is to balance the pick-ups properly for output.

Basically, as you move the pick-up position from the bridge towards the 12th fret, the strings vibrate on a wider and wider arc. The output from a pick-up is proportional to the mass of the vibrating string AND the distance it moves. So, all other things being equal, the closer the pick-up is to the bridge, the less output it will have. This is the reason why Strat pick-ups sets have a higher output pick-up in the bridge position and why humbucker sets are usually sold with a higher output pick-up for the bridge.

However, you have a degree of control over the output of a pick-up by adjusting how close it is to the strings. The closer a pick-up is to the strings, the great it's output. And this is what we use to balance the pick-ups when fine tuning the set-up. Because the magnets in the pick-up can interfere with the string's vibrations if they are too close, the rule of thumb is to adjust the loudest pick-up by tightening the mounting screws to move it further away from the strings. But you can make the quieter pick-up louder by loosening it's mounting screws to move it closer to the strings. Another rule of thumb is to keep the pick-up a minimum of 1/4" away from the strings when they are fretted at the last fret. So, a little judicious juggling of the pick-up heights should bring the pick-ups to similar volumes.

The second problem is in the standard (or 'traditional') wiring for pick-ups with individual volume controls. And the problem is the same whether you use a pick-up selector switch or not, so no need to consider butchering your bass to add a switch. Whether you use a selector switch or just link the outputs from the volume pots, you are connecting the pick-ups in parallel. With the pick-ups in parallel each pick-up places a load on the other one, and when you add a variable resistor (a volume pot) to each pick-up they start to interact in unusual ways which make the responses to volume changes quite extreme and difficult to control.

This has been frustrating guitarists for many decades now, Les Paul's and other guitars with the same wiring suffer exactly the same problems. But there are a couple of simple things you can do to improve matters.

In traditional wiring, the hot wire goes to the outside tag of the volume pot and the output from the volume put comes from the centre tag (which is the wiper in the switch) to the output socket. If you swap these two wires over so that the hot wire from the pick-up goes to the centre tag and the outside tag goes to the output jack, it changes the way that the pots load the pick-ups and allows you finer control when blending them together with the volume controls.

Where it MIGHT be worth making a further change is by swapping the volume pots for better quality ones. It's quite difficult to make a pot with a true logarithmic curve so most log pots approximate the log curve. The cheaper the pot, the worse the approximation is. And that tends to concentrate it's effect to the extremes of it's travel, all at the beginning and end.

So, step one balance the pick-up outputs by adjusting their heights. Step two, swap over the connections on the existing pots to make them work better. Step 3, replace the pots with better quality ones of the same value. And only then think about replacing pick-ups, but if you do want to change them here's a handy hint... Schaller Golden Age pick-ups are very, very, good and exceedingly cheap for what they are too.

Andy

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When the going gets weird, the Weird turn Pro.

I'm confused by in the reference to 'Schaller Golden Age'.

I thought Schaller did Golden 50's and Stew-mac did a golden age pickup range, I didn't think they were linked in any way, or do I have that wrong?

Thanks,

Grant.

<EDIT> I can't find a Schaller golden 50s bess pickup so I'm assuming you mean the StewMac golden age ones.

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I've never liked a solo violin, you need at least five for a proper fire.

Edited by RhinoTime (21/08/12 11:04 AM)

Thanks for the replies, especially the in-depth post Andy. Devon was great by the way, never saw any bands but the relaxing, fishing and surfing was great.

Right. I went to a rehearsal last night and used the bass for the first time through a borrowed ampeg bass amp (Ba115). I found i had to really drive the amp to get a decent vol level just in the small space we were using, and we were just practicing quite quietly. my lack of vol was not just my opinion from where i was standing but from everybody else. Tired a lot of EQ variations but to get a nice rounded bass sound with just enough punch it was vol that needed a lift. This suggests the pickups are inferior to start with. What more can you expect form a £179 guitar ( i paid £100 second hand). I know from using the amp before with other bass guitars it capable of rattling windows in small venues.

I actually really liked the sound the guitar and amp produced, played softly it was a nice deep round smooth sound but quite punchy when played more aggressively. A really great tone when doing Van Morrison's Brown Eyed Girl.

I have looked at the pickup position to start and recorded numerous single string hits to compare the levels. On the neck pickup the current strings are within 1 or 2 db. The bridge pickup has a similar difference across the strings but is on average -8db lower in output. I know these figures are not accurate as to the pickup outputs but more of an A/B comparison. Pickup lowering is not working as they seem to be as low as they will go as it is with the average distance between string and pickup being 4mm. All the screws are really tight so I'm not going to force them to investigate further until after the gig on sunday. The action is fine so i want to avoid lifting the bridge.

Thanks

Dave


The pot cover screws on the back are rounded and are as tight as hell so i can't get into there either. Another post gig job

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I eat kebabs when i'm sober!

Yes, you are right Grant, I conflated the two in my mind.

Actually, I did mean the Schaller Golden 50's not the StewMac Golden Age (although they are very good pick-ups with great value too).

However, a visit to the Schaller site is bad news, looks like they no longer offer any Bass Guitar pick-ups. I fitted a pair of their Jazz Bass Golden 50's to one of my brother's basses a year or two ago and they are excellent pick-ups.

So, sorry for the confusion and even sorrier to hear that Schaller are no longer making their excellent Bass Guitar pick-ups. However, I see they still make their Zither pick-up

Andy

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When the going gets weird, the Weird turn Pro.

Glad you had a good time in North Devon Dave...

OK.... by the sound of it someone has screwed in the pick-up mounting screws as far as they will go and then made sure they were tight. But it is a concern that the strings are so close to the pick-ups, 4mm is half the distance it should be and the pick-up magnets would be interfering with the string vibration.

I would still be inclined to remove the pick-ups and give everything a good check. It is possible that the pick-ups have dropped deeper into the body but the pick-up covers are wedged in tight. I would also make sure that there is a foam rubber pad or springs under each pick-up to help it adjust properly. I would also lubricate the threads of the pick-up mounting screws with candle wax before refitting them because they shouldn't be so tight.

Those pick-ups really should be further from the strings. And that will need to be resolved even if you decide to get replacement pick-ups.

While you are checking the wiring and swapping the connections on the pots you can measure the pick-up DC resistance. It's a crude measure, but you would expect them to read between 5k and 8k for a passive pick-up. If it is a lot lower than that, especially the jazz bass pick-up which is quietest, then the coil might be damaged/shorting and then you need to decide whether or not it's worth replacing the pups

Andy

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When the going gets weird, the Weird turn Pro.

Andy,
Have you ever tried putting two pick-ups effectively in series with a linear pot and taking a feed from the wiper?
Need some experimentation with track value but I would say 22k for starters.
Anyway, I would go active and fit a lil' mixer in there!

Ooo! And I did have a bass with a pick-up on a slide! Traded it for a Mersey Super 15.

Dave.

Quote ef37a:

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Andy,
Have you ever tried putting two pick-ups effectively in series with a linear pot and taking a feed from the wiper?
Need some experimentation with track value but I would say 22k for starters.
Anyway, I would go active and fit a lil' mixer in there!

Ooo! And I did have a bass with a pick-up on a slide! Traded it for a Mersey Super 15.

Dave.

---

Never tried that Dave, but filed away mentally for future reference. Thanks Although I do recall reading about it being used in the past and there is one big downside, the blended pick-up positions can't have either pick-up on full output. Replacing one restriction with another one. Which might be why...

I had a feeling you would opt for the active solution, there's a reason why basses started going active in the late 70's

Bass with a pick-up on a slide... that sounds to me like the Dan Armstrong designed Ampeg, or one of the later copies.

Andy

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When the going gets weird, the Weird turn Pro.

Morning A,
Yes it was a VERY cheap copy of something! It has been so long ago that I am not sure how I came by it, probably dragged in very early one morning by Son 20years or so ago. I still have a 100W TUAC solid state amp head here gathering dust, cost dad 25quid IIRC along with a box of guitar leads!

Dave.

Having a revisit

Now I'm off work for a month its time to do a few jobs and investigating this issue further is todays job.

Have managed to remove pickup screws and found there is no height adjustment, they are just bolted down with a 10mm strip of hard foam padding. neck pickup is made of 2 smaller pickups wired in series.

wiring as it is



i assume its a capacitor on the right hand pot

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I eat kebabs when i'm sober!

Good news and Bad news Dave.

The Good News is that the volume pots are correctly wired, so no need to swap the wiper and output tags on the pot. I've found a nice little piece by Ken Fischer of Trainwreck Amps that explains what is happening.

However, the Bad News is that your problem lies elsewhere.

A couple of things to check. You need to make sure that the Volume pots are Log ones, not Linear. And as you have enforced time on your hands you might enjoy reading The Secret Life of Pots in the FX Skills/How Too's section at GEOFEX. It might well be worth getting a couple of quality replacement 500k log pots first, but the Secret Life of Pots has some very good tips on modifying the taper of pots among other things.

Hope that helps keep you busy and brings you a step closer to solving the problem

Andy

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When the going gets weird, the Weird turn Pro.

Thanks Andy. 20 Years ago that would of been some very easy reading after just completing my C&G Micro computer technology course. Sadly its hard going now, as most things seem to be, but has triggered a few memory cells.

What would you call better pots,

http://cpc.farnell.com/bourns/pdb241-gtr01-504a2/pot-audio-500k-knurled-sh aft/dp/RE04622 ?

I have various density foam bits and bobs laid about at home so will be able to fashion some sort of happy medium when it comes to the pickup height adjustment.

Im going to strip out the electrics completely anyway as its a bit messy and i can then put a multi-metre on all the parts to see whats what.

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I eat kebabs when i'm sober!

Bourns pots are excellent Dave. The other good names to look out for are CTS and Alpha when it comes to guitars. And while the pic in the link shows a D shaft, the description is clear that it's a splined shaft, which is exactly what you need.

The only other thing that might catch someone out is the length of the threaded bushing for mounting the pot. Mainly a problem with Les Pauls, but it's good to be confident that the bushing is long enough to go through the scratch plate or body. The one you linked to should be no problem, it just over 9mm long.

When it comes to the foam pads, you need something with decent bounce to it, something that fights back when it's squashed And you want that resistance to last a good decade or two, not something that goes all hard, shrunken, and wobbly, after a few weeks or months.

And it's always worth stripping out all the electrics and rewiring from scratch with new hookup wire. In the past I've had jobs where I've spent days agonising over a multimeter that confirms everything is connected as it should be but there is still clearly a problem. I rarely bother now: the time it takes to draw a schematic of the existing wiring, study it to work out what it is doing and whether that makes sense, check online if I have any doubts about the schematic, then remove the loom, clean the pots and switches, and finally rewire with new hookup wire; is less than it would take to make the same schematic, research online if in doubt, and test with a multimeter that tells me I have continuity but my ears tell me that there HAS to be a poor connection somewhere to get that problem.

Basically, I can remove the old loom, clean and lube the pots, and rewire quicker than I can thoroughly test it with a meter. So for anything other than a vintage guitar where originality makes a massive difference to value, it's usually quicker and easier to just rewire

Andy

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When the going gets weird, the Weird turn Pro.

Thanks again Andy, the bass is actually loaded with alpha pots but considering the cost, replacing them isn't a problem. Will do my daily chores and have my afternoon nap then get the tools out.

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I eat kebabs when i'm sober!

Some numbers

Neck pickup - 8.20K ohm
Bridge Pickup - 5.25k ohm

Both vol pots range from approx 5/10ohm to 520ish K Ohm

Now the vol pots are marked Alpha B500K with B being, from what I've just read, a linear pot? The tone is an Alpha A500k

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I eat kebabs when i'm sober!

Quote Dave71:

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Some numbers

Neck pickup - 8.20K ohm
Bridge Pickup - 5.25k ohm

Both vol pots range from approx 5/10ohm to 520ish K Ohm

Now the vol pots are marked Alpha B500K with B being, from what I've just read, a linear pot? The tone is an Alpha A500k

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The numbers are all in the right ball park Dave. Regrettably, you can't always rely on the letters A and B stamped on a pot. Sometimes the A stands for audio, but there's no standard and it can just mean that they make the pot in Log and Lin versions and the letters have been allocated randomly in the product description.

The best way is to test with a multimeter. With the pot turned about halfway a lin pot would read about 250k and a log one about 50k.

However, if they are Lin pots it would explain the symptoms so it could be that you've found the problem. Fingers crossed

Andy

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When the going gets weird, the Weird turn Pro.

Going on that Andy i think its nail, hammer, hit! Both vol pots read around the 250k mark at roughly half travel. The tone pot however is around the 50k mark.

I have been doing some reading, mainly forums, and there is a lot of contradictory information out there but with several sources saying cheaper imported guitars and basses use linear pots for vol and log pots for tone.

People have also expressed their preferences but nobody has logged any issues relating to differing pickup outputs.

3 new pots it is to start. At least now they are out i can take some accurate measurements and get the best fitting replacements.

Will post back with results.

Thanks again

Dave

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I eat kebabs when i'm sober!

Quote Dave71:

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I have been doing some reading, mainly forums, and there is a lot of contradictory information out there but with several sources saying cheaper imported guitars and basses use linear pots for vol and log pots for tone.

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I would imagine that using the wrong pots on cheaper imports is more down to individual errors in the factories than design or intent.

When it comes to volume pots I would say that unless you have a very good reason to do otherwise (and I struggle to think of one) the consensus is that you need a Log pot. With tone controls it's more subjective, one pot will give a broader range of control whereas the other one will be more 'all or nothing'. The best option is the one that best suits how you use your tone controls.

If you are buying a new set of pots then how about this for a suggestion. Buy 2x 500k Log for the volumes. You already have 2x 500k Lin and 1x 500K log as the existing pots. If you were to buy a 250k Lin and/or Log you can experiment for yourself to hear what (if any) difference changing tone pot values and tapers makes for your purposes. And you could even get a selection of small caps (mylar/carbon/polyester film types rather than ceramic disk) between 0.01uf and 0.01uf and hear how that makes a difference. Worth trying 0.01uf, 0.022uf, 0.033uf, 0.047uf, 0.068uf & 0.1uf.

If nothing else, it'll give you something to do while you're recovering

Andy

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When the going gets weird, the Weird turn Pro.

New alpha pots fitted and the results are....

Original 'phasing' issue (vol drop when both pickups on full vol) is not as severe but the bridge pickup is still noticeably weaker. Have managed to get the pickups lower in the body with a limited amount of adjustment, the angle of the original screw holes restricts the pickup movement. In an ideal world the original holes should be filled and new vertical pilot holes drilled with springs to get better adjustment but I'm not sure that will make a vast difference.

I suppose its a good as its going to get without trying a new bridge pickup which is a 'round to it' job.

So for now its a closed case. Thanks again Andy for all the valuable advice, my guitars are next for some repairs/upgrades especially my Les Paul (epiphone) as I struggle to achieve a nice vol swell. More pot tinkering.

Cheers

Dave

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I eat kebabs when i'm sober!