Bad taper w/ Q-tuners PUs & 1 Meg-Ohm Pots

Can't help you on what to do there - I'm just running my Q-Tuners through a switch and on to the jack in both my Five and Six, and do all my control with my V-Bass. I love 'em more and more, especially since I'm often jumping around to different tunings down to F#0 and often big variations in gauge; here the tonal and string-balance setup that is possible with Q-Tuners reigns supreme.

They do low fat strings really well, really integrates those troublesome sub-E pitches nicely. I also like the extended and smoother top they provide, as some of those tunings are a little guitaristic on the skinniest strings.

stubbsonic said:

... I can't get the taper of the pots to work right...The pot comes on very suddenly during the first 15% of the knob's throw. It ramps up pretty gradually after that.

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hmm. the linear tapers might do that (jump up quickly from "off"), but i would have expected the audios to have the opposite issue, dropping off fast from "10".

the treble cap and/or the resistor will both exacerbate the first effect, as they leave either more treble (cap) or more everything (resistor) in the signal as the pot is turned down.

could your built-in direct box be changing something? maybe it would be worth hard-bypassing that circuit to see what happens.

You might have the audio taper pots wired backwards which would create something like you described. Try reversing the the two outside connections to the pot.

my vote?

ditch that quixotic balanced idea entirely, two volumes (pickups both have to go to the center lugs for independent operation) tone(?),and your coil-splitting switch. there's something to be said for a minimal signal path for purity of tone.

at that point, try the linear volumes with no caps or resistors on them.

Are those dual ganged pots? Do the tapers run in the same direction on both decks? For instance, blend pots have one side running the opposite.

And why are you running each coil to a volume pot? Just switch the coils before the pots, and use standard pots.

Your two decks of 1M is making them look like 500k pots anyway. Add them all together and you have a 250k load on the pickups.

When I get to this point in an experiment, I walk away for a while.

When I come back I break it down into the stages I need and the stages I want.

I would guess you need a working bass but you want balanced out.

Wire up the simplest approach, just volumes (buy new 1meg audio taper pots to be sure you got the right ones!), and give it a try. (If your switch arrangement is working 100% and not causing the problems, keep it) When you get that working, treat it as a single block. Then wire up your balancing transformer like it should be and connect the output of your finished stage 1 block. (I never used a transformer inside a bass, I went with a balanced line driver IC, so I'm of no use there)

Working with everything all a once is complicated, simplify until you can understand each piece before you pack them together as a whole.

stubbsonic said:

dual pots for balanced out (as mentioned on the other thread).

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I think that's your problem right there. You really can't get a balanced output from a pickup like that. Microphones have a balanced output, but that's from the transformer or preamp, and they don't have volume pots.

Balanced outputs are for noise cancelation in the cables.

My suggestion is to use standard pot wiring. You can still use 1M pots if you like, but by nature of the way guitars and basses are wired, they aren't balanced.

the thing is, that entire "balanced" idea looks like a solution in search of a problem. if the whole point was to reduce "noise", then what noise are we talking about?

i doubt it would do anything about hum produced by the pickup itself, which is coming through the air right into the coils.

in practice, 15 feet of shielded guitar cable between the bass and its first destination doesn't add any appreciable noise.

so now we're running pickups through all sorts of extra tone-robbing wire, pots, transformers and whatnot to "fix" a problem that isn't there to begin with.

the point of balanced microphones is to allow for literally a hundred feet of cable between the mic and the mixer, as well as multiple splitting of that signal, without appreciable loss or noise induced in the cable.

on top of that, it strikes me that the whole point of the q-tuners using 1 meg pots is to have as little "stuff" between the pickups and the destination as possible!

OK, as I mentioned before:

1) Microphone cartridges attach to a transformer before leaving the mic. That's why they are balanced. The floating ground comes from the center tap. If you just attached the cartridge up to the XLR it wouldn't work properly.

2) Microphones don't have a volume pot attached after the cartridge, or the transformer. It wont work.

3) Your amplifier does not have a balanced input. If you don't have one side of the pickup grounded, it wont work.

If you do want to do it, the easiest way is the way EMG does it. Take an op amp. One side of the pickup goes to (+), the other end goes to (-), and the connection between the two coils is the ground. Since humbuckers are differential in nature, that would give you the plus and minus swing.

And you probably wouldn't hear a difference. There's very little reason to balance the signal right from the pickup.

Humbuckers are already differential, that's how they cancel hum. Mics are balanced because they have VERY little signal. The coils are about 10 Ohms. The internal transformer steps that up and makes it balanced. This is to kill hum induced in the mic cable, not the mic. It has little to do with the signal voltage swing.

And still they need a preamp at the end. The coil doesn't pick up much noise partly because it's low impedance.

As far as:

The q-tuners are super quiet, so I can't really attest to an A/B comparison where the balanced signal was quieter than the unbalanced. The gain structure and impedance are so different that any comparison was not very practical. I will say though that I got a very hot signal that was very clean and VERY quiet!!

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Q-Tuners are just humbuckers. They aren't even shielded. The sideways coils help a little, and they have very little ungrounded metal in them. There is nothing in the design that makes them quiet.

The real test is to sit in front of your computer monitor... do you hear a buzzing noise? That's the lack of shielding. But shielding wouldn't look good in a clear pickup.

The gain structure and impedance of Q-Tuners is not all that radical. A BL-4 is either 12k or 14k. That's actually on the high impedance end of passive pickups.

The reason for this is they use air coils that don't have metal cores, so the inductance is lower. That's what helps them have the extended top end. But the lower inductance also means the output would be lower than a pickups with metal cores in the coils, so they have to wind them hotter. But you can wind pickups hotter with neo magnets without them getting muddy, especially with low inductance coils.

The neo magnets also make up for the low inductance, and don't contribute any inductance of their own. You will notice that the pole pieces don't touch the neos. This prevents the top end from being over the top by knocking it down a notch.

The other aspect of the Q-Tuner is the "side winder" setup of the coils. This gives them more of a single coil tone. The old Bill lawrence L-250 Strat sized pickups are made like that, but they only have the single blade pole in the middle.

So Q-Tuners are a very nice design, I like them, but nowhere as radical as an Alumitone or Transsensor. They don't even have coils, except for the small built in step-up transformer.

Obviously I have some experience with neodymium magnets and coil arrangements. And you can see everything going on inside a Q-Tuner. I wont show what's in mine though, but you can sit in front of a computer monitor with no buzz. Shielding isn't pretty however.

walterw said:

the thing is, that entire "balanced" idea looks like a solution in search of a problem....

the point of balanced microphones is to allow for literally a hundred feet of cable between the mic and the mixer, as well as multiple splitting of that signal, without appreciable loss or noise induced in the cable.

on top of that, it strikes me that the whole point of the q-tuners using 1 meg pots is to have as little "stuff" between the pickups and the destination as possible!

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+1.

You typed this up as I was typing mine.

It's no fault of stubbsonic though... you just have to watch what you read on the internet. The guy writing that is missing the point that guitar pickups put out a lot more voltage, and aren't running 100 feet of cable before they get to the mixer (think of those mic snakes).

SGD Lutherie said:

Q-Tuners are just humbuckers. They aren't even shielded. The sideways coils help a little, and they have very little ungrounded metal in them. There is nothing in the design that makes them quiet.

The real test is to sit in front of your computer monitor... do you hear a buzzing noise? That's the lack of shielding. But shielding wouldn't look good in a clear pickup.

{...}

So Q-Tuners are a very nice design, I like them, but nowhere as radical as an Alumitone or Transsensor. They don't even have coils, except for the small built in step-up transformer.

Obviously I have some experience with neodymium magnets and coil arrangements. And you can see everything going on inside a Q-Tuner. I wont show what's in mine though, but you can sit in front of a computer monitor with no buzz. Shielding isn't pretty however.

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Funny, I never noticed my Q-Tuners being noisy when I'm sitting at my computer, unlike many other pickups I've had. So I just cranked my amp and put my bass right up against my 19" CRT (that's right, old tech for better color accuracy in the price range, at the time I bought it anyway), and moved it to every practical orientation. I really wasn't hearing much that wasn't there before when it was 6' away.

Perhaps it's my shielded pickup routes and cavity, and the Q-Tuner's combination of elements including the air coil design, but I'm glad Erno didn't shield the top of the pickup because I've heard the effects of that before on other humbuckers: tone rob.

I really don't care if they are the MOST radical pickup ever devised, they really supply tone that works for me where others have not, and practical elements I get use out of like the three rows of adjustable hex heads ferinstance. I'm not ready to write them off simply because they aren't Bass Bars, or yours ; }