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Just installed a Q filter - nice

Dee-man

Dee-man

Supporting Member
Apr 6, 2004
3,376
2,683
SF Bay Area
#1
Howdy TB. I picked up a Q filter from Bill Lawrence (wildepickups.com) and finally got my bass back from the tech that wired it to the tone control on my P bass. The tone control is now a push-pull so I can use just the original tone pot, or just the Q when I pull it out.

Anyway, I'm no expert on this kinda stuff, nor do I have the eloquence of other TBers to describe tonality, but all I can say is - wow! This thing is cool. While the normal tone knob goes from very bassy to bright, the Q plays with the mids a lot, going from a very scooped slap-type sound, to a full-spectrum sound (similar to the regular tone with a little counterclockwise turn to roll off some treble). I can easily see keeping the Q on all the time, but regardless, it's nice to have the options, and to be able to make significant tone changes on the fly, as they say.

Perhaps the best news is that the Q filter only cost $24 (plus shipping/tax). So, if you can install these things yourself, it's quite a bargain IMHO. And, no, I'm not paid to say nice things about Bill and Becky and their nice stuff (including their low impedance cable/plugs).

Anyone else enjoy one of these filters or something like it? Please chime in. DM
 
#3
In 1987 when Ibanez introduced the SDGR bass the top of the range model SR1000E had what amounts to a Q filter like you describe...they called it ''Powercurve eq'' ..i was lucky to be able quite a few years ago to get one thru Ibanez spare parts and add it to my SR800LE bass ..first with Dimarzio PJ pick ups which were great but had some sort of earth buzz in them..so now it has EMG HZs..its a great idea and sound that doesnt seem to have taken off with manufactures in any great way...which is a shame as they sound great...the power curve eq only lasted 4 or so yrs and was discontinued

Leslie
 
#5
Thanks for the comments. I can't make sound clips, sorry. I'm not that technologically advanced.

As far as wiring to the volume knob, I don't know. You could contact Bill or Becky. You could definitely add another knob dedicated solely to the Q, if you want.

I'm going to add a Q to my other P bass, which seems well-suited to this because of the limited tone control. I have another bass that has a Glock preamp which I'm not going to add the Q to since I have bass, mid and treble controls already.
 
#9
I have one on one of my guitars. The Q-filter is a passive double coil that is wired as a tone control in parallel to a pickup. Its function is to decrease the impedance of the circuit, which flattens the resonant peak of the pickup, which our ears perceive as a drop in mids or an increase in clarity.

A capacitor/resistor bridge is usually wired across the coil to tailor how much low end is retained in the circuit. Yes, a lot of guys wire it to a push-pull, because it's not unreasonable to have either/or treble roll-off or (what is effectively) mid cut.

I find the effect subtle on guitar. I have not tried it on bass, but my custom fanned fret P-style bass does have a 15kohm humbucker in the "P" position that might benefit from it. I had not considered it before this thread; I might just have to now. I can see it modifying the large mid peak that a P-bass is known for, to help, among other styles, a slap contour.

Another thread with more links:
http://www.talkbass.com/forum/f38/bill-lawrence-q-filter-wiring-819280/
 
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#10
Thanks for the explanation, iiipopes. What you said you hear is what I'm hearing. It's not that subtle, in my limited experience, as compared to the standard tone control, but subtle changes within its range can be made.

Bill makes 1 Q for guitar, and a 3-Henry one for bass (I have no idea what Henry means). I got the one for bass.
 
#12
Henry is the unit measurement for inductance, just like ohm is for resistance, volt is for electromotive force and ampere is for current.

I don't know about actives. You'd probably have to contact the manufacturer of the pickups about that.

Yes, being passive, it can always be wired to its own separate control. Some folks dump the tone control altogether and wire the Q-filter in its place, others rout out and add another control. I like the either/or of the push/pull to retain the stock appearance and stock functioning of an instrument.
 
#16
I was playing with it again last night. Reminded me of one of the negatives: a buzz, like from a single coil hum, that is more pronounced than before. It goes away when you're touching the strings, and is of course only an issue with bedroom practice. I also tried it with a different amp (a MusicMan HD150 instead of an EA iamp micro), and some of the subtleties that I liked were not as prominent. But, at the very least, it adds new flavors, which is always nice.
 
#17
Dee-man said:
I was playing with it again last night. Reminded me of one of the negatives: a buzz, like from a single coil hum, that is more pronounced than before. It goes away when you're touching the strings, and is of course only an issue with bedroom practice. I also tried it with a different amp (a MusicMan HD150 instead of an EA iamp micro), and some of the subtleties that I liked were not as prominent. But, at the very least, it adds new flavors, which is always nice.
Click to expand...

The Q-filter itself is amazingly silent. I'm pretty sure it's actually a single coil, but shielded with mu-metal, which is well known for being "very effective at screening static or low-frequency magnetic fields, which cannot be attenuated by other methods" (wiki lift!).

If you're using particularly high inductance pickups and you weren't getting highs before, especially if you use a high capacitance cable and have your resonance rather low, you're going to hear noise from your pickup and circuit that was obscured by these factors. If it goes away when you touch the strings, it's clear the Q-filter is only "taking off the blanket" rather than adding noise independently.
 
#18
All traditionally wired passive basses, whether wired with single coil or hum-cancelling pickups (which a P-bass and a J-bass with both pickups full on are) can react to electrostatic noise when not touching the strings. The part of the circuit that a player touches, the strings through the bridge to the shield lug of the output jack, is the grounding. If you want any quieter, along with isolation, then that's what EMG's are all about. But since the Q-filter is designed for conventional passive high-impedance circuits, I don't know if it will work with an EMG setup. Only EMG will know.

The current offering of Q-filter is different from mine, but...the original Gibson humbucking pickup was designed by Seth Lover as an adaptation of filter chokes which had the humbucking, or noise cancelling characteristics many years before that in industrial applications, and is a well-known fundamental circuit for electrical engineers. In that regard, the older Q-filter I have installed on one of my guitars appears to be a double coil. Remember first that Bill Lawrence is an electrical engineer, so I'm sure his products are designed with maximum noise suppression possible in mind. That's why, for instance, his real L500 series pickups have the metallic plating on the "bucket" that the coils set in.

Summary: the Q-filter is not adding noise. As above, it's uncovering noise that's already there, from whatever source: neon lights, lights that have a rheostat dimmer on them, bad wiring, insufficient grounding or loose (white wire) neutral on the building wiring, bad connecting cable, bad design of whatever FX is in the chain, too many effects in the chain or too many collateral plug-ins causing a ground loop (that happened to me on a Korg tuner; a 3-to-2 prong adaptor cut the ground loop and quieted everything down), etc.
 

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