Loss of clarity w/ a single humbucker wired in parallel

[brendo613]

Hello all. I've had this problem on several Les Paul copies I wired, and I don't know a way around it. I'll recap how my circuit is.

Each humbucker is wired to a DPDT switch, allowing the coils to be hooked together in series or parallel. There's a phase switch on the neck pickup. From these mini toggles, signal flows to the 3 way selector switch near the neck, then to a single 500k volume pot, and finally to the output. The neck pickup measures 10k; bridge, 14k. (Of course, these figures drop to 1/4 their value in parallel mode.)

With either pickup in parallel mode & the volume all the way up, the benefits of having a humbucker in parallel are very noticeable; turn the volume down, however, and the signal becomes muddy and I get depressed. I've tried different treble-bypass cap / cap & resistor pairings, but perhaps because of varying preamp designs, I haven't found values that offer consistent response from amp to amp.

All over guitar electronic literature, one sees recommendations of 500k pots with humbuckers, and 250k pots with single coils to avoid high-frequency rolloff; what does one do with pickups whose DC resistance changes value?

[big_teee]

You might try wiring the Pots for indiviual volume control.
Wire the Pots like they are wired on a Jazz bass.
You should be able to roll one to any stage without effecting the other one.
I do that on basses.
T

[Mick Bailey]

Your volume pot is acting like a variable low-pass filter when you turn it down. A possible way round this is to add a small bypass cap to the pot to retain the top-end. I use a couple of clip leads on the pot and experiment to find a compromise value that works in all switch positions. I think the last one I did on ended up with a 4.7n cap.

[cbarrow7625]

Find a site that sells a 4PDT mini toggle. Use the additional poles on the switch to put an additional resistor in parallel with . e full pot and then one across the variable resistance of the wiper. You will have to play around a bit to find the right values for YOU. The lower resistances will reduce the low pass effect of the typical potentiometer as it is turned down. It should not be as amplifier Dependant as a bypass cap. Bypass caps are a bandaid in your situation.

Heck, if you really want to get into it find a custom dual stacked pot and change to a different pot altogether in paralllel mode. Kind of overkill though. You'll be able to get the same, or better, results from carefully selected resistors shunting the original pot.

[Mick Bailey]

What's your reasoning for a bypass cap being amplifier dependent? I have a few Pros and session players with bypass caps and they've not reported any problems. A bypass cap is no more a Bandaid than anything else.

[Chuck H]

Hello all. I've had this problem on several Les Paul copies I wired, and I don't know a way around it.

If you don't like the way it sounds, why do you keep wiring guitars like this? Not rhetorical.

I'll recap how my circuit is.

Not much help. We can't know how the tone and volume controls are wired for interactivity. We can't know if you're wiring the parallel function with the bobbins in or out of phase. We can't know what the peripheral loads are because of a few things. A schematic (with coil polarity indicated) would be a big help right now.

With either pickup in parallel mode & the volume all the way up, the benefits of having a humbucker in parallel are very noticeable; turn the volume down, however, and the signal becomes muddy and I get depressed.

That's funny as hell right there. A lot said with a paucity of words. Brilliant poetry.

The only way to avoid HF phase cancellation with two coils close together would be to put an inductor in series with one of the coils. This could add a little, or a lot of noise depending. It also complicated the switching necessities. And you'll still be fighting the low pass filter effect of the now relatively large resistance of the volume control because the otherwise low HF impedance of the parallel coils is shunted by the voltage divider series resistance.

We need a schematic to know just how this wiring is to give any definitive answers. But I really need to ask again... If you don't like the way it performs, why do you keep wiring like this? If the parallel coils is a tone you just can't live without, but you only like it with the volume up, leave the volume up. There are very few wirings that don't require some compromise to match styles in one way or another.

The only other suggestion I have would be to use 4pdt switch as BT suggested, but use it to change the volume control to a simple load when the parallel coils are selected. This would eliminate the added series resistance and perhaps the problem (until the volume is set very low). The taper of the volume control would be for $h!t though.

[Mick Bailey]

I re-read the OP and for some reason missed you'd tried various bypass caps and it didn't work for your particular setup. How did I miss that? My Mother told me I was stupid every single day until I was 26. She was right.

I still stand by that a carefully-selected bypass cap can work well to combat HF rolloff, but if there's something else going on with your setup at a more fundamental level then it needs investigating.

[J M Fahey]

If your pickups sound fine in parallel and full volume, then they are fine, period.
If volume turns muddy when lowering volume, get *one* amp which is often used (say ..... most of your customers play Blues into a tubed Fender? .... get one .... ) , plug your guitar into it, set your guitar volume to 6 and start trying RC compensations until you are happy that volume on 6 and on 10 sounds roughly the same.
That is your preferred choice.
Will it not be the best when both in series? Maybe.
Will it not be the best when using another amp? Maybe.
So what?
It's a compromise value, so set it up to sound best in the most used or important setting and accept what you get from it in other circumstances.

Or go active

[Mick Bailey]

Or go active

That's exactly my thought. I'd composed a reply on active electronics and then deleted it, thinking "what the heck...this is going to end up as an active v. passive debate"

In my view, once you've converted a guitar to active, you wouldn't ever want to go back.

[Chuck H]

In my view, once you've converted a guitar to active, you wouldn't ever want to go back.

Phooey! No classic Strats? No PAF's? No P-90's or Filter-Tron's? Even putting an onboard preamp into service with these pickups is tonal sacrilege! I'll not hear it (fingers in ears and going "LA LA LA LA LA LA LA ...")

[big_teee]

If your pickups sound fine in parallel and full volume, then they are fine, period.
If volume turns muddy when lowering volume, get *one* amp which is often used (say ..... most of your customers play Blues into a tubed Fender? .... get one .... ) , plug your guitar into it, set your guitar volume to 6 and start trying RC compensations until you are happy that volume on 6 and on 10 sounds roughly the same.
That is your preferred choice.
Will it not be the best when both in series? Maybe.
Will it not be the best when using another amp? Maybe.
So what?
It's a compromise value, so set it up to sound best in the most used or important setting and accept what you get from it in other circumstances.

Or go active

I agree with JM!
I test pickups all the time.
I always test them with the guitar volumes on high.
I do roll the tone controls around to see if they are in the right range.
Then after I determine the pickup clarity, I then try the vol pots to see if they are scratchy or not.
On humbuckers I've gone to higher ohm pots, everything is brighter and clearer, IMO.
T

[brendo613]

The stock wiring options remain available. This just allows for 8 more tones. Active could work. Interesting idea with the 4PDT.

I've played around with bypass caps the past few days & a 1000pf cap works best. Not an engineer here! Thanks for your input.

[Chuck H]

You could still use a 4PDT switch to add the 1000pf cap only when the humbucker coils are in parallel. I mention this because 1000pf is probably way too high a value for all the other tones. Like having your cake and eating it too! (Who the hell has cake and doesn't eat it? I always questioned that.?.)

[brendo613]

Good idea on the 4PDT Chuck. Cake sentiments agreed on, those self-unaware fools ... goodness is before them!

[Drewline]

I have used many treble bleed cap/ resistor combinations over the years. I have settled on 470pf cap on a 250K pot as my favorite. It seems to work well on single coils, humbuckers & split humbuckers IMO.