Les Paul project

[Yogi B]

Feb 12, 2021 7:28:56 GMT -5 cem said:

By the way, I also want to try a different treble bleed on this guitar. I like it as it is right now but the taper is bugging me (150k with 1nf cap in parallel).

Bugging you how? Presumably (if you're comparing it to the same pot without the treble bleed) you're finding that now the volume doesn't turn down quickly enough towards the maximum end of rotation, but sharply drops off to zero at the lower end of rotation. What taper of (volume) pots are you currently using?

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Often we talk about how the resistor in a parallel treble bleed makes a volume pot have a more linear taper, but that's only true if the pot you're starting with is a log pot (it doesn't make sense that you'd somehow be able to make a linear taper pot more linear now does it!). It's probably better to say that a parallel treble bleed makes the taper feel less logarithmic (or more anti-logarithmic).

As a linear taper can be thought of as a midpoint between a log taper and a reverse or (anti-) log taper -- adding the parallel resistor to a log pot does make it closer to a linear taper, but if you're already starting with a linear taper the resistor will make it closer to a reverse log taper.

Therefore, if you're using linear taper pots (or some of those fancy "vintage" 20%-30% (log) taper pots -- though I don't think you can readily get those as push-pulls, so probably not) and want to keep the exact same treble bleed, then the answer is to use log pots.

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If, however, you're already using 10% log taper pots there isn't much you can do without changing the values (and thus the response) of the treble bleed.

A series treble-bleed essentially means that bass frequencies are affected per the pot's normal unadjusted taper, whereas treble frequencies are affected per the taper as adjusted by the resistor.

For example below is a plot demonstrating this transition, all four lines represent a vintage PAF type pickup with a 10% log 500k volume pot at 50% rotation, however: the the blue line is a normal response with no extra components; the red line has a 150k resistor adjusting the taper, but no capacitor; the purple line is your current 150k and 1nF in parallel; finally the green line is 150k and 1nF in series.

So whilst you can see that the series treble bleed does give you the unaltered taper for the lowest frequencies, the overall shape of its response is quite different to the parallel treble bleed (and to the full-volume response).

I have read a lot of threads about treble bleeds on this forum. How come I have never come across this before. Did I miss it?

I don't know if we've had a specific discussion on how each treble bleed alternative affects the apparent taper of the volume control. In general the taper adjustment that occurs with the parallel arrangement is seen as a feature rather than a bug: fans of the series treble-bleed or '50s wiring need special "vintage" taper pots to achieve a middle ground between good for use as a volume and good for use as blending when both pickups are selected -- parallel treble-bleeds have that 'built in' (of course, assuming that you're starting with a regular 10% log pot).

[cem]

Alright. I finally got my friend to wire this diagram. Now there seems to be a problem. My friend is going to work on it again this weekend to see if he missed anything. But in the meantime can anyone vet this diagram Yogi B ?

Atm, the pickups dont seem to work. When tapped, only a very quite sound can be heard. Solo switch works though. The tap sounds are very clear and only the bridge pup works when the solo switch is on. Other switches are similar to the guitars nutral settings. Plus, there seems to be a ground issue that he somehow couldnt solve. And he said that he never had seen a 3 way switch wired that way. Probably the series parallel switch is getting things complicated. If it would help things get easier, we can skip the bridge activation feature. Because making one extra move to put the guitar in to series mode wouldnt hurt that much honestly.

So in short, heeeeeeeeelp:)