Comparing 4 Treble Bleeds

[stevewf]

Here are three models of treble bleed circuits that I've run across:



Sources: The "Parallel" Treble Bleed came from here (GuitarNuts2 forum) by JohnH in his own comparison of different treble bleeds. The "Falbo Idiot" came from another site here (jemsite forum); "Steve Newton" from here (tonefiend forum).

In order to make the differences as obvious as I could, I tried to diagram the three models, rearranging only the wires and otherwise keeping the exact some set of components.

My observations so far:
Falbo and Newton don't use the extra resistor that's present in Parallel. Perhaps the tone pot serves that resistor's role?
Newton seems like a 50's version of Falbo (or Falbo is a modern version of Newton).
It looks to me like Falbo's and Newton's designs shouldn't employ a no-load tone pot, whereas Parallel could do so.

Anyone have any predictions on how the resulting sounds will differ as the controls get turned?

[JohnH]

hi stevewf

Thats interesting! Thanks for posting.

So I had a go modelling those three with GuitarFreak:





These plots represent an SD59 pickup with both 500k pots. The treble bleed cap is always 1nF and the fixed resistor for the parallel version is 150k, (usually optimum for this arrangement)

The dashed blue line is a full-volume tone, tone at max, treble bleeds not active.

The other plots are all each set at about -5dB volume reduction, which involves a different volume pot setting in each one, from about 6 on the knob for the parallel TB, up to around 8 to 9 for the Newton, a bit less for Falbo.

Tone pot is set at max 100%, and at 50% ie 5 on a linear pot or about 6.5 on a log pot

The parallel TB keeps the tone and volume knobs fairly independent, if turned lower than tested here, tone remains somewhat consistent.

Falbo and Newton give a wide range of interaction between controls, which is great if the results are liked. Newton is generally brighter than Falbo (it has the added 50's wiring effect). Both will get very trebly if the volume is reduced down low. But this can be re-tweaked with the tone pot.

Interesting that within the range tested, all curves lie within a similar family of tonal shapes.

So its a choice of consistency versus adjustability!

But, with a guitar with rear access such as an LP, they are all easy to test with minimal wiring and parts needed.

[reTrEaD]

Jul 1, 2024 11:25:59 GMT -5 stevewf said:

In order to make the differences as obvious as I could, I tried to diagram the three models, rearranging only the wires and otherwise keeping the exact some set of components.

Nicely done. The way you laid the drawing out, makes it rather easy to spot the differing configurations.

Jul 1, 2024 11:25:59 GMT -5 stevewf said:

Falbo and Newton don't use the extra resistor that's present in Parallel. Perhaps the tone pot serves that resistor's role?

Not at all. When the tone pot is rotated counter-clockwise, that adds resistance in series with the treble-bleed cap. That makes it gradually more like a Kinman treble-bleed which functions far differently than a Parallel treble-bleed.

Jul 1, 2024 11:25:59 GMT -5 stevewf said:

Anyone have any predictions on how the resulting sounds will differ as the controls get turned?

JohnH handled that nicely. A few thoughts of my own:

A capacitor-only treble-bleed overcompensates and the overcompensation gets progressively worse the more the volume is reduced. And with tone on 10, the bottom two act exactly like a capacitor-only treble-bleed. For that reason, I personally would very much dislike them.

Without the treble-bleed capacitor, the Steve Newton is basically '50s wiring. '50s wiring inherently does a somewhat decent job of compensating for the loss of treble due to the cable capacitance, when volume is reduced and the tone is on 10. It accomplishes this because the loading on the pickup(s) decreases as the volume is reduced. But with the treble-bleed capacitor, that's not a feature. It makes the overcompensation of the capacitor-only treble-bleed even worse.

The 'magic' of the parallel treble bleed is that the resistor causes increased loading on the pickup(s), the more the volume is reduced. This mitigates the overcompensation issue.

[stevewf]

Thank you, JohnH, for running guitarfreak on that. And bravo for figuring our what settings to measure with it. I think I found a barrier when trying to the guitrafreak spreadsheet to run on my mac without buying the MS software... so I'll let that be my excuse for not quickly seeing what values to put in which spreadhseet cells. I fear that the real reason is that I don't really, really understand the components' roles, at least not much further than a player who's never opened a cavity cover. In any case, I'm grateful that JohnH sticks around to run it and post the results.

And thanks to reTrEaD for the added insights on treble bleeds. Up to now I've pretty much taken what I've read here at GN2 as a good black box solution, so the detail here is helpful.

[stevewf]

Oh, oops, and now I notice that I made the title of this thread about 4 circuits, but have only mentioned 3. Oops. So now I'm obligated to post this one:



It's got a resistor in parallel with the capacitor, but it only gets any action when the tone control is up high. It's called Steve Idiot because it fights itself (if I understand the posts above in this thread). My understanding: You want the resistor in parallel with the cap if you don't want to overcompensate for the cap's brightness when the volume control is turned down low. That's at cross-purpose with the use of the 2nd gang, above, since it instead will allow that extra brightness, only tamed by turning the tone knob down, in which case it'll deliver a double whammy of treble cutting. I'm sure there are other effects that I don't recognize.

By the way, for those who didn't click through the links above, it was Frank Falbo who called himself an idiot, not I. He also called himself a genius in the same post, and wished for a genius-pass filter.

[reTrEaD]

Jul 2, 2024 19:47:36 GMT -5 stevewf said:

It's got a resistor in parallel with the capacitor, but it only gets any action when the tone control is up high.

It would appear the pots are both at '10' when the wipers are at the left-most end of the resistive elements. If that's true, when the tone is at 10, there is a complete shunt of the treble-bleed cap and a direct connection between the wiper and the CW lug of the volume control. No bueno, imho.