Adding a treble bleed to neck volume pot when master has one already (53RI Duo Jet)

[Sea Devil]

I love this guitar to death, but the neck T-Armond has always overwhelmed the bridge pickup in the middle position. Just turn the neck volume down and it should be OK, right? Not so fast! There's a significant loss of treble when the volume is lessened even slightly, and that changes what the pickups sound like together. The neck pickup is contributing less, but what it does contribute is darker, so it needs to come down even more. By the time it's low enough to sound good with the bridge, it sounds terrible on its own -- too quiet, too bassy. It also starts to introduce hum because of the volume imbalance. Time for a second treble bleed!

Many factors contribute to how a treble bleed performs in a given circuit, and there are too may variables for someone with my limited understanding to weigh them in advance, so I just tried a few things.

First I went with the "classic" treble bleed: a 1000 pf/.001uf cap with a 100K resistor in parallel. It didn't work for me at all. The middle position was consistently hollow, nasal, and brash when the pickup volumes were balanced, and there was a fairly broad range in the pot's sweep where nothing much was happening. I clipped the resistor and liked it a little better, but the peak frequencis were still somehow off. I decided to go a little crazy and just add a .0033uf cap in parallel with the .001uf, thinking that might thin the sound at the top of the pot's sweep more, and the results were equally unsatisfactory. There wasn't nearly as much difference as I'd expected. As I turned the pot down, the sound thinned, but even more gradually and in an equally displeasing way. I messed around with cap values and landed on a .002uf. It works perfectly for my needs in this circuit. A slight turn of the volume knob, say from 10 to 8.5, and the sound is rich, bright, and full in the middle position while retaining both warmth and clarity (think Oscar Moore) in the neck position. A significant benefit is that the reduction in volume isn't great enough to affect hum-canceling in the middle position, which had been an issue with my first attempt.

I never tried a resistor in series, or any other value in parallel; I found my solution before considering those options. My results also directly contradict what multiple sources led me to expect; a higher value capacitor (with no resistor) retained more highs as the volume was rolled off. I'm not sure what to make of that.

My neck pickup is flipped so that the pole pieces and screws are in the same orientation as the bridge pickup, btw. This also helped to balance the pickups, but not enough. Now I can stay in the middle position more of the time and vary my sound by blending the neck pickup in to taste, which is one of the benefits of Gretsch's independent volume controls (as opposed to standard Gibson wiring). There's a nice, useful range, all within the top 20% or so of the pot's travel, before the hum starts to creep in. A "smidge" is usually all that's needed. Potentially undesirable, weird comb-filtered phase-canceling artifacts are still present, as they always are with RWRP pickups, but are supremely controllable with the lightest of kisses on the volume knob. (That filtering sounds great when the pickups mate well, btw -- not knocking it on principle!)

If anyone out there is experiencing a similar issue, give it a try. YMMV, of course, but it works for me.

(If one of our more technically minded members can explain why I got the results I did, I'd be happy to hear it!)

 

[Sea Devil]

As I read more about this, I think I get it. The higher value cap does in fact highlight lower frequencies, but they are probably around 2.4-3.6 kHz, maybe up to 4.2 kHz. That's where a guitar sounds bright, assertive, verging on aggressive, and generally loud. (Boosting those frequencies in a mix can result in rapid "ear fatigue," so beware!) The lower values and corresponding higher frequencies have a more pronounced effect on what's often called "presence," especially on old Fender circuits. That's generally 5.6 kHz and above -- up to 11-12 kHz in some cases, as on some Carvin amps. Overtones and color only, no fundamentals. So the peak I get with the .002uf is lower than I might get with a smaller cap, but it cuts through and plays better with the bridge pickup precisely because it doesn't phase-cancel the bridge's shimmery overtones. The neck pickup doesn't have a lot to say about those higher frequencies anyway, so it's all good. I think it will sit nicely in a live mix or a recording.

I have no doubt that the more standard treble bleeds are better for a master volume. I'm happy with the MV treble bleed that the guitar came with, although I rarely use it and the pot always seems to be dirty.

With this configuration, the two pickups do a good job of maintaining their respective voices when played in tandem, and that's what counts.

 

[Sea Devil]

A further note: the higher, "presence" frequencies are still there with this cap, and are more present than they would be with no treble bleed. The peak, however, is moved lower at the top of the pot's adjustment; the perceived effect is one of greater clarity and a better blend with the bridge, but without a glassy Byrds-like top end. Micro adjustments yield macro results. It's possible to fine-tune it with a nudge to optimize for a given range/set of voicings/area of the neck you're playing or for picking style, even to a lesser extent for the key you're in. The effect is like a wah pedal, very "tunable," with the whole usable range between 11 and 9 o'clock. Nearer to zero, it sounds tinny as hell on its own, but has long since ceased to be audible when combined with the bridge, so that's irrelevant. I won't ever turn it that low.