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Post by geo on Nov 21, 2011 3:49:44 GMT -5
I'm doing a rewire and I'm considering splitting a TBX tone control into separate bass-cut and treble-cut pots. Am I going to have to change anything or just straight up split the pot and it should all work fine? Any suggestions for fun things to try with this?
Correct me if I'm wrong, but I should be able to cut both treble and bass at the same time this way without one interfering with the other, right?
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Post by asmith on Nov 21, 2011 4:27:48 GMT -5
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Post by geo on Nov 21, 2011 4:52:12 GMT -5
Thanks for the warm welcome and speedy reply! I got a couple more questions for ya.
Any experience with this design, was it preferable to a TBX pot?
Is it supposed to be C1 = 0.022 uF or 0.0022 uF? Note 5 seems to suggest note 2 includes a typo. Also, looks like he's suggesting waaay less than 0.01 uF for C1 (he uses 470 pF), so is he just taking a huge hit in volume? (I'm assuming the signal loss isn't terribly frequency-dependent?)
I'd like to give no-load pots a try, I tried an EJ Strat and the middle pickup really has rawness to it without a tone control connected, any suggestions where I might find a 1M lin no-load and 500k log no-load?
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Post by asmith on Nov 21, 2011 5:33:32 GMT -5
Is it supposed to be C1 = 0.022 uF or 0.0022 uF? Oz specifies that the "uF" value was in the original design. I think it makes more sense if C1 used to be 0.0022uF, which is 2.2nF. That's in the region of what other bass-cut control designs have floated around on this board before. These capacitor-based tone controls work by attenuating frequencies past a certain threshold. Because a 470pF cap only lets a tiny bit of the total signal through, a lot of signal is "blocked" and there's a big drop in volume when it's turned all the way down. I fully recommend purchasing a few caps of different values and having a play. I however cannot put my money where my mouth is. I am from Yorkshire, England, and spending a pound is like losing a limb. A quick Google Shopping search for No Load Pot ought to do the trick. Or you can just buy regular ones and convert them to no-load with a little tinkering. |
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Post by geo on Nov 21, 2011 5:35:53 GMT -5
Thanks man, I'll give it all a try. Sorry if I seem to be answering questions I should be able to take care of myself, it's my first time getting my hands dirty with this stuff, so I'm pretty green and I'm trying to sort out all the theoretical bits before I start experimenting.
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Post by asmith on Nov 21, 2011 5:46:43 GMT -5
Sorry if I seem to be answering questions I should be able to take care of myself, it's my first time getting my hands dirty with this stuff, so I'm pretty green and I'm trying to sort out all the theoretical bits before I start experimenting. A duke with a name like a boot said, "Never explain, never apologise." They should write that over Wormwood Scrubs. Ask away, it's what we all signed up for. |
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Post by ashcatlt on Nov 21, 2011 9:14:22 GMT -5
Most pots are pretty easy to open up and cut the track. I use a xacto knife. Saves time, trouble, and expense looking for no load pots.
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Post by geo on Nov 21, 2011 9:56:13 GMT -5
Is this how you do it, or is this a crazy guy?
For this schematic, turning both pots into no-load pots and bypassing them both just leaves a 470 pF cap in the circuit. Is that basically going to be unnoticeable and just cut super-high frequencies? Except wouldn't that make the cut in signal all the more drastic? I'm a little confused what the end effect is here. Can someone help me out with this "signal cut" thing and possible remedies?
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Post by asmith on Nov 21, 2011 11:26:47 GMT -5
For this schematic, turning both pots into no-load pots and bypassing them both just leaves a 470 pF cap in the circuit. Is that basically going to be unnoticeable and just cut super-high frequencies? The 470pF cap is in series with the signal. Because caps only let frequencies higher than a threshold through, the 470pF cap will cut a lot of bass. At "10", that top pot is actually providing no resistance, letting the signal bypass the cap. Simple terms: No, it won't be unnoticeable. It's the equivalent of the Tone Control at "0." It will cut lots of bass. Having a "No Load Pot" for VR2 makes some sense. Having a "No Load Pot" for VR1 makes little sense. |
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Post by geo on Nov 21, 2011 12:54:41 GMT -5
Ah, gotcha. Much obliged, asmith. I really needa break out a book on this stuff and do the math a few times so I can think these things through for myself.
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Post by ashcatlt on Nov 21, 2011 13:38:34 GMT -5
You should also surf over to or Reference section, find the thread named "GuitarFreak", download and run JohnH's spreadsheet. I trust his macros. Pretty sure he's got bass cut in there now.
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Post by JohnH on Nov 21, 2011 14:29:02 GMT -5
You should also surf over to or Reference section, find the thread named "GuitarFreak", download and run JohnH's spreadsheet. I trust his macros. Pretty sure he's got bass cut in there now. Thanks for the plug. I haven't got a specific bass cut feature in those spreadsheet, but Ill take that on notice for the next version. On the no load pots, the video is good but it relates to a specific and rather fiddly type of pot. It looks like its a 16mm one. On the larger 24mm pots, its much easier to get at and usually the whole track can be lifted out once the back is removed. Its nice to hook up a multimeter across the ends of the track so you can watch the resistance increasing scrape by scrape. With similar techniques, you can increase the pot resistance in certain regions, by scraping around the edges of the track. I did that on some 500k pots that were reading 400k, to get them up to spec. J |
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Post by ashcatlt on Nov 21, 2011 21:00:31 GMT -5
I've only done a few, but they work. I just use the blade to cut through the track. One quick slice pretty much does it.
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Post by geo on Nov 27, 2011 11:50:41 GMT -5
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Post by newey on Nov 27, 2011 12:07:03 GMT -5
In general, if the pots are wired before the active circuitry, the values would stay the same. If wired after the active circuitry, the values will be decreased substantially, depending on the circuit involved.
You'll see active pups using anywhere from 10K to 50KΩ. seldom more than that though.
AFAIK, the cap values shouldn't change.
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Post by geo on Nov 27, 2011 18:03:52 GMT -5
These are tone controls, so they're in parallel with the active circuitry. I guess that means they keep the values given by asmith's diagram? I'm not sure what to take away from your response in regards to this particular setup.
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Post by newey on Nov 27, 2011 22:36:02 GMT -5
Well, I was just speaking generally. But it looks to me like the Dual-gang tone pots come straight off the 5-way switch, and then go on to the active "black box" to be processed in some fashion. From there, out to the vol and active control.
So I would think the value stays the same for the tone pots, but is less for the others.
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Post by geo on Nov 28, 2011 13:46:39 GMT -5
So I can use this schematic with the Clapton midboost kit without modification?
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Post by asmith on Nov 28, 2011 16:06:47 GMT -5
Yes, I'd say so. It would go where the tone control does on your Clapton Midboost diagram - before the active midboost circuitry - with the same values as before. |
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Post by geo on Sept 10, 2012 2:24:54 GMT -5
I've managed to locate a 500K linear mini-pot and a 1M linear regular-sized pot.
The mini-pot fits much more nicely, but only gives me 500K ohms to work with.
My current intentions had been to use the original 0.0022uF and 0.022uF capacitors.
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Post by reTrEaD on Sept 10, 2012 23:16:43 GMT -5
You really can't really compensate for pot resistance by changing the cap value. The maximum resistance dictates the height of the "shelf" at the bass cut end. Should be about -15dB for a 1Meg pot and about -11dB for a 500k pot. These numbers are based on a 200k load (250k volume pot and 1Meg amplifier input impedance.
Changing the cap will move the corner frequency. Higher capacitance = lower frequency.
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Post by geo on Sept 23, 2012 20:33:55 GMT -5
For C1, I've got a 100pF cap and a 0.0047uF cap I can use. Seeing as this is going on a strat, which of the two is more appropriate? I know this is something of a judgement call, but I'm looking for some seasoned input.
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Post by newey on Sept 23, 2012 21:19:19 GMT -5
100pf is only .0001µf. With that low a value, you'll see minimal effect if any.
.047µf is certainly usable for single coils, but conventional wisdom would be lower, in the .022 to .033 range.
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Post by geo on Sept 23, 2012 22:03:27 GMT -5
This is for the bass cut. The value I'm considering using is 0.0047uF. (Or, as you correctly saw, 100pF.)
For the treble cut I'm using 0.01 uF. (Is this a mistake?)
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Post by newey on Sept 23, 2012 23:04:01 GMT -5
It's in the range of personal preference. As Ozboomer noted in the footnotes to his design, the original value for C2 was .022µf. 0.01 will be a subtle difference.
0.00047µf (470pf) is what Oz suggested. The original G&L design apparently called for considerably more, .0022µf (2200pf).
Oz's suggestion is based on his testing, so you might give those values some close consideration.
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Post by geo on Sept 23, 2012 23:34:25 GMT -5
0.00047µf (470pf) is what Oz suggested. The original G&L design apparently called for considerably more, .0022µf (2200pf). Oz's suggestion is based on his testing, so you might give those values some close consideration. I have two capacitors that I can use for this purpose. 100pF and 0.0047uF. (NOT 0.00047 uF) Can you offer a recommendation between the two? How much of an issue will this be for me? The design uses single coil pickups exclusively. |
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Post by newey on Sept 24, 2012 5:48:32 GMT -5
I've never built the circuit, so no personal recommendations. Neither value is really in the range that has been suggested, one's 10X too high and the other's a bit low. 100pf seems closer to what you want, but I'd be prepared to try both values.
More to the point- caps are cheap, why are you limited to only those two values?
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Post by geo on Sept 24, 2012 15:11:14 GMT -5
I'd hate to spend $8 to ship a single cap (or a few caps) over the internet is all.
Are Oz's specs for humbuckers or single coils?
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Post by ashcatlt on Sept 24, 2012 16:40:56 GMT -5
Try each of the caps that you have! Heck, try them both - in series and in parallel. Have you got multiplies of these? 2 x 100pF caps in parralel will get you within tolerance of .0002uF. You can hear the effect of full bass cut external to the guitar if you've got a couplefew alligator leads.
I'm not sure that the properties of the pickups have as much effect on the bass cut as the do on the treble.
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Post by geo on Sept 24, 2012 16:43:59 GMT -5
I've got 2 of the 100pF, but that's still half the recommended capacitance. (Which is already a drastic reduction of the original.) So again, I can try that, but I'm not sure how well it'll turn out. And since this is a strat, I need to re-string with every re-wire.
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