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Gear Discussion Forums => Gibson Basses => Topic started by: georgestrings on August 02, 2016, 05:07:15 AM

Title: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 02, 2016, 05:07:15 AM
Has anyone tried this combination? - If so, what were the results? I dig the way my Gibson basses look and play, but would like the stock pups to sound a bit brighter and clearer - a little increased output wouldn't hurt, either...


    - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: Basvarken on August 02, 2016, 05:22:06 AM
I don't think choice of a different potentiometer would increase the output.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 02, 2016, 08:14:53 AM
I don't think choice of a different potentiometer would increase the output.

I have read that going from 500k pots to 1 meg pots will bleed off less treble, and sometimes allow slightly more output - but I have no direct experience with this...


    - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: amptech on August 02, 2016, 09:13:26 AM
I have read that going from 500k pots to 1 meg pots will bleed off less treble, and sometimes allow slightly more output - but I have no direct experience with this...


    - georgestrings

Slightly more treble if you use 1 meg (or just make your tone pot a 'no load on full' pot by scraping away the end of the resistance track) is possible, but i would not worry about doing this if more output is the goal. The pickup impedance is so much lower than the resistance of the harness/loom so that is mainly what the amp will see.

Just bypass the circuit and run the pickup(s) directly to the amp, and see if it's worth doing something.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 02, 2016, 10:27:48 AM
Slightly more treble if you use 1 meg (or just make your tone pot a 'no load on full' pot by scraping away the end of the resistance track) is possible, but i would not worry about doing this if more output is the goal. The pickup impedance is so much lower than the resistance of the harness/loom so that is mainly what the amp will see.

Just bypass the circuit and run the pickup(s) directly to the amp, and see if it's worth doing something.


More treble is definitely the motivating factor in this - I'd probably just run straight into the jack, except I want to keep the ability to blend pups, or completely roll off both in certain circumstances... Thanks for the input,


   - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: Dave W on August 02, 2016, 12:27:03 PM
Going to a 1 meg pot won't change the output, and it won't be any brighter than a 500k pot with it turned up all the way. The change will be the point at which it starts to roll off high frequencies as you turn it down. Unfortunately, with some pickups a 1 meg pot acts almost like an on/off switch rather than a gradual rolloff. I don't know how the TB Plus would react.
Title: Re: 1 meg pots and TB Plus pickups
Post by: Granny Gremlin on August 02, 2016, 01:23:48 PM
+1 to Amptech - try it straight to jack and see.  Sometimes, additional treble can increase clarity and give the illusion of higher output.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 02, 2016, 01:26:02 PM
Going to a 1 meg pot won't change the output, and it won't be any brighter than a 500k pot with it turned up all the way. The change will be the point at which it starts to roll off high frequencies as you turn it down. Unfortunately, with some pickups a 1 meg pot acts almost like an on/off switch rather than a gradual rolloff. I don't know how the TB Plus would react.

I appreciate your thoughts on this, but think you may be mistaken regarding tonal changes - for example, one typically uses 250k pots for single coil pups, and 500k for 'buckers - and from everything I've read, that's because of treble differences between the two pup types... I'll admit that I don't know this for sure, but there's a fair amount of info "out there" on this stuff, and it all seems pretty consistent...


     - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 02, 2016, 01:33:46 PM
+1 to Amptech - try it straight to jack and see.  Sometimes, additional treble can increase clarity and give the illusion of higher output.

Thanks - increased clarity/brightness is what I'm after most of all... I've considered going "no load", but can get the 1 meg pots a bit cheaper - and *think* they may make the difference I'm looking for... I figured I'd ask this forum, since there are plenty of people here who have experience with TB Plus pups - since I'll do the work myself, it really won't cost me much to swap both of my Gibson basses over...


    - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 02, 2016, 01:35:51 PM
Am I mistaken in the notion that using no load pots can produce the same effect as wiring straight to the jack??


   - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: Dave W on August 02, 2016, 01:43:46 PM
A tone control is a passive treble bleed circuit. With the tone control on 10, there's no bleed of treble frequencies to ground, no matter whether you're using 250k, 500k or 1meg pots. They're all equally as bright as the pickup will allow.

The only way you can make it a bit brighter is by eliminating the pot entirely, which removes its resistance load from the circuit. As amptech said earlier, you can do that either by removing the pot and wiring direct, or you can buy one of those no-load tone pots which do the same thing when the pot is all the way up, while still allowing you to roll off treble when you turn down.

Am I mistaken in the notion that using no load pots can produce the same effect as wiring straight to the jack??


   - georgestrings

Yes.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 02, 2016, 01:46:37 PM
A tone control is a passive treble bleed circuit. With the tone control on 10, there's no bleed of treble frequencies to ground, no matter whether you're using 250k, 500k or 1meg pots. They're all equally as bright as the pickup will allow.

The only way you can make it a bit brighter is by eliminating the pot entirely, which removes its resistance load from the circuit. As amptech said earlier, you can do that either by removing the pot and wiring direct, or you can buy one of those no-load tone pots which do the same thing when the pot is all the way up, while still allowing you to roll off treble when you turn down.

Yes.

You're definitely right about tone pots, but it's my understanding that higher value volume pots will have an effect on a pickup's treble output - although maybe I'm mistaken about that....


    - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: Dave W on August 02, 2016, 02:13:00 PM
You're definitely right about tone pots, but it's my understanding that higher value volume pots will have an effect on a pickup's treble output - although maybe I'm mistaken about that....


    - georgestrings

In theory, a 500k pot will load the circuit a little more than a 1meg pot. In practice, you won't be able to tell the difference in a blind listening test with both on max. OTOH, you should be able to hear a noticeable difference with no load, although it won't be much.
Title: Re: 1 meg pots and TB Plus pickups
Post by: Highlander on August 02, 2016, 02:54:02 PM
I have "straight through" as an option on my PC with each pup o/p on a different XLR pin... raw Mud and T'Bird... :mrgreen:
Title: Re: 1 meg pots and TB Plus pickups
Post by: amptech on August 02, 2016, 11:23:31 PM
A tone control is a passive treble bleed circuit. With the tone control on 10, there's no bleed of treble frequencies to ground, no matter whether you're using 250k, 500k or 1meg pots. They're all equally as bright as the pickup will allow.

..As bright as the pickup and tone pot will allow is more correct. Correct me if this is not the case with TB+ circuits, but with the tone pot on 10 you bleed the trebles through whatever resistance your pot value is to ground via the tone cap. Not that I'd ever bother changing the value to 1M, because as you said the pot will have more like an on/off function and have a lot of useless travel, but it answers georgestrings' question.
Title: Re: 1 meg pots and TB Plus pickups
Post by: exiledarchangel on August 03, 2016, 12:17:03 AM
I am not an expert, but I really don't find anything interesting on 1M pots. Maybe if you are a dog, or a bat, you will notice some extra brightness, but the taper of the pot is not good at all. If you are a guy that uses pots a lot, its better to bring back your treble using some other methods, like installing an onboard buffer in your bass.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 03, 2016, 04:20:02 AM
..As bright as the pickup and tone pot will allow is more correct. Correct me if this is not the case with TB+ circuits, but with the tone pot on 10 you bleed the trebles through whatever resistance your pot value is to ground via the tone cap. Not that I'd ever bother changing the value to 1M, because as you said the pot will have more like an on/off function and have a lot of useless travel, but it answers georgestrings' question.

Sure, with a tone pot, that's definitely true - but, what about using a 1 meg as a volume pot with a TB Plus??? That's what I'm really asking about - and so far, no one has spoken up that has actually tried it, that I'm aware of...


    - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 03, 2016, 04:50:07 AM
I am not an expert, but I really don't find anything interesting on 1M pots. Maybe if you are a dog, or a bat, you will notice some extra brightness, but the taper of the pot is not good at all. If you are a guy that uses pots a lot, its better to bring back your treble using some other methods, like installing an onboard buffer in your bass.

I really don't want to add an active circuit, I just want to "take the blanket off" these pickups, so to speak - while retaining the ability to blend them, or roll them off altogether in some situations(on stage or at rehearsal)

At any rate, it doesn't look like anyone here has ever actually tried a 1 meg volume pot with a TB Plus pickup, so I might end up being the guinea pig... I'll be sure to post the results if I end up trying this, though...


    - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: amptech on August 03, 2016, 06:03:33 AM
I really don't want to add an active circuit, I just want to "take the blanket off" these pickups, so to speak - while retaining the ability to blend them, or roll them off altogether in some situations(on stage or at rehearsal)

If you feel you want to take off a blanket, the pot trick (1M or no load) will not do that - not that much effect. Sounds like different pickups or stainless steel strings is more likely to have that much effect.

At any rate, it doesn't look like anyone here has ever actually tried a 1 meg volume pot with a TB Plus pickup, so I might end up being the guinea pig... I'll be sure to post the results if I end up trying this, though...

I have installed many 1M pots and a couple of no load pots for guitar players. There is a lot of talk now about how much you can change or 'sculpture' your sound by tinkering with tone pots and cap values. I personally don't think it is worth it, I just tried to explain what happens. Other than a direct out option on one of my own EB3's, I usually end up with stock wiring. Other than fender jazzmasters and some other, 1M pots aren't much used and for good reasons.
Title: Re: 1 meg pots and TB Plus pickups
Post by: Granny Gremlin on August 03, 2016, 06:48:52 AM
One thing that has been ignored here is the vol pot and the treble bleed there.  Quite sure that the corner freq of the bleed is well above what bass players mostly care about but maybe not. Treble bleed only happens when volume is not at full - when at full the resistance of the pot is at it's minimum so there is insignificant load and no bleed.  You can compensate for the treble bleed with a simple cap and resistor across the pot (google treble bleed mod). Again, trying the pup straight to jack will tell you what the maximum difference you could possibly make is.  Start there, see if that gives you something you want, and then come back and see how you can mod the circuit to get closer to that tone.  As people are saying, it's really a matter of a few degrees and not like some heavy blanket has been lifted.  Sometimes, that's just enough to make a dude happy, and depending on the pups it can make slightly more or less difference.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 03, 2016, 07:02:20 AM
OK, thanks, everyone - I appreciate everyone's input...


    - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: Dave W on August 03, 2016, 01:15:49 PM
FWIW, the '70s Tele Bass II (big humbucker edition) had 1meg volume and tone pots. I had a '77. Turning down the volume pot went to instant mud.
Title: Re: 1 meg pots and TB Plus pickups
Post by: Granny Gremlin on August 03, 2016, 01:17:30 PM
Hmmmn, I might have to get me one of those ;P
Title: Re: 1 meg pots and TB Plus pickups
Post by: slinkp on August 03, 2016, 03:23:16 PM
Other than fender jazzmasters and some other, 1M pots aren't much used and for good reasons.

Now you've got me curious. What's special about Jazzmasters that makes 1M pots appropriate?

I've never actually played a jazzmaster, but really like the sounds other people get from them, have a fantasy of owning one someday if/when I can justify a 6-string purchase.
Title: Re: 1 meg pots and TB Plus pickups
Post by: amptech on August 03, 2016, 10:57:19 PM
Now you've got me curious. What's special about Jazzmasters that makes 1M pots appropriate?

I've never actually played a jazzmaster, but really like the sounds other people get from them, have a fantasy of owning one someday if/when I can justify a 6-string purchase.

I replicated a couple of 58-64 era pickups last summer, for a guy who built a jazzmaster.  Last time I spoke to him, he still had not got around to the electronics - so I might have to put everything together :)

I could be wrong here (haven't got the schematics here) but the jazzmaster have a circuit with volume and tone that works on the neck pickup only, in addition to the main circuit. So the two 1M volume pots in paralell will make the reistive load 500K in total, at least for the neck pickup. I think they used linear taper pots too.
Title: Re: 1 meg pots and TB Plus pickups
Post by: Granny Gremlin on August 04, 2016, 10:03:29 AM
The 'lead' channel which bypasses the rest of the controls when the 'rhythm switch" is engaged has a 1 Meg linear volume pot but the tone pot is 50K linear (the thumbwheels on the upper horn).  Great guitar, but most people hate that part of the circuit and remove it (confusing and those thumbwheel pots tend to die a lot; flimsy and until recently, a bear to find replacements for).  The stock controls are both 1 meg regular size pots; volume linear, tone logarithmic.

Since only one set of control pots is in circuit at any time, I'm not sure the 1M + 1M in parallel = 500K thing is the reason.  Moreso I think it's to get all the treble that's possible out of the pups - they are known for that sound.  Don;t know much about what makes the pups unique but it could also be something there too (like their DCR that makes 1 Meg pots work better; not sure)

I've had to work on a few of them since it's what most of the indie kids use.  First jam of the latest band I'm in had all 3 guitards show up with Jazzmasters or variants.

(http://www.lindamaki.com/wp-content/uploads/2015/11/This-Is-A-Picture-Of-The-Electrical-Circuit-Which-I-Feel-Right-To-Make-Jazzmaster-Wiring-Diagram.gif)
Title: Re: 1 meg pots and TB Plus pickups
Post by: amptech on August 04, 2016, 11:38:46 PM
Don;t know much about what makes the pups unique but it could also be something there too (like their DCR that makes 1 Meg pots work better; not sure)


I think they have about the same DCR as a P90. The bobbin is really very much the same as a P90, but is forbon instead of plastic. I guess that the wire being wound directly around a short rod magnet makes them sound more fenderish than P90's. 
Title: Re: 1 meg pots and TB Plus pickups
Post by: Alanko on August 05, 2016, 12:45:38 AM
No amount of passive circuitry will add elements back to your tone that weren't there in the first place.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 05, 2016, 10:33:41 AM
No amount of passive circuitry will add elements back to your tone that weren't there in the first place.


No one is claiming that it will - however, it is a fact that different passive circuits will affect what passes thru them... Again, why do you think that 250k pots are typically used with single coil pups, while 500k are typically used with humbuckers??? Surely, you don't think that's just a coincidence, do you??


   - georgestrings
Title: Re: 1 meg pots and TB Plus pickups
Post by: amptech on August 05, 2016, 11:11:46 AM
No amount of passive circuitry will add elements back to your tone that weren't there in the first place.

No, but it can take it away, and that is what georgestrings is trying to compensate for if I understand him right.
Title: Re: 1 meg pots and TB Plus pickups
Post by: georgestrings on August 05, 2016, 01:18:59 PM
No, but it can take it away, and that is what georgestrings is trying to compensate for if I understand him right.

That's it, exactly - thanks... I don't want to drastically change the character of the instrument, just try to get a little more treble and clarity out of it, if possible...


     - georgestrings