halibut Posted May 13, 2014 Share Posted May 13, 2014 (edited) Hi, I've got an Epiphone Thunderbird IV with passive electrics. It's wired Volume, Volume, Tone (neck pickup volume, bridge pickup volume, both fed into the tone pot [url="http://images.gibson.com/Lifestyle/Support/Files/Schematics/BAT4.pdf"]http://images.gibson...matics/BAT4.pdf[/url]). It's B500k on both vols and A500k on the tone with a 100V 0.068uF cap. I'm finding it a little "dark" sounding, so I've been reading about tone pots and caps and wanted to check I've got the right end of the stick. With the tone pot turned all the way up (brightest tone) am I right in thinking that that's as bright as it gets? The cap with the tone all the way up has a negligible effect, and the cap only effects the tone as the tone pot is turned down? Swapping the cap will make no difference, and the only way to get it brighter is to increase the size of the pot? H. Edited May 13, 2014 by halibut Quote Link to comment Share on other sites More sharing options...
Davebassics Posted May 13, 2014 Share Posted May 13, 2014 You could decrease the size of the cap. Try a 0.047uF or even a 0.022uF. Otherwise, your logic seems good to me! Quote Link to comment Share on other sites More sharing options...
HowieBass Posted May 13, 2014 Share Posted May 13, 2014 (edited) I'm no expert so, just for curiosity's sake, this does interest me. As you say, changing the capacitor on the tone pot only takes effect once you start turning the tone down and in your case won't make it any brighter with the tone fully open. From what I've just read, if I've got this correct, if you increase from a 500K to a 1M ohm for the volume pots it will sound brighter at maximum volume for each pickup but the minute you back off the volume you'll see a sudden decrease in treble, and this is where a treble bleed capacitor comes in. If you're lacking treble with the volume backed off a little for the pickups then maybe try a treble bleed capacitor with the existing volume pots? Edited May 13, 2014 by HowieBass Quote Link to comment Share on other sites More sharing options...
BigRedX Posted May 13, 2014 Share Posted May 13, 2014 On a passive circuit there is always a little bit of top-end bleed to earth through the tone potentiometer and capacitor. However changing the values of the components is only going make a slight difference to the sound. Before you go spending money on this try an experiment. Remove the tone control completely from the circuit. This will be as bright as the sound of the bass will get. If that's not enough you'll have to look elsewhere for solutions to your problem. (I'd start with the tone controls on your amp) Quote Link to comment Share on other sites More sharing options...
halibut Posted May 13, 2014 Author Share Posted May 13, 2014 [quote name='BigRedX' timestamp='1399978796' post='2449491'] Before you go spending money on this try an experiment. Remove the tone control completely from the circuit. This will be as bright as the sound of the bass will get. [/quote] That's a good idea. Quote Link to comment Share on other sites More sharing options...
dannybuoy Posted May 13, 2014 Share Posted May 13, 2014 (edited) You can also get 'no load' tone pots that effectively disconnect themselves when turned all the way up. If you want a brighter sounding Epi T-Bird, also consider trying the new Classic Pro (which has different pickups) or the Pro (which is active). Edited May 13, 2014 by dannybuoy Quote Link to comment Share on other sites More sharing options...
uncle psychosis Posted May 22, 2014 Share Posted May 22, 2014 [quote name='BigRedX' timestamp='1399978796' post='2449491'] Before you go spending money on this try an experiment. Remove the tone control completely from the circuit. This will be as bright as the sound of the bass will get. If that's not enough you'll have to look elsewhere for solutions to your problem. (I'd start with the tone controls on your amp) [/quote] This! Quote Link to comment Share on other sites More sharing options...
halibut Posted May 22, 2014 Author Share Posted May 22, 2014 [quote name='BigRedX' timestamp='1399978796' post='2449491'] Before you go spending money on this try an experiment. Remove the tone control completely from the circuit. This will be as bright as the sound of the bass will get. If that's not enough you'll have to look elsewhere for solutions to your problem. (I'd start with the tone controls on your amp) [/quote] Would I need to remove the tone control completely? Or would disconnecting one leg of the tone cap, cutting the route to earth be enough to do it? Quote Link to comment Share on other sites More sharing options...
halibut Posted May 22, 2014 Author Share Posted May 22, 2014 [quote name='Meddle' timestamp='1400710222' post='2456403'] Crazy ideas time but... 'brighter' doesn't need to mean boosted treble. A passive bass cut will make the bass seem brighter as you are sending less 'mush' to the amp. [/quote] How would I go about trying this? I'm not sure I know what a passive bass cut is. [quote name='Meddle' timestamp='1400710222' post='2456403'] The other option is to replace the tone control with a varitone switch. I recently built one into a pedal, and I like being able to 'tune' the mids with it. Another option that can be built as a 'no load' device on one setting. [/quote] I think I may have seen something like this before. Is this based on a rotary switch with different caps on each switch position, soldered to a common ground? Like this: [url="http://www.diyguitarmods.com/custom-varitone-wiring.php"]http://www.diyguitarmods.com/custom-varitone-wiring.php[/url] If so, have you seen these before? [url="http://www.stellartone.com/Page.asp?NavID=147"]http://www.stellartone.com/Page.asp?NavID=147[/url] I suspect that's largely what's inside them. Pricey though from the uk distributer, but they sound nice. There's a demo of one here: [url="http://www.youtube.com/watch?v=vkgqmxfXKSc&feature=player_embedded"]http://www.youtube.com/watch?v=vkgqmxfXKSc&feature=player_embedded[/url] Quote Link to comment Share on other sites More sharing options...
BigRedX Posted May 22, 2014 Share Posted May 22, 2014 [quote name='halibut' timestamp='1400746603' post='2456528'] Would I need to remove the tone control completely? Or would disconnecting one leg of the tone cap, cutting the route to earth be enough to do it? [/quote] Provided that the capacitor is the only route to earth via the tone pot that will do it. Quote Link to comment Share on other sites More sharing options...
LawrenceH Posted May 22, 2014 Share Posted May 22, 2014 As alluded to already, volume pots themselves also contribute to perceived brightness through the height of the peak at resonance, as opposed to capacitance loading which alters frequency of that peak. For absolute max top end not only should you bypass the tone control but also the volume pots (wire pickups straight to output jack). If that's still not enough then you need to look elsewhere in the signal chain 1 Quote Link to comment Share on other sites More sharing options...
iiipopes Posted May 22, 2014 Share Posted May 22, 2014 If after opening up the tone circuit and running the pickup open it is still dark, it may be the pickups, since T-bird pickups are notorious for being so overwound. EMG makes a variety of drop-in aftermarket replacement pickups. [url="http://www.emgpickups.com/bass/thunderbird.html"]http://www.emgpickups.com/bass/thunderbird.html[/url] . The Hz, or passive version is not overwound, works well with both 250 & 500 kohm pots. For the most top end, EMG makes a DC version of the pickup if you want to change to actives. Quote Link to comment Share on other sites More sharing options...
neepheid Posted May 22, 2014 Share Posted May 22, 2014 [quote name='iiipopes' timestamp='1400772576' post='2456859'] If after opening up the tone circuit and running the pickup open it is still dark, it may be the pickups, since T-bird pickups are notorious for being so overwound. EMG makes a variety of drop-in aftermarket replacement pickups. [url="http://www.emgpickups.com/bass/thunderbird.html"]http://www.emgpickup...hunderbird.html[/url] . The Hz, or passive version is not overwound, works well with both 250 & 500 kohm pots. For the most top end, EMG makes a DC version of the pickup if you want to change to actives. [/quote] They only drop in replace Gibson Thunderbird pickups. Unless this is an Epiphone Classic IV Pro, they won't just drop in. Something to bear in mind. Quote Link to comment Share on other sites More sharing options...
fleabag Posted May 22, 2014 Share Posted May 22, 2014 (edited) [quote name='Meddle' timestamp='1400710222' post='2456403']The other option is to replace the tone control with a varitone switch. I recently built one into a pedal, and I like being able to 'tune' the mids with it. [/quote] Amen Anyone remember these ? Think they are proper inductor circuits that were built as drop in units for Jazzers mainly... I havent seen any on Ebay for a while ( American builder ) but i bought one a long way back, but kept it when i sold the bass. Its now been wedged into my Vintage MM Modder. They're pretty damn good and well built, and built neatly. Cant say if they were good VFM...i thought they were pricey, and the price varied between ( IIRC ) £60-ish > £85-ish. Mine is the expensive model, but i love it. Combined with the excellent Warman UK MM pup, its transformed my dull £99 bass into a classy £99 bass PS i agree with the vol drop as you click round on the 6 position switch, but i really only like the first 2 or 3 positions ( which are where the porky mids are ) Edited May 22, 2014 by fleabag Quote Link to comment Share on other sites More sharing options...
operative451 Posted June 18, 2014 Share Posted June 18, 2014 I have a similar issue with my metal-tastic flying V bass. I was wondering about going with a treble bleed capacitor on the volume control but i also wondered if its possible to reposition the cap on the tone to cut bass instead of treble? Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted June 18, 2014 Share Posted June 18, 2014 [quote name='operative451' timestamp='1403108766' post='2479903'] I have a similar issue with my metal-tastic flying V bass. I was wondering about going with a treble bleed capacitor on the volume control but i also wondered if its possible to reposition the cap on the tone to cut bass instead of treble? [/quote] Treble bleed caps can be great on skinny-string guitars, but I've yet to hear of anyone getting them to work well with basses. Yes you can create a passive bass control, like [url="http://www.glguitars.com/schematics/L-1500_L-1505_ClimaxBass_diagram.pdf"]this[/url] on a G&L bass. I use mine at about 80% just to tame the pickup's mahoosiveness a little! Quote Link to comment Share on other sites More sharing options...
rmorris Posted June 20, 2014 Share Posted June 20, 2014 [quote name='LawrenceH' timestamp='1400771338' post='2456846'] As alluded to already, volume pots themselves also contribute to perceived brightness through the height of the peak at resonance, as opposed to capacitance loading which alters frequency of that peak. For absolute max top end not only should you bypass the tone control but also the volume pots (wire pickups straight to output jack). If that's still not enough then you need to look elsewhere in the signal chain [/quote] +1 Start here and that's as bright as it gets so you can use that as a reference. One proviso is to go into an input ( amp / pedal / whatever ) that has a 'medium' impedance say 330KOhm to 1MegOhm. With passive pickups which have a lot of inductance lower impedance can give unusual though interesting effects and higher values emphasise a resonant frequency which you may , or may not , favour. It all depends on the exact characteristics of the pickup(s) but as a rule of thumb... tbh never really sure why such attention paid to passive 'on bass' tone options when you generally have much more control on your preamp / amp. Quote Link to comment Share on other sites More sharing options...
iiipopes Posted June 30, 2014 Share Posted June 30, 2014 Thanks. I didn't know there was that much difference in the pickups between the Gibson and the Epi T-bird basses. Quote Link to comment Share on other sites More sharing options...
pfretrock Posted September 20, 2014 Share Posted September 20, 2014 [quote name='BigRedX' timestamp='1399978796' post='2449491'] On a passive circuit there is always a little bit of top-end bleed to earth through the tone potentiometer and capacitor. However changing the values of the components is only going make a slight difference to the sound. Before you go spending money on this try an experiment. Remove the tone control completely from the circuit. This will be as bright as the sound of the bass will get. If that's not enough you'll have to look elsewhere for solutions to your problem. (I'd start with the tone controls on your amp) [/quote] A late post to this old thread but I'm interested as I have an epi T and have just been measuring the pickup inductance (and some spice modelling if anyone is geeky enough to need it). I'd agree with the above, The pickups are a whopping 10 Henries (compared with around 7.8 - 8H for quarter pounders and 4H for cheaper brands.). This will mean a lot of treble cut in a passive system. Removing the tone cap is only going to increase the treble cut point by a few hundred Hertz. Also as stated elsewhere a tone bleed on the volums pots ain't gonna work since the signal is already lost and nothing can get it back (other than amp settings). I'd check your amp lead, try another if possible and adjust the amp. How long is the lead and do you know the brand? But aren't TBs supposted to be dark? I can get all sorts of responses from mine by dialling in the Treble, Mid and Bass controls (on a simple amp). Quote Link to comment Share on other sites More sharing options...
Reversebird Posted September 25, 2014 Share Posted September 25, 2014 Sorry another late post: I have a bolt on neck Epi Thunderbird and an Epi Classic pro. I managed to tame the bolt on's darkness with decent 500k CTS pots and 0.033 paper in oil cap and then played it through a guitar compressor (Aria Ross/Keely clone) which rolls of the lows a bit and boosts the highs or at least that's the effect it has. I now have a twangy E string which still holds it's warmth and clarity. The Epi Classic Pro was definitely a bit brighter in standard out of the box form than the bolt on neck but I still changed out the cheap chinese pots for CTS ones 500k and 0.033 paper in oil cap. It now has a tone knob that change actually change the tone, in so far as it effects the pickups and how much brightness is available from each and the overall sound going to the amp. I think the Gibson designed pickups are a much needed upgrade in these excellent "budget" basses, you just got to get used to the sound and learn how to tame that sound to your needs. Quote Link to comment Share on other sites More sharing options...
KiOgon Posted September 25, 2014 Share Posted September 25, 2014 [quote name='pfretrock' timestamp='1411228071' post='2557718'] - - - - as stated elsewhere a tone bleed on the volums pots ain't gonna work since the signal is already lost and nothing can get it back (other than amp settings). [/quote] If the signal is already lost - no settings on any amp in the world can bring it back Quote Link to comment Share on other sites More sharing options...
pfretrock Posted September 27, 2014 Share Posted September 27, 2014 [quote name='KiOgon' timestamp='1411666252' post='2561751'] If the signal is already lost - no settings on any amp in the world can bring it back [/quote] You are correct and logical (I'm not logical sometimes). I was thinking about attenuation. Quote Link to comment Share on other sites More sharing options...
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