Sibob Posted August 28, 2007 Share Posted August 28, 2007 I'm going to replace the pots on my P-bass, because.....well.......they're knackered and before that.....they were rubbish! Ummm, what do i need? are there different quality pots? I'm a bit of an electronics r-tard so any info or suggestions is great! I'd be ordering from Allparts as their in the same town as me = no postage Cheers Si Quote Link to comment Share on other sites More sharing options...
The Burpster Posted August 28, 2007 Share Posted August 28, 2007 Si, If you are doing a std rewire there are two options..... 1. 2 x 250k (or 500k if you are using HOT pups) linear pots and the wiring diag is on here:- [url="http://www.seymourduncan.com/support/schematics/standard_pbass.html"]http://www.seymourduncan.com/support/schem...dard_pbass.html[/url] 2. there is a slightly different way of doing it with 1x Linear pot (as above choice) and 1x Logrithmic pot of the same value Which seems more prevelant on Jap P copies and if you choose to do it this way PM me and I'll get the wiring diag... Enjoy. Bob Quote Link to comment Share on other sites More sharing options...
BOD2 Posted August 28, 2007 Share Posted August 28, 2007 The pots for a P-bass are usually "logarithmic" (or "audio-taper") and not linear. A logarithmic/audio pot gives a smoother variation in volme throughout the travel of the pot, whereas a linear one would have all the variation at one end of the pot travel. Strictly speaking you should use a logarithmic pot for the volume control and a linear one for the tone control but no-one (including Fender) seems to bother about that but it should be logarithmic/audio for the volume. You also need to check the shaft of the original post and get the same shaft-type for the new ones (to ensure the knobs will fit ok). There are two shaft types - splined and solid. Just pop the knobs off and check what's underneath. Stock Fender P-Bass post are 250k log/audio and usually splined shafts. The best makes seem to be CTS or Alpha. Go for full-size and not "mini" pots. [url="http://www.wdmusic.co.uk/shop/products.php?category=317&page=4"]WD Music[/url] sell a big range. Quote Link to comment Share on other sites More sharing options...
Sibob Posted August 28, 2007 Author Share Posted August 28, 2007 I thought Log pots were the ones with all the variation at one end of the pot?? Now i'm confused lol The volume pot in the bass at the mo will have very little variation when turned, then will jump in volume, this to me is completley pointless! Si Quote Link to comment Share on other sites More sharing options...
BOD2 Posted August 28, 2007 Share Posted August 28, 2007 [quote name='Sibob' post='51707' date='Aug 28 2007, 12:46 PM']I thought Log pots were the ones with all the variation at one end of the pot?? Now i'm confused lol[/quote] Well yes you're right but that mimics the way our ears actually respond to volume - hence why log pots are often called "audio" pots. TBH fitting audio or linear pots will probably not make that much difference and it's something you would quickly get used to. Max volume and min volume would be the same with both, it's just the bit in the middle that would be different. Fender fit audio pots to their basses so most people generally do the same when they replace the pots. Quote Link to comment Share on other sites More sharing options...
Sibob Posted August 28, 2007 Author Share Posted August 28, 2007 I would say that the way the Volume increases/decreases on my Passive USA Jazz and my P-Bass copy is completely different. The Jazz is a smooth transition and the P-bass is how i described above, to my ears the later is pretty unusable in a gig situation if looking for subtle changes. Cheers for quick replies btw! Si Quote Link to comment Share on other sites More sharing options...
BOD2 Posted August 28, 2007 Share Posted August 28, 2007 [quote name='Sibob' post='51714' date='Aug 28 2007, 12:59 PM']I would say that the way the Volume increases/decreases on my Passive USA Jazz and my P-Bass copy is completely different. The Jazz is a smooth transition and the P-bass is how i described above, to my ears the later is pretty unusable in a gig situation if looking for subtle changes. Cheers for quick replies btw! Si[/quote] Have a look on the metal shell of the old pots for any writing. Usually that will identify the value and type of pot. If you find anything post it here and we can see if we can identify what you've got already then recommend what to replace it with. Quote Link to comment Share on other sites More sharing options...
Sibob Posted August 28, 2007 Author Share Posted August 28, 2007 So the old pots have "A500k" then the ohm sign after it, so obviously its two 500k pots (overkill for a passive bass?), dunno what the 'A' prefix means. They looked kinda small, but i didn't think anything of it! Just been to Allparts and picked up two 250k linear pots, got them back and tryed placing them in the bass, and they're too wide for the routing!! Cool.... lol So i it looks like the originals were 'mini' pots?! I think i'll just try sanding some of the rout away so the full size pots fit in! Si Quote Link to comment Share on other sites More sharing options...
BOD2 Posted August 28, 2007 Share Posted August 28, 2007 [quote name='Sibob' post='51791' date='Aug 28 2007, 03:57 PM']So the old pots have "A500k" then the ohm sign after it, so obviously its two 500k pots (overkill for a passive bass?), dunno what the 'A' prefix means. They looked kinda small, but i didn't think anything of it! Just been to Allparts and picked up two 250k linear pots, got them back and tryed placing them in the bass, and they're too wide for the routing!! Cool.... lol So i it looks like the originals were 'mini' pots?! I think i'll just try sanding some of the rout away so the full size pots fit in! Si[/quote] A500k = Audio (logarithmic) Taper 500 kOhm. B500k = Linear Taper 500 kOhm So you've had log taper pots but if the 500k value was too high then this could shift the usable part of the pot into a very small band. It'll be useful to know what difference you hear with 250k linear pots. Just out of curiousity, what make of bass is this ? Quote Link to comment Share on other sites More sharing options...
The Burpster Posted August 28, 2007 Share Posted August 28, 2007 Bod, my apologies. I typed it quick this am got my linear and log around my 4rse! [color="#4169E1"]Strictly speaking you should use agarithmic pot for the volume control and a linear one for the tone control but no-one (including Fender) seems to bother about that but it should be logarithmic/audio for the volume.[/color] My Blazer is exactly that set up! and not bad for it! 1 log and 1 Lin and wired slightly differntly but works very well and humless!! Bob. Quote Link to comment Share on other sites More sharing options...
Sibob Posted August 28, 2007 Author Share Posted August 28, 2007 (edited) Bod, thats interesting what you said about a 500k resistance affecting where the variation occurred compared to a 250k pot Well like i said, i purchased two linear pots, my dad said he has a few 250k Log pots hanging around so once i've sanded enough rout away to fit them in, i'll try them both, maybe make some sound clips, see what people think Oh and the bass is my old Encore P-Bass, mid nineties when they were actually ok basses lol. Nice Solid & weighty (not heavy) feeling body, same size and shape as a standard P (have laid a Fender P on top of it), not like the scaled down light-as-a-feather p1$$ Encore make now. Will have an Allparts maple Jazz neck fitted soon. I'll post before, during and after pics of the project in the 'Build' forum soon Cheers Si Edited August 29, 2007 by Sibob Quote Link to comment Share on other sites More sharing options...
Sibob Posted August 29, 2007 Author Share Posted August 29, 2007 (edited) Also...whats the difference between normal sized pots and mini pots?? *edit* Apart from the size!! Cheers Si Edited August 29, 2007 by Sibob Quote Link to comment Share on other sites More sharing options...
The Burpster Posted August 30, 2007 Share Posted August 30, 2007 Si, ^ nowt except size! Quote Link to comment Share on other sites More sharing options...
BOD2 Posted August 30, 2007 Share Posted August 30, 2007 ^ yep - what he said. No difference except the size. Japanese makers seemed to favour the mini-pots for some reason but they did the job just as well as the full-size ones. Quote Link to comment Share on other sites More sharing options...
Sibob Posted August 30, 2007 Author Share Posted August 30, 2007 So if theres no quality difference, then it would be prudent of me to just exchange the full pots i brought for mini pots to save having to increase the size of the cavity rout! Cheers guys! Si Quote Link to comment Share on other sites More sharing options...
The Burpster Posted August 30, 2007 Share Posted August 30, 2007 Indeed! B. Quote Link to comment Share on other sites More sharing options...
BOD2 Posted August 30, 2007 Share Posted August 30, 2007 ^ yes - what he said (is there an echo here ?) It wasn't clear from your original question that you had mini-pots already (I'd assumed it was a Fender which would have full size pots). It would certainly be less work to replace like with like. Quote Link to comment Share on other sites More sharing options...
Sibob Posted August 31, 2007 Author Share Posted August 31, 2007 [quote name='BOD2' post='52715' date='Aug 30 2007, 12:07 PM']^ yes - what he said (is there an echo here ?) It wasn't clear from your original question that you had mini-pots already (I'd assumed it was a Fender which would have full size pots). It would certainly be less work to replace like with like.[/quote] Yes i wasn't aware that the originals were mini pots to be honest, it didn't really register. It became quite obvious when i saw the replacements at Allparts but thought i'd try them anyway, but they didn't fit in the cavity. So yesterday i went and exchanged the large pots for mini ones, this time i went for log-volume & lin-tone. So everything's ready to be fitted, just waiting for the neck!! Cheers Si Quote Link to comment Share on other sites More sharing options...
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