Sir Spence Posted December 31, 2018 Share Posted December 31, 2018 (edited) I've just dug a 20 year old bass out of storage, to which I'd fitted a 3 band active preamp, blend switch and volume at the time Everything seems to work fine (amazed!) except the volume pot Symptom: No change for 90% of the sweep and then it rolls off very quickly - but it does roll off I've re-soldered the earth but still have the same issue - I'm guessing the pot value (and if so, what do I need ..250k or something different with the active pre?) ..or am I missing something bleeding obvious (again!) Edited December 31, 2018 by Sir Spence Quote Link to comment Share on other sites More sharing options...
itu Posted January 2, 2019 Share Posted January 2, 2019 A faulty connection or the pot? This can be seen as angle (X) vs. ohms (Y). You need pen & paper + multimeter. Desolder two of the three pot legs. Measure the resistance and draw it to a paper. http://www.resistorguide.com/potentiometer-taper https://incompetech.com/graphpaper/ Quote Link to comment Share on other sites More sharing options...
Sir Spence Posted January 2, 2019 Author Share Posted January 2, 2019 (edited) Thanks - I'm going to swap out the pot I suspect it's the wrong value of pot, but plan to put in a 250k and assuming my soldering skills are up to snuff, that should take care of any bad joints at the same time If you're suggesting working out the taper via the above method, something that works well on passive setups (can't speak for a circuit with a preamp) without the need to desolder, is to measure DCR at the jack on a single pickup as you turn it down the vol pot. If you see max resistance at '5' on the pot then it's linear, somewhere near '7' indicates a log pot. ..in this case is a log Alpha pot (B) Edited January 2, 2019 by Sir Spence Quote Link to comment Share on other sites More sharing options...
Sir Spence Posted January 2, 2019 Author Share Posted January 2, 2019 I've gotten to the bottom of this now, so posting for future reference I have the vol pot wired for 'independent' volume' - or at least it would be on a Jazz bass with dedicated vol pots per pickup to enable you to turn one off fully without cutting the sound for both I have the 'hot' from the preamp going to the wiper - that's the issue! 🙂 1 Quote Link to comment Share on other sites More sharing options...
BassBunny Posted January 3, 2019 Share Posted January 3, 2019 15 hours ago, Sir Spence said: I've gotten to the bottom of this now, so posting for future reference I have the vol pot wired for 'independent' volume' - or at least it would be on a Jazz bass with dedicated vol pots per pickup to enable you to turn one off fully without cutting the sound for both I have the 'hot' from the preamp going to the wiper - that's the issue! 🙂 Glad you got to the bottom of it as the original pot may not have been a 250k. Although pretty standard in passive instruments I have seen 50k, 150k .... in pre-amps. It depends on the design Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.