lemmywinks Posted June 5, 2015 Share Posted June 5, 2015 I have a piezo installed in a bass which I am going to hook up to an Artec SE2a preamp (omitting the blend knob), obviously there is no metal bridge installed (it's wooden with a piezo strip) so would I need to ground the volume pot to anything at all? Obviously the piezo ground is soldered to the body and 3rd lug of the volume pot but there is a cable coming from this, can I just remove it and not get any hum? Thanks! Steve Quote Link to comment Share on other sites More sharing options...
neepheid Posted June 5, 2015 Share Posted June 5, 2015 [quote name='lemmywinks' timestamp='1433504213' post='2791634'] I have a piezo installed in a bass which I am going to hook up to an Artec SE2a preamp (omitting the blend knob), obviously there is no metal bridge installed (it's wooden with a piezo strip) so would I need to ground the volume pot to anything at all? Obviously the piezo ground is soldered to the body and 3rd lug of the volume pot but there is a cable coming from this, can I just remove it and not get any hum? Thanks! Steve [/quote] I don't think it's necessary - hum is caused by electromagnetism picked up by magnetic pickups - a piezo wouldn't be affected by that, would it? Happy to stand corrected as I've never tried it before, but that's what my gut is telling me. Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 5, 2015 Author Share Posted June 5, 2015 Thanks, I'll get soldering tonight. Quite impressed with the Artec stuff, have the SE2 in a different bass and for the money they're great, especially for people like me who can't seem to wire a preamp without masses of wire everywhere! Quote Link to comment Share on other sites More sharing options...
HowieBass Posted June 5, 2015 Share Posted June 5, 2015 The output jack has a signal and a ground connection, I would have thought that any ground wires on any electrical components go to their usual places? Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 5, 2015 Author Share Posted June 5, 2015 The ground from the preamp (it's a prewired job) is going to the relevant place on the jack, there is another wire that comes soldered to the volume pot which goes to what would be the ground wire running under the bridge, only this bass has doesn't have a metal bridge so I was just wondering if it is ok to lose this. Quote Link to comment Share on other sites More sharing options...
HowieBass Posted June 5, 2015 Share Posted June 5, 2015 All ground wires, irrespective of how they are interconnected, should always end up at the jack socket ground tag - sometimes they're arranged in a daisy chain running from pot to pot (which I suspect is done more for neatness than electrical reasons). If something has a ground wire (like the volume pot) then it needs to be grounded. Quote Link to comment Share on other sites More sharing options...
scojack Posted June 5, 2015 Share Posted June 5, 2015 (edited) You can get hum from piezo too, ensure everything is well [u]shielded[/u] and earthed. Edited June 5, 2015 by scojack Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 5, 2015 Author Share Posted June 5, 2015 So if I take the presoldered wire coming off the volume pot body and attach it to the jack socket ground lug (along with the usual ground cable coming from the pre it should be ok? Quote Link to comment Share on other sites More sharing options...
Cyril Posted June 5, 2015 Share Posted June 5, 2015 I think you have to shield the cavity, (copper is the best). and if you have hum, maybe you can drag a ground wire from the tailpiece (is it body ferrules?) to the ground on the jack. Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 5, 2015 Author Share Posted June 5, 2015 There's two thumb screws which can be used to raise/lower the bridge, they might be an option if I get hum although I'm concerned about drilling holes as at the point where I'd have to drill the body gets quite thin. It's a Sinsonio stick bass and the large cavity is just in front of the bridge, there's an alarming lack of wood there compared to the rest of the bass! Quote Link to comment Share on other sites More sharing options...
Cyril Posted June 5, 2015 Share Posted June 5, 2015 ok, but if the bridge is wood, the strings won't be in contact with these screws, right? Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 5, 2015 Author Share Posted June 5, 2015 No, that's a good point! The strings anchor at the bridge end via the tuners, would involve drilling a very long hole though. Quote Link to comment Share on other sites More sharing options...
~tl Posted June 5, 2015 Share Posted June 5, 2015 I would expect that you would be fine without the bridge wire as long as you only have a piezo and no magnetic pickup. As has been mentioned, shielding the control cavity with copper foil should still help. All I can suggest is to try it without the bridge wire and see if you have a problem. If you don't then job done. if you do, it would be time to investigate how to earth the strings. Quote Link to comment Share on other sites More sharing options...
HowieBass Posted June 5, 2015 Share Posted June 5, 2015 [quote name='lemmywinks' timestamp='1433511651' post='2791723'] So if I take the presoldered wire coming off the volume pot body and attach it to the jack socket ground lug (along with the usual ground cable coming from the pre it should be ok? [/quote] Yes I reckon this is the minimum grounding you'll need to do; obviously if you shield the control cavity with foil you'll have to ground that as well. Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 5, 2015 Author Share Posted June 5, 2015 (edited) Ok so I wired it up and there's hum - lots of it! There is a strong hum present which only disappears when I touch one of the pots (volume or stacked bass/treble) and a quiter, higher pitched hum which disappears when I touch the strings. I have fitted a pretty much identical pre (the 4 knob version, SE2) to a different bass which just has a bridge ground and shielding on the control cavity cover so I guess this needs the supplied cable grounding at the bridge. Good news is that it sounds extremely good and I now have a (sort of) functioning Sinsonido. I'm thinking it might be easier to rig something up behing the bridge to make contact with the strings and feeding this through the existing hole for the piezo. Either that or trying to find small metal saddles to seat on top of the wooden bridge (with the piezo underneath). Also am I best wiring the piezos in series or parallel? There are two in there, had to get mandolin ones as the Sinsonido bridge mount is difficult to work around with a standard bass strip. Edited June 5, 2015 by lemmywinks Quote Link to comment Share on other sites More sharing options...
HowieBass Posted June 5, 2015 Share Posted June 5, 2015 Sounds like there's a grounding wire/connection to ground missing somewhere but without seeing how you've done it I can't offer much advice and I know pretty much nothing about piezo bridges though I can't see it being much different than any standard active bass wiring schematic bar the bridge ground wire. Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 5, 2015 Author Share Posted June 5, 2015 It's wired exactly like this, only I've disconnected the two tabs from the blend pot and wired them directly to the pickup. It's supplied with a long wire soldered to the body of the volume pot (and connected to the 3rd lug like usual), I soldered this to the jack ground whereas on a different bass it is soldered to the bridge ground. Apart from that they are wired identically and the other is quiet as a mouse. There's not much to go wrong with these as they're premade, you just have to solder the pickup, battery clip and jack in and you're away so I think it definitely needs a bridge ground which unfortunately means more modding for me. Been looking at tune-o-matic style bridge pieces, I think mounting that on a thin strip of soft wood over the piezo would do the trick and also get me better intonation. Just gotta find a cheap one which is the right size and preferably black! Quote Link to comment Share on other sites More sharing options...
Cyril Posted June 6, 2015 Share Posted June 6, 2015 Maybe the ground wire you soldered on the jack is not on the good lug, there is one for the negative from the battery and one wich is connected to the circuit ground. when you plug the jack, you connect negative to ground. Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 6, 2015 Author Share Posted June 6, 2015 It's soldered on the sleeve lug along with the preamp ground, the hot and switch wires coming from the pre are soldered to the tip and ring. Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 6, 2015 Author Share Posted June 6, 2015 Just thought for a quick and dirty fix I could just run a wire along the top of the bridge underneath the strings, should do until I can get something better sorted? Quote Link to comment Share on other sites More sharing options...
Cyril Posted June 6, 2015 Share Posted June 6, 2015 you can try it. Quote Link to comment Share on other sites More sharing options...
HowieBass Posted June 6, 2015 Share Posted June 6, 2015 (edited) Looking at the schematic for the SE2-A it seems to have all the necessary wires for the pickup (replacing the blend pot in your case), the volume pot, the battery clip and the output jack connected together via the preamp circuit board itself. The piezo ground doesn't get connected to the volume pot, it gets connected to the preamp. This suggests that if there was a spare grounding wire already soldered to the back of the volume pot (and not connected to the preamp circuit board via the dedicated connector) then this would be intended to be a bridge ground wire, as you indicated earlier - I think this could be removed rather than being connected to the output jack ground. As for trying to ground the strings when you have a wooden bridge, I've read that some people have an arrangement where they have a metal retaining rod threaded through the string ball ends which then gets fed via a grounding wire to the output jack - though some have argued this isn't needed. Edited June 6, 2015 by HowieBass Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 7, 2015 Author Share Posted June 7, 2015 Ah I'll try that, thanks. I don't think the ball end idea would work on this bass though, it's a headless and they're at the other end of the bass! Quote Link to comment Share on other sites More sharing options...
Cyril Posted June 8, 2015 Share Posted June 8, 2015 What kind of headless tuner is it? Is it a Daniel Fernandez bass? Quote Link to comment Share on other sites More sharing options...
lemmywinks Posted June 8, 2015 Author Share Posted June 8, 2015 Nah it's an Aria Sinsonido with bog standard tuners benind the bridge. Quote Link to comment Share on other sites More sharing options...
.gif.9ad672bb8b84505709f76b39c8c256ec.gif)
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.