donbenjy Posted July 19, 2006 Report Share Posted July 19, 2006 Hi, I've just bought a DB Lemon Fuzz homemade pedal, and when I try to plug it into my 9V DC power brick thing along with another pedal, the whoel chain goes dead! The fuzz works fine on its own, or in conjunction with battery powered pedals, just not when all are run off the same PSU! I can plug the fuzz and anything else in and stick something in each input, and they work, but as soon as I connect it to any input/output of something runing off the same PSU, it dies! Apparently, the designer says that it needs to be run on a seperate PSU, but it runs on a 9V battery so why not 9V DC? I obviously can't get hold of a wiring diagram, but I can describe the connections to the power jack if needed? Can anyone offer any suggestions to why this happens? I was thinking maybe the polarity of the jack is reversed? in which case i'd just need to move a few wires on the power jack... I've emailed the guy but no reply yet, so i thoguh i'd ask here! Would something like the VZex power plate, that converts a battery snap into a 9v plug thingy work? Cheers in advance for any help guys! Quote Link to comment Share on other sites More sharing options...
spazzyone Posted July 19, 2006 Report Share Posted July 19, 2006 check the the polarity on the fuzz and then the power supply sounds like its reverse to me Quote Link to comment Share on other sites More sharing options...
Sambo Posted July 19, 2006 Report Share Posted July 19, 2006 Ditto. S Quote Link to comment Share on other sites More sharing options...
JohnH Posted July 19, 2006 Report Share Posted July 19, 2006 Heres my guess, and it is just a guess - others please point out if it does not make sense. It sounds like your power supply works fine with this pedal on its own, but not with other pedals as well. That shows that the polarity of the supply and the pedal are compatible, ie, most probably the outer barrel of the power supply plug is positive and the inner negative? - which I believe is as for most pedals. It could well be that the signal ground connection (ie the wires that connect to the outer sleeve of the guitar cord and patch leads) is positive in this pedal and negative in the other pedals. Plugging two such different pedals into one power supply would connect positive to ground on one pedal and negative to ground on the other, hence shorting the power supply. If that is true, then a second power supply or batteries may be the easist answer, since the problem is inherent in the design. Such a grounding arrangement I have seen on designs for classic old-style fuzz boxes using Germanium transistors. Is that what this is? cheers John Quote Link to comment Share on other sites More sharing options...
donbenjy Posted July 19, 2006 Author Report Share Posted July 19, 2006 yep, that's exactly right! I got a reply from the guy, who said it's a positive ground connection, which means that the only real options are a battery or seperate PSU! I take it that there isn't any way at all to rectify this realistically? oh well, ebay it is then Quote Link to comment Share on other sites More sharing options...
Mr Alex Posted July 20, 2006 Report Share Posted July 20, 2006 Just reverse the wires on one of your daisy chains plugs. I do that all the time. Quote Link to comment Share on other sites More sharing options...
spazzyone Posted July 20, 2006 Report Share Posted July 20, 2006 um yup Quote Link to comment Share on other sites More sharing options...
donbenjy Posted July 20, 2006 Author Report Share Posted July 20, 2006 Just reverse the wires on one of your daisy chains plugs. I do that all the time. you sure? Its still centre minus... won't that just not work? It's just that the ground goes to the wrong tip bit...or did you mean in the patch cables as opposed to power cables? Quote Link to comment Share on other sites More sharing options...
lovekraft Posted July 20, 2006 Report Share Posted July 20, 2006 No, you can't just reverse the leads, because it's a positive ground pedal, so connecting it to any negative ground pedal on the same power supply shorts out the power supply. The only solutions are to either ground-isolate the pedal at the input and the output (probably not practical), or power it from a separate supply. If you really like the sound of it, buy a box of 9 volt batteries and cruise on. Quote Link to comment Share on other sites More sharing options...
donbenjy Posted July 20, 2006 Author Report Share Posted July 20, 2006 yep i'll just get a separate PSA Quote Link to comment Share on other sites More sharing options...
Mr Alex Posted July 20, 2006 Report Share Posted July 20, 2006 Hehe, sorry about that, I misread it to be it had the polarity of the dc jack reversed. I should've thought about the positive ground thing. This is why its much easier to just rectify AC inside the pedal. Sorry dude. Quote Link to comment Share on other sites More sharing options...
donbenjy Posted July 20, 2006 Author Report Share Posted July 20, 2006 lol no probs! I could put arecitifer in, but i'd still need a a 240VAC-9VAC transformer, which is like £2 cheaper than an AC-DC one anyway Quote Link to comment Share on other sites More sharing options...
lovekraft Posted July 24, 2006 Report Share Posted July 24, 2006 ...its much easier to just rectify AC inside the pedal.Easier, maybe, but noisier, usually, and more expensive, always! Even at production quantity pricing, a battery clip's a lot less hassle and expense than a rectifier bridge and flter caps! Quote Link to comment Share on other sites More sharing options...
Mr Alex Posted July 24, 2006 Report Share Posted July 24, 2006 Lovecraft, After looking at the prices for the rectifier and all that, I guess I'll have to agree. I'm not sure I can agree about it being noisier though, I've been prototyping a new product with a rectifier and regulator setup, that's sitting unboxed on the bench, and has no noise problems, and it contains 8 fet opamps. Even the scope agrees with me. I know every manufacturer want to keep cost to a minimum(I do too), but I just think anybody making something that requires a power supply setup, different from nearly every other pedal is just stupid. Alex Quote Link to comment Share on other sites More sharing options...
lovekraft Posted July 27, 2006 Report Share Posted July 27, 2006 Alex, I didn't say it was always noisier, but you have to admit that introducing any large AC signal that isn't the audio input into the box will invite noise problems - even control LFOs are subject to introducing unwanted artifacts unless very carefully implemented, and a big 50/60Hz current inside the shield just isn't a good idea if it can be avoided, especially for high-gain circuits. Congrats on doing the extra work to make it viable, but keep in mind that most manufacturers (even boutique operations) simply can't afford that kind of extra expense - after all, even if your pedal retails for several hundred dollars, the margins aren't huge, so you have to sell a bunch simply to keep body and soul together, and a few extra pennies on each unit really adds up! As for everyone sticking to a standard power supply, the original fuzz effects were almost all positive ground, so if you want vintage mojo, you can't expect modern convenience. Quote Link to comment Share on other sites More sharing options...
Mr Alex Posted July 27, 2006 Report Share Posted July 27, 2006 While I still think having to have a seperate powersupply is really stupid(mojo or not), I agree with all the stuff about AC noise in the same shield. Turns out, I don't have a problem with noise, because my dad made some changes to my schematic when he was doing my pcb layouts. Thanks to him, I get vintage mojo, and modern convenience. I can still run DC into the rectifier as well, so it just makes more sense to me. I think I've ranted off topic for long enough now. Quote Link to comment Share on other sites More sharing options...
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