Silent Fly Posted February 21, 2010 Share Posted February 21, 2010 [url="http://basschat.co.uk/index.php?showtopic=71973&view=findpost&p=752607"]Here[/url] Kirky asked a question that I think other people can find interesting. [quote name='Kirky' post='752607' date='Feb 21 2010, 10:52 AM'](...) Probably a dumb question, but is there any particular reason why some effect pedals adopt a negative centre and others a positive? Martin[/quote] It is an excellent question. IMO, there are two school of thought. Centre positive has the advantage that the external part of the connector is negative so it can electrically touch the enclosure. This allows the usage of non-isolated connectors for the power supply. Centre negative has another, more complex advantage. If more pedals are in series, they share the same ground. This is because the patch cables that connect them connect the enclosures together. Please note that patch cables use shielded cables that have the outside connected to ground. If it is all powered by batteries (one for each pedal) there is only one ground connection that propagates nicely from the amp, to the last pedal, to the first pedal to the bass/guitar. If the pedals are daisy chained with a single power supply, things get more complicated: inevitably there is a second chain of ground connections that propagates through the power supply chain. This creates a problem: the enclosure + patch cable + power supply create a loop. One loop for every pedal. This type of loop is called ground loop and it is bad news because it is more or less like an aerial that picks up electromagnetic noise. The situation would improve if we shielded the power supply cable. Unfortunately, we can’t shield the power supply with ground - we would end up doing exactly what we want to avoid. However... if we shield the power supply with the positive and we run the negative inside the shielded cable, the ground loop is mitigated. Building a shielded cables with the centre negative but with the connector centre positive is a mechanical nightmare so we have cables and power supply connectors with centre negative. Quote Link to comment Share on other sites More sharing options...
gnasher1993 Posted February 21, 2010 Share Posted February 21, 2010 Thanks for that, Max! That cleared up alot of questions I've been wanting answers to . Quote Link to comment Share on other sites More sharing options...
Kirky Posted February 21, 2010 Share Posted February 21, 2010 Took me a couple of reads, but I think I understand. Thanks for your time. However I still don't understand why you, for example, make some of your pedals (Thumpinator, Ultratone etc) with a centre positive connector whilst others (H1, D1) are centre negative. Doesn't that just make the provision of a power supply more difficult if you happen to have both sorts on your pedal board? Quote Link to comment Share on other sites More sharing options...
Silent Fly Posted February 21, 2010 Author Share Posted February 21, 2010 [quote name='Kirky' post='753253' date='Feb 21 2010, 09:05 PM'](...) However I still don't understand why you, for example, make some of your pedals (Thumpinator, Ultratone etc) with a centre positive connector whilst others (H1, D1) are centre negative. Doesn't that just make the provision of a power supply more difficult if you happen to have both sorts on your pedal board?[/quote] You are absolutely right. There is a very simple explanation: I made a terrible mistake in writing the website. All [sfx] products are powered 9V, centre negative, 2.1mm connector. [i](I just corrected the web site it should be ok now)[/i] Quote Link to comment Share on other sites More sharing options...
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