Post by thread:[EE]: 660mH inductor

Hi, I've been looking at guitar pedal designs, and all the wah circuits I've come across use a 660mH (or there abouts) inductor. AFAIK this is quite a large value, my 2 weeks research haven't helped me find out how to build / buy one to this value. I found a site telling me an opamp can be used, but I feel my calculations must be wrong (needing resistors in the gigaohm range etc!)... I would be extremely grateful if anyone could help me out here with a supplier URL or circuit! :) Thanks, Kieren Johnstone (typing left-handed with a double-broken right arm!) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Well a quick google found that Renco in the US make chokes to 270mH. If you want one ready made perhaps a Valve Radio society/advertiser may have something after all valve radios often had chokes in the henries range. Alternatively it is not that difficult to wind your own (well a broken arm might be a problem) using a toriod. What frequency or reactance does it require? If your dodgy on XL or N= here is a quick webpage for you http://recording.org/users/kev/Inductors.htm Colin -- cdb, spam_OUTbodgy1TakeThisOuToptusnet.com.au on 20/09/2002 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Forget the chokes. All you need is a manually sweeping bandpass filter between 200hz and 5khz. An opamp will do the job. I've seen numerous schematics on the web but I haven't saved the links. Will look in my archives for them. I don't know why you want to reinvent the wheel when you can buy a new one for about US$35 with an average price of US$75.. www.doctormusic.net/product.asp?pid=198&sec=acc The biggest problem in building your own is the mechanical portion unless you have a good sheet metal shop. Rick Kieren Johnstone wrote: > Hi, > I've been looking at guitar pedal designs, and all the wah circuits I've come across use a 660mH (or there abouts) inductor. AFAIK this is quite a large value, my 2 weeks research haven't helped me find out how to build / buy one to this value. I found a site telling me an opamp can be used, but I feel my calculations must be wrong (needing resistors in the gigaohm range etc!)... I would be extremely grateful if anyone could help me out here with a supplier URL or circuit! :) > > Thanks, > Kieren Johnstone (typing left-handed with a double-broken right arm!) > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

If you need just one, how about using a small transformer. Perhaps either the primary or secondary of a wall-wart will be what you need. Ignore the unused winding. And of course remove any rectifiers. I just moved my office and haven't been able to locate my henry-meter or else I'd already have checked a few wall-warts for value in order to back up this suggestion. Cheerful regards, Bob -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics