MXR Envelope Filter

[Echorec]

Hi everyone, did anyone notice this auction? 50 original PCBs from MXR on their long discontinued Envelope Filters + schems & board layout...my question is how do you come across things like that to sell? I just thought some board members might be interested int hese. Cheers everyone


http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3710752265&category=22669

Echorec

[Mark Hammer]

Actually, the history of this begins a couple of years ago.  A fellow (Bill or Bob something) bought up a bunch of boxes of old MXR stuff left over from the old days, and began selling it as he slowly worked his way through it and discovered what it was.  He originally announced it on Ampage some time back.  The first out of the box were Dynacomp boards, and I gather the EF boards took a while to "discover" (i.e., recognize what they were and figure out how many were piled in the boxes).  Since that time, every now and then another item or set of items shows up on E-bay.

There is no real magic to these particular boards.  I've made a number of EFs from photocopies of the one I had way back when.  I guess the things to keep in mind about these boards is that they are laid out to fit a Hammond 1590B box (and its Eddystone equivalent), and assume certain component properties as well, such as the use of bent-flat lower-voltage ceramic and tantalum caps.  I don't think that is particularly restrictive, but it is something to keep in mind before blowing all your disposable cash on higher voltage greenies and axial caps.  Fitting the board into a 1590B will also require you to solder the CMOS chips directly to the board and forego sockets, although use of smaller package pots may make sockets feasible for those a little tentative about their ability to avoid static.

If you ARE capable of making your own boards and have not particular chassis-size preference, the A-Gua workalike that Francisco Pena put up on Tonepad is a fine layout that makes it a little easier to install some mods.  I've done some of the mods with the original layout, but there are some awkwardnesses you need to put up with that are much easier to do with the A-Gua layout.  Your choice.

Certainly, though, the technical info accompanying the boards makes project assembly pretty easy and straightforward.