Sunday, October 5, 2008

Beeswax and paper caps SS preamp

Most DIYers build audio gear because they have a need for a device or they just like to build equipment. I built this OP amp (OPA2134) based preamp because I liked the idea of using beeswax and paper caps. These are 1uf Jupiter caps and according to the advertising, are hand made. They ARE covered in beeswax that is for sure. I timber sub-floor was placed on computer stand-offs which themselves have rubber grommets around them. The rubber grommets and timber base are used to help control cct. resonance. The cct. boards, tiny in size, are also mounted on stand-offs and fitted with grommets. Only component leads are used to connect the individual components together on the brd. There are only three short straps on the cct. brd. and these are three earth straps made from silver wire. The Jupiters also have silver leads. Alps blue velvet attenuator and 4oz solid brass knob was used as much for decoration and smooth operation as for quiet running of the preamp.

20V DC is supplied to the preamp via a computer plug pack and a resistive voltage divider network provides +/- 10V to the brds. Each brd. has an individual power network with 2X 220uf low ESR caps. Power filtering and snubbing is provided also within the case. The preamp is two stage with gain and buffer and I used the Burr-Brown high performance chips on milled sockets. All solid pure silver wire is used for internal hook-up and WBT silver solder used also. A switch at the back allows selection between two input sources. The case is 2mm die-cast aluminum with two coats of epoxy enamel paint.

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