Brick wrote:That unit looks awesome! If you are willing to share the schematic it would make a great winter project.
Most of the 78's I have are from the 20's and 30's. I have some Edison disks as well, but don't know the first thing about what it takes to play those. I was planning to purchase the M78S, but will look for reviews, thanks for the tip. Right now the only 78 stylus I have is for a USB table I started digitising with before I started taking it more seriously.
A 2.5 stylus works for the Edison diamond discs. They spin at 80 RPM and are vertically recorded. Theoretically I believe they should play back flat but I use about a 300 Hz bass turnover to enhance the base and as much treble cut as required to make the noise acceptable. A stereo cartridge is needed to play these. I think the M78S is sold as a mono cartridge but I have to believe it is a stereo body with the channels strapped together. I don't know if the short is external and can be removed or not. Hopefully someone with experience with it will chime in. If you are really getting into this, there is a Pickering which may be a better choice as there are a plethoria of styli available for it. Different vintages of 78s take different styli for optimum results. You are stepping onto a slippery slope.
I will attach the schematic of my Legacy Preamp. It so far is not production friendly in that for the eq I first chose the resistors then calculated the cap values with no regard of their availability. I made them up by measuring caps which I bought at surplus stores and parralleling them to make up the calculated values. I did use decient film caps and COG ceramic to makeup the values.
I would be happy if you built one of these for youself and let me know how you like it. Of course if you are going to make this production ready and sell them we should talk.
The schemo is hand drawn and scaned (I still need to develop CAD skills) so some of it may be unclear. Do ask if you have questions.
I have no idea what happened to crop this image. Maybe JaS can fix it. The uncroped image is in the DIY section of the Gallery.