The ESP based DIY preamp, update 2.

Another PreFUNK update. I know I am pretty biased but this preamp is my absolute favorite. Not only from a functional point of view but it also sound great. It turned out the way I planned but a couple of details called for another update. The knobs where borrowed from a vintage Technics 8600 but did not fit flush with the front panel. I therefor bought a new set in machined solid aluminum.

They where quite expensive but the quality is great. I wanted to mount them flush but without having them rubbing against the front panel. I therefor took some self adhesive black velvet.

Marked the inner and outer diameter of the back of the knobs with a pair of compasses. I then cut it out with a pair of scissors.

I then put the velvet on the back of the knobs. I can now fit the knobs flush to the face plate without risking it to scratch the face plate. It also made it easier to get a uniform distance between the knobs and the face plate.

Another issue I had with the initial version was the rotary switch for source selection. It had a plastic shaft with a small wiggle to it. Not the solid feel I really wanted. The one I had chosen initially had 4 positions with a 36º angle. I only considered looks not availability. I could have made things easier by selecting a 30º angle instead. I would then have had a much larger assortment to choose from. I was now stuck with the 36º angle between labels on my face plate. The selection of 4 positions, 36º angle, rotary switches are small and the one I finally bought was more than 5 times the price of the original one. But it has the solid feel I was looking for. The new one to the left and the old one to the right.

Another issue that irritated me was the use of shielded interconnects that I felt was not any better than the twisted pair cables I used while prototyping. I like the twisted pairs better between boards so I decided to replace the ones not entering or exiting the "Faraday Cage". I also took the opportunity to change the order of the boards a bit. The rumble filter was initially positioned after the RIAA-stage and only used for the phono input. My next speaker build will incorporate a Linkwitz transform and it would therefor be beneficial with a steep high-pass filter not only for turntable rumble but for all sources. I ended up with the following layout (click to zoom):

And this is what the preamp looks like with the new set of knobs. I cant wait to hook it up to a updated PwrFUNK but I also have to build a new set of speakers for them. But that is another story...