Another Plateosaurus Preamp!

I'd previously built a couple of the PedalPCB clones of the Benson preamp - one for a friend to gig with, and one for myself. As these are a little tricky to get set up right, I only make them on request as a part of a custom order. Another regular had requested one as a larger batch of pedals, so I pulled out my last PCB and started working!

The circuit for the preamp is really fairly straightforward. There's only a few resistors, and I'm using all metal film 1% resistors for this build (mostly Yageo). All of the pF range capacitors are new production silver mica (Cornell Dubliner if memory serves). The nF range capacitors are all metal film (WIMA). The uF capacitors are electrolytic (Nichicon). Most of the work for the circuit is done by a trio of J201 transistors. I still have a few through hole transistors lying around, so I haven't had to resort to using SMDs yet. There are also three trimmers which are used to set the bias on Q2 and Q3, and the resistance coming into Q1.

Getting the board populated was straightforward. I ended up using my normal aviation grade hook-up wire from Tube Depot for the power and audio jack connections. These are all insulated with heat shrink tubing. I'm using 2.54mm ribbon cable to connect the main PCB to one of my "Steggo" daughter boards for the 3PDT stomp switch. Once everything was together, I got it tested and biased, which always takes a little bit of time to get right on these.

Once again I'm using a laser-etched enclosure. Unfortunately I accidentally queued up the version with the "Bass" and "Treble" controls reversed. I asked the recipient whether he wanted those hand wired as I'd done with my first build, but he said go ahead and leave them reversed as it would make the pedal unique. So that's what I did!

Sount wise it sound exactly like the one I built myself. I was able to put them both in series and match settings across the range to make sure that it was biased and behaving correctly. I'm now out of boards for these, but wouldn't mind building more if the need arises as they are a sort of fun build.

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