Early this year, I wrote a post about simple RIAA correction with opamps. Although it doesn’t involve tubes (yet), I recently completed a PCB-based build based on this post. This was both to test the calculations/theory as well as good practice in PCB design.
This ultra-simple phono preamp runs on just a pair of 9V batteries for power and utilizes a mix of feedback and passive EQ for RIAA correction. The batteries should last about 24 hours (playing time), but a bipolar AC-derived supply could be substituted without trouble. Gain is easy to adjust with just a couple of resistors (set at 40db in my build). The bill of materials runs about $25 with 5532 opamps and 5% tolerance WIMAs.
I’m planning on building a couple of these with coworkers and basing build instructions and any revisions on the experience. I do have some extra boards from this first run. Shoot me an email if interested!
5 Replies to “One little project comes to fruition”
Looks awesome. I’m surprised the batteries last so long but I think I’d still like an AC power supply if I’d be using this in my main setup.
I’m estimating the battery life at about 5ma per opamp but have not yeah measured it in practice. I can make up some simple ic regulated bipolar boards as well.
Part of the idea here with 9v batteries was to minimize any danger/complication that might discourage new builders, so separate AC supply as an option makes sense.
I’m impressed. I have been trying 12u7 radio tubes in my experiments. They are really good sounding.