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!
wauwatosa tube factory 
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.
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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.
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I’m impressed. I have been trying 12u7 radio tubes in my experiments. They are really good sounding.
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