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Olson AM-221

Stereo Phono Preamplifier

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Olson AM-221



re: AM-221

I have one of these that appears to have been home-built as a kit. The phono-tape switch seems also to change the EQ which is not reflected in the posted schematic. Also, the two channels on mine reverse the halves of the tube. In other words, the 123 side is the final output on left while the 678 side is final output on the right

On further inspection, I find the NAB-RIAA EQ is not being altered by action of the phono-tape switch; that function has been bypassed by someone. In other words, my unit is like the diagram uploaded to here. Also, the value of the extant feedback capacitor in my unit is more like 400pF. My plan is to re-establish proper EQ curves by re-creating a switchable EQ path.

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