Monday, September 12, 2011

Universal - 4S preamp MKIV

This is the forth of these Super Simple Single Stage (4S) valve preamps. This was not designed by me but for me and has come after building three others and posting results on the diyaudioprojects forum. The others (see earlier posts) were specifically designed for the 12AU7 dual troide. This breaks away from that theme and will work with any of 12Axx available. This includes: 12AX7, 12AU7, 12AT7 and 12AY7.

Once more there is only one cct. brd. (this time strip board or veraboard) and holds both the PS and the amp itself. Expensive Solen caps were used in The Black but in this build MKP caps were used and less expensive parst and construction all round. With the right tube in place its sound is very close to The Black.

Housed in a Hammond Al case and quite sleek looking it is powered by the same 24VAC wall wart power pack the others are. It is quiet and has extensive gain. After some listening and comparing its performance across a number of different valves the Universal delivers a detailed sound with solid bass and airy mids and highs. The best valve tested with it so far is the 12AU7 Golden Dragon. Very easy to listen to all day!