• Item: 6SN7 SRPP preamp  
  • Type: retro-thermionic - "Cadence"  
  • Posted: 15 August 2021  
  • Builder: mwhouston  
  • Country: Australia  
  • Comments: 0  

6SN7 preamp

After building yet another SRPP 6SN7 preamp for another, who had his onw tubes, I build this one to used the spare Psvane Grant Fidelity 6SN7 Spheres I had. A few changes from the previous one but similarities to others. Big difference is the colour - Hammertone Copper. Other preamps I have used the same colour but not with the Hammond Wood chassis.

Similar to others with with the Danish Jensen copper paper and oil output caps. Before discontinued they were quite expensive. Other similarities are the final filter cap in the preamp which is a Russian PIO 4uf with a Russian 0.1uf snubber. Fine silver plated hookup wire and Alps Blue Velvet pot round it off with the 4oz solid brass gold plated knob. This time resin tube sockets and not the usual ceramic. Cheeks are treated with a high grade finishing oil which dries to a hard glossy wax finish while lifting the grain. Nice.

Using an earlier PS which is choked and relies on an external 24VAC 1A wall wart I found the sound quite a jump up from all other preamps built with the same tubes. Also in this build I used 1W carbon film resistors except the grid resistor which is metal film. There is only three resistors in each channel and the two main Rs in the signal path are the carbon film. Ck is a low ESR type. Is this the carbon Rs the secret to the better sound or is the expensive caps? Whatever bass has a whole new depth and texture, mids crazily engaging and textured and treble super smooth and sweet.

This preamp was built to sell and move on the spheres. Not sure that is going to happen any more.


No comments. Leave your comment below.

Leave a Comment