Sunday, October 4, 2020

“Illusion” - 6SN7 SRPP preamp in a plastic jiffy box

 

















Mostly from parts on hand in da lab this simple 6SN7 SRPP preamp was constructed. Having a universal PS makes making many preamps very inexpensive. Of course when it comes to sales the preamp and PS go and therefore I have to make another PS. Constructed in a large plastic jiffy or projects box this great looking preamp ("Illusion") was primed and top coated with copper hamertone epoxy enamel spray paint. A tough and cool looking finish.

The tubes are Ozzy Miniwatt 6SN7 GTAs. On the tube tester both tubes test "88" well into the good zone and closely matched. Under the bonnet is a turret brd. I have a bag of these and it is time to use them up. They come with heavy ceramic sockets and flashy gold plated hold downs. Illusion has two selectable inputs and one output and Al foil lines the inside and bottom of the preamp. 

A switch at the front selects between inputs. A standard pot is on the output so all of the input signal is amplified before volume level is set. Russian military PIO caps are on the output and there is no input caps. Never a problem. Input impedance is 300K. There is a mix of multi-stand and solid core copper wire and WBT silver solder used throughout. Metal film resistors are used.

The sound is solid, grounded and feels relaxed and natural with good drive and bass. It gives me great satisfaction to use primarily parts on hand (vintage tubes been in da lab for well over twenty years). To now have those inexpensive parts in a working great looking and excellent sounding preamp and so cheap to build, is gratifying.  An enjoyable building and listening experience.   

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