Tuesday, August 28, 2018

"Grace" - 6SN7-SE preamp




I would generally never post an incomplete project but due to extreme interest in this project, from my retro-thermionic facebook page, I have decided to post. The tubes are limited edition Psvane Treasure 6SN7-SE  globes or bulb shaped. They are strikingly beautiful with their gold metal and ceramic bases, quaint shape and gold markings. This build will not only be about a great performing preamp but an extremely beautiful build. 

Keeping as much gold as possible in parts selection the knob attached to a 22 step stepper attenuator is 4oz of solid brass and gold plated. The six RCAs (two selectable inputs) also gold and the standard "retro-thermionic" name plate polished brass. The white sprayed chassis and wooden cheeks complete the lush look. The cheeks are rubbed with a finishing oil to lift grain and protect. A XLR connection on the back will bring in power required. Next phase is to wire the preamp.




"VoXUno - 12P" - with Markaudio drivers







These Markaudio - 12P driver based speakers relies on the one 8" driver handling from very low to very high frequencies. They may not have the super deep bass of a couple of 12" bass drivers or the airy highs of titanium tweeters but they do cover an extreme range and cover it well. What they do better than most multi-driver speaker is image perfectly. They produce a believable well scaled image and with the right amp will produce 40hZ. At 92db of efficiency they work well with low power amps. 

The boxes are about 90ltrs and are built to the design provided by Markaudio. The port is provided by a short front baffle board. Its dead quiet until 40hZ then comes into play. The boxes are braced and dampened with bitumanised heavy Al foil and Dacron.  There is no Xover but connect direct to the amplifier. Grills attach magnetically are best removed when speakers are in use. I'm extremely pleased with these simple and inexpensive drivers, so much from so little.








Saturday, August 4, 2018

Lagoon Take 2




The original Lagoon had a few noise issues and was not suitable for the intended user. When I got it back I wanted to take it back to a 4S single stage tube preamp. The second in the 4S series, the MKII or in my build "The Black", was the one I wanted to build. This series eventually lead to the 4SU (Universal) tube preamp. The MKII was a better tuned version of the rough original and more suited to the 12AU7, a tube I preferred in preamps. Not only that I had some Psvane "T" series MKII tubes which I have enjoyed in the past.

I had all parts on hand and was determined to only use parts on hand for the amp brd.  Metal film resistors and silver solder plus some MP caps. The rest of the preamp was complete so I only need to make the preamp section. The MP caps are metalized paper in oil. 

On some early listening the preamp sounds good. Unfortunately Lagoon can only drive into high impedance power amps. OK for me because that is what I intend to use it for. For an image of the back of Lagoon refer to an earlier Lagoon post.