Bass pre-amp

[jaysg]

TubeCAD article covers voltage doublers. There's a side-bar on page 15, about magnetizing the core. This article and explains why the Alembic design is inferior and provides a better circuit.

http://www.tubecad.com/january2000/page14.html

I just looked at the 1999 schematic at Geo. Still wrong for the first triode. Beyond that, regardless of what Alembic did, the fuse and power switch should both be on the hot line. The schematic infers that the fuse on the neutral line.

[wui223]

http://moosapotamus.net/IDEAS/F2B/alembic.htm

Maybe we should take a look at this schematic.

[RPmanen]

Moosapotamus has a nice power supply, Its a lot like what R.G. described in his first post.
What kind of power rating do these transformers need? 30VA? I'm asking because like Charlie, I would like to build it in a 1U rack space, and it looks like cascading transformers would make things fit easier. Basically, the lower the power rating, the more space I can get between the transformers and the audio path.

Rob

[wui223]

I built this preamp using a pair of 500mA trans wired back-to-back. But the output is overdriven.