AUTOFORMER PROJECT

Dave Slagle hand winds these outstanding autoformer units. I built a nice walnut case around a pair for a friend. Each lead is a loop, pulled out as Dave winds and all that is needed is a good quality switch, some nice jacks, and suitable case. I actually ended up building the box twice because the first version, a finger jointed purpleheart box, did not meet my expectations. The joints opened up, probably a reaction to the type of glue I was using. But this simple walnut version, with it's top and bottom painted aluminum plates and walnut cap, turned out to be very elegant and classy. The most difficult process proved to be the gloss black paint on the aluminum plates. Three trips to the autobody shop and they still aren't perfect, even though only the edges are seen under the walnut top. The plates seen in these photos were not the final pieces that were sent on their way. I tried my hand at painting them and found that my workshop is just too dusty to achieve a clean glossy top coat.

A few comments on the sound-

I would never claim to have a high resolution system, but the sound was stunning. It seemed to mesh very well with my 300B amp proving that this amp does indeed have nice top end extension. Things just sounded more open and effortless. I had similar results with my prototype 6N1P/2A3 amp. 

Not the case with my little SE EL84 Zen-clone. This amp has never excelled at sounding bigger/more powerful than it really is and the Autoformer made that even more noticeable. The textures were still superb, but this flea sized amp really needs something to provide more drive on it's inputs. 

Discussions I have had with the owner of this Autoformer have led us both to believe that this device may or may not perform very well in every system. As we understand it, source and amp impedance are the limiting factors, but there may be other forces at work here also. The folks on the Tube DIY board on the Audio Asylum site can explain the theory of why it might or might not sing in your system...they are the true experts in tube audio design.