Here is the schematic for the little 1 watt 12B4 amplifier that got me started on the road of parafeed SE. When I was designing it, I tried to keep costs low but not low enough to skimp on quality parts in the audio signal loop. I think any preamp that can put out 1Vrms can drive this thing to full power. I have received e-mail requests every 2 weeks or so for the schematic since I first put up the offer a year or two ago in the asylums. I redrew that schematic to make it look a little neater as well as to revise the parts used. Those that have built it and reported back are quite satisifed with the sonic results whether it's used for an amp driving regular speakers or for headphones. The 6N1P and 6H30Pi are in relatively healthy supply and 12B4's can be had at prices so low it's ridiculous. I think I had bought 6 pair of 12B4's for $35 when I was sourcing parts for the amp. Don't let that fool you into thinking the 12B4 is a bad tube.
For sound characteristic, it has a full, lively sound to it. The midrange for this amp is *large* and sophisticated (bass and treble are clean and solid as well). For the amps I've built since this one, I've tried to duplicate the midrange sound but I think I've come up a little short (even with 6h30Pi driving parafeed TJ300B to magnequest all permalloy tfa-2004). The 26 preamp driving this little amp really rolls my shorts. It kinda disappoints me that I spent 7 times the money in part costs on the 300B parafeed monoblocks and I still wasn't able to properly match the midrange immediacy and delicacy of this little amp. If only I could make it more powerful.....
Tom §.