KT88 Mono Block:  Triode connected KT88s make BIG sound, excellent for electrostatics.  They feature a long-tailed pair input stage, DC coupled to a long-tailed SRPP pair drive stage.  Now on loan since I have become an single-ended amp enthusiast.  (Thumbnail shows original construction before a complete re-design). 

6SN7 PP Line Stage:  Intended for use with the KT88 PPP amps and now on loan with those amps.  It originally  accompanied a CD player modified using Sowter 8347 DAC mu metal cored step-up transformers.

 

EL34 PP Integrated:  Incorporating a quality phono-stage, this amp can be switched on-the-fly between triode and ultra-linear operation.  Single stage gain/drive by true  "long tailed*" 6SL7 pair.  *Pentode Constant current source.  Now modified to a 'power long-tailed pair' output stage topology.

 

6AS7PP:  4WPC Class A stereo amp.  Using inexpensive toroidal power transformers for the output transformers (credit to Steve Bench for this idea).  The drive stage is of the Mullard type, benefiting from later technology constant current sources.  The output stages similarly benefit, being configured as 'power long-tailed pairs'.  It is an excellent sounding economical and compact amp.  Though a tube rectifier is not shown, slow B+ turn-on is included to give the 6AS7 tubes an easy life.

 

Calrad SA30 Rebuild:  I got this cheap via Ebay.  A lousy design with decent output transformers, it formed the basis for a fun project.

 

 

Pentode PP with Cathode Feedback: I saw this on eBay and found it's appearance and price attractive so in a moment of weakness I bought it. It did not work, as you will read... So a great opportunity for some creativity and fun!