just bought 5x Siemens DL620 (nearly the same as DL92, but f.e.lower heater voltage):
i already had bought 5x Lorenz DF61 (nearly the same as DF91, but also f.e.lower heater voltage):
This company here manufactures custom made tube amplifier output transformers (for example input impedance 1.5, 3.0, 4.5 KOhm, output impedance 2, 4, 8, 16 Ohm, 300 mW) all parameters selectable, up to Studio quality which means 15Hz to > 30Khz +- 0.1 dB !!!!:
using this tubes and very small output transformers it should be possible to build a real portable MINI TU-05 !
Edited by GermanGuy - 9/15/13 at 11:47am