This preamp is based on Ale Moglia’s design that can be found at http://www.bartola.co.uk/valves/dht-pre-amplifier/26-dht-pre-amplifier-gen3/. Thank you Ale.
- PSU and amp in a compact design (same enclosure). This comes with a noise level compromise.
- low and high gain options. Using LL2745 in Alt Q (2.8:1) and Alt R (5.6:1) I have option for 3-4dB (low gain) or 9-10dB (high gain). Again this comes with a compromise: low gain has low Zout (about 300 Ohms), high gain has higher Zout ( about 1k)
- power transformers and chokes are home-made using Edcor laminations(EI87x1.4″). The power transformer, in addition to the end bells has a 5 mil copper screen connected to earth ground
Some pictures during building:
More about sound and measurements to follow…