Datasheets can be found here
We have the two most popular amplifier designs are in these two publications. The Williamson and the Mullard amplifiers.
Mullard Circuits for Audio Amplifiers (opens in new tab)
The Williamson Amplifier (opens in new tab)
If you are undertaking a project which requires a transformer not on our products page, please Contact Us and we will create a design for you at no cost. If you are happy with the design we can then quote you for its manufacture.