How many of my projects are started just I got an idea out of the blue?! I'd say, most of them. When glancing through some issues of the Australian journal Silicon Chip, there was a article how to build a simple PP-amp from 6L6s and cheap 100V line transformers. Output power limited to approx. 10W.

In a way this is a great piece. It is cheap, the power and voltages are loww giving the tubes a very long life. It's all mounted on a sturdy PCB. When buying the PCB from Silicon Chip, you can also get a packet of hard-to-find components (blue LEDs?!)

On the downside - low power, odd components. Read something abou the use of line transformers like that. Complicated connection of power transformer including some oddities in the PSU, where a link that is to be attached on some occassions shorts a diod in a rectifier bridge.
Some of the schematics are complicated like turn-on delay, a transistorised gyrator to smooth the HV. There's a complicated ciruitry to switch off the speakers when inserting headphones.

As it all started with problems with the turn-on delay (faulty cap), then no signal to the speaker connections, a blewn fuse I have given the amplifier a short rest before continuing but I am VERY tempted to disable the turn-on delay and shorting the transistor in the filter ciruit as well as shorting the realys for the headphones.



Sorry no schematics - Copyrighted!





Introducing The Currawong

Currawong Pt1

Currawong Pt 2

Currawong Pt 3

Modifying the Currawong

New transformer for Currawong

Currawong - the kit

M1115 Transformer

Use of 100V line transformers

Another Currawong build