Home > Power transformers > 0-190-275V 20W power transformer

0-190-275V 20W power transformer

Choice of output voltages up to 160mA and 3A for heaters; create an amp with switchable B+!

I specced this power transformer to be very flexible, able to run medium-power single-ended amps and low-power push-pull amps. The first step was to choose high voltage windings to suit a range of projects. I looked at popular amp projects and chose the following:
* The 0-190V winding produces around 260V when rectified - great for EL84-based amps. There's the full 160mA available, so you can run a pair in push-pull, parallel SE or even in stereo.
* The 0-275V winding gives typically 360V when rectified - designed for octal power valves (EL34, 6L6, etc) in more powerful SE amps (15W or so). This also has 160mA available, so it's also perfect for push-pull amps with lower-power valves, such as the EL84 and 6V6.
* The 190-275V winding is also available, and gives around 115V when rectified. This is a 'freebie' - a side effect of the two main values I chose - but it adds a really useful option to use in amp projects...

...Switchable B+!

With these asymmetrical windings, there are three combinations available to run into the rectifier bridge. This means you can use a 3-position rotary switch to get a switchable B+ supply in your amp. With the ratios given you get:
* Full power from the 0-275V winding
* Half-power from the 0-190V winding
* 1/10th power from the 190-275V winding
It's like an ultra-simple version of Power Scaling (see Kevin O'Connor's London Power Website for the cost of a switch! With 3A at 6.3V available for heaters, this is a very flexible transformer for amps up to 18W or so in output.

Dimensions & info

It's 78mm wide, 70mm deep and 64mm tall, with standard solder lugs for all primary and secondary connections. It's available in a lay-down style, to drop through a rectangular cut-out in the chassis (such as that on AC04 small and AC02 medium chassis). The rectangular cut-out should be 54x49mm, and the four 4mm mounting bolts are on 64x51mm centres. This type has a dual 120/240V primary winding.
NOTE: Although the Amp Maker web shop is currently closed, you can order this transformer directly from the manufacturer right now: CLICK HERE

This lay-down transformer drops through a rectangular hole in the chassis
This places all solder lugs safely inside the chassis for direct wiring to the amplifier circuit


Price: £36.00
inc VAT
Quantity
NOTE: Amp Maker is closed for a whole year, reopening in Autumn 2019. See Home page for details.