• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Power Transformers


2002-08-25 2:59 pm
Hi there
I am wanting to build a Class A guitar amp.I have the circuit and the parts list.
The only problem is finding a Power transformer for Australian
240 V primary.I can easily find the correct transformer from the USA and at a good price.i nead the same thing but with Ozzie specs.
Can anyone suggest a good resource for Power Transformers
I suppose a UK source would be ok as well



2002-01-07 6:02 pm
Hi Steve,

Some more details would help, like transformer secondary voltages, VA ratings etc.

The only real difference between a trannie that's for the US and Australia should be the primary voltage.

Here are some off the top of my head as a general resource,
http://www.farnell.com (select Aust)

And then there's always the Yellow pages.



2002-01-07 6:02 pm
Hi Steve,

In your first post, I missed the magic word, <i>guitar</i>, and all the talk around here wrt class A is normally about sand amps.

Tube trannies aren't common, and customs can cost a lot of money. Here are a couple of possibles that haven't already been mentioned.

<a href="http://axis.jeack.com.au/~lucas/index.html">Black Art Audio</a> in Victoria. I have a power trans from Lucas' workshop I bought off a friend. Beatifully made, but might be expensive.

<a href="http://www.users.bigpond.com/triode/index.html">Lancroft</a> in Sydney, do power transformers too <i>I think</i>. I'd be worth a call, his work is excellent.

<a href="http://www.turneraudio.com.au/">Turner Audio</a> in Canberra, who like Lancroft and Black Art specialise in signal transformers, but might do them, or could refer you to someone who could.

<a href="http://www.lundahl.se">Lundahl</a> do some nice C core power trannies, but they only have a single secondary B+ winding, do you'll need a bridge rectifier instead of a fullwave and a resistor in series with the rectifier heater winding to bring it down to 5V. The Australian distributor is on the website. The LL1649 is probably the closest match, and IIRC, they're about $A250, but don't quote me please.

Since this is a DO IT YOURSELF project, you might try what I did - take a toroid isolation transformer and put your own filament winding on it. You'll have to pass on using the tube rectifier, though, as you'll only get 240 VAC for a full-wave bridge (I suppose you could use a 5Y3 for half the bridge, though, and sand diodes for the other half...

In my case, I used a 80 VA toroid with 120:120 Volts and a doubler to get B+ of 290V or so. The 240:240 transformer is avaialble from a number of vendors (just don't get one like Plitron's with the potted center). 50 turns of 18 gauge gives a 6.3V winding good for 3A. Some pictures on my site at http://www.audiophool.cjb.net