who knows about transformers? please help

[clumsygenius]

So I made the mistake of chosing a schematic for an amp before i looked at the power source it needs, and now im in quite a pickle. after I had ordered the parts for this amp, I realized that the trasformer which the genius designer of this schematic has recommended is non-existent, as in no company sells it. the circuit needs + and - 56 volts and the designer has recomended a 40-0-40 transformer (to my understanding, he means 80 volts center tapped).but all the transformers Im finding on mouser and such are at most usually 24v, some go up to 56v center tapped (wich would give me -+ 28v) and after that they jump to 120v c.t. which gives me +-60v, which is too high. basically I need a transformer that after regulating it and everything, it can supply + and -, 56 volts ( or somewhere in that range, preferably on the lower side), to my transistors.

heres a link to the schematic and instructions:
**broken link removed**

does anyone know what transformer I can use?? or can I wind one my self and if so what is the minimum amount of turns I need to have a decent transformer?

 

[Nigel Goodwin]

You need to find a better place to buy your transformers from, 40-0-40 is a fairly normal sort of rating, common in power amplifiers. Don't forget it needs to be high enough wattage as well.

Here's one example:

https://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=4209201

 

[whiz115]

I realized that the trasformer which the genius designer of this schematic has recommended is non-existent, as in no company sells it. the circuit needs + and - 56 volts and the designer has recomended a 40-0-40 transformer

Every design has it's own needs of current and voltage so it's impossible for a store to have transformers for every need. The best you can do is what Nigel proposed or try to find a local store that winds transformers in you area and ask what you want.

 

[BeeBop]

... the circuit needs + and - 56 volts

... Im finding on mouser and such are at most usually 24v, some go up to 56v center tapped

does anyone know what transformer I can use?? or can I wind one my self and if so what is the minimum amount of turns I need to have a decent transformer?

Then why not use two 56V transformers, and just disregard the center tap?

 

[Diver300]

You could use two 20 - 0 - 20 transformers, each rated to 150 - 250 VA. They will have the correct current rating.

Join the primaries in parallel (connect both to the mains supply) and put the secondaries in series. Check the voltage across the ends. It should be about 80 V ac. If it is less than about 2V you have probably got one secondary the wrong way round.

All you need to do is ignore the centre taps of the transformers. The point where the two transformers are connected is what you use as the centre tap.

 

[RODALCO]

Your 40 - 0 - 40 volts transformer will give +56 0 -56 Volts dc after it has been rectified and smoothed via a large size capacitor.

10000 uF or larger on each leg of the supply is needed.
Go for 63V or higher voltage rating and 105°C temp.

 

[Bob Scott]

You could find a supplier for the Hammond 165N80. (40V-0-40V @320VA) The specs are here:

http://www.hammondmfg.com/165.htm

You could back-order the Amveco Magnetics AA53752-038 (38V-0-38V @375VA toroidal) from Digikey. Digikey part number AA53752-038-ND.

Personally, I'd stay away from this amplifier circuit. Read all the caveats! The design looks ready to fail from instability, heat and power breakdown. This will disappoint you big time, especially after spending big bux on parts and time. I'd seriously consider a more efficient and much cooler running class D amp with MOSFET outputs. There are so many advantages. See here:

**broken link removed**

Bob

 

[eblc1388]

I would say your range of choice of transformer is quite large.

The original author did indicate in his webpage(see quotes below) that the amplifier is stable from +/-5V supply up and the supply can go all the way up to 70V.

Your choice of transformer can thus be from 36V-0-36V to anything under 50V-0-50V, giving you quite a large range of selection. One can use a higher voltage transformer and has more headroom reserve but keep operating at a continuous power of less than 300W.

The amp is actually at reasonably stable operating conditions with as little as +/-5 volts!

For maximum continuous power, a 50-0-50V (500VA or more) transformer will be needed. This will give a continuous power of about 450W, and peak power of over 500W is possible.