60v too high

[polyal]

i need to replace a 300w stereo power amp ( board ) with a 100w stereo power amp
can i drop the 60-0-60v dc supply to 35-0-35v dc
without replacing the transformer?
regards
polyal

 

[davenn]

hi polyal
welcome

Yes you could, but it would be some what involved.
It would be far easier, quicker and probably cheaper to replace the transformer.

cheers
Dave

 

[duke37]

This would be possible but would not be worthwhile and any fault in the control circuitry could finish the amp.
If it is a transformer with visible laminations, it could perhaps, with dedication, be rewound with 60% of the original turns. If it is a toroidal transformer, this will be too difficult.

 

[polyal]

thanks for the replies

is there a suitable way of splitting one 60v rail into 30-0-30 using a virtual earth
thanks in advance
polyal

 

[duke37]

This is possible, you would need two equal resistors (1k?) in series with the centre connection going to a pair of npn transistors in darlington connection and also a pair of pnp transistors. The emitters should be connected together as the virtual earth. In theory, the net current should be zero so with fat capacitors on the output the power dissipated in the transistors should be low. The necessary size of the heat sinks would be determined by experience.

 

[polyal]

thanks for the relpy...is there anywhere i can see this config ( links etc )
regards
polyal

 

[duke37]

This is the idea I had, perhaps others could comment.

 

[polyal]

hi duke ...thanks for that..will investigate
cheers
polyal