hi guys i am a newbie here and wanted to ask a question abt transformer capacity.
I am building a 2 channel chipamp on 1875
i wanted to parallel 2 1875s per channel
Now what is the transformer capacity i should go for?
assuming 40 w per channel
it is 80 watts total
and a efficiency of 80% will a 100VA t/f with 18 0 18 do for my chipamp??
i asked because when going through the posts i noticed that for all chipamps the minimum t/f rating everyone was using was a 160VA
is it because they are easily available or any other specific reason??
I am building a 2 channel chipamp on 1875
i wanted to parallel 2 1875s per channel
Now what is the transformer capacity i should go for?
assuming 40 w per channel
it is 80 watts total
and a efficiency of 80% will a 100VA t/f with 18 0 18 do for my chipamp??
i asked because when going through the posts i noticed that for all chipamps the minimum t/f rating everyone was using was a 160VA
is it because they are easily available or any other specific reason??
Actually choosing a transformer rating is not quite as straight forward as you might think. If you look at the transformers from commercial amps they are often less than a calculation of load at maximum power output would suggest.
Take the quad 405 the Input power is stated as 80-320 Watts, (VA), depending on volume. As most of the time the volume listeners use is much less than maximum, the transformer is able to take brief overloads.
Transformers mostly fail by overheating. Excess current (usually protected by fuses), can cause catastrophic failure, but long term milder overheating also shortens their life. So brief overloads can be absorbed by the thermal mass, but at a cost in terms of life-span. Of course there is a limit to that, but for commercial designs this results in cost savings.
When experimenting, running close to the limits may be acceptable, but for long term reliability I recommend playing safe and running transformers cool. The small additional cost is worth the peace of mind, and who knows, you may want to build a more powerful amp next time.
Take the quad 405 the Input power is stated as 80-320 Watts, (VA), depending on volume. As most of the time the volume listeners use is much less than maximum, the transformer is able to take brief overloads.
Transformers mostly fail by overheating. Excess current (usually protected by fuses), can cause catastrophic failure, but long term milder overheating also shortens their life. So brief overloads can be absorbed by the thermal mass, but at a cost in terms of life-span. Of course there is a limit to that, but for commercial designs this results in cost savings.
When experimenting, running close to the limits may be acceptable, but for long term reliability I recommend playing safe and running transformers cool. The small additional cost is worth the peace of mind, and who knows, you may want to build a more powerful amp next time.
@rjb
thank you
I just wanted to know how the t/f was chosen.
cost is a factor
but i ll take your advice and play safe by going for a bigger t/f
thank you again.
thank you
I just wanted to know how the t/f was chosen.
cost is a factor
but i ll take your advice and play safe by going for a bigger t/f
thank you again.
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