On an old class A single transistor amp a while backwhen I was young. Transformer was from an old VCR before most used SMPS. I got a very loud speaker with 16 ohms and 8 ohms. I ran the DC through the secondary coil to the collector of the transistor, boy that thing got hot 
on only 12V or less! I have since wanted to try that again, but on a class AB amp just for stepping up the voltage.
on only 12V or less! I have since wanted to try that again, but on a class AB amp just for stepping up the voltage.Re: you are in the right way
No I have not tried it yet. I am still looking into the best option for driving the speaker. This is only one part of the whole intercom project.
Yes this would be to far to get shipped to Canada. We have 120V and 240V in Canada. The residential service circuits are in 120Vac.
Would a 120Vac to 24Vac do? Will the frequency of the audio signal be OK since these transformers are made for 60Hz? There is also the size to consider.
EWorkshop1708 said:
No I have not tried it yet. I am still looking into the best option for driving the speaker. This is only one part of the whole intercom project.
sakis said:
Yes this would be to far to get shipped to Canada. We have 120V and 240V in Canada. The residential service circuits are in 120Vac.
Would a 120Vac to 24Vac do? Will the frequency of the audio signal be OK since these transformers are made for 60Hz? There is also the size to consider.
A transformer transform impedances as the square of the turns ratio. If your speaker is 45R and the amp is designed to feed 4R, then the impedance ratio is just over 11. The square root of 11 is approx 3.3, so this is the transformer ratio (1:3.3) that you need.
A low power transformer with a 35V secondary and a 120V primary would work as the step-up, but you may be able to source some of the transformers normally used in 70V-line speakers with the appropriate tapping.
A low power transformer with a 35V secondary and a 120V primary would work as the step-up, but you may be able to source some of the transformers normally used in 70V-line speakers with the appropriate tapping.
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