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Calculating transformer winding ratio for 600 ohm > 8 ohm
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RockyRaccoon:
I have designed an amplifier with an output impedance is around 600 ohms. I want it to drive an 8 ohm speaker, so I am trying to calculate the proper transformer winding. I’m finding very little information on this so I’ve come here to ask for help — how do I calculate the proper transformer winding ratio to turn a signal with 600 ohms of resistance to a signal with 8 ohms of resistance? If it’s a common enough ratio I’ll order it but if not I have a machine that I use to wind guitar pickups that I’ll use to make it myself. Thanks!
Benta:
The rule is that impedance transformation is the square of the winding ratio.
In your case sqrt(600/8) = N.
RockyRaccoon:
--- Quote from: Benta on January 25, 2019, 06:27:39 pm ---The rule is that impedance transformation is the square of the winding ratio.
In your case sqrt(600/8) = N.
--- End quote ---
So I’m understanding you properly, the ratio should be 8.66:1?
600/8 = 75 and the square root of 75 is 8.66
Thank you.
DaJMasta:
Exactly. You can find RF transformer calculators around the net that will confirm this, also can give you an idea of losses for a given core material. Here's one that gives you a bit more than just turn ratio, but there are many options: https://www.changpuak.ch/electronics/broadband_transformer_matching.php
For good low frequency response, you're going to want a good number of turns.
floobydust:
You won't get a lot of power, maybe a few W at most unless your 600 ohm source is capable of a lot of output voltage, like a Pultec EQ.
To experiment, a 120V-12.6V power transformer is around 9.5:1 turns ratio. So 600 ohm input and 6.6 ohm output.
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