I have a couple of Hammond 307A line matching transformers and I'm interested in using them to take a speaker output level and convert to line level signal that can used into a keyboard amp. I've attached a pic of the 307A specs. Is that a practical use for the 307A and can anyone suggest a circuit?
Thanks.
Thanks.
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Just try it.
The first issue is that speaker level may be 10X higher than line level. There is no reason for the transformer to work that hard only to turn-down after. Also some amps may not like to see a transformer naked.
You want to pad-down about 10:1. The impedances are very far apart. Pad design is trivial. I would reach for 1K and 100r to make a divider. The transformer faces the 100r. This is a low impedance relative to 500r which will maximize bass extension.
The 1K will dissipate about 8/1000 of the amp power. If you face 1,000 Watt monsters it should be 10 Watt (and maybe 2K or higher). A Champ would get away with a 1/4W part, but I would not bother to build that small. Note that if a $100 gig is a no-pay because your line feed burnt-up on the first song you will regret not spending a buck on a fat resistor. The 100r should not be a thermal problem before the sound man complains you are overdriving his input.
The first issue is that speaker level may be 10X higher than line level. There is no reason for the transformer to work that hard only to turn-down after. Also some amps may not like to see a transformer naked.
You want to pad-down about 10:1. The impedances are very far apart. Pad design is trivial. I would reach for 1K and 100r to make a divider. The transformer faces the 100r. This is a low impedance relative to 500r which will maximize bass extension.
The 1K will dissipate about 8/1000 of the amp power. If you face 1,000 Watt monsters it should be 10 Watt (and maybe 2K or higher). A Champ would get away with a 1/4W part, but I would not bother to build that small. Note that if a $100 gig is a no-pay because your line feed burnt-up on the first song you will regret not spending a buck on a fat resistor. The 100r should not be a thermal problem before the sound man complains you are overdriving his input.
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