In Reply to: RE: Wiring autoformer as HF attenuator posted by Randal P on July 31, 2016 at 16:51:55:
without the parallel resistance, your crossover frequency would drop. 1uF would get the crossover down to 3KHz at higher attenuation levels.if you have a multimeter or VOM, temporarily disconnect the L-pad and measure and record its values at the center, high, and low positions. That will give an idea of the impedance available seen by the capacitor for different taps.
looking at an old wirewound 8 ohm pad as as resistor, I can get around 43 ohms on the high range and below 1 ohm on the low end. Half way might be around 25 ohms.
If you didn't have the parallel input resistor, then 6dB attenuation would reflect 64 ohms impedance for a 16 ohm driver (assuming it was a pure resistance) and 0.33uF might give ~8KHz crossover with a 16 ohm load, or 0.68uF with an 8 ohm load.
those are very high-end looking autoformers - I've been happy with Bob Crite's model which allows 1dB steps.
Karlson Evangelist
Edits: 07/31/16 07/31/16
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Follow Ups
- RE: Wiring autoformer as HF attenuator - freddyi 17:41:42 07/31/16 (6)
- RE: Wiring autoformer as HF attenuator - Randal P 18:37:17 07/31/16 (5)
- RE: Wiring autoformer as HF attenuator - freddyi 21:32:03 07/31/16 (4)
- RE: Wiring autoformer as HF attenuator - Randal P 09:03:54 08/01/16 (3)
- RE: Wiring autoformer as HF attenuator - D Mike 09:22:48 08/01/16 (2)
- RE: Wiring autoformer as HF attenuator - Randal P 12:53:49 08/01/16 (1)
- RE: Wiring autoformer as HF attenuator - freddyi 15:28:05 08/01/16 (0)