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Old 28th April 2004, 06:07 PM   #1
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Default One more attenuator question

Gents,

A real quick question. I have the chance to get a 10Kohm 8 section attenuator on the cheap. It would be nice to use it on my Aleph 1.7 P project. What effect would the impedance mismatch have on the preamp since the preamps output impedance is 5K ohms. The input attenuation is 10K so it would work well for the input. What would happen if I only attenuated the input?
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Old 1st May 2004, 06:40 PM   #2
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I'm also working on my Aleph P 1.7, and as far as I uderstood I don't have to regulate the input signal, because gain is same all the time and it's regulated with feedback resistor (2K pot or fixed resistor). I just have to put attenuator on the output signal, bacause there is no need for regulating input signal. Am I right? If I'm not please explain what did I misunderstood!
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Old 2nd May 2004, 12:50 AM   #3
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I am not sure either. I hope someone out there gives us some insight.
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Old 2nd May 2004, 09:22 AM   #4
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Default Re: One more attenuator question

Quote:
Originally posted by kilowattski

What would happen if I only attenuated the input?

In his Bride of Zen article, Mr Nelson Pass clarifies your question:

ˇ°Normally you see the volume control potentiometer at the input to the preamp circuit, and in this way you can insure that the input will not be overloaded. Placing the potentiometer at the output has two advantages, however, the first being that all circuit noise will be attenuated as the volume setting is reduced. Placing the volume control at the output allows the input of the gain stage to look directly at the source. This improves the bandwidth and distortion of the circuit by providing a lower RC figure for the input capacitance of the MOSFET. If you desire to place a potentiometer at the input of the circuit, feel free to do so...ˇ±

I hope this will help.
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Old 2nd May 2004, 11:59 AM   #5
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jh6you,

Thank you! That is exactly the information I was looking for.
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Old 2nd May 2004, 12:54 PM   #6
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Kilowattski,
So what did you decide to do with that 10K attenuator? Where will you put it?
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