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Old 13th August 2004, 01:11 PM   #1
DarkOne is offline DarkOne  Slovakia
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Default Attenuator via feedback in preamp

hello,
It was quite interesting to me to see thread Monolithic SuperSymmetry with Current Feedback about supersymetry. Here's the circuit http://www.diyaudio.com/forums/attac...?postid=129558. It may be good idea to build an preamp on. But I don't have any experience making preamp (I've made some power amps, but no preamp). First I've been thinking about clasic variable resistor at the input, but I think it might be better to see full signal at the input and then attenuate, but attenuator at the output might vary output impedance. So finally I think that it might be best to perform attenuation inside preamp stage - varying feedback resistor.
It this method good or not within that circuit?

I know about some circuits that perform attenuation without varying output impedance, but I'd like to avoid them. I want low output impedance, which I can't have using these circuits. So I'm looking for other way.
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Old 13th August 2004, 02:39 PM   #2
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The idea of Fb volume was discussed recently and the cons outweighed the pros from what i recall.

Why don't you consider a volume control sandwitched between two active stages?
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Old 13th August 2004, 03:48 PM   #3
DarkOne is offline DarkOne  Slovakia
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It's just because I want to use only one stage in preamp for simplicity. I'd like to make it as simple as possible, but if cons outweighted pros in this application I'm asking, attenuator-preamp or preamp-attenuator topology is better?
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Old 13th August 2004, 04:08 PM   #4
eLarson is offline eLarson  United States
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I would go something like fixed attenuator per input device, followed by your gain stage, followed by a lower-impedance variable attenuator at the output for controlling the output level.

With this method you can tailor the input levels of each of your input devices so that you are always running in the "sweet spot" of the gain stage. Also, you won't be struck with big differences in sound level when switching between inputs.
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