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Old 3rd November 2003, 11:13 AM   #1
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Default Leach amp input sensitivity

Hi
How i can change input sensitivity for my Leach from now around 2V to around 1,3V.
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Old 3rd November 2003, 12:08 PM   #2
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Try changing R-19 to something smaller. Might affect the sound, but if you don't like it, put the original R-19 back in and figure out how to get more drive from your preamp.

See http://users.ece.gatech.edu/~mleach/lowtim/fdbk.html for an explanaiton of the feedback scheme
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Old 3rd November 2003, 12:23 PM   #3
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Is the Leach amp capable of 40 V rms out (with the PS you have got)?

The amp has gain of 21, a rather normal value. Don't have too much gain beacuse you only get more noise.

The gain is set by (R17+R18)/R19 + 1
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Old 3rd November 2003, 01:14 PM   #4
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Default Changing feedback values

Changing R19 is best done with a scope and a variac or a light bulb. It takes less than a second to blow output transistors once the amp burst into hf oscillation. Cheers.
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Old 3rd November 2003, 10:54 PM   #5
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if i am not mistaken, increasing the voltage gain to get better sensitivity have an impact on bandwidth, the amps were designed to have a bandwidth of 8mhz, this is fixed so that increasing the voltage gain, decreases the closed loop bandwidth...
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Old 4th November 2003, 06:37 AM   #6
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Quote:
the amps were designed to have a bandwidth of 8mhz
I believe you meant a gain bandwidth product of 8MHz.
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Old 4th November 2003, 08:14 AM   #7
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hi mcp,
yes, my mistake, its actualy gain bandwith product!!!!
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