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3rd November 2003, 06:12 PM
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#1 |
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diyAudio Member
Join Date: Oct 2003
Location: Toronto
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The Ultimat GainClone!
A MUST Conditions:
1. No DC present at the Source output. 2. The pot MUST be of a good quality or Make-Before-Brake attenuator switch. Otherwise danger of lots of DC voltage at the output. 
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3rd November 2003, 07:21 PM
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#3 |
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diyAudio Member
Join Date: Apr 2003
Location: Cambridge
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Just a quick point, but you do realise that these circuits do go against what was mentioned before in the other thread about the resistors being mathced for the + and - inputs to ensure minimum DC offset at teht output due to the input bias currents?
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3rd November 2003, 07:29 PM
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#4 |
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diyAudio Member
Join Date: Oct 2003
Location: Toronto
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You are absolutely right. Some people are willing to put-up with some (up to 60mV) on the output (due to the imbalance at the input that you are talking about). I think the other problem would be the unpredictability of the offset (different amps have different Ib)
I'd sacrifice some purity and use a decoupling input cap. That’s what I'm doing. |
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3rd November 2003, 10:58 PM
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#5 |
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diyAudio Member
Join Date: Dec 2001
Location: SIUE, Illinois, USA
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i think a resistor in series with the noninverting terminal has been used for the purpose of DC offset protection. also, turning the ground for the feedback into a DC voltage will allow you to trim away the DC offset so that it is lower. this adds noise though.
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if only it could be used for good, not evil... |
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3rd November 2003, 11:03 PM
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#7 | |
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diyAudio Member
Join Date: Apr 2003
Location: Cambridge
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Quote:
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3rd November 2003, 11:07 PM
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#8 | |
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diyAudio Member
Join Date: Dec 2001
Location: SIUE, Illinois, USA
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Quote:
it wouldn't be dc then would it? in anycase, DC offset causes a turn on and turn off pop in most amps. annoying.
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if only it could be used for good, not evil... |
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3rd November 2003, 11:08 PM
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#9 | |
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diyAudio Member
Join Date: Dec 2001
Location: SIUE, Illinois, USA
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Quote:
in in series with the input basically. really from classic analysis it does nothing. kinda like the resistor to ground in the inverting config. ideally does nothing.
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if only it could be used for good, not evil... |
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3rd November 2003, 11:15 PM
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#10 |
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diyAudio Member
Join Date: Apr 2003
Location: Cambridge
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You mean R1?
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