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Chip Amps Amplifiers based on integrated circuits

Making preamplifier...
Making preamplifier...
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Old 20th December 2017, 01:33 PM   #21
Mooly is offline Mooly  United Kingdom
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The 0.47uF input cap should be a small film type (preferably).

The others are all electrolytics. This time the plus end always goes to the opamp for all three.
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Old 20th December 2017, 01:39 PM   #22
diy1995 is offline diy1995
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I see. In that case I will use 22uF. I'm even thinking of using another bigger capacitor and selector switch between 22uF and something bigger, for the moments when I'm in the "drop that low" mood. If that makes any sense.
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Old 20th December 2017, 01:47 PM   #23
Mooly is offline Mooly  United Kingdom
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If you look at the scales you can see that even the 1uF cap is only around -3db down at 20Hz.

Here are four different values and their effect. Look at the circuit at the bottom to see the value list. We are just looking at 1 Hz to 1kHz now to make it easier to see.
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Old 20th December 2017, 01:56 PM   #24
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Oh I see. But is there any disadvantage in using bigger capacitor? If not I would use 100uF then. Because when it comes to bass, I want to squeeze as much as I can.
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Old 20th December 2017, 01:59 PM   #25
Mooly is offline Mooly  United Kingdom
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The only possible disadvantage is that you might notice larger switch on thumps as things charge up. That problem affects all circuitry though.

Ideally you should be using a speaker delay relay on the main amplifier output to make it all totally silent.
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Old 20th December 2017, 02:11 PM   #26
diy1995 is offline diy1995
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That will not be the problem because my amp has turn on delay. I also follow the rule: first turn on everything from source and amplifier as the last one.

What about resistors. Can they all be 0.25w? I know that I will get 0.25w in the store now, anything other will have to be ordered.
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Old 20th December 2017, 04:46 PM   #27
Mooly is offline Mooly  United Kingdom
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All 0.25 watt is perfect for the preamp.
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Old 20th December 2017, 05:06 PM   #28
Keruskerfuerst is offline Keruskerfuerst  Germany
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For your preamp, you need a gain of 20 dB.
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Old 20th December 2017, 06:32 PM   #29
diy1995 is offline diy1995
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Why 20dB?
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Old 20th December 2017, 06:38 PM   #30
Mooly is offline Mooly  United Kingdom
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I wondered where that had come from as well

One thing to remember... running on a single 12 volt supply will limit the output to around 3.2 vrms. That means that for a gain of 12db (as we have set it up for) you will not be able to apply more than around 850mv rms to the input. Any more and it will clip.
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