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Chip Amps Amplifiers based on integrated circuits

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Old 29th November 2020, 02:06 PM   #171
Mooly is offline Mooly  United Kingdom
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Complete novice alert! *don't read if easily annoyed by stupid questions*
Have a read at this and scroll down to 'Figure 8'.

Potentiometers (Beginners' Guide to Pots)
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Old 29th November 2020, 03:26 PM   #172
Puffin is offline Puffin  United Kingdom
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I love a happy ending
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Old 29th November 2020, 03:50 PM   #173
GooseyGander is offline GooseyGander  France
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I love a happy ending
None more than me!
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Old 29th November 2020, 04:49 PM   #174
Puffin is offline Puffin  United Kingdom
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I well remember my first point to point GC. I was sooo happy when I got popping and buzzing out of it.....It Lives!......it was some time before it was playing music but when it did it was worth it.
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Old 29th November 2020, 05:42 PM   #175
GooseyGander is offline GooseyGander  France
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Yes, same here! It’s been a while, but so worth it and I’ve learned so much. I don’t know whether I’d have tried it if it wasn’t for a lockdown, so every cloud....��. Also if Mooly hadn’t stepped in and helped me the way he did I would probably have given up. And I’m not going away yet either!
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Old 29th November 2020, 05:54 PM   #176
Mooly is offline Mooly  United Kingdom
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And Iím not going away yet either!..........
Oh heck, so what's next on the to do list
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Old 30th November 2020, 10:26 AM   #177
GooseyGander is offline GooseyGander  France
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Here's what it looks like. It's in an mdf case with a perforated aluminium top and a wooden front. It sounds just SO good! I am slightly surprised I have to turn it up quite a way to get it loud, but there's no doubt the quality is there
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Old 30th November 2020, 11:48 AM   #178
Mooly is offline Mooly  United Kingdom
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That looks great so there is no stopping you now

There are two things to remember with 'having to turn it up quite a way'

First, that is an effect of using a linear rather than a log pot. It will start off OK and then you seem to have it turn it up lots to get any more volume. Ultimately both types give exactly the same levels, they just vary in their position on the dial for a given volume.

The addition of those two resistors I mentioned earlier (just soldered to the pins of the control) change the linear to a log type response.

Secondly, if you find that even on full volume it is not going loud enough then that means that the amplifier isn't sensitive enough for the source you are feeding it from.

You have two choices with that... either add a preamplifier or increase the gain of the circuit you have. Increasing the gain is easy...

The two resistors circled on the diagram set the voltage gain and it is calculated as (Rfeedback/Feed backreturn)+1

So we have (22000/1000) + 1 which is 23.

If you want a bit more gain then you could reduce the 1k a little to lets say 680 ohm. That would give a gain of (22000/680) + 1 which is 33.

I would advise you keep the 22k as it is so as to preserve the DC balance of the amplifier.

Do not make the 1k to low in value although even values down to 470 or even 330 ohm should be OK.

Also never make the 1k much higher (which would reduce gain) because the circuit relies and needs a minimum gain factor to be stable. Higher gain is often more stable and some argue actually sounds better because of the lower feedback factor.

If you change anything then always try it with the bulb first just to be sure all is OK.
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Old 30th November 2020, 11:51 AM   #179
Puffin is offline Puffin  United Kingdom
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Here's what it looks like. It's in an mdf case with a perforated aluminium top and a wooden front. It sounds just SO good! I am slightly surprised I have to turn it up quite a way to get it loud, but there's no doubt the quality is there
Very nice.
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Old 30th November 2020, 11:58 AM   #180
Mooly is offline Mooly  United Kingdom
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This shows the effect of altering the feedback return resistor. The input voltage is a constant and is the centre low amplitude trace.
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