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Chip Amps Amplifiers based on integrated circuits

Making preamplifier...
Making preamplifier...
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Old 19th December 2017, 05:47 PM   #1
diy1995 is offline diy1995
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Default Making preamplifier...

Hello,
I need to make preamplifier for my DIY STK442-090 amplifier.
It plays good, but I know that it can go way louder.
Now I have few ICs and I want to know which one would be the best and also another factor is quantity of external components needed because I will be making it on prefboard.
I have:
BA4558N

4558D

KA4558

I have at least two pieces each.

Another thing is I would like to make preamplifier that will give 12dB boost, because I have pro level audio power amplifier that has +4dB input and I need to connect it to -10dB input.
What about that one?

Thank you for help!
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Old 19th December 2017, 05:59 PM   #2
Keruskerfuerst is offline Keruskerfuerst  Germany
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You need a power supply.
You should use a better audio amp like OPA2134PA or more advanced.
A volume control chip from TI.
Gives a Gain of +20 dB.
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Old 19th December 2017, 06:31 PM   #3
diy1995 is offline diy1995
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Quote:
Originally Posted by Keruskerfuerst View Post
You need a power supply.
You should use a better audio amp like OPA2134PA or more advanced.
A volume control chip from TI.
Gives a Gain of +20 dB.
Hello,
yes, I know that I will need power supply.
ICs that I listed aren`t good enough? They were used in hifi components...

"A volume control for chip TI" you mean for example PGA2311? I had a look at the datasheet and found out that this is digitally controlled, is there any good alternative that is analog controlled? I really don`t need it to be digitally controlled and this just makes it more expensive to build...

Thank you for help

Last edited by diy1995; 19th December 2017 at 06:39 PM.
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Old 19th December 2017, 06:37 PM   #4
Mooly is offline Mooly  United Kingdom
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Making preamplifier...
You can run an opamp from the main amp rails via a simple resistor/zener supply. The 4558 is OK but could be swapped later for something better.

The 4558 is dual opamp so only one device needed for stereo.

So you need a voltage gain of 4 (12db) which is easy using a 10k and 3k3 feedback network.

If you tell us the supply voltage of the main amp then we can work out the power supply details.
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Old 19th December 2017, 06:45 PM   #5
diy1995 is offline diy1995
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Hello,
In that case I will use a socket so I can swap it later if needed.
Power supply for the main amp is 31-0-31vdc, but I will add 12vdc supply because I need it for VU meter and I have transistor that have wires for 31-0-31vdc and 12vdc...

I need input signal gain between a laptop and power amp (this is another power amp for PA not the first one). So I guess this is the voltage gain right? Can I get more information on that? For that one I would like it to sound good, because the power amplifier sounds amazing (Zeck PT7 2 x 450w @ 8ohm)

Thank you

Last edited by diy1995; 19th December 2017 at 06:48 PM.
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Old 19th December 2017, 06:50 PM   #6
Mooly is offline Mooly  United Kingdom
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Making preamplifier...
Well the opamp can be fed from two resistors (one for each rail) of 1500 ohms and with a 12 or 15 volt zener to ground to stabilise each rail. A classic resistor/zener shunt.

For a low current VU circuit you could also use a standard 12 volt regulator running off the 31 volt rail. In fact that would be perfect for the opamp as well. The negative 12 rail would still be the resistor and zener.
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Old 19th December 2017, 06:56 PM   #7
Mooly is offline Mooly  United Kingdom
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Making preamplifier...
Like this:
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Old 19th December 2017, 07:20 PM   #8
diy1995 is offline diy1995
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So this IC needs +12 and -12, not just +12 and GND?

I don`t need 12dB gain for the amplifier with +31-0-31 supply, I don`t know how much gain I do need for that one. I think that I should use a trimmer and adjust it by listening to see how much can I push it before clipping.

I need preamp with 12dB gain for another amplifier. I will have that preamp in it`s own enclosure with it`s own power supply.

So for the second preamp with 12dB gain I can use your schematic, just without r2, r4, zener diodes and 12-0-12 power supply?
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Old 19th December 2017, 07:57 PM   #9
diy1995 is offline diy1995
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I can`t get 10uF in the shop near me, can I use any other value?
I see that you used 100k load in the simulation. My amp has 10k input. Should anything in schematic be changed because of that?
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Old 19th December 2017, 08:50 PM   #10
adason is offline adason  United States
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I know this is in chip amp section, but sometimes even 3 transistor preamp can sound amazing...
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