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Chip Amps Amplifiers based on integrated circuits

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Old 19th December 2017, 11:56 PM   #11
PRR is offline PRR  United States
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The STK442-090 has gobs of gain in reserve.

Make these resistors smaller.
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Old 20th December 2017, 08:32 AM   #12
Mooly is offline Mooly  United Kingdom
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Originally Posted by diy1995 View Post
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?
You could make a single rail (0 and 12 volt supply) but it would be a different circuit to this one. This one would not work on single rail.

Do you want a single rail design ?

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Originally Posted by diy1995 View Post
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?
The 10uF acts as a DC block and also forms a high pass filter in combination with the impedance of the load.

If your amp has a 10k input impedance then you could use a 22uF cap. When the amp is built and working, be sure to connect the electrolytic cap to match the DC offset of the opamp.

In other words, if the DC voltage at the opamp output pin is positive (for example +100mv) then connect the + of the cap toward the opamp.

If the opamp output pin is negative (for example -100mv) then connect the negative of the cap toward the opamp.
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Old 20th December 2017, 12:29 PM   #13
diy1995 is offline diy1995
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Originally Posted by adason View Post
I know this is in chip amp section, but sometimes even 3 transistor preamp can sound amazing...
I will use 4558 ICs because I have them.
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Old 20th December 2017, 12:35 PM   #14
diy1995 is offline diy1995
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Originally Posted by Mooly View Post
You could make a single rail (0 and 12 volt supply) but it would be a different circuit to this one. This one would not work on single rail. <snip>
Thank you for explanation.
Yes I would like to make it single rail. Because I will use 12v adapter for second opamp (for my Zeck amplifier)

And I will need 12-0 power supply on my DIY amp anyways for Vu meter and fan.

Is this the right design for single rail?
My professor showed me this design for single rail today. He sad that I need to calculate value for c1, c2, r1 ,r2, but well... I have no idea how to.
20171220_142213.jpg

EDIT:
I won`t be making preamp for my DIY amplifier because user "PRR" told me to make 2 resistors on the amps circuit smaller and I will get higher gain.
Now I just need "the 12dB boost" one for my Zeck amp

Last edited by diy1995; 20th December 2017 at 12:49 PM.
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Old 20th December 2017, 12:39 PM   #15
diy1995 is offline diy1995
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Originally Posted by PRR View Post
The STK442-090 has gobs of gain in reserve.

Make these resistors smaller.
Thank you for this tip. Looks like I won`t need preamp for this one at all.
So gain will rise linearly? For example 1.8k / 2 = 0.9k, that means double the gain? thank you
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Old 20th December 2017, 12:50 PM   #16
scottjoplin is offline scottjoplin  Wales
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This is about setting gain in op amps but the same applies in your situation, I hope it helps
Use the equation for non-inverting amplifier YouTube
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Old 20th December 2017, 01:01 PM   #17
Mooly is offline Mooly  United Kingdom
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Originally Posted by diy1995 View Post
Is this the right design for single rail?
My professor showed me this design for single rail today. He sad that I need to calculate value for c1, c2, r1 ,r2, but well... I have no idea how to.
Its basically OK. Give me 5 minutes....
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Old 20th December 2017, 01:16 PM   #18
Mooly is offline Mooly  United Kingdom
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Like this. The one you showed is inverting... which probably doesn't matter unless absolute phase bothers you in the design.
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Old 20th December 2017, 01:20 PM   #19
diy1995 is offline diy1995
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Originally Posted by Mooly View Post
Like this. The one you showed is inverting... which probably doesn't matter unless absolute phase bothers you in the design.
Thank you. I will use this desing. I noticed that u used 100k load. Is the circuit ok for 10k?

Capacitors are all bipolar?

Last edited by diy1995; 20th December 2017 at 01:24 PM.
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Old 20th December 2017, 01:31 PM   #20
Mooly is offline Mooly  United Kingdom
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The 100k load is just to correctly terminate the output and to provide a known and reliable path to charge the output cap. A resistor should always be present in that location but it is best to keep the value high.

The output will drive a load down to 600 ohms for most audio opamps. The lower the final load resistance, the bigger the output cap needs to be in order to maintain bass response.

Here is your 10k load added and using 22uF and then 1uF. See how the bass rolls off.
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