Hello to all,
here I have preamp, but I want amplification 10x. So If I understand well, based on R5/R12 amplification should be 10 times. Correct?
If I want have it just 5x then R15 should be 440 ohms, right?
Thanks for help! 😉
here I have preamp, but I want amplification 10x. So If I understand well, based on R5/R12 amplification should be 10 times. Correct?
If I want have it just 5x then R15 should be 440 ohms, right?
Thanks for help! 😉
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R5 and R12 are not related since they are connected to different op-amp inputs. As depicted the pre-amp is configured as unity gain. To set the gain other than 1x you need a resistor from the inverting input (pin 6) to ground. Then use the gain equation 1+R5/R* to calculate the resistor values. Here R* is the missing resistor from the inverting input to ground.
Regards,
Oleg
Regards,
Oleg
With 2200 and 220 it would be 11 times. With the same values you would have 10 times, but only if you use inverting mode.
I found some Wishay DALE 680ohm. So 2200/680=3,24
But what stands for 1+? Plus the 1 of the value R5? Or it is +1 amplification?
You know, making a website with eshop is for me much more easy! 😎
As it is standard in mathematics you first multiply or divide and only then add or subtract, so you first divide R5/R* and then add 1 to the result...
So I think this is the final version:
I added C3 and C6 220p polystyrene capacitor. I saw that in one Yamaha input curcuit. And 220 ohm resistor after inputs (although don't know why it should be there). R6 should be prevention with cap 100nf against oscillations.
Some ideas how this could be improved?
We all want superior sophisticated high grade ultra fidelity pre-amp with astonishing sound
Don't we?
I added C3 and C6 220p polystyrene capacitor. I saw that in one Yamaha input curcuit. And 220 ohm resistor after inputs (although don't know why it should be there). R6 should be prevention with cap 100nf against oscillations.
Some ideas how this could be improved?
We all want superior sophisticated high grade ultra fidelity pre-amp with astonishing sound
Don't we?
1) You want to have decoupling between each supply rail and ground, not just between the rails (so change C4/C5). Also 1000uF in parallel with the 100nF decoupling cap is very high - read the data sheet for the LME49720 for recommended values.
2) Your input arrangement looks a bit weird to me, why do you have the 1M//220pF before the input cap and not just a cap in parallel with the 100k resistor?
2) Your input arrangement looks a bit weird to me, why do you have the 1M//220pF before the input cap and not just a cap in parallel with the 100k resistor?
Hi Milan,
you power supply blocking is a bit non-typical. The way I have seen this is to have a ~330µF Low ESR e-cap from each supply rail to Ground and as near as possible to each OPAmp-Supply-Pin a 100nF NP0 Ceramic to Ground. The blocking between the supply rails is an additional option, so far as I understand.
Regards,
Winfried
you power supply blocking is a bit non-typical. The way I have seen this is to have a ~330µF Low ESR e-cap from each supply rail to Ground and as near as possible to each OPAmp-Supply-Pin a 100nF NP0 Ceramic to Ground. The blocking between the supply rails is an additional option, so far as I understand.
Regards,
Winfried
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1) Done.
2) I saw 220pf in yamaha preamp scheme, I thought it will be good idea to have it. And 1M was recommended here for discharging caps C1 and C2
My suggestions:
1) Move R8 and R9 right in front of the noninverting inputs. This is the normal place to add some noninverting input protection from the outside world (per Jung);
2) Move C3 and C4 and place these across R5 and R10. Change value to 220 pF for a -3 dB turnover calculates to about 330 kHz which won't appreciably affect op amp speed;
3) The gain of the op-amp will also increase DC offsets. Since you don't have output coupling caps, consider placing 470 uF electrolytic caps between R7 and R12, respectively, to audio ground. Nichicon UES series NP is a good choice here. The low-end - 3 dB turnover frequency computes to about 1.25 Hz and DC is minimized at the op-amp's output;
4) Place your bypass caps for Vcc and Vee supply leads at each op amp pin to ground, not between the +/- voltage rails. Use 0.1 uF film type at a minimum;
5) If the following stage is mostly voltage transfer and not power transfer, you can further decouple the op-amps' Vcc and Vee with a 100 ohm resistor in series and use an electrolytic "reservoir" cap (e.g., 100u/25V) in parallel with a film cap directly to the IC supply pins;
6) Depending on the following stage or device, consider adding a build-out resistor (typically 50-100 ohms) at the output of each op-amp. See the datasheet for more detail about this to help stabilize the circuit into capacitive and inductive loads. I would include it regardless. Often, the feedback resistor is connected to the far end of the build-out resistor to keep gain constant regardless of any voltage drop across the build out, but the feedback capacitor MUST always be connected right to the op amp output. Otherwise, if the feedback cap is also placed after the build-out, excessive phase shift results beyond the phase margin of the op-amp and can cause ultrasonic oscillations.
Paul
1) Move R8 and R9 right in front of the noninverting inputs. This is the normal place to add some noninverting input protection from the outside world (per Jung);
2) Move C3 and C4 and place these across R5 and R10. Change value to 220 pF for a -3 dB turnover calculates to about 330 kHz which won't appreciably affect op amp speed;
3) The gain of the op-amp will also increase DC offsets. Since you don't have output coupling caps, consider placing 470 uF electrolytic caps between R7 and R12, respectively, to audio ground. Nichicon UES series NP is a good choice here. The low-end - 3 dB turnover frequency computes to about 1.25 Hz and DC is minimized at the op-amp's output;
4) Place your bypass caps for Vcc and Vee supply leads at each op amp pin to ground, not between the +/- voltage rails. Use 0.1 uF film type at a minimum;
5) If the following stage is mostly voltage transfer and not power transfer, you can further decouple the op-amps' Vcc and Vee with a 100 ohm resistor in series and use an electrolytic "reservoir" cap (e.g., 100u/25V) in parallel with a film cap directly to the IC supply pins;
6) Depending on the following stage or device, consider adding a build-out resistor (typically 50-100 ohms) at the output of each op-amp. See the datasheet for more detail about this to help stabilize the circuit into capacitive and inductive loads. I would include it regardless. Often, the feedback resistor is connected to the far end of the build-out resistor to keep gain constant regardless of any voltage drop across the build out, but the feedback capacitor MUST always be connected right to the op amp output. Otherwise, if the feedback cap is also placed after the build-out, excessive phase shift results beyond the phase margin of the op-amp and can cause ultrasonic oscillations.
Paul
These are a part of a low pass filter in his circuit. Rather optional, if you ask me. Protection...never ever used such, but then i am a minimalist and remove all non-essential parts 🙂
I would never add a non-essential electrolytic along the signal path in order to remove 1mV of offset. But that's me, i tend to hear these things 🙂
