Higher output of TL082

[Ragnwald]

I´m going to change the resistors marked in red at the schematic below, to get more gain, so i nead adwise of resistor values.

It´s a two way crossover filter, that has cracy to low output.
All OP-amps are TL082CP.

Anyone give me a hint where to go?

http://web.telia.com/~u49831149/HigherOutput.jpg

[Nrik]

You could just increase the values of the marked resistors.
Double value = double amplification.

However, you will might 'hit the roof' in the subwoofer filter.
You have allready 20 times amplifications, and if you use for example +-15volts supply then your filter will clip at 0.75V input signal.

What is the value in VR2 and at what position do you normally use this pot?

Because if it is only operated in the lower part, you might dont really need extra gain here, so just change the values of the satellite filters

[Ragnwald]

Originally posted by Nrik


However, you will might 'hit the roof' in the subwoofer filter.
You have allready 20 times amplifications, and if you use for example +-15volts supply then your filter will clip at 0.75V input signal.

What is the value in VR2 and at what position do you normally use this pot?

Thank´s Nrik.

The voltage out for the main amps, is about half the voltage at the the input, from the pre amp.
I would be glad to have the same voltage out that is put in.
There is no way to drive the main amps to full output power, they nead about 1,5 - 2 Volt.

All pots are 20K and the ballance between woofers and tops are ok, when i turn woofer vol pot max.

The rail lines are about +/- 16Volt.

Any suggestions?

[Nrik]

hmm sounds strange - the filter it self should not alter the signal level.

Do you know the input impedance of your poweramp(s)?

If it has a low input impedance (Old electrocompaniet amps are at 1.2kohm) then R3, R6, R9 and R10 will form a attanuator with the input impedance of your poweramps.

You could reduce these resistors to 100 ohms, or at best add a unity gain buffer ot each output.

[Ragnwald]

I don´t think there is something special with the prestages and the poweramps.
I have preamps with NE5534, OPA627 and AD825 for driving input of the filter and mainamps are Rotel 1090, Behringer EP1500 (10K), Nad 2155, Audion Silver Night and some diy-amps, driven by the filter. Don´t know the inputimpedance of all of them, but no one nead much voltage for full power and the problem is the same for all of them, when i put the filter in between.

Is it normal to decrease power through a analog filter?
Could it be just missing output bufferstages, for driving my poweramps, as you suggested?

[Nrik]

Then I have no clue.
Maybe it is our measurement technique that cheats you.

Anyway - measurements aside - if you need more gain, you should just add more gain.
You could start by increasing the resistors in th feedback of the input amps. Just double them, and see what the result is. Be aware of clipping in the subwoofer. Test it with an oscillloscope, or listen for distortion with a full range speaker on the subwoofer output.

If you experience clipping, then go back to the original values, and add amplifying buffers to the output.
http://en.wikipedia.org/wiki/Operati...ting_amplifier
Use R1 = R2, try 4,7Kohms.
Regular buffers won't do the trick. It was only because I assumed the input impedance of your poweramps in combination with the 1Kohms output resistors attenuated the signal. But it seems to not be the case.


By the way - not that it is the source of your problems - the input amplifier inverts the phase. For optimum sound quality of your system you should reverse the phase somewhere else in your system also. Most easy done by switching the + and - to all your speakers - both sub and sat, an both left and right.

[Ragnwald]

Thank´s Nrik, i´ll try your suggestions.