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Adjusting gain on NE5532
Adjusting gain on NE5532
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Old 8th October 2017, 12:17 PM   #1
HumbleDeer is offline HumbleDeer  Belgium
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Default Adjusting gain on NE5532

Hi,

I recently got myself an ebay board with NE5532 chips as preamps.

New NE5532 Stereo Pre-amp Preamplifier Tone Board Audio 4 Channels Amplifier MO

I'm facing the issue that the pre-amp is causing too much signal gain. A passive pre-amp has too little.

I know the NE5532 or alike use capacitor/resistor values to determine the gain. Can someone help me find a combination to make its output apppropriate for a Sure AA-AB32221 board?

Sure Electronics' webstore 2 x 150 Watt Class D Audio Amplifier Board - TAS5613

Thanks a lot!
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Old 8th October 2017, 12:24 PM   #2
jazbo8 is offline jazbo8
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Adjusting gain on NE5532
Turn the volume down on the preamp?
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Old 8th October 2017, 12:31 PM   #3
Mooly is offline Mooly  United Kingdom
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Adjusting gain on NE5532
If you are unsure which resistors to change (easy but you need the circuit details to determine which) then the safest way is simply to add a low impedance attenuator to the output. The 5532 will fully drive 600 ohms and so something like two 470 ohm in series from output to ground would be a starting point. Take the output from the junction of the two and tweak the lower one up or down to raise/lower the level.
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Old 8th October 2017, 12:32 PM   #4
KatieandDad is offline KatieandDad  United Kingdom
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Put a voltage divider across the outputs of the pre-amp. Mooly just beat me to it. He is suggesting exactly the same.
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Old 8th October 2017, 12:37 PM   #5
scottjoplin is offline scottjoplin  Wales
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This is quite good and there's a link to a youtube video Op Amp Gain | Operational Amplifier Calculation Equations | Radio-Electronics.com
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Old 8th October 2017, 12:38 PM   #6
HumbleDeer is offline HumbleDeer  Belgium
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Quote:
Originally Posted by jazbo8 View Post
Turn the volume down on the preamp?
That would technically do it, but this wouldn't fix the issue. I would still be able to accidentally whoop the volume to the max.



Quote:
Originally Posted by Mooly View Post
If you are unsure which resistors to change (easy but you need the circuit details to determine which) then the safest way is simply to add a low impedance attenuator to the output. The 5532 will fully drive 600 ohms and so something like two 470 ohm in series from output to ground would be a starting point. Take the output from the junction of the two and tweak the lower one up or down to raise/lower the level.
And how can I determine which resistors I should be using? I don't have spare parts in drawers or alike, so I'd have to go and scavenge hunt for things. I know what a voltage devider is, and wanted to try one too, but decided it may be easier to tweak the board instead or something.
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Old 8th October 2017, 12:49 PM   #7
KatieandDad is offline KatieandDad  United Kingdom
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Try a 1K trimpot to ascertain the values you need.
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Old 8th October 2017, 12:52 PM   #8
jazbo8 is offline jazbo8
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Adjusting gain on NE5532
Quote:
Originally Posted by HumbleDeer View Post
That would technically do it, but this wouldn't fix the issue. I would still be able to accidentally whoop the volume to the max.
That's an operator issue, and has nothing to do with the design of the preamp. The volume control is included precisely for adjusting the gain/volume, so why do you want to make things harder for yourself, have too much time on your hands?
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Old 8th October 2017, 12:57 PM   #9
Mooly is offline Mooly  United Kingdom
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Adjusting gain on NE5532
You can only tweak the board if you know the circuit configuration. Having a tone control on there complicates things because you could end up altering the wrong part of the circuit.

The gain follows the standard relationships as shown in the diagram depending on whether they are configured as non inverting or inverting.

Increasing R1 lowers the gain for non inverting configuration.

Voltage gain equals (Rf/R1) + 1

For the inverting stage the gain is simply Rf/R1
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Last edited by Mooly; 8th October 2017 at 12:58 PM. Reason: Removed text
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Old 8th October 2017, 12:59 PM   #10
HumbleDeer is offline HumbleDeer  Belgium
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The NE5532's are only for gain staging. Tone control is done by a passive network. I'll see if I can obtain a schematic from the seller. That would work right?

And, which of those resistors is the one responsible for gain locking?
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