LM3886 Balance Control

manauman · 14th February 2013, 07:24 PM

I'm assembling a two-channel (stereo) chipamp LM3886 kit following the user guide and am looking for a simple way to control the balance between L and R channels. For volume control I am using dual-ganged 25K pots on the amplifier input as recommended in the amplifier board schematic. As for balance control, my first thought is to use another pair of dual ganged pots, each between amp IN and GND (a CW turn attenuates one channel while increasing gain on the other, a CCW turn does the opposite) but it is not clear to me how well this will work or whether it is a good idea. Any suggestions?

Minion · 15th February 2013, 12:05 AM

Generally you would use a dual ganged linear pot with one gang wired backwards so that when you turn the pot one channel increases in volume and the other channel decreases in volume ......

Cheers

Mooly · 15th February 2013, 06:46 PM

You can add a balance control in front of the volume pot. See fig 4 here,
Hi-Fi Preamplifier

DUG · 15th February 2013, 09:00 PM

Quote:

Originally Posted by Mooly

You can add a balance control in front of the volume pot. See fig 4 here,
Hi-Fi Preamplifier

That is the way I do it...saw it in a '70 stereo...used it ever since.

manauman · 18th February 2013, 02:12 PM

Thanks for the ideas. I'll let you know how it turns out.

Fcrawley · 19th February 2013, 04:22 PM

Look at LM1036 For the controls to your amp

manauman · 20th February 2013, 01:34 PM

Thanks, I was not aware of this IC. TI is sending me a free sample.

KatieandDad · 20th February 2013, 02:01 PM

There are some very simple ways to implement a balance control if you don't want to add extra amplification into your design.

The simplest way is to use a dual linear track pot with each half wired in reverse to the other (ie one side is increasing in resistance as the other is reducing). One side can be connected from the wiper of the Left volume pot to ground and the other side from the wiper of the Right.

With the "Balance Pot" in its centre position, both sides will be attenuated equally. As you move the pot off centre one side will attenuate more than the other, and at the extreme ends of the pot one channel will disappear completely.

You will lose a bit of gain but that can be recouperated in the other stages.

manauman · 22nd February 2013, 06:14 PM

Thanks, your suggestion seems to validate my original idea it seems. This amp is not actually going to be used for audio but for a chemistry experiment driving a pair of Helmholtz coils. I'll report back my results.

14th February 2013, 07:24 PM	#1
manauman diyAudio Member Join Date: Feb 2013 Location: Baton Rouge	LM3886 Balance Control I'm assembling a two-channel (stereo) chipamp LM3886 kit following the user guide and am looking for a simple way to control the balance between L and R channels. For volume control I am using dual-ganged 25K pots on the amplifier input as recommended in the amplifier board schematic. As for balance control, my first thought is to use another pair of dual ganged pots, each between amp IN and GND (a CW turn attenuates one channel while increasing gain on the other, a CCW turn does the opposite) but it is not clear to me how well this will work or whether it is a good idea. Any suggestions?

15th February 2013, 06:46 PM	#3
Mooly diyAudio Moderator Join Date: Sep 2007	You can add a balance control in front of the volume pot. See fig 4 here, Hi-Fi Preamplifier __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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15th February 2013, 12:05 AM	#2
Minion diyAudio Member Join Date: May 2006	Generally you would use a dual ganged linear pot with one gang wired backwards so that when you turn the pot one channel increases in volume and the other channel decreases in volume ...... Cheers

18th February 2013, 02:12 PM	#5
manauman diyAudio Member Join Date: Feb 2013 Location: Baton Rouge	Thanks for the ideas. I'll let you know how it turns out.

19th February 2013, 04:22 PM	#6
Fcrawley diyAudio Member Join Date: Mar 2006 Location: Georgia USA	Look at LM1036 For the controls to your amp

20th February 2013, 01:34 PM	#7
manauman diyAudio Member Join Date: Feb 2013 Location: Baton Rouge	Thanks, I was not aware of this IC. TI is sending me a free sample.

20th February 2013, 02:01 PM	#8
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	There are some very simple ways to implement a balance control if you don't want to add extra amplification into your design. The simplest way is to use a dual linear track pot with each half wired in reverse to the other (ie one side is increasing in resistance as the other is reducing). One side can be connected from the wiper of the Left volume pot to ground and the other side from the wiper of the Right. With the "Balance Pot" in its centre position, both sides will be attenuated equally. As you move the pot off centre one side will attenuate more than the other, and at the extreme ends of the pot one channel will disappear completely. You will lose a bit of gain but that can be recouperated in the other stages.

22nd February 2013, 06:14 PM	#9
manauman diyAudio Member Join Date: Feb 2013 Location: Baton Rouge	Thanks, your suggestion seems to validate my original idea it seems. This amp is not actually going to be used for audio but for a chemistry experiment driving a pair of Helmholtz coils. I'll report back my results.