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Old 21st March 2017, 03:56 AM   #1
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Default Help needed to increase the input gain on a TPA3116D2 amp

I want to use a smartphone as the audio source with my music going to the amp. It works, but the sound is really low unless I turn up the volume all the way up on my smartphone.

I bought the 2.1 amp below and the sound is a little low even with a 19 volt dc psu. I was wondering if there is a resistor that I can change or add a variable pot to increase the input gain.

The amplifier that I bought is here:- TPA3116D2 2x 50W +100W 2.1 Channel Digital Subwoofer Power Amplifier Board | eBay

Thanks
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Old 21st March 2017, 09:37 AM   #2
AndrewT is offline AndrewT  Scotland
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Turn the digital attenuator in the phone right up to maximum.
Or get a better source.
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Old 21st March 2017, 09:46 AM   #3
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In order to select the amplifier gain setting, the designer must determine the maximum power target and the speaker impedance.
Once these parameters have been determined, calculate the required output voltage swing which delivers the maximum output power. Choose the lowest analog gain setting that corresponds to produce an output voltage swing greater than
the required output swing for maximum power.
Pin 8 is the gain control.
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Old 21st March 2017, 09:59 AM   #4
gpapag is online now gpapag  Greece
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Quote:
Originally Posted by JonSnell Electronic View Post
Pin 8 is the gain control.
See page 14 :
http://www.ti.com/lit/ds/symlink/tpa3116d2.pdf

George
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Old 21st March 2017, 10:04 AM   #5
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Turn the phone volume all the way up and use the pot on the amp to control the listening level. If you leave the amp volume turned all the way up and use the phone to control the level, there will be hiss at low volume.
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Old 21st March 2017, 06:53 PM   #6
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Thank you all for the replies.

Turn the phone volume all the way up and use the pot on the amp to control the listening level. I did this and the sound volume is good, but I feel that itís still a little low as I still have to turn the pot on the amp all the way up as well as the volume control on the smartphone.

I think that I will have to read the schematic suggested and alter the resistor at pin 8. I just have to figure out what resistor for the pots, as I may need to put one on the subwoofer an well as the stereo channels.

Iím new to this, so I was wondering how should the pot be oriented. I know one end should go to pin 8 and the other to the ground, but what about the this pin on the pot?
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Old 21st March 2017, 07:04 PM   #7
irribeo is offline irribeo  Netherlands
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If you can post a picture without the heatsink, in good enough resolution, you can probably get very detailed help. Schematic is from TI datasheet and includes a mistake that might not be on your ampboard, but can't tell from vague Taobao/Ebay picture.
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Old 22nd March 2017, 09:17 AM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by james777 View Post
...........I’m new to this, so I was wondering how should the pot be oriented. I know one end should go to pin 8 and the other to the ground, but what about the this pin on the pot?
No.

Your volume potentiometer needs a Signal Input from the Source and sends a Signal Output to a Receiver.
The Signal Input from the Source is a two wire connection. You must use two wires from Source to vol pot. Connect the Signal Flow wire to an outer pin of the three. Connect the Signal Return wire to the other outer pin ("bottom" pin). Make sure the two wires and the terminations are close coupled all along the route. You can use coaxial cable to maintain this close coupling, the core is the signal flow wire and the screen is the signal return wire. If you use coax then keep the exposed core very short, keep the screen intact to as close to the signal connection as you can.

At the output the Signal flow wire is connected to the middle (wiper) pin and the signal return is connected to the "bottom" pin.
Again maintain close coupling of the signal Flow and Signal Return wires all along the route of the two wire cable, including the terminations.

You can identify the "bottom" pin by turning the vol pot all the way down to minimum and then using a continuity meter/ohm-meter to measure from wiper to outer pin. The outer pin that reads near zero ohms is the "bottom" pin. This pin will now have TWO wires. The signal RETURN wire going back to the Source and the Signal RETURN wire coming back from the Receiver.

On both sides of the vol pot you have two wires to transfer the signal. Both wires are SIGNAL wires. None are ground.

If you have a metal can around your vol pot or a metal shaft then these two metal parts should be electrically connected to chassis. Some would refer to these connections as grounding.
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Last edited by AndrewT; 22nd March 2017 at 09:24 AM.
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Old 22nd March 2017, 11:31 AM   #9
gpapag is online now gpapag  Greece
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Quote:
Originally Posted by james777 View Post
I’m new to this, so I was wondering how should the pot be oriented. I know one end should go to pin 8 and the other to the ground, but what about the this pin on the pot?
No. You will not install a pot there. See the attachment.
You have to access the circled resistors and change their values to obtain a higher gain.
With the values shown in the schematic you provided, the gain is 26dB.
You can go to 32dB or to 36dB

George
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File Type: png master-slave.PNG (591.1 KB, 70 views)
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Old 22nd March 2017, 10:31 PM   #10
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Quote:
Originally Posted by gpapag View Post
No. You will not install a pot there. See the attachment.
You have to access the circled resistors and change their values to obtain a higher gain.
With the values shown in the schematic you provided, the gain is 26dB.
You can go to 32dB or to 36dB

George
Thank you all for the replies.

I think that if I can just change the resistors as mentioned it will work. The only thing is that it looks like it was soldered my machinery as the resistors are really small, and I donít know if I can work on it, but Iím willing to give it a try.

Iím also enclosing some photos that I hope would help as suggested by ďirribeoĒ.

Thanks.
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File Type: jpg DSCN0624.JPG (901.5 KB, 63 views)
File Type: jpg DSCN0627.JPG (900.4 KB, 58 views)
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