Comments on: Pocket headphone amplifier

By: Digonto

Digonto — Thu, 06 May 2010 15:55:56 +0000

Seerharaman dada, thanks you a lot .

By: seetharaman

seetharaman — Thu, 06 May 2010 11:26:07 +0000

I have given you the idea for the volume control. For stereo application you require 2 potentiometers or a single stereo potentiometer. one potentiometer slider to Pin7 of the IC, and the other potentiometer slider to Pin no6 of the IC.
104 stands for 0.1uF.
1uF = 1000nano farad
1nano farad = 1000 Pico farad
1uF = 1000000 Pf
0.1uF = 100 nano farad (nF) = 100000 Pf..
If you use a 47K potentiometer use around 47 K in series with the pot before connecting to card output, This should match the line impedance 100K. or use a 100K pot, which are freely available, without any additional resistance.

By: Digonto

Digonto — Thu, 06 May 2010 10:04:23 +0000

Seetharaman dada,
Thanks for your reply . I don’t understand first line . You are saying-”Above Circuit” . But which circuit- are you saying above OPA134 Circuit ? But I have built same as circuit from the diagram of IC DATA SHEET of TDA2822 .

As your instruction, If I connect both channel (L+R) in Pin6, then it will be look like Bridge circuit (As Shown in the IC DATA SHEET). But I have stereo input . Can I ask- why will we input both channel in Pin6 ?

I want to add a volume control (I mean VR) in the circuit . please tell me How can I do that ?

And 0.1µF means 1000PF (0.1x100x100). That will be 10³ . Is my calculation right ?

And as you are Indian , then you should be familiar with GADMEI external TV card . I am using this amplifier for this TV card to my headphone . I need to set the volume of TV card to “Vol1″ . If I increase the volume to “vol2″ , then the amplifier output becomes so noisy . That means- This input line is so high for the TDA2822 .

So, I want to add an Resistance in input line . How much Resistor will I use for input Resistance ?

- Thanks

By: seetharaman

seetharaman — Thu, 06 May 2010 04:55:32 +0000

Hi Digonto You connect C1 of the above circuit to Pin 7 (pin 6 for the other channel) of the IC TDA2822. C6 & C7 can be either type and should be 104PF (0.1) not 102(0.001 that is 1000PF)
102 First two digit indicates the value and third is the multiplier as 10²
103 First two digit indicates the value and third is the multiplier as 10³ etc
Similar to colour codes but with numbers.

By: Digonto

Digonto — Wed, 05 May 2010 22:34:54 +0000

Hello Seetharaman,
As your advice I have built a mini headphone amplifier with TDA2822M today . I have built the circuit same as test circuit (Stereo) shown in the Data Sheet . I have used a 9V PP3 battery to power the circuit . Now I want to add a volume control in circuit . Where and how will I add the volume control ? Can u give me feedback or a diagram ?

And for C6 & C7 0.1µF capacitors- which will I use- Is it 102PF (Ceramic disc) or 2A102J (polyester film)? I have used 102PF capacitor . Is it OK ?

- Thanks

By: seetharaman

seetharaman — Mon, 08 Mar 2010 07:32:31 +0000

For the above application DIP8 pin TDA2822M FCI Semiconductor Dual Low-Voltage Power Amplifier in bridged mode is most suitable. You may refer to manufacturers application/datasheet. can work from 2 to 15 volt into 4to 32 ohms load. this ic is used in most walk-mans.

By: stex

stex — Mon, 08 Mar 2010 00:30:45 +0000

thanks for the help, ill try to find the part

By: admin

admin — Sat, 06 Mar 2010 06:21:08 +0000

reply to stex
LF151 is possible a substitute for OPA134

By: stex

stex — Fri, 05 Mar 2010 14:34:25 +0000

Mate, i cant find OPA134 anywhere…is there a replacement for it? help asap

By: stranger

stranger — Wed, 17 Feb 2010 13:25:00 +0000

the ic1 opa134 is very costly..any cheaper alternative?