Headphone amp

[audioguru]

With 100 ohms in series with the outputs then the output caps can be only 100uF for very good bass response.

 

[Nigel Goodwin]

The LM1458 is a dual lousy old 741 opamp that is noisy, distorted and runs into trouble above only 9kHz.

This is Audioguru's personal crusade :lol:

741's and 458's are used in huge numbers of amplifiers and audio equipment, and perform their job perfectly well. In a properly designed circuit they aren't noisy, they aren't distorted, and the frequency response is ample.

I tried replacing the 741's in the front end of a mixer/amp using TL072's (or whichever is the single one?) - I only did two of the four channels and compared them at a gig. Fed from 600 ohm microphones you couldn't tell any difference between the different channels.

However, there seems little justification for buying 741's these days, you can get far better devices for less money.

 

[audioguru]

Hi Nigel,
You were just lucky you got a lousy old 741 with noise and distortion less than the ambient at your gig because they don't even have a noise or distortion spec'.

Yes, you might as well use a low noise, very low distortion, wideband and cheap opamp designed for audio. :lol:

 

[Overclocked]

With 100 ohms in series with the outputs then the output caps can be only 100uF for very good bass response.

So in place of the 470uF Cap I could use that OR upgrade it too 1000uF?

 

[Dr.EM]

1000uf should be plenty.

 

[audioguru]

You can hear down to 20Hz but you're lucky if your speakers go down to 40Hz.

LM386 output coupling capacitor:
100uF, 100 ohm resistor feeding an 8 ohm earphone: -3dB= 16Hz
470uF, 100 ohm resistor feeding an 8 ohm earphone: -3dB= 3.4Hz
1000uF, 100 ohm resistor feeding an 8 ohm earphone: -3dB= 1.6Hz!

If you have common 32 ohm headphones then the -3dB cutoff frequency will be 22% lower. :lol:

 

[Overclocked]

Ok So what ive learned so far:

On Pin 1 going to Pin 5, Replace the RC circuit values with 15k and 0.1uF Correct?

On the output Pin 5, I place a 100ohm resistor after the 470uF Cap, Correct? And leave everything else except the above change alone

Look at the circuit below. Ive made changes on it. The did only one channel so you can see what I did.

**broken link removed**

 

[audioguru]

I think it should be wired like this. Use a ceramic disc cap with very short wires at pins 5 and 6. Use a metalized plastic film cap at pin 1.

 

[Overclocked]

Ah ok I see now

Thanks for all your help!

 

[anthony ng]

sorry i m a beginer can everyone tell me what is the bonding IC for the Headger PSP earphone

 

[audioguru]

sorry i m a beginer can everyone tell me what is the bonding IC for the Headger PSP earphone

What is "bonding"?
What is "Headger PSP"?

 

[anthony ng]

sorry it is headbanger earphone. There is a bonding IC in the PCBA. Can you tell what is it Bonding ic for it ..

 

[audioguru]

What is a bonding IC?
The Headbanger project uses a 1/4W LM386 power amplifier IC for each channel made by National Semiconductor.