Problem with mini amp circuit

[wellington]

I've build a mini amp to use with my xbox (audio out) and headphones, from a 10 years old magazine. The problem is that the final output is to loud and distortion are very high, looks like i have a loud input with low volume, very strange.

Since i am a circuit builder not a developer, i need some help to change this circuit to be a little more soft and clean.

Thanks

View attachment 35515

 

[audioguru2]

Hi Wellington,
Maybe your amp's output is distorted because it is too loud. Turn-down its 10K input volume control.

Your very simple amp circuit has nothing in it that gives low distortion. Use a better circuit, like an LM386.

 

[wellington]

Thanks again audioguru.
I have done some tests here, and find out that if i change that 4k7 resistor to something like 100k the sound gets much better, but still look like a over amplifyed sound like a guitar overdrive (sorry don't know the name, is the one that distorts the sound).

The volume control cracks the sound if is set too low and distorts high frequency.
Maybe using a LM386 will be better, i was thinking about to use the TA8217P ...

 

[audioguru2]

Wellington,
Wait a minute, but "loud input with low volume" and "the volume control cracks the sound if it is set too low" both indicate that the volume control may be wired incorrectly. If the volume control's slider is wrongly connected to the x-box's output, then when you turn it down it is shorting that output, without changing the mini-amp's input/output very much. Please check that. Also, the volume control should be logarithmic, not linear.
I had a hard time reading Toshiba's TA8217P Japanese data sheet, but it seems to be designed for 4 ohm speakers, not 32 ohm headphones (aren't yours?), and needs many capacitors. There are headphones amp chips available that use few if any capacitors.

 

[wellington]

Thanks audioguru, i miss words to express my self :'(
It was like a overdrive, sounds like it's loud but is not, distorted sound with volume control.

Never mind, i've fixed ;D ;D ;D
This was the changes that i've made, now the sound is very clear and smoth with no distortion

About the TA8217P i have the ENG data sheet, send me an email or a PM then i send you over.

View attachment 35517

 

[audioguru2]

Wellington,
Good, you have fixed it.
Its 47uF input cap must have been shorted or very leaky.
Use a 1000uF output cap for better bass with 8 ohm headphones or speaker. 100uf is small for 32 ohm headphones, 220uF would be better.

Never mind the Toshiba chip. I forgive the 2nd World War, but I don't like Toshiba since they were banned from the American market for awhile for being caught (10 years ago?) selling American secrets to USSR or N. Korea.

 

[wellington]

Thank you audioguru for the tips.

The board of this circuit is very small and can't handle a 1000uF cap, also the box that i have put this boards is small too.

With that changes i have a clear (flat) and soft sound, to make the circuit punch the bass a little, using this diagram i use R/C (R7, C6) in parallel with the 180k resistor it will give a good bass, but also kill a good range of the high frequency and drop the final output to half.

To fix that, i change the values of R/C, R is 220R and C is 100uF, still give a good bass and some midle range frequency and still cut the output in half, so I reduce the 180K resistor value to something like 68k.

Now this solve some of the flat sound, but when build this circuit i did not know this site, what is very good, so i will drop this and make the one in the link above.

By the way, i did not know about Toshiba selling secrets, a japanese company doing such a thing is very rare.

 

[audioguru2]

Wellington,
The Mini-box 2W amp is much better than the other simple amp.
I think that its capacitor C2's polarity is backwards.