TDA7266M Amplifier, little/no base

[spilihps]

Hello!

So i "wired" up a small and simple amplifier project on a prototype board. For a little radio project im working on.

To much of my surprise it really sounds good. Both very low noise and the clarity is really great.
However, the bass is very low or almost none existent. Firstly i thought it might me my Si4703 FM chip that is not tuned properly. So then i tried both my mobile phone, and a regular stereo as input. And its really really low base on those also.

Im not sure what im missing, My output is a regular Samsung 6ohm 20w bookshelf speaker.


The circuit consists of the two diagrams attached to this. The TDA7266m is from the datasheet, and the tl072(used as a pre-amp) is from the link in the picture.

[HB9EVI]

Try with a bigger cap on the input; with those 0.22u and the input impedance, you have a high pass with a -3dB corner freq. of 24Hz. Go with 1u for a try

[MasterT]

TL072  can't work at +5,

(1) VCC+ and VCC– are not required to be of equal magnitude, provided that the total VCC (VCC+ – VCC–) is between 10 V and 30 V.

http://www.ti.com/lit/ds/symlink/tl072.pdf

[Audioguru]

EDIT: Its (+) input is biased at half the supply voltage.
Of course the TL072 needs a minimum supply voltage of 10V but more is better.
Why is the preamp inverting with an extremely low input impedance of 1K? The datasheet for the radio IC says that its minimum allowed load is 10k. Maybe that is why the bass is cutoff.
All my preamps are non-inverting with an input impedance of at least 100k.

[spilihps]

Sorry, i might have attached the wrong schematics on the 072.

I do remember that i changed the design due to a problem with the first one i tested.

I am out right now but will confirm this when i get home again

But it is fed with the same supply as the TDA about 12v.

[spilihps]

Thanks guys for your help.

I can confirm that i posted the wrong TL072 circuit.

Also tried to feed the main amp directly and the bass is back.
However, always fun to learn something new, so why not.

So the problem is in the pre-amp that i have apparently failed miserably with 

So instead of hunting down what circuit i did go for i better just hook up a new one.
Do you guys have an idea or pointer on a circuit that would be suitable?

[MasterT]

http://www.redcircuits.com/Page60.htm

[spilihps]

Thanks! That’s a great link with information also.

However it calls for 20v minimum. I would like to be at 12V or 15V. would it be to far off?

[MasterT]

Anything between +10 and +30 is fine

[spilihps]

Great! Thanks.

Will try to build this and report back. Really like the bass-boost feature, going to be fun to play around with!