TDA7293 circuit = half wave rectifier

[booj]

My first try putting an amp together using this chip. Any suggestions gratefully accepted.

[teemuk]

To tell the truth, it's a mess.

- Does it have an input resistor at all? It is Essential!
- If the 0R1 current feedback resistor is being omitted then the feedback resistors with shunt capacitor need a low resistance parallel resistor, otherwise the feedback loop's impedance and closed loop gain will be way too high for any practical use
- Halfwave rectified power supply and +-12V supply voltage? For this the TDA7293 is pretty much overkill.

[Jazz P Bass]

TDA7293

Should have just followed the datasheet.
Link:http://www.st.com/stonline/products/...re/ds/6744.pdf

[booj]

Thanks for the response teemuk and jazz p bass! Just looking for some input. I'm basically following the Marshall AVT100 schematic.

avt100x-60-02-iss1[1].pdf

avt100x-61-02-iss2[1].pdf

avt100x-62-02-iss3[1].pdf

Yes, it's a mess teemuk. Your point being?

I have the datasheet. I'm just trying to copy a circuit minus the FDD circuit.

[J M Fahey]

1)There's no reference at all to TDA7293 on any of those PDF's you post .
being:
Attachment 7657 <-- preamp/front PCB
Attachment 7658 <-- PSU+Tube/back PCB
Attachment 7659 <-- Discrete Power amp using SAP16P/SAP16N enhanced power transistors.
2) I think you got useful input: "Follow the datasheet" ; that's better advice than what Marshall did.
3) We can't even figure how the signal input gets in.
There's no indication on the schematic, no input jack symbol or label.
4) The power supply is a mess, for *any* power amplifier intended to drive a speaker.
Ripple will destroy the sound.

[Jazz P Bass]

CT Bridge Rectifier

Start with a good power supply.
Center tapped bridge rectifier for +Vdc & -Vdc.
Link:Diode bridge - Wikipedia, the free encyclopedia
You really should capacitor couple the input.
I do not think Pin#9 should go above 5 Vdc.
You have it connected to V+.

[booj]

Thankyou for your replys and your patience! Ok, for starters here is something that may make more sense. This is the amp that uses the TDA7293 in the output stage.

avt50_60_02.pdf

avt50_61_02.pdf

avt50_62_02.pdf

I really appreciate your direct responses to such an awful post. I'll get back on this and maybe show a picture of this thing when I get it going.

[Enzo]

Page 2 of 60-02 shows the power amp circuit. Really it is pretty basic. The details around the 7293 are on the upper right corner as to connections, CN5 and CN4.

For the IC pins themselves, drawing 62-02 covers that.

C13 is the input to the power stage, but please note there is a feedback sample from the output back to IC5b before that point.

Duplicating the power amp stage itself should work, but you will want to include the stuff to the right, especially R58 and C92, your stability network. You could eliminate the headphones stuff if you like.

BUt a TDA7293 data sheet. should have a sample circuit that would work. And if you wne to the chip manufacturer's web site there may even be "application notes" which are articles written specifically to help someone design their part into a useful circuit.

Here, not only does this data sheet have sample circuits, it even provides circuit board layouts you can copy to make your own boards for it.

http://www.st.com/stonline/books/pdf/docs/6744.pdf

[booj]

Yes, I'm following you Enzo. The 10 ohm and the .22 are important.
I did fix the circuit to an extent. Just the basic fix. Got down to just following the scat from the data sheet which is posted here


I'm just an irresponsible kid with a new toy and can't wait til it's unwrapped to do something with it.
I'll try to be a little more responsible and do more homework before posting about a new issue to me.
I'll work on this monster for a while and get back on this post when I've accomplished making a good basic circuit.