help in building TDA7294

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
hii,
i want to build a amp with TDA7294, i have a pcb layout which i m attaching i would like to know if its ok. or do i need to do anything else,
if i keep the mute and standby pin open is it fine or do i have to attach a capacitor ,

if i have a transformer 20 0 20 @ 4.5 or 5 amps is it ok,

i would appriciate al the help i get regard the pcb,
thanks a lot guys

i have successfully built and used TDA7265 at + - 18v @4ohm with out burning thing chip for last 3 years but i want a change now. and in bombay i havent found any original 3886 or 1875 so i have to go with 7294 as i have managed to get some samples ( 100% original)
how to go about it,,,
 

Attachments

  • 7294_1.jpg
    7294_1.jpg
    25.7 KB · Views: 1,261
Hi, To be able to help you out we really need the circuit diagram with component values on and preferably the manufacturer for the CAPs.

Also the images you have attached are rather small which makes it difficult to tell what is going on.

Ideally please attach top layer, (bottom layer if present) and a seperate silk screen with reference designators. That way we can tell which components on the sch are where on your PCB circuit.

It looks like you don't have any local decoupling on the chip amp. If this is the case then this is definately a problem, this chip goes unstable into low impedances without close local decoupling of arround 22uF(You may get away with this as the bulk decoupling is close). I would also recomend 100nF very close to the chip to reduce the risk of HF oscillation.

Regards,
Andrew
 
Last edited:
hii,
i want to build a amp with TDA7294, i have a pcb layout which i m attaching i would like to know if its ok. or do i need to do anything else,
if i keep the mute and standby pin open is it fine or do i have to attach a capacitor ,

if i have a transformer 20 0 20 @ 4.5 or 5 amps is it ok,

To operate mute and standby, you need at least a resistor.

Your transformer is fine.
 
Hi, To be able to help you out we really need the circuit diagram with component values on and preferably the manufacturer for the CAPs.

Also the images you have attached are rather small which makes it difficult to tell what is going on.

Ideally please attach top layer, (bottom layer if present) and a seperate silk screen with reference designators. That way we can tell which components on the sch are where on your PCB circuit.

It looks like you don't have any local decoupling on the chip amp. If this is the case then this is definately a problem, this chip goes unstable into low impedances without close local decoupling of arround 22uF(You may get away with this as the bulk decoupling is close). I would also recomend 100nF very close to the chip to reduce the risk of HF oscillation.

Regards,
Andrew


hey Andrew...
thanks for the de coupling reminder, i was planning to directely solder the 100nf capacitor on the pin of the iC, my power filter capacitors are samsung-4700uf 50V, or Elna as i dont get panasonic or black gate, so i have to stick with what i get in market, i have made it with schematics from the datasheet for one IC, and the power supply has 4700 + 4700 on each rail with 100nf with each 4700uf /63v or 50 v. i was concerned with what to do with mute and standby pin if i leave it open is it ok.
 
To operate mute and standby, you need at least a resistor.

Your transformer is fine.

hii
i have left the mute and standby pins open is it ok, could you share you pcb layout. i m some what nervous with this amp as i have to add a dir9001 + PCM1794 wiht optical input, Plus TDA7439 there is lot of things going in this amp, and running out of time, my budget is ooo short right now, so i dont know i might stick to my TDA7265 ( 25 +25) as i find it a bit expensive for the speakers , i m picking up pioneer fulrange from parts express, as it fiting my budget, or a tymphany 4.5" still confused on it,, i m severly cash strapped,
more tips please
aditya
 
Mimimum 3 parts to work standby and mute.

Mute is a normally off switch and member of the input circuit. Connect the pin to a 10k resistor.

Standby is a normally off switch and member of the power/output circuit.
Connect the pin to a 20k resistor.
Also connect the pin to a 10uF capacitor.

The opposite end of both resistors connect to V+ at the same place. This looks like "Y" connection.

The opposite (negative) end of the one 10uF cap connects to power ground at exactly the same place as the ground centerpoint that's typically in-between your onboard power caps.

Parts (about 25 cents). . .

Mute: a 10k resistor (from pin to V+ via 10k) to operate the switch.

Standby: a 20k resistor (from pin to V+ via 20k)to operate the switch and a 10uF cap (from standby pin to 0V power ground via 10uF) to interpose a minuscule delay for soft start feature and the cap is also necessary to reduce noise.

EDIT: From the official diagram provided by the manufacturer, you may omit the 10uF capacitor that was supposed to time-delay the mute feature. But, don't omit the 10uF capacitor from the standby feature. See PAGE ONE of the TDA7294 data sheet. ;)
 
Last edited:
. . .my power filter capacitors are samsung-4700uf 50V, or Elna as i dont get panasonic or black gate, so i have to stick with what i get in market, i have made it with schematics from the datasheet for one IC, and the power supply has 4700 + 4700 on each rail . . .

These large caps are great for your power supply board however. . .

For TDA7294, use 220uF//100nF at the chip pins.
You can add more capacitance after a cable run of at least 10cm or longer.
 
Last edited:
mute and standby pin,,,

These large caps are great for your power supply board however. . .

For TDA7294, use 220uF//100nF at the chip pins.
You can add more capacitance after a cable run of at least 10cm or longer.

hiii
i need to know if i dont use the mute and standby pin , ie leave them as it is , then is it ok, like not even a capacitor connected to them , would that let the amp operate or i need the capacitor. \

for some reasons my transformer is droped to 16 0 16 /4.5 amps dont know how its going to sound
 
I don't know if that was exactly the fault, but a few years ago (when I knew much less about electronics) I built some TDA7294 chip amps and I got blown ICs at first while I was leaving the mute/standby inputs floating (with the RCD networks in place).

Actually I was charging the capacitors by feding 35V to the mute/strandby PCB inputs and then leaving them open. The capacitors would take several minutes to discharge to the point where the sound starts fading and then... humm!! and blown IC.
 
Last edited:
I don't know if that was exactly the fault, but a few years ago (when I knew much less about electronics) I built some TDA7294 chip amps and I got blown ICs at first while I was leaving the mute/standby inputs floating (with the RCD networks in place).

Actually I was charging the capacitors by feding 35V to the mute/strandby PCB inputs and then leaving them open. The capacitors would take several minutes to discharge to the point where the sound starts fading and then... humm!! and blown IC.

That must have had a different cause, because what you describe is exactly, what the datasheet shows. Close the switches and charge the capacitors to any voltage between 3,5 V and 40 V to unmute. Open the switches and let the capacitors discharge to below 1,5 V to mute.

Which means, my former post is wrong. You do need voltage on those pins to operate the amplifier. So, if you don't want to use the suggested components from the datasheet, because popping noises don't bother you, you need to connect the stand-by and mute pins to the positive rail. Leaving them floating or grounding them means the amplifier will be muted and in stand-by.
 
hii
in bombay go to amar electronics, he used to sell them for some thing like 50 to 65 per peice, i want to konw where i can i buy LM1875 in bombay, and which is better lm 1875 or tda2050,

I never try lm1875 but experienced member says lm1875 is good. I experienced tda2050 and it is good for low frequencies.

If you refer ESP's project 72 In circuit description on 2nd para "You can also use the TDA2050 (from SGS-Thompson), which has almost identical performance and (remarkably) the same pinouts! "

Now I wish to use tda7294 for woofer either mono or bridge. I am looking for best suitable circuit with minimum components.
 
Aditya, What do you think about attached picture ?

nice. i did find a onlie solution check out a chinese website called gorge and charle's. i found two tda7294 layouts and u can convert the page using altavista language convertor. - babel fish
the link is ---- ³ìªv¬dº¸´µ¹q¤l¹q¸ôºô check out and the pdf at the end of each article has a pcblayout which is ready for tonner transfer,

i m though making a tda7294 pcb layout for my self, you see i have put one of the designs as an attachment, on the first page of this post.

where are you from as in which city,
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.