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Old 28th October 2009, 06:45 PM   #1
sexya is offline sexya  India
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Default help in building TDA7294

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,,,
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Old 28th October 2009, 08:15 PM   #2
sexya is offline sexya  India
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Default top view with components

here is a top view with the components on top,
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Last edited by sexya; 28th October 2009 at 08:18 PM.
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Old 31st October 2009, 05:13 PM   #3
gfiandy is offline gfiandy  United Kingdom
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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 by gfiandy; 31st October 2009 at 05:19 PM.
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Old 2nd November 2009, 01:50 PM   #4
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Quote:
Originally Posted by sexya View Post
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.
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Old 3rd November 2009, 03:54 AM   #5
sexya is offline sexya  India
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Quote:
Originally Posted by gfiandy View Post
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.
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Old 3rd November 2009, 04:09 AM   #6
sexya is offline sexya  India
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Quote:
Originally Posted by danielwritesbac View Post
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
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Old 3rd November 2009, 06:10 PM   #7
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Default 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 by danielwritesbac; 3rd November 2009 at 06:15 PM.
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Old 3rd November 2009, 06:17 PM   #8
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Quote:
Originally Posted by sexya View Post
. . .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 by danielwritesbac; 3rd November 2009 at 06:20 PM.
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Old 14th December 2009, 05:57 PM   #9
sexya is offline sexya  India
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Default mute and standby pin,,,

Quote:
Originally Posted by danielwritesbac View Post
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
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Old 14th December 2009, 07:01 PM   #10
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The TDA7294 will work with pins 9 and 10 floating or connected to ground. You do not need the resistors and capacitors. The drawback is that you may experience pop noises, when powering the amp up, when you don't use those components.
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