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Old 2nd January 2010, 01:19 PM   #31
sexya is offline sexya  India
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hey how about the new changes i just did. Thank daniel. Please check these and let me know.
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Old 2nd January 2010, 03:08 PM   #32
pra3718 is offline pra3718  India
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Amp in stand-by position when no input single. Is that possible ?
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Old 2nd January 2010, 05:07 PM   #33
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The circuit you have repaired for Pin 9 (standby) looks like the datasheet and that will work really well.

The circuit you have for Pin 10 (mute) looks really bizarre. It doesn't need three resistors. Charge up both the cap and pin 10 with just one resistor to V+.
However, if you would like to save space, Pin 10 doesn't require a capacitor. It does require the resistor Example: Pin 10 with a single 10k resistor to V+.

I don't like it that the board may interfere with and/or block some of the heatsink. Most TDA7294 boards do this, but its still an unfortunate thing to do. Perhaps try to avoid laying circuit traces rearwards of the amp chip?

EDIT: The 47uF (or 22uF) bootstrap cap need to be a bit farther away from the heatsink so that the cap doesn't overheat and leak.

That's all I can think up right now.

Last edited by danielwritesbac; 2nd January 2010 at 05:17 PM.
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Old 2nd January 2010, 05:38 PM   #34
sexya is offline sexya  India
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hii
thank you for the reply
1) the feed back resistor is on the bottom , and heat sink i m using is (P4 old one) and its cooled with a fan,
2) even i dont like to drag tracks on the back of the chip, but thats the only way to reduce the feedbck path , ( LM1875 would work well wiht a smd register without coming in path of any tracks pin 2 and 4 )
3)47Uf is quiter away from the heat sink i have checked it, and i ahave used a bigger foot print fro it,
4) my man concern is i probably wont get enough power as i due to some financial issue had to satifisy wiht a 34 CT /5 amps and my speakers are 8ohms
so i dont know how much out put i would get , datasheet shows some thing like 35 watts max,
and my speakers are 45watts continus powr - dayton dc130 classic woofer and hivi tweeter 30 watts 8ohms
need to make a speaker box thats going to be a big thign for me.
my TDA7439 firmware is ready so not issue with that luckly
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Old 2nd January 2010, 05:43 PM   #35
sexya is offline sexya  India
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actually i jsut saw the datasheet again , i think i have done the 9 & 10 pin correctly , 10 is mute with diode parrallel to resistor and this is in series with 10k , to vcc
and 9 is capacitor pulled up . m i wrong in interpreting some where
please let me know
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Old 2nd January 2010, 09:55 PM   #36
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Quote:
Originally Posted by sexya View Post
. . . My main concern is I probably won't get enough power as i due to some financial issue had to satisfy with a 34 CT /5 amps, and my speakers are 8 ohms, so I don't know how much output I would get; datasheet shows some thing like 35 watts max, and my speakers are 45watts continus powr - dayton dc130 classic woofer and hivi tweeter 30 watts 8ohms; need to make a speaker box thats going to be a big thing for me. . .
DC130? The 5-1/4 woofers? Power? Um? Double-Voight, also called Half-wave box? That's two quarter wave boxes, one feeding the other, one behind the other (inverted) with the horn output at top. Its colloquially termed "ceiling cannon" and yes that is a lovely challenge, but then you can use DC130 and "power" in the same sentence. Is this a pop quiz?

34ct transformer, which is 17-0-17 vac, right? Then its 25-0-25 DC at the output of your power supply board.
It is fine for those woofers with TDA7294.

If you gave DC130 more power, it would x-max with a sort of loud "pop" sound. The DC130 are quite durable and could withstand a lot of that, although its not musical with frequent x-max noises.

SO, if you want to push DC130 to x-max with TDA7294 and your 34vct transformer. . . bridge the TDA7294--its really easy with your board. To do it, you connect a resistor between the NFB cap and the Bootstrap cap--see the datasheet for more details.

p.s.
Personally, I would like to see available space to use 2 of 100uF cap per each rail (makes 200uF). And, this is because its difficult to find (and near impossible to source) signal grade hi-fi caps in sizes larger than 100uF. ST doesn't make the cleanest amps, but they can get really clean if given a Lot of extra effort with the power supply. EDIT: and if the power is really clean, then your heatsink will work just fine without the fan.

Last edited by danielwritesbac; 2nd January 2010 at 10:00 PM.
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Old 2nd January 2010, 09:59 PM   #37
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Quote:
Originally Posted by sexya View Post
actually i jsut saw the datasheet again , i think i have done the 9 & 10 pin correctly , 10 is mute with diode parrallel to resistor and this is in series with 10k , to vcc
and 9 is capacitor pulled up . m i wrong in interpreting some where
please let me know
The board will work fine.

However, both mute and standby can use simple "capacitor pulled up" which is simpler.

For "simplest" you can omit the capacitor from the mute; however, its just fine if the board has a spot to install that capacitor. So, the "places to put extraneous parts" is not a problem.
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Old 3rd January 2010, 03:00 AM   #38
sexya is offline sexya  India
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hii
u mean to say that if i have 100 uf or 330 uf instead of the 2200 nichicon , per rail it would nice, or i need to keep both of them , i didnt really get that point,
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Old 3rd January 2010, 03:44 AM   #39
sexya is offline sexya  India
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hey daniel i would would be going in for a two way box not a half voight,
hve a look at TDA7462 ( its got subwoofer control) i m planning to work on its software,
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Old 3rd January 2010, 03:54 AM   #40
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Quote:
Originally Posted by sexya View Post
hii
u mean to say that if i have 100 uf or 330 uf instead of the 2200 nichicon , per rail it would nice, or i need to keep both of them , i didnt really get that point,
Well, here it is: The TDA7294 "can" react badly with extra heat and muddy sound if there are any caps larger than 330uF at the amplifier board. SO, put the big caps on the power supply board. Check out the discrete amplifiers in the solid state forum because the majority do the exact same thing.

P.S.
My personal preference would have room to put 2 of 100uF for the v- rail. . . and 2 of 100uF for the v+ rail. . . and a single 2uF (polyester tweeter cap) from v+ to v- at the amplifier board. This is quite clear sound.
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