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Old 29th September 2012, 04:26 PM   #21
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ah, thatone.
forgot about it, 1557 does not have a diagnostic output.

Actualy You can go with any value as long as it is larger than 10K ohm.
//not even sure its needed if the diagnostic output is not used at all....
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Old 30th September 2012, 08:38 AM   #22
Kitax is offline Kitax  Latvia
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well it is needed... i thought that i didnt need it too... that's why i didnt get the 10k rezistor... :P
actually i wanted to change it only because the 4 rezistors didnt look too safe, to leave there... :P
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Old 30th September 2012, 11:44 AM   #23
balerit is offline balerit  South Africa
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Quote:
Originally Posted by balerit View Post
Well that's why I designed my amp with an input buffer, you can increase the gain if need be. If you have to add a preamp then use a TDA 7630 or TDA1524 and build a dedicated preamp. I use the TDA 7630 in my Camm EquiTone preamp and it is the best preamp that I have heard. I am currently building a new preamp to test the TDA1524 chip.

Arty I stand corrected on the 8560, the 1562 is an class H amplifier.

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Sorry guys, the preamp ic is TA7630p, got too many tda's in my head
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Old 30th September 2012, 12:28 PM   #24
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just stick to passive tone controlls.
chip has enough beef to handle it.
Maybe as a way of improving it a buffer could help.
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Old 3rd October 2012, 02:47 PM   #25
Kitax is offline Kitax  Latvia
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i want to calculate, how fast my 7Ah battery is going to hold the tda8560q on various input voltages, how should i do that?
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Old 3rd October 2012, 07:05 PM   #26
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so.. say You drive 4 ohm speakers.
from a single 12v battery this chip will have something like 8v max output voltage.
we assume this swing.
so, 8/4 = 2A current.
this is stereo, so it will be closer to 4 A.
7/4 is 1,75 hours at full blast volume.
Does not sounds a lot.
but consider, that You will more than sure not run it at full blast.
I would estimate at least 3 hours of loud music.

//notice, one may argue that the amp has a certain % of efficiency, and a number of losses are to be included. But allso notice that speakers have impedance, my estimation is based on an ohmic load and constant current draw. //
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Old 4th October 2012, 01:00 PM   #27
Kitax is offline Kitax  Latvia
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where did you get the 8v output?
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Old 4th October 2012, 02:13 PM   #28
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see datasheet.
test condition RL = 4 ohm
output power = 17w @10% THD.
P = U*I
P as power, U as voltage, and I as current.
I = U/R
where R is our load.
so P = Uˇ2/R
or sqrt(P*R) = U
witch is sqaure root of 68.
A tiny bit over 8 volts.

btw, it was only estimated.
Real life figures will differ.
It will be less output voltage since 10% THD sounds terrrible.
I would say that from a single 12v rated battery 8 volt output swing is on the edge.
Most likely You won't even utilise half of it.
It will be loud enough, given You use more or less efficient speakers.
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Old 4th October 2012, 02:58 PM   #29
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It may sound odd, but a 7Ah SLA isn't likely to provide 7 amps for an hour, or 3.5 amps for two hours, or even 2.33 amps for three hours.
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Old 4th October 2012, 06:22 PM   #30
Kitax is offline Kitax  Latvia
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well you could have just sait "the datasheet"couse i know how to do the math but thanks anyways ^_^

and sofaspud: that doesnt surprize me at all, but how do you explain it?
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