Tda7265

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Audio seemed fine. Altho I have not hooked it to decent speakers yet. absolutely no pop or noise on turnon or turnoff. standby function works beautifully.


The only thing I can say is its much simplier then the one included with the 7265 datasheet. The standby function is done with some simple resistors and a cap and the feedback path is MUCH shorter. He has spots for many components including filters on the inputs. I chose to omit many parts, atleast for now. I did however leave the zobel and input caps.


I'll ask my friend (Randy Rubin) if I can share the schematic\PCB layout. If he says yes i'll post images. Same guy that did my PCBs for my biamp's and crossovers. This board was donated to me for free as a project to mess with, so I'm not really in a spot to willingly give out its design.
 
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Seems to be pretty much complete other then some pieces of blue protective plastic i need to peel off of the aluminum face :)
I need to put a scope on it tho either i'm imagining it or I'm hearing a very high frequency noise. like 15-17KHz continuously from both speakers. Perhaps noise from the SMPS supplies? Or it may just be completely in my head due to the horrid apple speakers im testing with.

two knobs = bourns 10K pots with a 20K resistor each to ground. I'm using them as volume\balance knobs. due to the 20K resistor they don't make a huge difference on volume but allow me to change the level + balance a fair amount which is what I was after. switch in center = standby/on. Not the best IMO but it does the job and the amp was built 100% with parts from friends and my stash. I didn't have to spend a cent :)


An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.
 
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OK I need some opinions.

I have the amp hooked up at work to a dell PC and my gain is insane. I have the mixer all the way down to 0 and still have too much gain.

My feedback is set up for a gain of 32. The datasheet says you want to be greater then 25dB.

My pots on the input are 10K with a 20K resistor in series to ground. The chip has an internal load of 25K. I used the 20K resistor to try and keep my input impedance something respectable.

I'm thinking to drop the input level I can put a 10k or 20K in series with the input between the rca jack and the pot and just running the other side of the pot straight to ground. This will give me far more control with the volume pot as well as still maintain over 20K input impedance.

Reason I have 10K pots in the first place is this amp is built 100% from free parts. I'd like to keep it that way ;)
any opinions?
 
Amp is done. Works great now with the 10K pots straight to ground.

$5 chipamp + a free board from a friend + a bunch of free parts, hardware and two samsung tablet 19V switching power supplies from another friend = wow

I am really impressed. I expected the amp to work decent but this by far exceeds my expectations especially driving a 4 ohm load.
 
TDA7265 (class AB) was meant for mainstream consumer electronics. With fine THD characteristics (0.02%) but moderate output power (25W/8 Ohm). STMicroelectronics still marks TDA7265 as “active” while class D is taking over. I could buy two ICs for less than $2 and a good looking PCB using two TDA7265 ICs in BTL-coupling for another $2. In BTL-coupling, the TDA7265 can deliver around 50W but only in 8 Ohm.
The PCB is flawless but not including DC offset adjustment which I added myself. With BTL-coupling the DC offset can exceed 100mV.
The assembled board worked in first attempt and revealed a flawless sound with solid bass. On a par with LM1875 and LM1876.

The TDA7265 ICs I got appear of correct origin and the result of selling out of a stock that may soon be obsolete. I can suggest this inexpensive chip-amp construction to less experienced DIYs and those more experienced who just wants something simple but with high SQ. With 8 Ohm speakers, the power is sufficient for most of us at home.

Appended is a schematic of the board. The values listed are those suggested on the board. Values in parenthesis are the values I used instead. The offset adjustment circuit is added in the upper left corner.
I did not use trim-potentiometers but preferred fixed resistors (R1 and R2) for stability reasons.
 

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I'm af not a "Feinschmächer" at your level but it is has a sound similar to a well constructed LM1876 or LM1875, just with more power. It is not for those who aim at a well-build TPA3255 or a Neurochrome 3886DR.
It runs off a 2x18V supply and the price is very modest. For once, I believe the chips are genuine and the PCB is well made (except for off-set adjustment).
Ideal for "noobs" or those who have realized that power is not the most important. Ideal for horn-speakers with high efficiency or a bedroom with book-case speakers.
 
Osvaldo, you are absolutely right. The 20K (typ.) input impedance can be overcome with an OP-AMP based input buffer. Actually, my pre-amp is a TPA6120 based DIY head-phone amplifier with OPA2134 input buffers. The TPA6120 can drive almost anything.
My aim with this simple amplifier construction is to encourage young DIYs to start with something simple and cheap that will hardly go wrong. When they after 3-6 months get tired of it, the 10$-15$ investment can be put aside and they can try something a little more challenging. With this construction they will still learn a lot and the sound is actually very fine. I have in more cases seen self-declared "noobs" start-up with something rather complex (and powerful) that is likely to go wrong just from a look at the ambitions.

NB: We are ready to take over the summer from you.
 
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Hi FF

So you mean 4k7 and 100R on the top left corner. but at the second look i see at the pins 11 the resistor R1 and at the other chip the R2. what values?

chris

Sorry Chris, I missed this posting while I was cruising around with my camper in the German rain.
R1 and R2 are individually chosen such that the DC-offsets at the BTL outputs are as close to zero as possible after 15 minutes of stabilization. I managed 10-20mV. As I recall the resistor values, they where different for the two and in the order 10K<R<1M. The values have to be chosen to fit the exact TDA7265 specimens.
Also rain in Vienna and rain just messed up the F1 Grand Prix in Hockenheim. Why can't we just have 26 degrees, a blue sky with a few white cumulus clouds and a slight dry breeze? What do we have the EU for?
 
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please do not fell pushed by my posts ;)
Thanks FF! for your perfect explanation


i am sorry that you have no nice trip.....yes actually the nice summer as you described is not existing any more....cold May- switch on - super hot summer ?:confused:





1 week Italy and 1 week in the area of Therme Loipersdorf (styria) was perfect.:)
 
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