youve low potential compared to others
I always wear cotton and not nylon or other static generating materials.
Hiss from tda7294 when music is playing
Hi,
I have built tda7294 based on the exact schematic shown on the datasheet. I am hearing hiss (may be around 600 to 800hz-not very sure) when music is playing. This hiss stops after 2 or 3 seconds after music and starts 1 or 2 seconds after music starts.
Otherwise amp is dead silent.
Can anyone aware of this symptoms?
Set up
3 way active crossovers
All 5 channels (4 stereo and mono subwoofer) are driven through tda7294 with 28v rails (20-0-20 transformers) each stero channel is having its own transfer and 10000uf per rail capacitors. There are no speaker protection circuit or anything between amp and speaker.
Source is bluetooth receiver and rca inputs with push button switch as source selector.
Regards
Goutham
Hi,
I have built tda7294 based on the exact schematic shown on the datasheet. I am hearing hiss (may be around 600 to 800hz-not very sure) when music is playing. This hiss stops after 2 or 3 seconds after music and starts 1 or 2 seconds after music starts.
Otherwise amp is dead silent.
Can anyone aware of this symptoms?
Set up
3 way active crossovers
All 5 channels (4 stereo and mono subwoofer) are driven through tda7294 with 28v rails (20-0-20 transformers) each stero channel is having its own transfer and 10000uf per rail capacitors. There are no speaker protection circuit or anything between amp and speaker.
Source is bluetooth receiver and rca inputs with push button switch as source selector.
Regards
Goutham
The tda7294 has a minimum gain before it starts to become unstable.
I think its about 22.
You could change R4 to 1K but that's about the limit.
I used 270K for R1, R2 and R3. And multilayer ceramic 470nF for C1 and C2. See figure 1 in the datasheet of TDA7294.
Take special care in the equality of R1 and R3 to avoid offset at the output.
I used these big resistor values to reduce capacitances and avoid the use of electrolytic for signal purpose.
Take special care in the equality of R1 and R3 to avoid offset at the output.
I used these big resistor values to reduce capacitances and avoid the use of electrolytic for signal purpose.
Manual say
CLOSED LOOP GAIN HAS TO BE >24dB
But it does not say it's because of possible instability.
I checked, I used it with low voltage gain.
Then I can say with certainty that there is no instability using lower gain.
On the other hand, I experimented IC overheating with the boucherot cell.
perhaps the boucherot cell has problems because of the low gain. Maybe that's what they refer to in the manual. But my solution is
NOT to use boucherot cell. My amplifiers are not used with long cables. then I should not have problems.
Under volting is sure to make it work better. So aim for 20+20vac transformer or maybe even as high as 22+22vac transformer, and see my sig line for the rest.
40 watts of that in stereo, would be like a big storm indoors. You could aim a little lower if it is for use in a house.
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