I just built a bluetooth boombox using the SANWU Tda7492p amp and a 4ohm speaker, 3s2p battery pack with a voltage elvator climbing the voltage up to 21v. Right now it's connected on only one channel and I have to set my phone to mono output. I'm trying to look up how to output the stereo signal to the one speaker.
I know it isn't possible to bridge this amp but I can parallel it but I'm not sure how? I saw this Why Not Wye? (Summing Box), but not sure how to wire it. Can I just use the R+ and L- on the speaker and a dummy load on R- and L+?
I know this has been asked before but I can't seem to find a concrete answer to this.
Thanks
I know it isn't possible to bridge this amp but I can parallel it but I'm not sure how? I saw this Why Not Wye? (Summing Box), but not sure how to wire it. Can I just use the R+ and L- on the speaker and a dummy load on R- and L+?
I know this has been asked before but I can't seem to find a concrete answer to this.
Thanks
I would actually like to see if anyone can help here as well. I currenlty have an smsl a2 on my desk and love the sound, and was considering a pair of $16 7492 boards from PE. I'm also wondering if you can bridge these and run them as little monoblocks with separate power supplies. I've already got a pair of 90W laptop bricks just waiting to be used.
It seems like these little chips have a slightly relaxed mid-range, or at least, I can listen to this amp for hours on end with no fatigue, yet there's still decent imaging.
Thanks in advance for anyone who can help us new guys out.
It seems like these little chips have a slightly relaxed mid-range, or at least, I can listen to this amp for hours on end with no fatigue, yet there's still decent imaging.
Thanks in advance for anyone who can help us new guys out.
I can see no mention of PBTL in the data sheet.
http://www.st.com/content/ccc/resou...df/jcr:content/translations/en.CD00211320.pdf
So you can use just one channel...drive one input and short the inputs to the other (via caps) and put some termination resistor on the unused output.
http://www.st.com/content/ccc/resou...df/jcr:content/translations/en.CD00211320.pdf
So you can use just one channel...drive one input and short the inputs to the other (via caps) and put some termination resistor on the unused output.
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Thanks for the reply. I ordered one from PE yesterday afternoon, should have it in a few days.
First thing I do is make sure the heatsink is torqued evenly, and I'll probably put a little thermal paste too. This will be a little father's day gift, and if all goes well I'll get a few more for friends.
First thing I do is make sure the heatsink is torqued evenly, and I'll probably put a little thermal paste too. This will be a little father's day gift, and if all goes well I'll get a few more for friends.
Feedback problem
[image]Image:7492amp|center[/image]
Okay, got her wired up to a 90 watt power supply and she's rockin. One problem though: It's getting feedback! As soon as she sits silent for more than about 4 or 5 seconds, the humming starts. As soon as you play music it goes away. From this picture, can anyone tell something I did wrong? Does it need to be grounded some other way? Put into a box for shielding?
As far as sound goes: It seems to have even more power than the smsl A2, which has a 120 watt supply that came with it. The supply that came with the A2 feels lighter and cheaper than the HP brand one I'm using. Getting a lot more bass and punch, but I'm going to check and see if that isn't just my phone output. I can pretty much max out some klipsch rp-160's, although there is a touch of distortion and slight falling apart at the very top end. I'm impressed with the power either way, I rarely listen at full tilt like that, at least on that particular system.
Going to see if my phone is the reason for the extra power, but I'm still wondering what contributes to this 16 dollar amp (32 with power supply) blowing the doors of the 80 dollar amp. I would take the smsl apart and post pics, but I don't know if it's in bad taste to post a manufacturer's board here. I would switch PSU's but I already soldered this one a bit. I do have a backup 90W hp supply, but it's only 2 prong and not 3 like this one. "Discovery requires experimentation."
BTW, I do realize this is hardly considered DIY, but I do plan on etching my own boards very soon, it's the main reason I'm here. All in due time, having a ball reading the "blowtorch" thread right now. 🙂
Oh, and big thanks in advance for anyone taking the time to help, mucho mucho appreciado.
[image]Image:7492amp|center[/image]
Okay, got her wired up to a 90 watt power supply and she's rockin. One problem though: It's getting feedback! As soon as she sits silent for more than about 4 or 5 seconds, the humming starts. As soon as you play music it goes away. From this picture, can anyone tell something I did wrong? Does it need to be grounded some other way? Put into a box for shielding?
As far as sound goes: It seems to have even more power than the smsl A2, which has a 120 watt supply that came with it. The supply that came with the A2 feels lighter and cheaper than the HP brand one I'm using. Getting a lot more bass and punch, but I'm going to check and see if that isn't just my phone output. I can pretty much max out some klipsch rp-160's, although there is a touch of distortion and slight falling apart at the very top end. I'm impressed with the power either way, I rarely listen at full tilt like that, at least on that particular system.
Going to see if my phone is the reason for the extra power, but I'm still wondering what contributes to this 16 dollar amp (32 with power supply) blowing the doors of the 80 dollar amp. I would take the smsl apart and post pics, but I don't know if it's in bad taste to post a manufacturer's board here. I would switch PSU's but I already soldered this one a bit. I do have a backup 90W hp supply, but it's only 2 prong and not 3 like this one. "Discovery requires experimentation."
BTW, I do realize this is hardly considered DIY, but I do plan on etching my own boards very soon, it's the main reason I'm here. All in due time, having a ball reading the "blowtorch" thread right now. 🙂
Oh, and big thanks in advance for anyone taking the time to help, mucho mucho appreciado.
Attachments
Okay so I changed outlets, no fix in ground loop hum. I also switched to the 2-prong power supply and no change either. I'm beginning to think this is coming from the input side.
Going to disconnect the inputs and power it up, see if the hum comes back.
AAaaand, that's it, it's coming from the input side.
Disconnected input and powered it up, no hum. When it powered down there was a little mini-pop as the power supply emptied out, so I know it was running. Also, I changed inputs to the computer earlier and got a different pitched hum (higher in pitch).
Now the question, how to eliminate the hum from the input side without using one of those gawdawful ground loop isolators. I'm thinking of jacketing the small input cable and running it back ground, maybe to the heat sink since I don't have a case? lol.. I better do some more reading first.
Going to disconnect the inputs and power it up, see if the hum comes back.
AAaaand, that's it, it's coming from the input side.
Disconnected input and powered it up, no hum. When it powered down there was a little mini-pop as the power supply emptied out, so I know it was running. Also, I changed inputs to the computer earlier and got a different pitched hum (higher in pitch).
Now the question, how to eliminate the hum from the input side without using one of those gawdawful ground loop isolators. I'm thinking of jacketing the small input cable and running it back ground, maybe to the heat sink since I don't have a case? lol.. I better do some more reading first.
In the end, it's just noise getting into my signal. The computer power supply is one source but doesn't totally get rid of it. It's not very loud anymore, I repositioned wires and played around a bit. I'll look more into shielding.
Also, about volume levels: I hooked it up to the same computer I had the A2 on, and this amp is indeed louder. I wonder if this has anything to do with gain settings. I feel a dissection of the A2 coming very soon. Both amps have the same sonic character, with the A2 being a touch more laid back sounding, and not just in the volume department.
Okay enough ranting, I'll go handle my grounding issues.
It seems that even with little reading, ground loops are a problem in the audio world just as is getting the perfect blue in fireworks, or acheiving the perfect edge with knives. I can live with a little noise for now, I've got plenty of other amps for now, and plenty of reading to do.
Also, about volume levels: I hooked it up to the same computer I had the A2 on, and this amp is indeed louder. I wonder if this has anything to do with gain settings. I feel a dissection of the A2 coming very soon. Both amps have the same sonic character, with the A2 being a touch more laid back sounding, and not just in the volume department.
Okay enough ranting, I'll go handle my grounding issues.
It seems that even with little reading, ground loops are a problem in the audio world just as is getting the perfect blue in fireworks, or acheiving the perfect edge with knives. I can live with a little noise for now, I've got plenty of other amps for now, and plenty of reading to do.
Concerning noise: There are 2 directions to investigate, one is ground loop through power supply earth connection (like direct connection from earth to DC output GND, in conflict with a probably earthed sound source) which can be opened and a 10nF~100nF capacitor inserted in series for AC earth coupling only, and/or 2 back to back diodes), the other direction is the fact that TDA7492 has balanced inputs, see J8 and J9 in datasheet, although these might not be implemented in PCB, and no CMRR (ground noise attenuation, common-mode rejection ratio) is specified (ST is not a premium IC manufacturer), but sure it is better than unbalanced.
Concerning paralleling: The limiting factor is channel-to-channel gain, DC offset and freq response mismatches, resulting in channels fighting one to another in some degree. The output inductors parasitic resistance would be the limiting factor for the amount of crossed current between channels. Depending on tolerances and the value of this parasitic resistance, it may work without overheating or it may overheat. Needs empirical test, as again ST is a budget IC brand.
EDIT: For making a "ground noise cancelling input" using the balanced inputs of the IC consider that the IC can be destroyed if the voltage difference from the floating input ground to power ground is not limited, as with two back to back diodes and/or a ~100r resistor.
Concerning paralleling: The limiting factor is channel-to-channel gain, DC offset and freq response mismatches, resulting in channels fighting one to another in some degree. The output inductors parasitic resistance would be the limiting factor for the amount of crossed current between channels. Depending on tolerances and the value of this parasitic resistance, it may work without overheating or it may overheat. Needs empirical test, as again ST is a budget IC brand.
EDIT: For making a "ground noise cancelling input" using the balanced inputs of the IC consider that the IC can be destroyed if the voltage difference from the floating input ground to power ground is not limited, as with two back to back diodes and/or a ~100r resistor.
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Thank you very much Eva. Please give me a day to put together a schematic to upload so that I am very clear as to what I should do. I 'think' I understand but with electricity would like to be absolutely sure. Been bit a few times and it scares me every time.
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