Hi,
I own 2 x 30 Watt RMS 4,6 Ohm loudspeakers 70mm x 70mm x 55mm.
I tried them drived by a TDA7492P but Increasing the volume the sound is distorted.
What is in your opinion the best Class D amp to drive them?
Thanks!
I own 2 x 30 Watt RMS 4,6 Ohm loudspeakers 70mm x 70mm x 55mm.
I tried them drived by a TDA7492P but Increasing the volume the sound is distorted.
What is in your opinion the best Class D amp to drive them?
Thanks!
That's a possibility, but the only way you'll get 30w with a 12v supply is with a 2 ohm speaker / load.
P = U^2 / R, so the maximum power you can push into 4ohms is closer to 15w (and maybe around 10w into 6ohms).
The bluetooth-ness of that "only" introduces an(other) unknown...
P = U^2 / R, so the maximum power you can push into 4ohms is closer to 15w (and maybe around 10w into 6ohms).
The bluetooth-ness of that "only" introduces an(other) unknown...
Hmm, BTL is more like 24Vpp from a 12V supply, which is 8.5Vrms. With this into 4R: -> 8.5Vrms^2/4R = 72Vrms/4R = 18W.
12W into 6R
9W into 8R
9W vs. 18W is just 3dB.. barely noticeable or "just a bit louder".
12W into 6R
9W into 8R
9W vs. 18W is just 3dB.. barely noticeable or "just a bit louder".
18W maybe at 10% THD 😉 But then again, it also depends on the efficiency of the speaker(s), for each impedance "class"...
Basically yes, but optimistic.
20/22Vpp is closer to Real World, because all transistors (even if used as switchers in Class D) have some drop across them, twice that if bridged.
So realistic power before clipping is closer to 15W RMS.
Not bad, but not much either, and amp can easily clip when pushed.
20/22Vpp is closer to Real World, because all transistors (even if used as switchers in Class D) have some drop across them, twice that if bridged.
So realistic power before clipping is closer to 15W RMS.
Not bad, but not much either, and amp can easily clip when pushed.
So could it be enough increase the voltage to, e.g. 14v or should I switch to another Class D, maybe the 3116?
Thanks 🙂
Thanks 🙂
Have you considered trying a 7498 advertised at 100W (although I'm skeptical you'd get this, and you likely would need more than 12v powering it).
For this price below not much risk trying!
http://pages.ebay.com/link/?nav=item.view&alt=web&id=292118769477&globalID=EBAY-US
I've also had good results by adding a large-ish electrolytic cap ~0.1F across the power leads with the 7492. I'm using:
E36D160LPN124TC79M United Chemi-Con | Capacitors | DigiKey
Finally I found the mods at this posting to be very effective:
TDA7492 Amp
Hope this helps.
For this price below not much risk trying!
http://pages.ebay.com/link/?nav=item.view&alt=web&id=292118769477&globalID=EBAY-US
I've also had good results by adding a large-ish electrolytic cap ~0.1F across the power leads with the 7492. I'm using:
E36D160LPN124TC79M United Chemi-Con | Capacitors | DigiKey
Finally I found the mods at this posting to be very effective:
TDA7492 Amp
Hope this helps.
Good, I was also considering options to mod it. I will try the cap solution.
So which would be the best option to power it, are 12v enough or should I try to increase it?
Thanks!
So which would be the best option to power it, are 12v enough or should I try to increase it?
Thanks!
How much power do you need / want to get out of it?
No matter what chip you go with, you're limited by your power supply, and virtually all of them will distort at the same level if you power them with only 12v.
Can't get away from good ol' Ohm's law (the one i used earlier, P = U^2 / R; P is power, U is the RMS voltage across the load, so 0.7 times the supply voltage; R is the nominal impedance of the load or speaker).
To get even close to the advertised power specs, you'd need to power them with close to their maximum nominal supply voltage (24-26v or so).
No matter what chip you go with, you're limited by your power supply, and virtually all of them will distort at the same level if you power them with only 12v.
Can't get away from good ol' Ohm's law (the one i used earlier, P = U^2 / R; P is power, U is the RMS voltage across the load, so 0.7 times the supply voltage; R is the nominal impedance of the load or speaker).
To get even close to the advertised power specs, you'd need to power them with close to their maximum nominal supply voltage (24-26v or so).
I'd like to power the loudspeakers at their maximum power, how much can I squeeze them? so I will also try powering the 7492 with 24v (8v-24v). It also have 2 dip switches for 21.6dB, 27dB, 31.1dB, 33.6dB. The distortion is less on 21.6dB, setting it at 33.6dB looses bass power and produces more distortion. Increasing the voltage will also make it possible to set 33.6dB?
Thanks 🙂
Thanks 🙂
As famous Audio veteran Enzo says: "the amplifier is that thingie between the Power Supply and the Speaker" meaning: you can only get so much peak voltage at the speaker terminals as you have available at the power supply (minus a couple Volts losses) which of course determines available power, headroom, etc.
No matter what amp you connect between that supply and speaker, even if 100% efficient, you won´t get more out than you put in.
So in a nutshell: if current amp is not enough, build a larger one, with the corresponding higher voltage (and current) power supply.
Any other amp you hook up to the original one won´t change much, if t all.
From what you say, a 30 to 60W per channel amp will be fine to improve headroom and usable level.
No matter what amp you connect between that supply and speaker, even if 100% efficient, you won´t get more out than you put in.
So in a nutshell: if current amp is not enough, build a larger one, with the corresponding higher voltage (and current) power supply.
Any other amp you hook up to the original one won´t change much, if t all.
From what you say, a 30 to 60W per channel amp will be fine to improve headroom and usable level.
I don't know if I really understood your question, the signal is bluetooth audio. Those speakers came from an old, broken Bose SoundDock, so I replaced the electronics with the 7492 and it didn't sound loud and clear as the original. So do I have to leave dBs to the lowest value? The quoted by Enzo is an interesting and real point of view.
It has been often observed that the higher the gain on these class-D chip-amps, the more noise you get on the output, so it's generally agreed you'll want to set that to the lowest selectable value.
I'm using a 15V Mean Well power supply which works well. I was using a 12V wall wart at first and heard distortion on peaks, but after beefing up the power supply and adding the big cap i haven't been able to produce any distortion. I believe this is simply because the new power supply provides more available current and isn't depleted like it was with the wall wart. I also noticed a distinct improvement in transient impact and dynamics with the new power supply and cap.
Another note, I'm using this on a small fairly high efficiency desktop system, biamped and actively crossed over at about 300Hz so the amps aren't very stressed.
Another note, I'm using this on a small fairly high efficiency desktop system, biamped and actively crossed over at about 300Hz so the amps aren't very stressed.
Aside from the voltage, the wall warts usually don't have enough power.
If you want more power and the (low voltage) power supply can deliver it, you could still go for a buck converter (dc/dc converter). They aren't expensive anymore and a real solution, or, if you want to look at it from another side, it gives you a much better, greater choice of amplifiers.
If you want more power and the (low voltage) power supply can deliver it, you could still go for a buck converter (dc/dc converter). They aren't expensive anymore and a real solution, or, if you want to look at it from another side, it gives you a much better, greater choice of amplifiers.
A pretty usual (and often dirt cheap) way to power these smaller class-D amps is old laptop power bricks.
I'd rather go for used brand-name ones, than new crap chinese ones, but they're 19v and anything between 3A and 6-8A, so plenty of juice available.
Stick with HP / IBM / Lenovo / Dell ones, and if you can see the label, Delta / LiteOn / HiPro / AcBel are the usual (and pretty good quality) suspects 😉
I'd rather go for used brand-name ones, than new crap chinese ones, but they're 19v and anything between 3A and 6-8A, so plenty of juice available.
Stick with HP / IBM / Lenovo / Dell ones, and if you can see the label, Delta / LiteOn / HiPro / AcBel are the usual (and pretty good quality) suspects 😉
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