Announcement

Collapse
No announcement yet.

Why so few higher powered Class D stereo amp boards?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Craig

    Comment


    • #32
      As a mathematical approximation, when you increase the supply voltage by 50%, which is what you did going from 16 to 24 volts, you increase the available power output 125%, more than doubling. Of course this assumes the current availability also increases proportionally, no components are subjected to too much voltage, there are no heat related limitations, etc.
      Paul

      Originally posted by tomzarbo View Post
      So I gave the amp 24v and ran it from the intended preamp. The difference between 16v and 24v is pretty substantial.

      Louder and cleaner... it will work for sure. Now I'm even more impressed with that amp!
      with bass heavy music playing for 5 or 6 min I only registered 90 degrees max on the heatsink. Seemed to be coasting heat wise.

      Not to toot my own horn, but this radio is going to be pretty awesome if I do say so.

      Thanks again all for the guidance.
      TomZ

      Comment


      • #33
        Originally posted by Paul K. View Post
        As a mathematical approximation, when you increase the supply voltage by 50%, which is what you did going from 16 to 24 volts, you increase the available power output 125%, more than doubling. Of course this assumes the current availability also increases proportionally, no components are subjected to too much voltage, there are no heat related limitations, etc.
        Paul


        Well, that explains it!
        Yeah, it was much better, sounds like I wanted it to all along. Now to finish it up!

        TomZ
        *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
        *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

        *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

        Comment


        • #34
          Originally posted by tomzarbo View Post
          ... Louder and cleaner... it will work for sure.
          Thanks again all for the guidance.
          TomZ
          With the 24 V supply, you get more headroom from the increase in power. At 16 V, you were likely into clipping looking for more power.

          Comment


          • #35
            Can anyone tell me is there any class D amplifier for guitears. I don't undestant much about amplifiers but I'm learnig how to play the quitar for a couple of years and I want to buy an amp for performances I'm going to give. I'll appreciate any advice

            Comment


            • #36
              Originally posted by JoeCaWWW View Post
              Can anyone tell me is there any class D amplifier for guitears. I don't undestant much about amplifiers but I'm learnig how to play the quitar for a couple of years and I want to buy an amp for performances I'm going to give. I'll appreciate any advice
              I built a stereo 2x12 cabinet to use with my Line 6 Helix. I used the Sure 2x100 board and the matching Meanwell power supply. If you go this route, you will need some sort of preamp in front of it. I use the Helix, but any of the current modeling pedals will work. On the cheap side, something like the Joyo American pedal is awesome as a 'Fender' type preamp.

              Comment


              • #37
                I am amazed at the distortion figures on some of these. There are a few that look reasonable but 10% THD at rated power is not ideal

                Comment


                • #38
                  Originally posted by stephenmarklay View Post
                  I am amazed at the distortion figures on some of these. There are a few that look reasonable but 10% THD at rated power is not ideal
                  None of them are 10% at normal levels, they just use that to show a higher rated power than what you can actually get cleanly.
                  Electronics engineer, woofer enthusiast, and musician.
                  Wogg Music
                  Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                  Comment


                  • #39
                    Originally posted by wogg View Post
                    None of them are 10% at normal levels, they just use that to show a higher rated power than what you can actually get cleanly.
                    I pulled this one at random

                    https://www.parts-express.com/sure-e...board--320-301

                    • Power output (w/ 24 VDC power supply): 50W x 2 (6 ohms, THD 10%), 40W x 2 (8 ohms, THD 10%), 25W x 2 (6 ohms, THD 0.05%), 20W x 2 (8 ohms, THD 0.1%)

                    I am not impressed with a rating of 50x2 when 20w at 8ohms is 0.1% distortion.

                    I have a “normal” class D amp rated at 2x30 rated 0.005 at full power. That is what my expectations are.

                    Comment


                    • #40
                      That's just how some of the manufacturers list the boards - Sure always states the THD 10% and then THD 1%. I just ignore the 10% number.
                      You can find a Sure board that says it is a 50W board and PE may have a little amp using the same chip and call it a 15W amp because Sure is stating it with a THD 10% and PE is using THD .01%.

                      Comment


                      • #41
                        Originally posted by stephenmarklay View Post

                        I pulled this one at random

                        https://www.parts-express.com/sure-e...board--320-301

                        • Power output (w/ 24 VDC power supply): 50W x 2 (6 ohms, THD 10%), 40W x 2 (8 ohms, THD 10%), 25W x 2 (6 ohms, THD 0.05%), 20W x 2 (8 ohms, THD 0.1%)

                        I am not impressed with a rating of 50x2 when 20w at 8ohms is 0.1% distortion.

                        I have a “normal” class D amp rated at 2x30 rated 0.005 at full power. That is what my expectations are.
                        Your best reference will be to lookup a data sheet on the chip used. Here's the TDA7492 used on that Sure board. With a 20V supply at 1kHz it's at 0.05% distortion right up to almost 20W where it increases dramatically (figure 20 page 18). Of course, that will depend primarily on the power supply voltage, and secondarily on the gain and board setup, but you'll get a much better idea of the real capability.
                        Electronics engineer, woofer enthusiast, and musician.
                        Wogg Music
                        Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

                        Comment


                        • #42
                          Originally posted by wogg View Post

                          Your best reference will be to lookup a data sheet on the chip used. Here's the TDA7492 used on that Sure board. With a 20V supply at 1kHz it's at 0.05% distortion right up to almost 20W where it increases dramatically (figure 20 page 18). Of course, that will depend primarily on the power supply voltage, and secondarily on the gain and board setup, but you'll get a much better idea of the real capability.
                          Thank you Wogg. really 20W is probably sufficient anyway. it is just the marketing that is a bit optimistic.

                          Much appreciated.

                          Comment


                          • #43
                            Originally posted by stephenmarklay View Post

                            Thank you Wogg. really 20W is probably sufficient anyway. it is just the marketing that is a bit optimistic.

                            Much appreciated.
                            As Wogg noted, forget the 10% THD watt ratings from the mfgs - marketing showmanship.

                            The major class D chips from TI, STmicro, etc, do a good job. When they're not driven into clipping expect < .3% THD at power. That said, power out is dependent on two things: power supply voltage and the speaker impedance (notwithstanding chip limitations). My rule of thumb is "clean" W rms = (PSV-1)2 / (2*SPR). That is based on physics and semiconductor losses for typical modules based on these chips.

                            Some examples:

                            24 V PS and 8 ohm speakers yields 33 W rms (66 W rms for 4 ohm speakers).
                            18 V PS and 8 ohm speakers yields 18 W rms (36 W rms for 4 ohm speakers).
                            12 V PS and 8 ohm speakers yields 7.5 W rms (15 W rms for 4 ohm speakers).

                            The "50 W x 2" ratings you may see reflect the chip's thermal limitation. But if you have a 24 V PS and 4 Ohm speakers you'll get 66 W rms (without a problem with music assuming the chip has a good heat sink and airflow). And that's worst case.

                            I recommend a 24 V PS for any of these amps. You don't have to use all the power the 24 V PS can give, but it provides a lot of headroom when needed.

                            Comment


                            • #44
                              I had been hesitant to go the full 24v because of the 'warnings' on the product page, even though you've even previously tried to asswage my fears Mike... but you're absolutely right... it seems that these amps can take it just fine.

                              I've been doing some near full-output temperature testing on the TDA7492 amp: https://www.parts-express.com/tda749...2x50w--320-606 and with the video player preamp faceplate feeding the source material it's peaking at around 120 or so degrees on the heatsink. That's pretty chill for a legit' amplifier producing real output. I like that little amp a lot more now. It's not until the very last three or four clicks on the preamp that it starts sounding harsh, but by then the woofers are going pretty much berserk at that point so it's a wash. Of course, I can get the preamp turned up to full and the ND91's are still alive, so the preamp determines a lot in this equation, but I think the amp is really doing a phenomenal job putting out some real power in a tiny size.

                              TomZ

                              *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                              *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                              *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

                              Comment


                              • #45
                                Originally posted by Millstonemike View Post

                                As Wogg noted, forget the 10% THD watt ratings from the mfgs - marketing showmanship.

                                The major class D chips from TI, STmicro, etc, do a good job. When they're not driven into clipping expect < .3% THD at power. That said, power out is dependent on two things: power supply voltage and the speaker impedance (notwithstanding chip limitations). My rule of thumb is "clean" W rms = (PSV-1)2 / (2*SPR). That is based on physics and semiconductor losses for typical modules based on these chips.

                                Some examples:

                                24 V PS and 8 ohm speakers yields 33 W rms (66 W rms for 4 ohm speakers).
                                18 V PS and 8 ohm speakers yields 18 W rms (36 W rms for 4 ohm speakers).
                                12 V PS and 8 ohm speakers yields 7.5 W rms (15 W rms for 4 ohm speakers).

                                The "50 W x 2" ratings you may see reflect the chip's thermal limitation. But if you have a 24 V PS and 4 Ohm speakers you'll get 66 W rms (without a problem with music assuming the chip has a good heat sink and airflow). And that's worst case.

                                I recommend a 24 V PS for any of these amps. You don't have to use all the power the 24 V PS can give, but it provides a lot of headroom when needed.
                                Thank you very much. I am going to try the 2.1 amp. I appreciate the clarification. For sure with a 24V PS, there is more than enough clean power.

                                Comment

                                Working...
                                X