Announcement

Collapse

Midwest Audio Fest

It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
See more
See less

Interesting Power Supply Issue...

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

  • #31
    Originally posted by tomzarbo View Post
    Yes, I was really surprised to hear it continue to play even when only the positive lead was connected, but then I knew that the common input ground lead must be completing the circuit somehow.

    When I unhooked the input lead from the amp, the noise went away, so did the power to the faceplate. So you're saying that I should hook up the L and R leads to the input, but bypass the ground lead on the input and see what happens then? I have those tiny little 'grabber' plugs that can hold onto a small wire, I guess I could use those to do that.

    Thanks for the help and thought you put into this, I appreciate it.
    TomZ
    Yup, I'm suggesting leaving the +- DC power connected to the faceplate board, but lifting the audio signal ground out of the 3 pin connector. over to the amp. Lift either the amp or the faceplate side, shouldn't matter which.

    I feel your pain on this... when I did my little combo bass amp update I had 2 pre-amp boards at the top of the cab, the power supply at the bottom, the crossover board on the back panel, and the power amp on the back panel, all interconnected with various signal and power cables. It had a hell of a buzz and I spent many hours trying different connections, modifying boards, giving up, stewing over the problem when I should've been sleeping, thinking of other things, trying more stuff... Generally a terrible curse for an OCD engineer, but stragely fun since solving problems is why I love engineering in the first place. I ended up with way too many band aids built into that project to get the buzz down to an acceptable level, someday I may scrap the pre-amp / crossover board combo and re-build.
    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

    Comment


    • #32
      Originally posted by tomzarbo View Post
      Is there a way that I can figure out how many amps/miliamps that the preamp unit draws with a multimeter? Actually, I have a bunch of those smaller DC/DC converters, maybe I could try one of those just for fun since it's free to do so.
      ​Ooops: some of those so-called "DC/DC converters" are not isolated: they have a common ground for the input and output. You need an "isolated DC/DC converter". I should have been clearer on that. The isolated converter will have no continuity between Vin- and Vout-.
      The isolated converter was the only way I was able to get rid of the noise for my DIY WiFi speaker ("Act").

      ​You could use a multimeter to directly measure the current draw or you could just measure the voltage drop across a resistor in series with the preamp. You are expecting a current draw in the range of 100ma to 300ma, so a 1 to 10ohm resistor in series with the preamp would work. Measure the voltage drop across the resistor, divide by the value of the resistor, and that result is the current draw. Make sure the Bluetooth device is actively communicating so that you can see the maximum load.

      Your description of what Wogg suggested is correct. Try that first. If that approach looks promising but you still have induced noise, you might be able to get by with an audio isolation transformer between the preamp and the amp.
      Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

      Comment


      • #33
        I suspect that the signal ground in both units is identical to the PS DC ground. Easy to check with an Ohm meter.

        To check the faceplate current draw, put your DVM on DC amps and attach one lead to the battery plus and the other to the faceplate dc + input (it doesn't matter which lead is on the battery +, the DVM wil just show negative amps if they are reversed).

        Start at the highest setting (usually requires moving the read lead to the "Amp" position on the DVM - usually up to 10 amps). If you read less amps then the next lowest setting, then you can switch to a lower scale (and move the red lead back to the normal hole for all the other measurements.). In the pic below, the unit measures to 10 amps on that setting and up to 999 mA on the ma setting. I've seen lots of units where the mA setting only goes up to 200 so be mindful.
        Click image for larger version

Name:	DVM.png
Views:	1
Size:	155.8 KB
ID:	1358526

        Comment


        • #34
          So I tried to use my little DC/DC voltage buck converter device between the common 12 PS and the faceplate/preamp unit.

          Neil, I guess I have one of them that has a common ground for in and out terminals because when I hooked up the faceplate/preamp unit, I had the noise still. Well, I had them, so I tried it just for the fun of it.

          This is for the new T amp unit by the way....

          I hooked up the preamp using only the L and R positive leads from the amp to the preamp unit. I left the ground unhooked...... and I STILL have the same noise.

          I'm going to see if I can check the faceplate current draw... but can I do your prescribed procedure with a power supply? I can't seem to find a battery that is close to 12V... well I guess I could use a 9v battery, it will work with as little as 6 volts. Let me give it a try with the 9v battery. I only have a cheap Harbor Freight Tools freebie multimeter to work with, but it does seem to have DCA settings, so I'll give it a try. I think I really need a high quality multimeter.

          Thanks guys, I'll report back if I don't blow myself 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


          • #35
            That would take a pretty big explosion, ya know... Likely an 'abombinable' one...
            Heehee...

            At any rate I'm learning from your progress on this one since I still have the 3 of those amp boards.
            Thanks for informing,
            Wolf
            "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
            "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
            "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
            "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

            *InDIYana event website*

            Photobucket pages:
            http://photobucket.com/Wolf-Speakers_and_more

            My blog/writeups/thoughts here at PE:
            http://techtalk.parts-express.com/blog.php?u=4102

            Comment


            • #36
              So I tried to use a 9v battery to check the amp draw, I seemed to be having issues, so I used one of my 12v power supply units.

              I put the dial on 10A for DCA and it read about 80 for the Bluetooth portion and a high of about 105 for the FM radio portion of the faceplate input.
              I'm thinking that was about 100 milliamps... it read around 30 when it was just in standby mode with the word "off" on the screen.

              I checked this YouTube review of the unit and he seems to agree.....

              Click image for larger version

Name:	Faceplate Preamp current draw.JPG
Views:	1
Size:	39.5 KB
ID:	1358591

              So about 100 milliamps draw, that was with the volume all the way up as well. Seems efficient enough. I did this with the 12v, 2 amp power supply with the ground plug.

              Neil, I'm going to pick up one of the DC/DC converters that you mentioned... I think this one is what I need? https://www.digikey.com/products/en?keywords=SPB03C-12

              I'm also going to get one of the isolators that you and Wogg suggested. Do you think this one from PE would work? https://www.parts-express.com/boss-b...lter--265-4041

              I'm going to lick this yet!

              Thanks a lot guys!

              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


              • #37
                Originally posted by Wolf View Post
                That would take a pretty big explosion, ya know... Likely an 'abombinable' one...
                Heehee...

                At any rate I'm learning from your progress on this one since I still have the 3 of those amp boards.
                Thanks for informing,
                Wolf
                No KaboooOOOOOOMmmmmmmm! at least not this time.

                Man, I really hope you don't have the same issues I'm having. I'm going to pick up a few more of those amps to see if I got a few bad ones, but for now I'm trying to work with the 12V T amp since it's at least quiet on it's own.

                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


                • #38
                  Originally posted by tomzarbo View Post
                  .. I think this one is what I need? https://www.digikey.com/products/en?keywords=SPB03C-12

                  ​No--that one requires 36V-72V input. The "B" version uses 18V-36V input, and the "A" version is for 9-18V. Also, there aren't any of the B or C versions in stock at Digikey and the lead time is 10 weeks. Most of those modules have a limited input range, but Meanwell has the SPBW series for about the same price, and it has a wide input range:

                  Digikey has 4 in stock. That will give you the flexibility to use different power amps from 12V to 36V. Mouser has lots of them in stock. That would be a good part for PE to carry!

                  ​Your measurements show that the 3W supply is more than adequate, and you could get by with a 2W supply or maybe even less. But the price wouldn't change much.

                  I'm also going to get one of the isolators that you and Wogg suggested. Do you think this one from PE would work? https://www.parts-express.com/boss-b...lter--265-4041
                  ​Yes. That one looks better than the one I linked to. It's just a signal-level transformer and that one is large enough to work well at the lower frequencies. You used to be able to walk into Radio Shack and buy one of those, but them days are gone...
                  Free Passive Speaker Designer Lite (PSD-Lite) -- http://www.audiodevelopers.com/Softw...Lite/setup.exe

                  Comment


                  • #39
                    Originally posted by neildavis View Post

                    ​No--that one requires 36V-72V input. The "B" version uses 18V-36V input, and the "A" version is for 9-18V. Also, there aren't any of the B or C versions in stock at Digikey and the lead time is 10 weeks. Most of those modules have a limited input range, but Meanwell has the SPBW series for about the same price, and it has a wide input range:

                    Digikey has 4 in stock. That will give you the flexibility to use different power amps from 12V to 36V. Mouser has lots of them in stock. That would be a good part for PE to carry!

                    ​Your measurements show that the 3W supply is more than adequate, and you could get by with a 2W supply or maybe even less. But the price wouldn't change much.



                    ​Yes. That one looks better than the one I linked to. It's just a signal-level transformer and that one is large enough to work well at the lower frequencies. You used to be able to walk into Radio Shack and buy one of those, but them days are gone...
                    Thanks a lot Neil,

                    I ordered these parts and hopefully I can get this fixed up and noise free by next weekend. I really do appreciate all the guidance.

                    I just can't believe how many issues there can be with items that most probably consider plug-and-play audio toys!

                    I have a snow day due to the storm, so I'm in the basement finishing up the other radio. I decided to make two of them since I was cutting parts, I stopped working on the second one, but now that the finished radio is in limbo, I'll finish construction of radio #2.

                    Thanks again everyone... updates hopefully soon!

                    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


                    • #40
                      Would a battery interface work? Use the power supply to charge the batteries?
                      John H

                      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                      Comment


                      • #41
                        Originally posted by jhollander View Post
                        Would a battery interface work? Use the power supply to charge the batteries?
                        I bet it would work. I tested it off of a lower voltage battery and it worked noiselessly. I actually thought about it briefly... But since it's a gift... I want it as easy as possible to deal with. Plus, the battery pack would have to be external, there's just no more room left inside this thing without changing the tuning higher, and I'd hate to do that... it sounds really nice at this point. If I do end up going to MWAF this year I'll bring it, I'd love to have you hear it!

                        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


                        • #42
                          No inDIYana for you this year?
                          John H

                          Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                          Comment


                          • #43
                            Tom,

                            Do any of the power supplies you've tested have a ferrite bead? That "bulge" in the DC cable usually within an inch or two of the DC plug? If not that's what I would try.

                            The bead's parameters are specifically selected by design to suppress the HF noise on the power cable generated by the brick's switching frequency. Genuine Dell PSs all have the bead. If you or a friend have such a laptop supply, I would try it on the TDA7402 amp to see if it's quiet - tap the DC plug with some wire for testing. If the TDA7492 is quiet that's a good indication that the face plate will like that DC source as well. An adjustable linear regulator (<$1 on aliexpress) could be used to step down the voltage for the face plate: 19 V - 12 V = 7 V difference. At 100 mA, that's 0.7 W heat dissipated by the regulator.

                            In the pic, there are the words "buck converter". That's not true. An LM317 is a linear regulator. And the dead give away is the heat sink mounted to it. If you see ad for a regulator with a surface mount chip and no heat sink, then it's a buck inverter and generates ... drum roll ... HF switching noise.

                            Reg.png

                            Comment


                            • #44
                              Originally posted by jhollander View Post
                              No inDIYana for you this year?
                              Not this year. I'm trying to hold off on building new stuff and get some projects buttoned up that have been partially completed for some time. I have two subwoofers that I'm going to be putting veneer on today Lord willing. Also, my version of Ben's N.E.H.D. need finishing as well...and I still haven't totally finished up the 'Bantam MTM's' from last years inDIYana. There are a few others, but you get my drift! It was a lot of fun last year, though.

                              Originally posted by Millstonemike View Post
                              Tom,

                              Do any of the power supplies you've tested have a ferrite bead? That "bulge" in the DC cable usually within an inch or two of the DC plug? If not that's what I would try.

                              The bead's parameters are specifically selected by design to suppress the HF noise on the power cable generated by the brick's switching frequency. Genuine Dell PSs all have the bead. If you or a friend have such a laptop supply, I would try it on the TDA7402 amp to see if it's quiet - tap the DC plug with some wire for testing. If the TDA7492 is quiet that's a good indication that the face plate will like that DC source as well. An adjustable linear regulator (&lt;$1 on aliexpress) could be used to step down the voltage for the face plate: 19 V - 12 V = 7 V difference. At 100 mA, that's 0.7 W heat dissipated by the regulator.

                              In the pic, there are the words "buck converter". That's not true. An LM317 is a linear regulator. And the dead give away is the heat sink mounted to it. If you see ad for a regulator with a surface mount chip and no heat sink, then it's a buck inverter and generates ... drum roll ... HF switching noise.

                              [ATTACH=CONFIG]n1358680[/ATTACH]
                              Yes, two of them had that bead right by the DC plug. They seemed to be just as noisy as the others. I do have some of those same linear regulators and I did use it between the PS and the faceplate unit. I did this with several of my 12v units to bring the voltage down to 8-9 volts to the faceplate. I still had the noise, and that was with the lower powered T-amp board that was quiet on it's own.

                              I think it might just be my house and everything in it......Oh my gosh... EVERYTHING is making noise! I just got a new heater installed (recent switch to natural gas) and it's whining like a preschooler! It's variable speed fan sounds like a 747 Jumbo Jet taking off when it spools up downstairs. I half expect a "Fasten Your Seat belt" light to come on and for the stewardess to tell me to lift my tray to the 'upright position' as our house lifts off of its foundation and rises to the sky! Actually, I'm real happy to be off of Propane, it's super-cold around these parts and my wife loves having the heat cranked just a bit higher.

                              Anyway, Mike, I'll try what you suggested again with the other amp and the 16v ps, that one had the bead on it as well. Actually, I have a bunch of different ones, I can try out what I have to see if any of them reduce the noise any. Talking with my father yesterday, he wondered if I wasn't being to critical.... that when the music was playing you didn't notice it so much. I see his point, but I actually could hear it, even with the music fairly loud, and when it's paused, it really sounded prominent, I just can't give that to someone like that. If I got a radio like that from a store, I'd take it right back in a heartbeat... so I appreciate you guys helping me figure this out.

                              More to come...
                              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 tomzarbo View Post

                                I think it might just be my house and everything in it......Oh my gosh...
                                May not be a far fetched idea. Have you tried it at any other location then your house?

                                My neighbor's business is building tube guitar amps that the musicians love (ala Fender, Marshall). He's convinced that the power to his house has issues / gives him grief when he does final QC on an amp going out the door.

                                On a different note, maybe it's something running in your house (though I can't think of anything that runs constantly other then electronics on standby). Years ago, I had a situation where my laptop WiFi would drop every day at 3:30 pm, like clock work. Drove me nuts for a month. The cause: the girlfriend's daughter would get home from school and immediately get on her cordless phone using the same frequency band.

                                I have two different TPA3116 amps here and many switch mode supplies - all not in use. I'll due some testing tonight for noise (hope my hearing is up to it).

                                Comment

                                Working...
                                X