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PE Subwoofer Pre-Amp - Exposed

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  • #31
    Looks like PE has a new board. R7 is removed and the pots look different. Also looks like the cap values changed. I have one on order to test and compare. Sure has some good mono amps I would like to test with it. I never got a chance to test the updated board but have a list of items on my bench to test in the next few weeks.

    https://www.parts-express.com/variab...ntrol--320-671
    "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

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    • #32
      Originally posted by Gordy View Post
      Looks like PE has a new board. R7 is removed and the pots look different. Also looks like the cap values changed. I have one on order to test and compare. Sure has some good mono amps I would like to test with it. I never got a chance to test the updated board but have a list of items on my bench to test in the next few weeks.

      https://www.parts-express.com/variab...ntrol--320-671
      Thanks for looking into this Gordy,
      I'm interested in hearing about your thoughts on it. Hopefully it works as advertised and expected.

      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


      • #33
        Originally posted by tomzarbo View Post

        Thanks for looking into this Gordy,
        I'm interested in hearing about your thoughts on it. Hopefully it works as advertised and expected.

        TomZ
        Hey Tom,

        I had parts to modify another board. They're not needed now since the board has been updated. Send me your address in a PM and I'll mail them to you.

        Comment


        • #34
          Originally posted by Millstonemike View Post
          Hey Tom,

          I had parts to modify another board. They're not needed now since the board has been updated. Send me your address in a PM and I'll mail them to you.
          Out of curiosity, did PE contact you when they updated the SKU. Or did you work with PE to upate the SKU?
          "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

          The Madeleine
          The Roxster
          Swopes 5.0
          Acoustic Panels
          Living Room Make Over

          Comment


          • #35
            Originally posted by Gordy View Post

            Out of curiosity, did PE contact you when they updated the SKU. Or did you work with PE to upate the SKU?
            I never interacted with PE on this. I did post a review on the product page.

            Comment


            • #36
              Corrected Post: Be aware that the old board with the issues outlined here (part # 320-670) is on clearance for $3.95. The updated module is part # 320-671.

              Be aware that the old board with the issues outline hear (part # 320-671) is on clearance for $3.95. The updated module is part # 320-671.
              Last edited by Millstonemike; 10-06-2017, 10:25 AM. Reason: corrected part # and typos

              Comment


              • #37
                Originally posted by Millstonemike View Post
                Be aware that the old board with the issues outline hear (part # 320-671) is on clearance for $3.95. The updated module is part # 320-671.
                I think the old module is 320-670
                "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

                The Madeleine
                The Roxster
                Swopes 5.0
                Acoustic Panels
                Living Room Make Over

                Comment


                • #38
                  Originally posted by Millstonemike View Post
                  Hey Tom,

                  I had parts to modify another board. They're not needed now since the board has been updated. Send me your address in a PM and I'll mail them to you.
                  PM Sent, thanks!
                  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


                  • #39
                    Originally posted by Gordy View Post

                    I think the old module is 320-670
                    You are correct. I've been making typos all day. The last one was about $40,000 off the correct figure. Shisssh.

                    Comment


                    • #40
                      Originally posted by Millstonemike View Post
                      You are correct. I've been making typos all day. The last one was about $40,000 off the correct figure. Shisssh.
                      If it was not for spell check, I would be a mess.

                      don't know how I feel about that. You put a good amount of work and time into fixing a flawed product. I think they should have least provided co-star billing in the new SKU description.
                      "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

                      The Madeleine
                      The Roxster
                      Swopes 5.0
                      Acoustic Panels
                      Living Room Make Over

                      Comment


                      • #41
                        Click image for larger version

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Views:	2
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ID:	1347957
                        Track your package Here


                        Originally posted by tomzarbo View Post

                        PM Sent, thanks!
                        TomZ

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                        • #42
                          Originally posted by Millstonemike View Post
                          [ATTACH=CONFIG]n1347957[/ATTACH]
                          Track your package Here


                          Thank you Mike.
                          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


                          • #43
                            Just received the new SKU. Looks like the caps have been changed and resistor has been removed. But the pots are still A10Ks. I ordered a cheap mono amp from the Zon that should be here in a few days and hopefully will get to test it then.
                            "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

                            The Madeleine
                            The Roxster
                            Swopes 5.0
                            Acoustic Panels
                            Living Room Make Over

                            Comment


                            • #44
                              Originally posted by Gordy View Post
                              Just received the new SKU. Looks like the caps have been changed and resistor has been removed. But the pots are still A10Ks. I ordered a cheap mono amp from the Zon that should be here in a few days and hopefully will get to test it then.
                              Remember the old dig "Am I speaking Chinese?" Maybe that's needed now

                              The original pots were 50K ohms. I spec.'d 20K for the modified board but 20K pots are somewhat rare compared to others.

                              LP Filter: With a 10K pot and R6 & R8 remaining at 4.7K ohms, (hard to tell colors in the PE photo), the minimum LP Fc will be 73 Hz (up from 43 Hz in my version). Maybe not so much an issue for smaller 2.1 systems. The maximum LP Fc remains the same at 228 Hz. See the green line in the graph - mod 3. Replacing R6 & R8 with 10K resistors will get you a minimum F3 of 54 Hz. But the maximum LP Fc will revert back to 107 Hz - again, not so much an issue if your looking for a lower Fc.

                              Gain Stage: If R1 & R2 remain at 4.7K (hard to tell from PE photo) and the gain pot is 10K, then the maximum gain will be reduced to 2.1x; down from ~10x maximum gain. And that could be a big issue matching sub volume with the L-R speakers. Replacing R1 & R2 with 1K resistors will get the gain back up to 10x gain. But ... the HP Fc will rise from 3 Hz to 34 Hz in the band pass filter integrated in the gain stage..And trying to select values to replace R1 / R2 and C1 / C2 to compensate becomes a mess.

                              Gordy, maybe you could measure R6 & R8 to confirm their values.

                              Geez ... good thing I saved one more set of components to mod the original board. "The old adage :If you want something done right ..." Click image for larger version

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ID:	1348037
                              Last edited by Millstonemike; 10-07-2017, 03:39 PM.

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                              • #45
                                Originally posted by Millstonemike View Post

                                Remember the old dig "Am I speaking Chinese?" Maybe that's needed now

                                The original pots were 50K ohms. I spec.'d 20K for the modified board but 20K pots are somewhat rare compared to others.

                                LP Filter: With a 10K pot and R6 & R8 remaining at 4.7K ohms, (hard to tell colors in the PE photo), the minimum LP Fc will be 73 Hz (up from 43 Hz in my version). Maybe not so much an issue for smaller 2.1 systems. The maximum LP Fc remains the same at 228 Hz. See the green line in the graph - mod 3. Replacing R6 & R8 with 10K resistors will get you a minimum F3 of 54 Hz. But the maximum LP Fc will revert back to 107 Hz - again, not so much an issue if your looking for a lower Fc.

                                Gain Stage: If R1 & R2 remain at 4.7K (hard to tell from PE photo) and the gain pot is 10K, then the maximum gain will be reduced to 2.1x; down from ~10x maximum gain. And that could be a big issue matching sub volume with the L-R speakers. Replacing R1 & R2 with 1K resistors will get the gain back up to 10x gain. But ... the HP Fc will rise from 3 Hz to 34 Hz in the band pass filter integrated in the gain stage..And trying to select values to replace R1 / R2 and C1 / C2 to compensate becomes a mess.

                                Gordy, maybe you could measure R6 & R8 to confirm their values.

                                Geez ... good thing I saved one more set of components to mod the original board. "The old adage :If you want something done right ..."
                                A starting frequency of 73hz is a real downer. It seems that if they would have just used 20k pots this would be a non issue. The 10k on the gain really looks like a mess. R values below

                                R1 = 10k
                                R2 = 10K
                                R3 = 10K
                                R4 = 10K
                                R5 = Missing
                                R6 = 4.7k
                                R7 = MIssing
                                R8 = 4.7K
                                R9 = 10k
                                R10 = 215

                                Going back over your initial notes, I don't see anything about removing R5. How does this impact?



                                "A dirty shop is an unsafe shop, if you injure yourself in a clean shop you are just stupid" - Coach Kupchinsky

                                The Madeleine
                                The Roxster
                                Swopes 5.0
                                Acoustic Panels
                                Living Room Make Over

                                Comment

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