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PE Subwoofer Pre-Amp - Exposed

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  • Millstonemike
    replied
    Originally posted by bolson2011 View Post

    I haven't modified the original module, I recreated (or at least tried to) it based on your recommendations and the schematic provided, with the changes in place. Essentially, I'm trying to make it work as a variable high pass filter, leaving only ~80-120hz and below pass through that particular filter.

    I guess I should say that I haven't purchased the original module, or the update to it.
    I'm not so sure I can help you with that. Debug a home built board from afar.

    But the need for this type of module arises from time to time. And there isn't an off-the-shelf module that performs.

    When I tested the Sanwu pre-amp, its performance seemed identical to the original PE mode; same two issues. One may not matter. Your target range is close / within the Sanwu's range (and the PE for that matter). The other, decreasing volume with decreasing frequency was a show stopper. But that only requires removing one resistor. The part (ebay / aliexpress) is ~$8 sjipped.. If you want to try that route, let me know. I'll it out and take a look to see if it's feasible.

    If you really need one, I start with the new module and replace parts (both Pots - 50K & 20K - and add back a 10K resistor, IIRC). the parts will cost you ~$10 at DigiKey

    Leave a comment:


  • bolson2011
    replied
    Originally posted by Millstonemike View Post
    I'm confused: "​... make it work as a variable high pass filter, leaving only ~80-120hz and below pass through..."

    Low pass leaving only ~80-120hz and below; or
    High pass leaving only ~80-120hz and above.

    One or the other ...
    My mistake. I want to use it as a subwoofer pre-amp, letting only ~80-120hz and below through.

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by bolson2011 View Post

    I haven't modified the original module, I recreated (or at least tried to) it based on your recommendations and the schematic provided, with the changes in place. Essentially, I'm trying to make it work as a variable high pass filter, leaving only ~80-120hz and below pass through that particular filter.

    I guess I should say that I haven't purchased the original module, or the update to it.
    I'm confused: "​... make it work as a variable high pass filter, leaving only ~80-120hz and below pass through..."

    Low pass leaving only ~80-120hz and below; or
    High pass leaving only ~80-120hz and above.

    One or the other ...

    Leave a comment:


  • bolson2011
    replied
    Originally posted by Millstonemike View Post
    There really wasn't a problem with the input resistors R1 & R2 or a resistor required across RP1.

    Are you trying to modify the module according to my original recommendations? Be aware, circa post #28 there are suggested mods for a totally different application and do not apply to the original mods..
    I haven't modified the original module, I recreated (or at least tried to) it based on your recommendations and the schematic provided, with the changes in place. Essentially, I'm trying to make it work as a variable high pass filter, leaving only ~80-120hz and below pass through that particular filter.

    I guess I should say that I haven't purchased the original module, or the update to it.

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by bolson2011 View Post
    The original part #320-670

    But I recreated the schematic that you linked in the original post in the picture attached.
    There really wasn't a problem with the input resistors R1 & R2 or a resistor required across RP1.

    Are you trying to modify the module according to my original recommendations? Be aware, circa post #28 there are suggested mods for a totally different application and do not apply to the original mods..

    Leave a comment:


  • bolson2011
    replied
    The original part #320-670

    But I recreated the schematic that you linked in the original post in the picture attached.

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by bolson2011 View Post
    I'm using a 12v DC power supply, 2A output.
    That's plenty. Which version of the pre-amp do you have? Please post the exact PE part number.

    Leave a comment:


  • bolson2011
    replied
    I'm using a 12v DC power supply, 2A output.

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by bolson2011 View Post

    I've recreated this schematic, but I seem to have a big problem with significant over-driven signal. The signal is able to pass through the circuit, but is heavily distorted and is still "full-range," if that makes sense. The distortion is so bad that it just sounds like garbage.

    I've tried upping the resistor values for R1 and R2, as well as putting in a resistor in parallel with pins 1&3 of RP1A.

    Any thoughts on how to remedy this issue?
    What is the PS voltage you are using for the module?

    Leave a comment:


  • bolson2011
    replied
    Originally posted by Millstonemike View Post
    Correct. If its not connected, I use a "c" like shape to denote a connection doesn't touch another. Is that really old school? With R7 removed, the schematic looks like this:

    [ATTACH=CONFIG]n1320222[/ATTACH]
    I've recreated this schematic, but I seem to have a big problem with significant over-driven signal. The signal is able to pass through the circuit, but is heavily distorted and is still "full-range," if that makes sense. The distortion is so bad that it just sounds like garbage.

    I've tried upping the resistor values for R1 and R2, as well as putting in a resistor in parallel with pins 1&3 of RP1A.

    Any thoughts on how to remedy this issue?

    Leave a comment:


  • Millstonemike
    replied
    I've tested the Sanwu 2.1 pre-amp module in this thread. It suffers from the same issues of the original version of the PE sub-woofer pre-amp

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by a4eaudio View Post
    Ignoring that the particular implementation of these crossover boards may have problems...assuming there was a board with correct implementation...if I wanted to run two subwoofers, could I run the signal from pre-amp to a single variable crossover board, then split the RCA out with a Y-adapter and run the signal to the two subs separately? That way I know I have the same crossover and gain rather than implementing two separate boards?
    The output impedance of the pre-amp module is 200 ohms. That is low enough to drive the line level inputs on two sub amps (barring some unusually low input impedance).

    But, however, take notice ...

    The original module is no longer available to mod as originally posted. And the new version has more issues than the original - totally useless. I just received a third party module and will be evaluating soon.

    Tune in next week, same Bat time, same Bat channel ...

    Sub Pre Amp.jpg

    Leave a comment:


  • a4eaudio
    replied
    Ignoring that the particular implementation of these crossover boards may have problems...assuming there was a board with correct implementation...if I wanted to run two subwoofers, could I run the signal from pre-amp to a single variable crossover board, then split the RCA out with a Y-adapter and run the signal to the two subs separately? That way I know I have the same crossover and gain rather than implementing two separate boards?

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by thekorvers View Post

    Never cared much for the solder suckers, even the expensive ones. I prefer to use the simple inexpensive copper braid. Try that. It wicks the solder right out:

    https://www.parts-express.com/nte-sw...-5-ft--341-556

    https://www.parts-express.com/nte-sw...-5-ft--341-550
    You know, I never tried copper braid. I'll have to give it a go. I used a $1.79 solder sucker from Fleabay when I modified Gordy's board. though it required some finesse and experience.

    Leave a comment:


  • thekorvers
    replied
    Originally posted by Gordy View Post

    Please dont blame yourself. Your work and expertise is much appreciated. now if I could learn a better way to desolder Than buying an expensive electric solder sucker. I also looked on Mouser (because it is 3 hours away) and could not find 25k pots. I think 20's will be just fine. I need to order some single gang 10k's and will throw a few in that order and 10k resistors.
    Never cared much for the solder suckers, even the expensive ones. I prefer to use the simple inexpensive copper braid. Try that. It wicks the solder right out:

    https://www.parts-express.com/nte-sw...-5-ft--341-556

    https://www.parts-express.com/nte-sw...-5-ft--341-550

    Leave a comment:

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