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PE Subwoofer Pre-Amp - Exposed

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  • thekorvers
    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
    When I studied electrical engineering ( in Europe a long long time ago) schematic standard was when 2 lines cross without a dot at the junction, no connection is made. When 2 lines cross and there is a dot at the junction, a connection is made. The only place I see this in your schematic is to the right of C8, where it says Nominally 1/2 Vcc. So this schematic is not very consistent, something I see a lot these days.

    I miss proper protocol and standards of the old days, not only in engineering, but in life in general. Things are often done so sloppily nowadays. (I think this may be a senior citizen's rant).

    Leave a comment:


  • thekorvers
    replied
    Very nice job Mike. Good research and write-up.

    I bought one of these a little while ago to check out, but had not done anything with it yet. I do dislike having to hunt down parts and having to modify it just to make it work properly. I prefer things that work properly right out of the box.

    I agree that PE should contact the supplier/manufacturer and specify the modifications needed. At least they should offer a parts kit for the modification at modest cost or suffer much reduced sales now that the word is out.

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by wogg View Post

    ​It's missing the node dot in the schematic, should be on the same connection where R4 and R5 meet.
    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:

    Schematic.jpg

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  • wogg
    replied
    Originally posted by Wolf View Post

    I don't see anything else connected to the other end of C8 in your schematic, or is it not all shown? That would leave it out of the circuit. That's why I asked.

    Later,
    Wolf
    ​It's missing the node dot in the schematic, should be on the same connection where R4 and R5 meet.

    Leave a comment:


  • Wolf
    replied
    Originally posted by Millstonemike View Post

    C3 is regulation on Vcc. C8 is regulation on the 1/2 Vcc still connected to the 1/2 Vcc point between R4 & R5 even after R7 is removed.

    A and B are both audio tapers. Unfortunately, even the quality pot mfg.'s (e.g., Bourns) didn't specify the version of the A taper.
    [ATTACH=CONFIG]n1320160[/ATTACH]
    I don't see anything else connected to the other end of C8 in your schematic, or is it not all shown? That would leave it out of the circuit. That's why I asked.

    Later,
    Wolf

    Leave a comment:


  • Gordy
    replied
    What a great write up! Thanks Mike! My father stills tells me to this day, don't make you hobby your job. Wise indeed.

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  • Millstonemike
    replied
    Originally posted by Chris Roemer View Post
    Maybe DA should hire you as an R&D consultant? It certainly SEEMs so!

    A wise old colleague once said; "Never make the mistake of mixing your avocation with your vocation." Besides, I'd rather help you gents out when I can. Many here certainly helped me.

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by tomzarbo View Post
    So basically, you're removing the .22 cap and reusing it elsewhere in the circuit.
    The only new components are the .1 cap and the pot? Correct

    Would you be able to provide a part number suggestion from Digi-Key for the .1 uf cap to get this all in one order? Digi-Key doesn't seem to offer a 0.1 uf in a narrow size. Try a KEMET RSBDC3100AA00J, its a box cap w/ correct lead spacing but it's a little larger than the one I used from my parts bin. It should fit. If it doesn't, let me know and I'll mail you some.

    Again, thanks so much for the help making this thing a hugely better product. I have plans for two projects that will use this upcoming.

    I'm sending the modified unit back to Gordy next week. Maybe you should wait until he tests it out. I've only had this up on the scope, not a live test.

    TomZ
    1

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  • Chris Roemer
    replied
    Maybe DA should hire you as an R&D consultant? It certainly SEEMs so!

    Leave a comment:


  • tomzarbo
    replied
    So basically, you're removing the .22 cap and reusing it elsewhere in the circuit.
    The only new components are the .1 cap and the pot?

    Would you be able to provide a part number suggestion from Digi-Key for the .1 uf cap to get this all in one order?

    Again, thanks so much for the help making this thing a hugely better product. I have plans for two projects that will use this upcoming.

    TomZ

    Leave a comment:


  • Millstonemike
    replied
    Originally posted by Wolf View Post
    Okay- A and B are what taper? A = audio/log? B = linear? or vice versa?

    Oh- the 100uF (C8) polarized cap that is then removed from the circuit by way of removal of R7- Can you just then parallel it then with the 220uF (C3) cap to add to the PSU regulation?

    Thanks, Mike- you really did good here!

    Later,
    Wolf
    C3 is regulation on Vcc. C8 is regulation on the 1/2 Vcc still connected to the 1/2 Vcc point between R4 & R5 even after R7 is removed.

    A and B are both audio tapers. Unfortunately, even the quality pot mfg.'s (e.g., Bourns) didn't specify the version of the A taper.
    Audio Taper Curves.jpg

    Leave a comment:


  • Wolf
    replied
    Okay- A and B are what taper? A = audio/log? B = linear? or vice versa?

    Oh- the 100uF (C8) polarized cap that is then removed from the circuit by way of removal of R7- Can you just then parallel it then with the 220uF (C3) cap to add to the PSU regulation?

    Thanks, Mike- you really did good here!

    Later,
    Wolf

    Leave a comment:


  • wogg
    replied
    Originally posted by DanP View Post
    The mods you made would have added to the piece cost minimally if implemented by the manufacturer, and they didn't just make the device better - they were the difference in being useful in the intended application or not. So I have to ask the question... why would a manufacturer make a device that doesn't work when they could have so easily made one that does?

    Dan
    ​Possibly engineered by someone that wouldn't use it as intended. The solution doesn't change cost to manufacturer at all, like for like part swaps +- pennies. Perhaps this will lead to a revision. Perhaps someone at PE could pass this along to the supplier?

    Leave a comment:


  • tomzarbo
    replied
    This is an awesome set of mods sir. Thank you for taking the time to do this. I plan on giving this a try soon.
    There are some majorly smart dudes on this board!
    TomZ

    Leave a comment:


  • DanP
    replied
    The mods you made would have added to the piece cost minimally if implemented by the manufacturer, and they didn't just make the device better - they were the difference in being useful in the intended application or not. So I have to ask the question... why would a manufacturer make a device that doesn't work when they could have so easily made one that does?

    Dan

    Leave a comment:

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