Leach Amp Sub Pre-out

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jrhgohawks

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Joined 2004
I am finishing up a leach amp and I was thinking of adding a sub-pre out. I am pretty new to all of this and I was wondering how to do it. I assumed I would just tap off of one my volume controlled input lines and throw it through a LPF. Any thoughts would be greatly appreciated.

Thanks

Justin
 
J

jrhgohawks

Member
Joined 2004
I am a little new to the DIY Audio realm so I apologize for my naivete. I just built a two channel Leach amp but I want to add a subwoofer preout, not a preamp. I wish to hook them up to my existing speakers/subs. Is a sub preout simply an LPF or even simpler an input tap? I have looked for documentation but haven’t been able to find anything. Also, if it is just and LPF does anyone have one that can accommodate the 60V+ rails of the Leach amp?
 
BobEllis

BobEllis

Member
Joined 2003
To do it "right" you'll need something like what Viktor showed - it is an active crossover that sends the top end to your leach and provides a separate output for your sub.

You may be able to get away with a Y cable if thesubwoofer amp has a built in crossover that will allow it to mate properly with your main speakers. Suppose that your mains are ported and have an F3 of 50 Hz. If the subwoofer amp XO is fourth order and allows XO frequencies below 50 Hz, it may work, but a proper active XO that takes the response of the mains into account will probably sound better.
 
J

jrhgohawks

Member
Joined 2004
Ok sounds good. I will build it. I didn't realize exactly what it was before. I did have a couple of questions about the schematic though. What are the 1k5, 3k9, 1M2, and 82E resistors on the schematic? Are they supposed to be 15k and 39k? But what about the others? Also can I get away with just 1/4 watt for these? Finally, any one have suggestions for good selector switches?

Thanks,
Justin
 
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