Tweaker's Asylum

• Question regarding eliminating the chokes on an amp circuit. Jim R 23:20:31 01/31/01 (1)
  In Reply to: Risch Line Filter Confusion!??!??! posted by Hantra on January 31, 2001 at 15:58:14:

  This was a nice post - it helped me to understand different branching options better. I have a followup question though.

  Do I understand you right that it is acceptable (and safe) to branch off an amp circuit right before the L1 & L2 inductors (ie. eliminating the inductors). If this is correct, would you still use the last capacitor and varister (C4 & V2) at the outlet.

  Thanks for your help.

  
  
  

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  • Re: Question regarding eliminating the chokes on an amp circuit. BobM 14:49:44 02/01/01 (0)
    In Reply to: Question regarding eliminating the chokes on an amp circuit. posted by Jim R on January 31, 2001 at 23:20:31:

    As for safe - you'll have to ask an EE, but branching a circuit for 4 outlets or so is probably fine. Just look at any power strip.

    If you want an amp outlet that is not choked then just run + and - wires from the incoming bundles (where the 3caps & varistor are connected) to the back of the amp outlet. I would definitely still use the cap and varistor on the outlet end of the schematic.

    I actually built the full monty, with separate chokes for each outlet. The chokes didn't work well with my amp (McCormack DNA .5 Deluxe) - it lost dynamics. I took Lukasz's suggestion and took all but about 10 turns off of the chokes for the amp circuit. This improved things a lot, but there was still a minor dynamics loss without any real noticable "cleaning up". I installed an DPDT switch so I could bypass the chokes and do a very easy A/B comparison.

    I wound up leaving the switch bypassing the chokes. I also added one additional mod of my own. I took an Audio Prism Power Line Filter, opened it up and attached a + and - wire, then plugged it into the back of the amp outlet. It definitely smoothed things out more so than without it without any ill effects that I can hear.

    So the bottom line is the amp circuit has extra capacitance and surge protection without the choked filtering.

    Enjoy,
    Bob

    
    
    

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• Re: Risch Line Filter Confusion!??!??! BobM 16:21:49 01/31/01 (3)
  In Reply to: Risch Line Filter Confusion!??!??! posted by Hantra on January 31, 2001 at 15:58:14:

  Basically, you can do this once for all outlets (single set of chokes), or you can branch off the base schematic and isolate each outlet (to some degree) with separate chokes. Yes, the chokes are the expensive part.

  If you want to use a single set of chokes then do this:
  - Branch off the schematic at the back end of the chokes, making separate sets of + and - wires to each outlet. This meand run separate + and - wires from the chokes to each outlet.
  - Insert the remaining capacitor and varistor into the back of the outlet where the wires are crimped.

  If you want to branch and get some isolation, here's what you need to know:

  - Do you see the capacitors and varistor where the line comes in? That is common to all - connect your incoming power cord and these components together as per the schematic.
  - Then run separate + and - wires for each outlet to separate set of chokes (1 set for each outlet). You will have a good size bundle of wires where they commonly join together for each leg (+, - and ground).
  - Run separate + and - wires from the chokes to the outlet.
  - Insert the remaining capacitor and varistor into the back of the outlet where the wires are crimped.

  A couple words of caution.
  - You may not want to choke all of the outlets, so don't run off and buy a whole lot of varistors just yet. Some amps don't like the chokes. I suggest choking some and leaving some as purely surge proteted with extra capacitance. Do an A/B and see what works for you.
  - If you want chokes on your amp outlet you should double them up in parallel. This means 2 chokes (in parallel) for the + and 2 chokes (in parallel) for the - leg. I believe Jon states this in his notes.
  - Check out Lukasz's notes on the subject. He made some very good suggestions and modifications to Jon's basic design.
  - But most important of all - have fun building it.

  Enjoy,
  Bob
  
  

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  • Re: Risch Line Filter Confusion!??!??! indy 13:10:57 02/03/01 (2)
    In Reply to: Re: Risch Line Filter Confusion!??!??! posted by BobM on January 31, 2001 at 16:21:49:

    Bob,

    Would it make a different installing the cap and MOV before the duplex?

    indy
    
    

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    • Re: Risch Line Filter Confusion!??!??! BobM 13:06:23 02/05/01 (1)
      In Reply to: Re: Risch Line Filter Confusion!??!??! posted by indy on February 03, 2001 at 13:10:57:

      I asked this question of Jon some time ago. His answer - "the closer the cap & varistor are to the outlet = the better. So plug them into the back of the outlet where the wires are inserted."

      Enjoy,
      Bob
      
      

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      • Thanks (nt) indy 13:23:52 02/05/01 (0)
        In Reply to: Re: Risch Line Filter Confusion!??!??! posted by BobM on February 05, 2001 at 13:06:23:

        
        
        

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