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Thread: dave slagle pre build

  1. #1
    Join Date: Oct 2009

    Location: Birmingham, UK

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    I'm Phil.

    Default dave slagle pre build

    Building a dave slagle pre , using a seiden 2 pole 23 step attenuator , I understand the wiring from the autoformers but its wiring the switch that has me thinking this
    is from his site ,

    Thats all there is to it! Pay close attention to the switch rotation. When the switch is rotated all the way counterclockwise (off) this is where the ground connection goes, then as you rotate the switch clockwise you simply connect the taps in order (-42, -39 etc.). If you reach full volume (the signal in lead) and still have remaining taps on your switch, simply connect them all together or insert a stop to prevent any contacts from being left open. Further questions about hookup can be asked in the forum.



    its the ground connection that has me confused , if you connect the first pin of the switch to earth it then joins with the output which would give you a short , or am i missing something , any clues phil.
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    Last edited by oceanobsession; 26-11-2019 at 19:36.
    Phil.

  2. #2
    Join Date: Mar 2008

    Location: Galashiels

    Posts: 12,978
    I'm inthescottishmafia.

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    Yes, that’s what you want with the volume fully counter clockwise, means there will be zero output, which is what you want.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  3. #3
    Join Date: Apr 2012

    Location: United Kingdom

    Posts: 2,136
    I'm Richard.

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    The input connects to one end of the AVC winding. The ground to the other end, as he says. The output (wiper on a pot) connects to the moving contact on the switch. The input to the power amp will indeed be grounded at full attenuation (just like a pot), but the output from the pre will not, as the signal has to pass though the whole of the winding to get there.
    Does that help? I'd be interested in the results, as I use a TVC on the output of my 01A pre, but considered a Slagle AVC.

  4. #4
    Join Date: Mar 2008

    Location: Galashiels

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    They are very good indeed, I built one a good while ago. Sold it on when I got hold of some Tribute autoformers, not sure they are much better if at all though.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  5. #5
    Join Date: Oct 2009

    Location: Birmingham, UK

    Posts: 374
    I'm Phil.

    Default dave slagle pre build

    So basically the 42db attenuation would still allow some sound from the speakers , so the first segment OFF position joins ground and output , this
    would be like the 2 wires touching in a pair of interconnects . isnt this a short . phil.
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    Phil.

  6. #6
    Join Date: Mar 2008

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    Yes, but that's fine, won't do any harm.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  7. #7
    Join Date: Oct 2009

    Location: Birmingham, UK

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    I'm Phil.

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    Hi dick , when i get the soldering sorted ill let you know how it sounds , i think i understand now about grounding the output , cheers for your help phil.
    Phil.

  8. #8
    Join Date: Oct 2009

    Location: Birmingham, UK

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    I'm Phil.

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    Quote Originally Posted by Ali Tait View Post
    Yes, but that's fine, won't do any harm.
    cheers for your help , phil.
    Phil.

  9. #9
    Join Date: Apr 2012

    Location: United Kingdom

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    I'm Richard.

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    Quote Originally Posted by oceanobsession View Post
    So basically the 42db attenuation would still allow some sound from the speakers , so the first segment OFF position joins ground and output , this
    would be like the 2 wires touching in a pair of interconnects . isnt this a short . phil.
    Ah, no. There are three wires here, and the important one, the output from the pre, is never shorted. Input to power amp is. Whenever I test a power amp for faults, I generally start with the inputs shorted to minimise spurious noise.
    ABD.

  10. #10
    Join Date: Apr 2012

    Location: United Kingdom

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    I'm Richard.

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    Quote Originally Posted by Ali Tait View Post
    They are very good indeed, I built one a good while ago. Sold it on when I got hold of some Tribute autoformers, not sure they are much better if at all though.
    I have a Glasshouse TVC upgraded with Sowter transformers, used as a stand-alone unit or at the output of the 01A DHT pre (input pot turned to max) as the volume control. If I was closer (to practically anywhere, I live in Plymouth!) it would be interesting to compare the two.
    ABD.

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