Passive preamp question

Discussion in 'DIY Discussion' started by la toilette, May 3, 2008.

  1. la toilette

    la toilette Downright stupid

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    I'm planning on making a passive preamp using a stepped attenuator, but what value resistors are best to go for?

    A friend of mine has used a 50k but I read an article on enjoythemusic.com that suggested that 10k was a better option.

    There's a seller from hong kong on ebay that I plan to buy from; tube_buyer.....seems cheap enough at about £17 delivered!
    http://cgi.ebay.co.uk/Attenuator-24...photoQQcmdZViewItemQQ_trksidZp1742.m153.l1262
     
    la toilette, May 3, 2008
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  2. la toilette

    Parkandbike

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    I was told that it should be 20k or 10k for ss amps, but I have a vague recollection of reading that different values may be needed for valve amps (I may be wrong on this and I am sure someone will know).

    The one on your link seems to be very good value if it is a ladder attenuator- as it seems to be. I had a couple of 10k mono stepped attenuators made up for me by the Parts Connexion and they were a LOT more than this. Nevertheless in common with many people I subsequently found that a TVC is more enjoyable (obviously others think differently!).
     
    Parkandbike, May 3, 2008
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  3. la toilette

    Corky 20th Century survivor

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    Corky, May 3, 2008
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  4. la toilette

    LiloLee Blah, Blah, Blah.........

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    Ignore corky on this one these may not be dale resistors, but you put one together for the same cost inc delivery.

    I would recommend 20K. Obviously you DIY, so in the future you may play with DAC's and if it's one you put together yourself (I'm think NOS DAC) then most work best into 20K load.
     
    LiloLee, May 4, 2008
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  5. la toilette

    la toilette Downright stupid

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    Thanks for the comments, I might even get a selection of 2 or 3 of different values as they're such a good price, as they may come in useful in the future.

    I know what you're getting at corky, but at this price it's still a steal, as lilolee says.

    Happy days!
     
    la toilette, May 4, 2008
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  6. la toilette

    speedy.steve

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    speedy.steve, May 8, 2008
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  7. la toilette

    la toilette Downright stupid

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    Hi Steve, someone else has also mentioned the TVC passive to me, and another alternative, but they might be beyond my diy capabilities although I will be bearing it all in mind. There is more to all this than I first thought (I was intending to go for the simplest attenuator/selector/in/out with no additional components at first, but it seems that this has limited applications) so it might be a while til I get started - lots of reading first!

    Also, I just bought a pair of Tannoy DMT 10's on fleabay, so I may have to sell off some other unused stuff to pay for anything else!
     
    la toilette, May 10, 2008
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  8. la toilette

    robM

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    Hi

    My ultra limited experience with all this is it is best to use 50K as you never know what the output capacitor (if any) of the preceding source component has on it's output stage. A 10K pot is low if you have a CD player with a 1uf output cap (which mine had at the time). It took me a while and a lot of internet searching to find out that not all sources have the same size of output capacitor which when fed into a passive pre pot affects the low frequency.

    As for TVC..... I had one but it just couldn't drive anything longer than a 1.5m interconnect. After that you can hear the system change drastically. I think this is why a lot of folks prefer a gain stage to drive the interconnect length.

    Rob
     
    robM, May 27, 2008
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