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Thread: autotransformer

  1. #1
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    autotransformer

    hello,
    i would like to know the formula for attenuations of tapped autotransformer, if someone can help me, thanks.
    Phil

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    Question: 09-24-2003, 05:46 PM
    Answer: 02-10-2005, 05:37 AM

    Is that service or what!?

    Ok. I put this graphic together after lifting the tapped autotransformer pic from here - http://www.allaboutcircuits.com/vol_2/chpt_9/5.html

    This is something I've been meaning to put together for a very long time.

    I am indebted to David Smith for supplying the fundamental formulas for my spreadsheet.
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    Modeling a tapped autotransformer courtesy of David Smith.
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    Another model using my software showing the spice data

    David's LEAP Crossover Shop software is better in that it automagically calculates the secondary inductance value.
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    Senior Member Guido's Avatar
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    Hey,

    good stuff Thanks.

    Is there some formula to convert it to this series and parallel R/L substituting circuit?

    You somewhere posted this for the 3145 network but it would be useful to be able to convert all the other networks with these tapped AT's
    BLS Reference on Passlabs XA 30.5 + Everest DD66000 clone on Pass XA 100.5

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    Quote Originally Posted by Guido
    Is there some formula to convert it to this series and parallel R/L substituting circuit?
    Not that I know of. Those conversions were all done the hard way. Greg Timbers supplied the original voltage drives along with a few suggestions and I had to plug and chug until the voltage drives looked identical. I never did get around to doing the 4315, L65, S21, or L220. I think Tim G might be able to import voltage drives into SoundEasy and do something with them.

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    Quote Originally Posted by Giskard
    Question: 09-24-2003, 05:46 PM
    Answer: 02-10-2005, 05:37 AM

    Is that service or what!?

    Ok. I put this graphic together after lifting the tapped autotransformer pic from here - http://www.allaboutcircuits.com/vol_2/chpt_9/5.html

    This is something I've been meaning to put together for a very long time.

    I am indebted to David Smith for supplying the fundamental formulas for my spreadsheet.

    hello,
    i just see (saw?) your post, you don't forget me !
    i'm very happy ...
    very good post, thanks. fonzy
    Phil

  8. #8
    Senior Member Bruno GINARD's Avatar
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    Hi Fonzy,

    I send you a P.M about this case

    Regards
    Bruno

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    Senior Member Guido's Avatar
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    Quote Originally Posted by Giskard
    Not that I know of. Those conversions were all done the hard way. Greg Timbers supplied the original voltage drives along with a few suggestions and I had to plug and chug until the voltage drives looked identical. I never did get around to doing the 4315, L65, S21, or L220. I think Tim G might be able to import voltage drives into SoundEasy and do something with them.
    OK, so building 4315, L65, S21, or L220 will be a challenge
    At least we have the 3145 circuit.
    BLS Reference on Passlabs XA 30.5 + Everest DD66000 clone on Pass XA 100.5

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    RIP 2011 Zilch's Avatar
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    Somebody should give us a little tutorial here. What's this about? How does it apply?

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    55030 Tapped Autotransformer

    In this particular instance, used to make the 52978 "1.55mH" tapped autotransformer in the LX80/LX80A/LX300/N333/3131/3133
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    Tapped autotransformer shown above measured:

    red to black - 1.51 mH 0.69 ohms DCR
    1st yellow to black - 0.39 mH 0.48 ohms DCR (-6 dB)
    2nd yellow to black - 0.27 mH 0.42 ohms DCR (-7.5 dB, spec'd as - 8 dB)
    orange to black - 0.14 mH 0.39 ohms DCR (-10 dB)

    red to 1st yellow - 0.36 mH 0.46 ohms DCR (-6 dB)
    red to 2nd yellow - 0.52 mH 0.48 ohms DCR (-4.5 dB)
    red to orange - 0.75 mH 0.52 ohms DCR (-3 dB)



    Using the fomulas posted in #2 above for a 1.51 mH inductor:
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  13. #13
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    Quote Originally Posted by Zilch
    Somebody should give us a little tutorial here. What's this about? How does it apply?
    It's a way to model tapped autotransformers to simulate voltage drives. Once the voltage drive has been simulated one can replace the tapped autotransformer with resistor pads and regular inductors which will yield the same voltage drive. It's probably easier to do with something like SoundEasy or LEAP Crossover Shop than with something like pSpice.

  14. #14
    Senior Member Bruno GINARD's Avatar
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    Sowter

    Hi all,

    After a PM exchange with Giskard, i would like to inform you about the availability of autotransformers :

    2 months ago , i had a talk with a FRench Hartsfield owner ( a Classic Audio Repro) about autotransformers versus L Pad.(IMO L.Pad are ALL poor quality and very imprecise component).

    He gave me the information that this kind of transformer was available at SOWTER UK, as a particular order.

    http://www.sowter.co.uk/

    Then, we decided to order 10 of them in January.THey are on the way from UK to France for the present.
    The conditions of the contract included 9 positions, from -1 to -10 db.Contrary to the JBL original parts, those transformers DO NOT includes the L circuit. THerefore you have to instal the inductor separatly, thus the 10 stepped selector with the different resitors in front of the circuit.( scheme included)
    The price of each transformer is about 140 €/180 $ without local taxes.

    I hope it could help!

    Warmest regards,
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    Bruno

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    Measured impedance curve of 1.55 mH tapped autotransformer without and with preceding 7.5 ohm parallel resistor.
    This is the load the 16.5 uF capacitor sees.
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