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Thread: DIY phonostage.

  1. #471
    Join Date: Jan 2016

    Location: Shenfield

    Posts: 573
    I'm Slav.

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    What's optimum current should be running through Calvin power transistors , I have 19mA only , shouldn't be close to 30mA?

  2. #472
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    Not sure there is no information on the guide best I can say is If you can have a look at the Paradise Builders tread on Diyaudio post 3053 (I can not and just have little info as I got banned for posing 5 or 6 X )

    I am going to have a play whit the buffers tomorrow (messed one up whit same heavy welding)
    I am thinking about putting a square wave from the scope trough passive inverse RIAA and paradise then have a look at the picture Will this work?

  3. #473
    Join Date: Mar 2017

    Location: Liverpool

    Posts: 766
    I'm Sandro.

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    On my build whit 2SK170 and PN4391 output transistors2SA1930
    I have set r5 and r7 whit a pot in parallel to the 22Homesresistors
    The current through the combination is given by
    V across the resistor over the resistance I=V/R
    I have the following r5=15R 483 mV 32.2 mA
    R7=15R 497mV =33.12
    Changing the resistors to 6.8Rgive me the following
    R5=6.8 297 mV 43.6 mA r7=6.8 294 mV 43.2

    Changing the setting on the offset pot R8 changes thecurrent through bot resistors
    The V drop for R5 R7=6.8 R at 30 mA should be around 200 mV
    I now I have 210 mv on R5 and 202 mV on R7
    A small adjustment of R7 increase current on Q6 and reducethe current on Q3
    I have now R5 =208.7 mV and R7 208.7 mV
    Small tweak ¼ turn on R8 and now volts drops are 201 and 200mV
    One thig I have not done so far is fit a trim pot on R2 andtry that
    Obviously the gains and Ids of the transistors /Jfet has aplay in the results I got
    Still much more should be said on the Calvin Build guide

  4. #474
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,898
    I'm Simon.

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    Sandro the original Calvin buffer thread has more info in it.
    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

  5. #475
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,898
    I'm Simon.

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    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

  6. #476
    Join Date: Jan 2016

    Location: Shenfield

    Posts: 573
    I'm Slav.

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    Quote Originally Posted by Bksabath View Post
    On my build whit 2SK170 and PN4391 output transistors2SA1930
    I have set r5 and r7 whit a pot in parallel to the 22Homesresistors
    The current through the combination is given by
    V across the resistor over the resistance I=V/R
    I have the following r5=15R 483 mV 32.2 mA
    R7=15R 497mV =33.12
    Changing the resistors to 6.8Rgive me the following
    R5=6.8 297 mV 43.6 mA r7=6.8 294 mV 43.2

    Changing the setting on the offset pot R8 changes thecurrent through bot resistors
    The V drop for R5 R7=6.8 R at 30 mA should be around 200 mV
    I now I have 210 mv on R5 and 202 mV on R7
    A small adjustment of R7 increase current on Q6 and reducethe current on Q3
    I have now R5 =208.7 mV and R7 208.7 mV
    Small tweak ¼ turn on R8 and now volts drops are 201 and 200mV
    One thig I have not done so far is fit a trim pot on R2 andtry that
    Obviously the gains and Ids of the transistors /Jfet has aplay in the results I got
    Still much more should be said on the Calvin Build guide
    I like the idea of trimpots ,
    how do you match bipolars and jfets , DCA55 is not much of a help , any quick to build circuit ?

  7. #477
    Join Date: Jan 2016

    Location: Shenfield

    Posts: 573
    I'm Slav.

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    Quote Originally Posted by sq225917 View Post
    I use the values from the notes, not the schematic and have always built with j107 and 5102 or whatever the match is. I use mje350 and 220pf caps. On the shunt I run 8.2 ohm 5 watt non inductive wire wound five watts and heat output is modest if you use a 300mA choke regulated power supply/ pre regulator and stick to 25.5- 26v under load into the shunt.

    .
    Simon
    where did you get those MJE350 bipolars , for some reason I can't get 2SA1381 to work , what's the best way to match them? Same applies to J107 ?
    You've mentioned on DIYAudio testing Calvins as standalone unit , do you power them from Paradise boards with disconnected In ,Out, Gnd , just shortened with 100k?

  8. #478
    Join Date: Mar 2010

    Location: Sheffield

    Posts: 2,898
    I'm Simon.

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    yeh, just short the input with 100k. I'll be doing a Mouser order tonight/tomorrow would you like me to add a quad of MJE350's for you?
    Kuzma Stabi/S 12", (LP12-bastard) DC motor and optical tacho psu, Benz LP, Paradise (phonostage). MB-Pro, Brooklyn dac and psu, Bruno Putzeys balanced pre, mod86p dual mono amps, Yamaha NS1000m

  9. #479
    Join Date: Jan 2016

    Location: Shenfield

    Posts: 573
    I'm Slav.

    Default

    Quote Originally Posted by sq225917 View Post
    yeh, just short the input with 100k. I'll be doing a Mouser order tonight/tomorrow would you like me to add a quad of MJE350's for you?
    It would be great , can you order 8 so there is something to choose from and if you don't mind 8 of J107's , I'd like to start fresh ( ordered matched Pf5102 earlier today) , PM me how much I owe you (I'll participate towards shipping charge if applies) .
    How do you match these Simon?
    Regards

  10. #480
    Join Date: Jan 2016

    Location: Shenfield

    Posts: 573
    I'm Slav.

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    Simon
    What values of C1&C2 you use , Calvin manual says MJE/MJD 350 ( C1,C2 = 100-47pF)

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