Finally a difference I can hear

Discussion in 'Tube Audio' started by eickmewg, Dec 14, 2018.

  1. eickmewg

    eickmewg AK Subscriber Subscriber

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    Over the years I've accumulated several preamps and amplifiers. I've always been surprised that all this gear sounds pretty much alike in various combinations. Lately I've been using a Transcendent Sound Grounded Grid preamp with 12AU7 tubes I built from a kit with a Latino VTA ST120 also kit built and running KT120 power tubes and 6SN7 drivers.

    I like the Grounded Grid but the kit came with some near bottom-of-the barrel components. In particular, the output capacitors looked like the cost $5 per 100. I quickly replaced these about three years ago with Russian PIO caps but I used 0.22 uF caps instead of the original 1 uF values. In response to a question regarding output cap values and frequency response, AKer Gadget explained cap value and frequency rolloff. It appeared the 0.22 uF value might be restricting low frequency response.

    I decided to get some Mundorf EVO oil and aluminum caps in the specified 1 uF value and swap out the PIO's. I was immediately surprised by the improved low bass response. This simple and quite inexpensive mod I can really hear! Maybe I don't have lead ears after all.
     

     

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  2. savatage1973

    savatage1973 AK Subscriber Subscriber

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    Now try some different 12AU7 tubes and listen for the differences--some are VERY apparent.
     
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  3. gadget73

    gadget73 junk junkie Subscriber

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    Cool. Glad it made a noticeable difference, though I suspect the value more than the type of cap explains that. If you want to drive yourself nuts you can spend a pile of cash on different caps of the same value and see what that does.
     
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  4. 6DZ7

    6DZ7 Super Member

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    Mod? Or just getting back to square 1...
     
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  5. eickmewg

    eickmewg AK Subscriber Subscriber

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    Well, this was a bad experiment in that more than one variable was changed. Mundorf EVO or change in value? So, I won't characterize it as a mod, just a pleasant result :beerchug:.
     
  6. 6DZ7

    6DZ7 Super Member

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    A .2 cap would be 20% of the design value. With the associated resistance in the original design, like Gadget said, would probably change the rolloff, and what was its specified output impedance ... and plugged into what..... brand of cap isn't going to be a factor, % tollerance could be... the original could have worked just fine. No way to know if it's gone. Happy endings are all that matter.
     

     

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  7. FB night

    FB night Active Member

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    On the ST-120, 0.22uF capacitance is the standard for the coupling capacitors, so upping to 1uF would be a modification.
     
  8. primosounds

    primosounds Powered with pure tube sounds. Subscriber

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    IIANM the cap change was on the preamp.
     
  9. primosounds

    primosounds Powered with pure tube sounds. Subscriber

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    How did you come by replacing the 1.0uf with 0.22uf ? That really is quite a big difference especially on the output of the preamp. I realize that is all "dust in the wind" but i would really wonder if you did not hear a big difference between the 2 cap values.
     
  10. eickmewg

    eickmewg AK Subscriber Subscriber

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    In my defense :), back when I was considering changing the cheap output caps in my Grounded Grid, I found a link to Troel Gravesen's page (http://www.troelsgravesen.dk/GG.htm) where he talked about modifications to the Grounded Grid. He used a wide variety of caps, including 0.22 uF Russian PIO caps. He ended up liking Mundorf Supreme caps best and said nothing negative about the PIO's and at the time I was unaware of the potential frequency response issues. So, I didn't just pick th2 0.22 uF cap value out of the hat and there was rhyme to my reason, but as you said, primosounds, now just "dust in the wind."
     
  11. FB night

    FB night Active Member

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    Yup, you are correct, I misread the post.
     

     

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  12. brud

    brud AK Subscriber Subscriber

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    Interesting discussion - just finished my first SE build and am really liking this space / hobby
    It fascinates me that the changing of caps has an audible effect on the music - novice comment i know !

    “Electronics old and new “ on Youtube has published a similar topic restoring a Quad 33/303 ( sorry i know it’s not valve based) , however he shows the difference using a Oscilloscope - again sorry I have a science training - he makes no comment re the “listening test “.

    Fascinating stuff

    There is also a great resource by Richard Brice “Music Electronics” in 2 volumes - worth s read

     
  13. gadget73

    gadget73 junk junkie Subscriber

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    Discussions over different types of capacitors and how they sound are endless. Talk about different values are a little easier to get through just because you can do some math to explain some of the differences.

    I tend to lean more towards the side of measurements, just because objective data is far easier to discuss than perception.
     

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