Added bypass cap to Harvard - WHOO!

Discussion in 'Shock Brother's DIY Amps' started by jsnwhite619, Oct 11, 2019.

  1. peteb

    peteb Friend of Leo's

    Posts:
    4,200
    Joined:
    Apr 25, 2003
    Location:
    Cascadia
    The playing and the tone are great.


    Before I read the comments I thought it sounded slightly hazy, then when I read the comments I thought that makes sense if the NFB is non operational, similar to a 5E3. on a second listen I thought it has a nice smokey flavor.



    even though it has the smokey or hazy character it has plenty of high end and harmonics



    Your later comment says it is too bright. It probably sounds brighter in real life than on the recording.



    what happens when you turn the tone control down?
     
  2. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    35
    Posts:
    2,646
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Ok, the speaker was a big part of the "problem". I tried it through my cabinet with the Cannabis Rex, and it was a huge difference. I like the clean better with the 1258, but the no-NFB brightness was definitely better with the C-Rex. I even took the bright cap off & back on before the speaker swap. That helped, but it lost that hard edge to the overdrive that kept the definition of the notes.

    I think I'm going to take the bypass cap off of this one though. Either way, it's kind of a one trick pony, but the clean side is a better trick for my playing these days. I don't want to mess with the board at this point of trying to modify things. But, if/when I do it again, I'm going to design it with the Princeton Reverb style NFB and experiment with the bypass cap and probably switch.
     
  3. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    35
    Posts:
    2,646
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Oh, yeah, I forgot to say that if nothing else, it was a great learning experience to hear the difference ONE capacitor can make. That single 2uf bypass cap changed the cleanest amp I've built into the dirtiest. With the NFB sorted out, it could be one serious hellraiser.
     
    Snfoilhat likes this.
  4. peteb

    peteb Friend of Leo's

    Posts:
    4,200
    Joined:
    Apr 25, 2003
    Location:
    Cascadia
    I have defeated a NFB before and thought I noticed only a slight difference. Now I am not remembering what I did.



    this thread makes me want to experiment with the NFB.


    on my 6G2 I want to clip in a cap, 25-25?, across that resistor, or a 2 uF?


    on a champ, the 47 resistor could by shorted to ground.
     
  5. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    35
    Posts:
    2,646
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    On a different note, after taking the cap off today and rebiasing it, I took it back inside and tried it out. I brought my meter in so I could adjust it as I went. First time I checked it inside - without changing anything - my plate voltage was 20v lower than before. I just happened to check the wall voltage in my shop before I closed it up, so I checked the hot lug on the switch. 4-5v lower on every outlet in my living room than my shop/garage that is on the same panel box. 122.9v outside. Upper 118v in the living room. Amounted to roughly 20v drop in B+, and the bias dropped 10% to the upper 40% range.

    Sent from my moto g(6) using Tapatalk
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.