1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

5F1 buzz or no buzz?

Discussion in 'Shock Brother's DIY Amps' started by BjornSynneby, Mar 20, 2021.

  1. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    Hello friends!

    I am finishing up a 5f1 build and I’m uncertain if I have a buzz problem or just a great amp with a single coil guitar...

    The buzz is in both chanels can be controlled by the knobs on the guitar and the volume knob on the amp. So the buzz enters somewhere between guitar pickup (single coil) and volume control on the amp, right?

    When I change to my archtop with humbucker the amp is silent until some buzz btw 10-12 on the amp volume knob.

    Images:

    [​IMG]
    [​IMG]
    [​IMG]

    I filtered the rectifier voltage with two ceramic resistors (0,02uF, 1000V) parallel to the JJ5y3s inputs as mentioned by Rob Robinette to decrease 100Hz buzz but no difference.

    I have isolated input and output jacks and connected ground connections; (output jack sleeve to B+3 filter ground and input jack 1’s sleeve to input jack 2’s sleeve.) No difference.

    Is this just how a single coil sounds in a tweed amp? When I have come this far I can not seem to let go of trying to ”improve” things...

    The volume pot is still not isolated...

    Then I have one more question:

    I have 368V on the JJ6V6s plate and 20,2V over the cathode resistor (470R, 10W). That, with an assumed screen current of 2mA, makes a dissipation of 14,2W (102%). The amp is loud with headrom which I like but should I bias cooler to be safe?

    B+1 is 383V
    B+2 is 319V
    B+3 is 277V

    PT is 340-0-340
     
  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,386
    Joined:
    Dec 30, 2019
    Location:
    california
    The bias is fine. No worries.

    The buzz. Have you tried swapping the output transformer primary (or secondary) leads? Possibly positive feedback.
     
  3. Nickfl

    Nickfl Friend of Leo's

    Posts:
    2,550
    Joined:
    May 24, 2016
    Location:
    Florida
    Its probably the guitar. Is the amp noisy with nothing plugged in? Does the noise intensity change if you move to another room or move around the room you are in/point the guitar in a different direction? Is the chassis in the cabinet with the back panel on or just on your work bench? Do you have a humbucker guitar you could plug in or a single coil with a humbucking position on the selector switch to try and see if that has an effect?

    Your bias numbers are fine, 100%+ is standard in a single ended cathode biased amp. A JJ is capable of handling a good bit more than 14W so that isn't really even that high for that tube.
     
  4. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,386
    Joined:
    Dec 30, 2019
    Location:
    california
    I don't see the Center Tap connection for the high tension.
     
  5. Otis Fine

    Otis Fine Tele-Afflicted Silver Supporter

    Posts:
    1,292
    Joined:
    Jun 3, 2016
    Location:
    Chicago, Illinois
    I can't help, but these are top notch pictures!
     
    Pick_n_Strum, BjornSynneby and puddin like this.
  6. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    I swapped the OT primary leads when I had a squeal at first startup. Can I swap the secondary leads aswell?
     
  7. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    It’s at B+1 filter ground.
     
  8. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    Yes I tried moving my single coil jazzmaster around and it behaves as it should changing hum and buzz levels as an antenna. And in the middle position it became silent. Also I tried my archtop with humbucker and it silenced the buzz. I have not yet shielded my backplate and I am testing without it.

    With this info I can conclude that the buzz comes from the guitar, right?
     
    Nickfl likes this.
  9. Nickfl

    Nickfl Friend of Leo's

    Posts:
    2,550
    Joined:
    May 24, 2016
    Location:
    Florida
    Yes, and don't switch your OT leads again. If you had a squeal and switching them silenced it then you are where you should be with negative feedback.
     
    Lowerleftcoast likes this.
  10. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,386
    Joined:
    Dec 30, 2019
    Location:
    california
    ^^^^
    +1

    The buzz seems to be from the guitar single coils.:)
     
    BjornSynneby likes this.
  11. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    Haha! This wonderful world of discoveries.
     
  12. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    It is not noisy when nothing is plugged in. But when you increase the volume above 10 there is buzz (nothing plugged in). But that is how it should be I think.
     
  13. pfarrell

    pfarrell TDPRI Member

    Posts:
    55
    Joined:
    Jan 26, 2021
    Location:
    Upstate, NY
    I built two champs at the same
    time. Both had a buzz that attenuated with the vol/pwr switch... and therein lay the issue.

    I moved the fuse to the bottom of the amp, put a power switch in its place, moved the AC off the volume pot. No more buzzzz.

    Great amp(s).
     
  14. corliss1

    corliss1 Friend of Leo's Platinum Supporter

    Posts:
    4,755
    Joined:
    Sep 13, 2008
    Location:
    Lansing, MI
    In before the standard "get some space between the big resistor and cathode bypass cap so it doesn't get cooked" comment.
     
  15. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    That sounds like a great idea!

    Hehe. Yup you are right. I have to get a bypass cap with longer legs or a smaller sized cathode resistor.
     
  16. King Fan

    King Fan Poster Extraordinaire Ad Free Member

    Posts:
    6,356
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    That would help, though you’d also need to find some space for the cap, laterally. It can be done, bending other bits out of the way. Or (*note* I haven’t tried this with a big ol' wirewound, but they do have stout leads) you elevate the resistor above the cap, like one of those NYC parking lots with car elevators.
     
  17. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    Another good idea! The cathode resistor is 10 watts and I can’t really feel any heat coming from it though.

    As it is now the cap and resistor are 1-2 mm separated and I have bent the legs of the filter caps and the resistor as much as I can but its tight.

    One plan is to put in a 5watt resistor which is smaller. This will give the bypass cap some more space. On my 5E3 builds I have placed the cap piggyback-hovering above the resistor.
     
    Last edited: Mar 24, 2021
  18. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    Measuring heat between bypass resistor and cap. Had this setup running for ten minutes and I managed to push it to 35 deg. Celsius (95 Fahrenheit). I think I am alright.

    [​IMG]
     
    King Fan likes this.
  19. jimgchord

    jimgchord Tele-Afflicted

    Age:
    47
    Posts:
    1,556
    Joined:
    Apr 3, 2018
    Location:
    victor,ny
    If it is silent with nothing plugged in, you are likely just experiencing normal single ended amp/ single coil guitar noise. On 10 it should hiss a little, but these are best at 3-5 so it doesnt much matter. May want to reflow some of those questionable solder joints though.
     
  20. BjornSynneby

    BjornSynneby TDPRI Member

    Age:
    49
    Posts:
    26
    Joined:
    Nov 22, 2018
    Location:
    Göteborg
    I get buzz when increasing the volume with nothing plugged in. I will try moving the power switch function out of the signal path at the volume pot as pfarell suggested here above.
     
    King Fan likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.