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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Nfb switch on 5e3 clone

Discussion in 'Amp Tech Center' started by Stevo1956, Nov 14, 2017.

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  1. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    Hi guys
    Wondering if anyone can help me out here.
    I built this clone 5e3 off eBay about 8 years ago and found some info about a nfb switch .
    I did the mod but in one position of the switch I get a squeal
    Not loud but not good.
    This amp has the Bruce Collins volume mod 2 separate that don' interact anymore.
    One last thing I was a newbie when I built this so forgive me for not getting any terms correct when asked a question.
    Thanks in advance for any help ,stevo
     

  2. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    You need to swap the two wires that go to pin 3 on each power tube. What's going on is the polarity is reversed, so the negative feedback becomes positive feedback, turning the amp into a miniature air raid siren.
     

  3. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    Thank you for your response
    After some reading I also realised I never removed the bypass cap
    The amp sounds great in 2 positions on the switch
    Also I forgot to mention I have 4 8 and 16 ohm taps and am only using the 16 ohm tap an that where I soldered my resistor.
    I do not have an impedance switch either.
    Thanks again for any info
    I stopped playing this amp for a while now I just rediscovered how good it does sound
     

  4. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx

  5. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    The kit I built years ago has a different
    Layout where as the the v2 bypass cap an resistor attach at the Same point unlike on robs amp.
    I removed cap completely but did not know where to hook up that last wire.
    When I clipped one end of the cap an attached the the wire from the switch I had 2 usefull sounds if the transformer wires were out phase wouldn't it sqeaul in all positions.
    It's been a while doing these mods but know all safety precautions to do so I don't kill myself .
    Thanks again for any input .
    Stevo
     

  6. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    Switch the wires on the output jack....easier... That's what I did..
     

  7. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    Thank you for your help.
    I decided to remove that mod because
    To swap all the wires and change my amp from something that still sounds good to me was not worth it.
    I am glad I joined this board
    There is a ton of reading I need to do
    An people are very helpful thanks to all
    Stevo
     
    Thin69 likes this.

  8. misterdontmove

    misterdontmove Tele-Meister

    200
    Mar 25, 2011
    Connecticut
    I used Rob Robinette's mod with a 3 way switch and it's a great mod. You are correct, the second position on the switch lifts the cathode bypass cap, and the third adds negative feedback, with the cathode bypass cap lifted. I don't know if the negative feedback works with the cathode bypass cap in place?

    Mine needed the polarity switched and squealed like a pig,but the switch described above resolved it. I live with it in position 2 almost all of the time. I'll add the negative feedback sometimes in very low volume situations, but position 2 with the cathode bypass cap lifted really is the S#!T.
     
    robrob likes this.

  9. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    Thank you for your help
    I may just revisit this mod again
    I just didn't want to start ripping my amp amp apart after 5 years of no amp building or any repairs of any kind .
    Specialty when the amp is working fine thank again
    Stevo
     

  10. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    No, the cathode bypass cap will sink the NFB signal to ground. A workaround is to place a 47 ohm resistor between the cathode resistor and ground and reduce the NFB resistor to 870 ohms. This will prevent the bypass cap from eating the NFB signal.
     

  11. misterdontmove

    misterdontmove Tele-Meister

    200
    Mar 25, 2011
    Connecticut
    There's not too much ripping involved. Most of the work and all of the components is right near the extension speaker jack. It's easily reversible, but you won't want to, and with the stock position on the switch, you won't need to. The only thing I keep going back in to mess with is the amount of negative feedback. I keep increasing the amount of resistance for less and less feedback. There is a noticable volume and brightness drop with the addition of negative feedback, and I'm finding less is best. It is a tweed deluxe after all. No use making it into something it ain't!
     

  12. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    First off thanks for your reply
    I have 4, 8 and 16 ohm outputs should I diconnect those and cap them off because I'm only using the 16 output
    Then I can just turn that Jack 180 degrees and change the to wires
    I have one ground wire that connects all three taps at once.
    So by eliminating those other 2 it would be very easy to reverse the wires
    Again thanks for your input
    This is a great place for people like me to get information
     

  13. ce24

    ce24 Friend of Leo's

    Jan 26, 2008
    Idahoastan
    I modded the mod by putting 3 way on..on..on switch between the NFB mod resistor to switch between 3 different values.....I'll give kudos to dtar for this mod....easy to do and works well.
     
    D'tar likes this.

  14. D'tar

    D'tar Tele-Holic

    946
    Jan 11, 2013
    WNY
    Definitely worth revisitng the mod...

    You can use the 8 ohm tap to feed the nfb circuit, check robs sight for suggested values.... Even tho you are using the 16ohm for your output. The signal is still available on the 8ohm tap.

    I do like my three levels of nfb:)
     
    Last edited: Nov 19, 2017 at 4:36 PM

  15. tombob

    tombob Tele-Meister

    Age:
    44
    319
    Jun 25, 2010
    Sonora, TX
    I'm seriously thinking about doing a 5e3 kit before too long. I just finished a 5f6a Bassman that I'm really happy with and I really enjoyed building so a 5e3 seems like a good next project. I've always liked the tweed Deluxe but it really pushes one to keep up in a group/band situation so I've been thinking about ways to help with headroom. I'm thinking having NFB available should help with headroom. Have those of you that have tried it found that to be true?
    I'm planning on using a bigger, 2x10 cab with very efficient speakers to help and maybe trying 5881s in it (with a 10w cathode resistor and higher voltage rectifier tube) to gain bit more too.
     

  16. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    Rob all I can say to you is thank you for your wealth of knowledge
    That you share with everyone
    An taking the time to help really a newbie again who is just getting back into working on amps again
    Thanks stevo
     
    robrob and tombob like this.

  17. tombob

    tombob Tele-Meister

    Age:
    44
    319
    Jun 25, 2010
    Sonora, TX
    I agree wholeheartedly Stevo. I started working on amps because there wasn't a decent tech within 175 miles of me for years so it was either learn to change filter caps, bias tubes and do minor repairs or buy a solid state amp. When I got interested in doing more than just minor repairs I started reading and talking to others on here and I learned more than I ever could have on my own. There's some great folks on here with a wealth of knowledge.
     
    robrob likes this.

  18. tombob

    tombob Tele-Meister

    Age:
    44
    319
    Jun 25, 2010
    Sonora, TX
    Since everyone on this thread is familiar with the 5e3 I had another thought to put to all of you. Since I've been planning a build I've started looking at schematics and layouts and it looks like a lot of the volume interaction that the Deluxe is known for is in the shared tone control. It would be easy enough to use a dual ganged pot to separate them although it might be handy to maybe move the power indicator light to the ground switch spot and add another tone so each channel has it own. I just wonder if it's really worth doing though.

    I'm editing my post adding this on...
    RobRob, I found where you had disconnected the normal channel from the tone control to stop the volume controls from effecting one another as much. What do think about the sound/performance of the 5e3 with the channels connected through the tone vs not connected?
     
    Last edited: Nov 21, 2017 at 6:31 PM

  19. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    The interaction between the 5E3's controls are part of the amp's charm and offers a way to tweak the amp's gain. You lose that if you separate the controls but the amp does become less idiosyncratic. I don't recommend the mod.
     

  20. Stevo1956

    Stevo1956 TDPRI Member

    Age:
    61
    9
    Nov 14, 2017
    Pflugerville tx
    Just my 2 cents worth I have to agree with Rob Rob I now wish I never did the Bruce Collins mod with separated volume controls and absolutely no disrespect to Bruce the mod worked as described no complaints whatsoever
    However I wish I able to learn to appreciate the interaction between the 2 channels.
    Little did I know I had ready changed out the coupling caps and was there but instead of doing 1 mod at a time I did like 3
    Long story short going back to the original 2 pot volume interaction then after maybe redo the nfb mod .
    This time 1 mod at a time .
    As always this is the best forum for learning an asking questions
    Happy holidays to all
     

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