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Starting a 5F11 Vibrolux build - bias question

Discussion in 'Shock Brother's DIY Amps' started by jsnwhite619, Dec 12, 2016.

  1. King Fan

    King Fan Tele-Afflicted Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Jason, you've likely seen it, but this helped me understand my bias circuit.

    http://el34world.com/charts/Biascircuits.htm

    Also I can't tell from your photos, but where are your 1ohm resistors mounted? Which wires go to those pins?
     
  2. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    Ok, I finally got somewhere. I twisted two of my 33k resistors together and replaced the single 33k I had on there. Fired it up and adjusted the pot to
    -25.4v bias
    26.2 mA at the 1-ohm resistor
    310v on the plate

    At least now I know my meter works and I'm not completely crazy. The bias pot is probably set at 10-10:30 on the dial - I guess all the way left would stop at 7:00. If I used Rob's calculator correctly, it says I'm at 58% dissipation, 8.1 watts, and just a little below average 60% of 27.1 mA. Now, this has all been after swapping to the lower power 275-0-275 primaries from the 315-0-315 -- 422v at first, 377v after the swap, now 310v after adjusting the bias pot resistor.

    Am I in the ballpark now?

    Thanks. I don't think I'm been this much trouble on here in a long time...:D
     
  3. dankilling

    dankilling Tele-Afflicted

    Oct 28, 2014
    Lehigh Valley, PA
    Yep, you're in the ballpark. Tune your voltages to your liking, re-bias to 60-65% and you're all set!
     
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  5. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    Thanks, you and everyone else so far. Since I've brought the plate voltage down by 70 volts with the bias pot correction, I'm thinking if I should try the higher voltage 315v primary again (currently 275v) and see what I get. I wonder if my setup was so far off the first time that it might be a better choice now that maybe I can get the voltage backed down.

    After adjusting again to 62.5% I have
    -24.8v bias
    307v on the plate
    28.3mA at the resistor.
    My bias pot is now a bit over 26K total (the 2x33k together) with the 10K sweep.

    Voltage on the 5Y3 side of the 100K resistor is 292.8v. Diode side of the 100K is 165.8v
    B+ is
    312v
    310v
    238v
     
  6. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    yes - go back to the original transformer windings. Your plate voltage now is too low. My Mojo kit came with a 350-0-350 power transformer, and I am getting 396 VDC on the plates at 65% dissipation. With your transformer at 315-0-315, you might be right close to the original Fender design of 340 volts on the plate.

    And I think in the long run you will find it better to change the value of the 100k resistor. I'm not sure why I think that, it just seems that way to me. Maybe I'm wrong and someone will explain why. I just do this stuff with "seat-of-the-pants" technology.
     
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  7. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    I swapped the primaries back to the 315v, and this is looking better I think.

    After adjusting again I have
    -32.94v bias
    373v on the plate
    24.7mA at the resistor.
    Voltage on the 5Y3 side of the 100K resistor is 338v. Diode side of the 100K is 193v
    B+ is
    377v
    374v
    289v

    Rob's Bias Calculator says I'm at 65.8% dissipation. So, it looks like I'll be leaving the higher voltage primaries on there. Thanks everyone for all the help, and please chime in if there is something else I should address. This thread can be a case study for 5F11 voltage and bias - haha.

    Now to get started on the cabinet.
     
    Last edited: Mar 15, 2017
    dankilling likes this.
  8. dankilling

    dankilling Tele-Afflicted

    Oct 28, 2014
    Lehigh Valley, PA
    How's it sound now? That's the important part ... ;)
     
  9. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    For the few minutes I had to try it out, I may be in love. Still running into my Pro Jr cab I built with a Veteran 10, but I really like the snap and definition, I don't know how much has to do with the speaker yet, but the Tele just chimes and gets some real hair on it when it starts cranking. Still haven't tried my Les Paul through it, but I can only imagine it will be amazing. Seems like a lot of people have been building these on here lately, and I can see why. I have a Raging Cajun that I'm going to try too. It is a lot louder than the Warehouse speaker, but I'm interested to see what it will do.

    Again, if anyone sees any issues I missed, especially concerning the bias resistor setup I ended up with, please let me know!
     
  10. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Your voltages look really good with the high voltage windings.
     
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  11. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    Yeah, I've looked around at other threads about them and I was thinking that i must have gotten things sorted out alright.

    Do you have any thoughts on the resistor values mentioned above - lowering the bias pot resistor vs lowering the 100k off the rectifier? It is actually measuring around 96k as it is. I'd like to say I'm done, unless there is a reason to raise or lower the voltage at one place instead of another. I listed the voltages before and after the 100k resistor a couple posts above, if it matters.
     
    King Fan likes this.
  12. dankilling

    dankilling Tele-Afflicted

    Oct 28, 2014
    Lehigh Valley, PA
    If you like how it sounds, run it like it is and don't stress about the 4k difference. Most resistors are 5% tolerance anyway.
     
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  13. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    yes, it sounds like you're done. I would just leave it for now and play the amp for a while. You're right on target with the bias. Good work, congrats on a job well done. You and I are now "Brothers of the 5f11 Kit".
     
  14. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    Man, it was a little more work than I expected -- no bias tap, swapping primaries twice, bias pot resistor change twice, a bias so cold I thought my meter was broken, and, initially, tubes so hot @ 420v I think one was red plating at first - but I learned more than I ever can by just reading about it. I can read a page 100 times and wonder what I just read. It takes actually working on it for things to sink in.

    But back to the amp, I have the chrome chassis for this one, and my plan is to do it proper with Tweed instead of the wood finished cabs I usually do. I love my 5e3, but this SOUNDS like a Fender amp, so I want it to look like one. So far, between me and for friends, I've built several of the Tweed models -- Champ, Princeton, Deluxe, Super, and now this Vibrolux. I have a feeling I might have a new favorite. When I heard that tone and added up what I have in it, I am thankful for Shock Brothers!
     
  15. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    did you do a thread about your Super build? I am interested in that.
     
  16. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    I've done two for friends here at home. The second one is here now to add speakers. I built a 4x10 bassman cabinet for it and we put a pair of Veteran 10's for early breakup. Now he's decided on 2 Ragin Cajuns to put in the other slots for a louder & cleaner options -- yeah, it's a huge amp.
    Those being the only other fixed bias stuff I've messed with, as well as the Super's unique, giant choke setup, had me pulling my hair out too. Now that I've been educated with the Vibrolux, I'll add the resistors and check out what his Super is doing in the bias dept.
    The two of them were both Mojo parts kits, but differed in two ways -- transformers & speakers. The first had Mercury transformers, a Celestion Gold, and an ET10. The second had Mojo's PT & OT, and a big Hammond choke - 150-200mA range, and the two Veteran 10's. Both guys were extremely happy with the end result, but I definitely preferred the second. The first was very clean & loud pretty high up the dial, and I'm not a Celestion fan, he loves them. But it had more of a Blackface sound & feel to me.
    The second, and I'm sure speakers played a big part, sounded like what I would expect an old Tweed amp to sound like. Here is a clip of it, channels jumpered and cranked up pretty good with a Les Paul. The Ragin Cajuns came in this week, so I'll see how they sound soon. The Vet 10's are 94dB 20 watts, the RC are 100db 75 watts, so he ought to be able to go either way for the situation. If I get a chance this weekend, I'll see if I can do some kind of demo video while I have it here. For that matter, I can hook the 5F11 into a couple different cabinets and throw that into the mix too! I just have to figure out how to get the wife out of the house for a couple hours...haha.
     
  17. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    Well, a friend came by today and I had him playing my Tele while I messed with the knobs, and this thing sounds great! I love the 10", but I plugged it into my Deluxe cabinet with the Warehouse G12Q - basically the big brother of the Veteran 10 - and I think I may have to go with the 12" in the end. It definitely added some fullness to the sound.

    But we couldn't believe how sensitive the amp is. You can hear the pick clacking on the strings with a soft touch, hear your fingers sliding. EVERYTHING that happens on those strings come through. Cleans are a fat and warm but great definition. Cranked up and the Strat pickup on my Nashville Tele sounded better than I've ever heard it. A big thing I noticed was the tone knob doesn't get nearly as muddy as the 5E3. With the tone backed all the down to 1 it still was a usable tone, just quieter and softer, not muffled. I still don't think the Tremolo is quite right. It's really fast & the "depth" doesn't seem to do a whole lot. After turning them back & forth for a while, I never got more than a "yeah, I can kind of hear it now" level. But I don't have anything to compare to, so I don't know what it should be doing.

    All in all, though, it is a fantastic sounding amp.
     
  18. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    the tremolo on mine is very distinct. You might have to search through Youtube videos to find some examples of what it should sound like. I don't really like tremolo too much, and have never ever used it for anything.
     
  19. jhundt

    jhundt Poster Extraordinaire

    Age:
    63
    Mar 23, 2003
    Netherlands
    I checked my tremolo and found that the slowest setting gives 40 beats in 10 seconds, so about 240 bpm. My Princeton Reverb, which I modified for a slower rate gives 24 beats in 10 seconds, so about 144 bpm. I like that better, but still never use it.
     
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  20. jsnwhite619

    jsnwhite619 Tele-Holic Ad Free Member

    961
    Sep 10, 2013
    Georgia
    Wow! If 240bpm is right, it may be right. I'll probably be looking into that mod. I think Rob posted the caps to change a little earlier in the thread. That just seems to fast to use as a guitar effect. It almost sounds like a slap back instead of tremolo. Although, with the natural echo & reverb in the garage, I was able to kinda get Chris Stapleton's sound in "Tennessee Whiskey" that sounded pretty cool.

    Sent from my XT1585 using TDPRI mobile app
     
  21. King Fan

    King Fan Tele-Afflicted Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Yeah, do what Rob said. Should take you down in speed a nice amount.

    But hmm, max intensity should get you a *lot* of trem.
     
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