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18 watt variation

Discussion in 'Shock Brother's DIY Amps' started by Fiat_cc, Apr 12, 2017.

  1. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Zep, in the 5E3 Deluxe the Normal channel goes to V1A pin 2 and the Bright channel goes to V1B pin 7. The only difference between the two channels is a bright cap on the Bright channel volume pot.
     
    Last edited: Jul 16, 2017 at 11:01 PM

  2. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    Steering the conversation in a different direction, do tubes care about being operated on their side? Obviously most amps have them facing up or down, and this one will too once it's in a cab, but for initial testing and fine tuning etc, all the tubes will be lying on their side, with the chassis flat on the table. Are they happy enough like that?

    Edit: I did Google it, and it seems there are differing opinions. However, I feel pretty confident that for a few hours of testing purposes, I'll get away with it.
     
    Last edited: Jul 17, 2017 at 4:02 AM

  3. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    And another question...
    Would lowering the value of the 2.2M resistor (R7), that feeds the intensity pot increase the max intensity?

    I'm trying to get a proper grasp of how all the parts of the different circuits work.
     
    Last edited: Jul 17, 2017 at 6:11 AM

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  5. Zepfan

    Zepfan Friend of Leo's

    Nov 30, 2013
    Horn Lake, MS
    My Silvertone 1482 has the tubes on their side. Only problem is when the sockets get loose, the tubes are more likely to fall out during transporting the amp and the movement of tubes in their sockets could cause some unwanted sounds in your amp.
     

  6. Zepfan

    Zepfan Friend of Leo's

    Nov 30, 2013
    Horn Lake, MS
    Guess that could happen with the tubes facing down too.
     

  7. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    True. I have tube retainers on all sockets though, so should be ok. I'm really worried about hot spots and heat disipation ...
     

  8. Bill Moore

    Bill Moore Tele-Holic

    When I was young most all electronics were tubes. We used to put radios in every position, (including sideways), as space would allow wherever we were working. I never replaced any tubes!
    I recall an old Philco radio that was too wide for the table next to my bed always was on it's side.
     

  9. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    Thanks Bill.
    I figured I'd be fine, but safer to check. The more stupid questions I ask, the less things I'll mess up, and eventually I can move on to less stupid questions...
     

  10. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    So I spent an hour mucking around today. Somehow I'd left power tube grid stoppers out of my schematic and layout. It seems people often use 1k5 for 6V6 tubes, but I used 8k2 as per the original Marshall 18 watt circuit. I also move the reverb pan away from the PT. Reverb is now very serviceable and doesn't seem noisy at all, and the trem was much better. I did a bit of chop sticking which improved the trem further, and all in all it's sounding pretty good. There is some slight buzz that goes away when I touch the chassis, so I may need to check grounding, and my guitar is noisier than usual, but the room I have to work in here is full of noisy fluoro lights, so need to try in other locations.

    So, the issues I still have are:
    * slight buzz that goes away when I touch the chassis or pots
    * a very slight thumping in the trem at higher speed or intensity settings. It's a very baddy thump, and is in tome with the trem. Barely noticeable when playing but very audible when not.
    * reverb and trem switching. I didn't really have time to play with this a lot, but the reverb switch seems to work fine, but the trem switch just doesn't, and if both switches are plugged in, the reverb switch can trigger issues in the trem circuit. When just reverb switch plugged in, it does what it should, just trem switch plugged in, it doesn't really do anything, but it does slightly effect the sound. The weirdest thing is when I plug the reverb switch into the trem socket, it sets of a crazy oscillation. A kind of high pitched squeal.

    Can anyone help trouble shoot these issues? I still need to try chop sticking in the controls side of the board, so I might sort out the trem thump there, but equally may not. Buzz that responds to touching chassis, and weird footswitch behaviour/trem circuit squeal?

    Here's a quick and dodgy vid I made. It doesn't show the foot switch issue, but you can here the verb and trem working quite nicely, and at the end, the trem thumping. It's rough and raw, and there are all sorts of loose items buzzing on the desk etc...
    My Tele Deluxe, through 18 watt prototype, through the Eminence RF10C 10" that's in my Bassman Micro.



    Cheers,
    Reuben
     
    Zepfan likes this.

  11. Engraver-60

    Engraver-60 Friend of Leo's

    Age:
    65
    Jan 6, 2008
    Franklin, TN
    At the end of that video, I can definitely hear the tremolo thumping. Overall, sound great to my ears. What reverb tank did you use? and does the reverb have a large range of control?
     

  12. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    The reverb tank is Mod brand 4AB3C1B. It sounds bigger and lusher than I expected. It's close to full in parts of that video though. I find that there isn't a huge difference in running mix st full and turning down the dwell control vs the opposite. I'd hoped it would shorten the reverb tail a bit, but it really just sounds like turning it down. There's still a useable range of sounds though.
    I'm confident I'll solve the thumping soon enough, then on to this weird foot switch business.
     

  13. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Yea, a dwell control is just a reverb input volume so it doesn't adjust "dwell" time. The marketing department named that control :D
     

  14. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    Haha, yep. I figured with less signal going in to the tank it might alter the sound in a different way to the mix control, but audibly they seem to do pretty much the same thing.
    I'd probably elect to give that control a fixed value, and make room in the front panel for something else. If I also dumped the MV control, I could fit a full TMB tone stack, but I wonder if I'd then need an extra triode as well?
     

  15. Bitsleftover

    Bitsleftover Tele-Meister

    Age:
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    112
    Oct 17, 2016
    Cheshire UK
    So how would you tame the length of the reverb tails? Is there an adjustable parameter for doing that on the fly or is it just a case of installing a medium or short decay tank?
    Great sounding build btw. Right up my street!
     

  16. jonrpick

    jonrpick Tele-Afflicted

    Mar 17, 2014
    Marietta, GA
    I was thinking a short decay tank but I'm curious what others will say.
     

  17. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    Yeah, I think a shorter decay tank would be the option. I'm quite happy with the reverb sound, but I do feel like, in a sense, I have a wasted pot on the front panel.
     

  18. Fiat_cc

    Fiat_cc Tele-Meister

    Age:
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    Oct 8, 2016
    Melbourne, Australia
    I had a small tinker today. Not a lot of time, but here is what I learned.

    I replaced the wire from the board to the footswitch RCA jack with shielded cable. I grounded the shield at the RCA, and made sure it was not connected to anything at the board end. I also put a 0.01uf ceramic cap between the tip of the TCA and ground. I also required the footswitch with two core shielded cable (one wire to tip, one to ground, and the shield connected to ground at one end).
    So even without the footswitch plugged in, the shielded cable from board to RCA made the ticking much worse. I snipped the cap, which didn't fix it. Then I snipped the shield, and that took me back to square one. The shielded cable to the footswitch itself didn't help much at all either.
    If I touched the shield of the board to RCA lead to ground, instant loud ticking. I checked with my multimeter, and there was no continuity to anything.
    I think the RCA socket is simply too close to the reverb transformer wiring, as the reverb controls do effect the ticking sound.
    Next idea is to try moving the RCA socket away from the reverb transformer to in between V1 and V2.

    I metered all my ground connections and they all measure less than 0.3 ohms, so I don't think I have a ground issue.

    Does this all sound sensible to those in the know?
     

  19. Snfoilhat

    Snfoilhat Tele-Meister

    Age:
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    Apr 8, 2016
    Oakland, CA
    In the reverb tank documentation they recommend always driving the tank to saturation, and then you would add some kind of mix/volume control after the reverb recovery stage, like on a classic Fender amp. If your reverb driver has enough power to fully drive the tank, then the tails will be as long as the springs were calibrated for. Reducing that power with the Dwell control does shorten the tails, which you can hear for yourself if you play through a reverb device with a full range (0 to saturation) of power, like a 6K6/6V6/6BQ5-driven reverb. Dwell might even work noticeably in a parallel 12AT7 (I haven't heard it but I know some manufacturers include the control on their amps--is it marketing or substance? Not sure). A short decay tank on a switch might be cool, and very likely someone's done it. A blend control between two tanks (short and long decay) running simultaneously?

    One concrete example: high dwell plus low mix versus low dwell and high mix do sound different on a Fender stand-alone reverb (6K6-driven), including in the apparent decay.

    After spending months playing mine, I feel like the reverb 'tone' control (a regular high-cut like many other tone controls) is maybe more useful than dwell, and if I only had two openings on a control panel I would choose 'reverb' or 'mix' and tone over dwell. Cutting off the nastier/metallic high end makes my ears happy, lets me run higher wet settings than I might otherwise. The character of the reverb changes across the sweep. YMMV

    I think if we were to calculate the power of the single 12AX7 triode driver, we'd find it not covering but a fraction of the full power range of the tank, and so the effective dwell of the amp is always already 'turned down,' just as was expected earlier in the build thread. Cheers

    'Drive Circuit Considerations'
    https://www.amplifiedparts.com/tech-corner/spring-reverb-tanks-explained-and-compared
     
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