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Please weigh in on 5e3 transformers

Discussion in 'Shock Brother's DIY Amps' started by theprofessor, Dec 28, 2017.

  1. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Get yourself a single-coil GEE-tar, D'tar!

    So you went from a stock .0047μF (= 4700 pF) tone capacitor to a .0008μF (= 800 pF) one? What, pray tell, is the overall effect? :)

    Is it this? (to cite the linked discussion)

    "So, here it is: change the tone cap from .005 to .0007 (680pf). In my case I had a bunch of mica caps (for the bright channel) and some ran a little high, and that's what I used. I also tried .0003 and .001 and neither seemed as right; .0005 should do okay. (To be clear, we’re talking about changing the tone cap, not the bright channel cap.)

    Now, what happens is that the amp's tone is the same as before but the edge can be dialed out while the gain and mids are still there because the cutoff frequency starts much higher. The tone control is now useful at settings below 8 and the change has created a new range of smooth, early overdrive crunch that the amp didn't have before because the tone was too shrill. (Strat bridge pickups sound especially good.) My Tweeds always had a little harshness at early breakup and that is now gone. As before, however, the effect of the tone control is diminished as the volume (bright channel) is increased, but now there is more gain at moderate-high settings - even with the tone control full-off - meaning that going from volume 10 to 12 is not going to add anything but sag and edge.

    So there you have it. Thinking about it now, I suppose the tone circuit - as designed - is the single biggest contributor to Fender’s Tweed era sound; and while it’s nice to have that original edge, it’s much better to be able to dial it down, if desired.

    What’s nice also is that it’s not really a modification of the circuit, just a change in a cap value – a value to which an old capacitor in an old amp might have drifted, and with said change the tone circuit (although, of course, still a low-pass filter) is perhaps better envisioned as a high-cut control."
     

  2. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    I do set up and repairs for a few locals so there's not a complete void!

    With humbuckers, I feel the tone control is more useable and affective. My memory failed me... I believe now I use 700pf. I would need to get in the chassis to be certain. I auditioned a few different values.

    Useless bit of info...

    "D'tar" is how my once 2yr old son pronounced guitar.:) He loves to strum the d'tar!
     
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  3. jsnwhite619

    jsnwhite619 Tele-Afflicted Ad Free Member

    Sep 10, 2013
    Georgia
    Mine too. This was with Allman Brothers at the Beacon in the DVD player. My wife freaked out because his fingers were raw from strumming the strings for so long. I said there can't be more than 2-3 guys in history who played a guitar that much at 2 years old...

    1515175921189.jpg
     
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  4. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    Awesome!!!
     
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  5. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Hardly useless! That's the stuff of life! I wish my kids were still young enough to say stuff like that. Love that picture, @jsnwhite619 !
     
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  6. creekrat

    creekrat TDPRI Member

    Age:
    35
    73
    Feb 22, 2017
    Grove, OK
    Looks like I’m late to the party. I used the upgraded transformers from classictone. Forget the model numbers but the power transformer is the one that has taps for 355-0-355 and 330-0-330. For output I used the one with 4, 8, & 16 ohm loads
     

  7. Phrygian77

    Phrygian77 Tele-Holic

    821
    Apr 30, 2016
    Crawfordville, FL
    Before my first post to this thread, I did some poking around on the web looking for 5E3 examples, with voltages, that were built with the 40-18021. I could find any. I guess you didn't include the model number in your build thread.
     
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  8. D'tar

    D'tar Tele-Afflicted

    Jan 11, 2013
    WNY
    I'll add some data to that thread when I get to my PC next week.
     

  9. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    I'm putting together a parts list for a 5e3 build currently as well, and I've selected the http://www.classictone.net/40-18027.html for a PT. I'm going for a slightly lower B+ with the 315-0-315 winding, and the 6.3 winding has a CT. I'm going to use a WY3GT solid state rectifier since there's no good reason not to, really. Reduces heat on the PT (no filament draw) and more reliable.

    For the OT I've picked the http://www.classictone.net/40-18090.html, just because it's not much more for the added flexibility.
     

  10. Wyatt

    Wyatt Tele-Holic

    856
    Nov 3, 2004
    The PT is too small for the 5E3 chassis cutout. A 5E3 has mounting bolts spaced 2-1/4" by 2 13/16". That PT has them spaced 2" by 2.5". This isn;t an issue if you are rolling your own chassis, but it is if buying off-the-shelf.
     
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  11. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    Yeah I noticed that... have to do some creative mounting. Or I may decide to use the Allen TP22D; I like the voltages on that one, and it's a higher quality part, and will likely run cooler.
    Thanks for the warning though, and thanks also to @theprofessor for his excellent synopsis of suitable PT's to check out.
     
    Last edited: Jan 17, 2018
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  12. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    RL, you know 10^3 what I do about amps, so take this in the spirit of rhetorical, idle thoughts about my tone goals, which are not necessarily yours.

    I happen to like vintage-y specs in general, but even more than other amps, I wanted for my 5e3 to make sure I put in all of Leo's 'flaws that turn out to be features.' So I went with Leo's tube rectifier and tried to target the basic PT specs he used. If I'm right, the sag, bloom, and limited headroom of the 5e3 start with that power supply.

    A multi-impedance OT, of course, is cool beans. :D

    Again, I'm not questioning -- I'm just thinking out loud about *my* decision process. There are many fine ways to skin any of Leo's cats. And BTW, whatever you do, I'm looking forward to a build thread. :)
     
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  13. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    I totally agree, and I have thought much about that very thing... trying to keep the things that matter as stock.
    The weber copper rectifier simulates the drop from a tube, without the disadvantages and current draw of a tube filament, so that's an easy decision for me. Other than period-correct authenticity reasons, I can't think of a good reason to use a tube rectifier, personally.
    The Allen PT is similar enough to the vintage types, but is just better built, and has the lower voltages I want. I'm not going for max clean headroom power, which is what running the output stage at very high voltages does for you, and besides, I believe the original tweeds ran at something like 325-0-325 on the PT's, at the lower line voltages.
    But I'm with you on the vintage thing, where it matters.
     
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  14. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Re: vintage voltages. I'm expecting around 370V with the PT I'm using on my 5e3 build. I'm prepared to use zeners to get it down to 350V, if necessary. 325-0-325 at 110 line volts sounds like a nice recipe. Of course we have to finagle things a bit to get close to the same recipe.
     

  15. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    I'm guessing more like 390-400v B+, with 120vac line in, with your 660v secondary. Note that 660v spec is at 120ma, and you will likely be drawing much less.
    But it's a slippery target. The factors are ac line volts, dc resistance of your secondary winding, internal resistance of your 5Y3, and your current demand, which depends on how hot you bias your 6V6's. So my guess could easily be off.

    I'd be interested in knowing the measured dc resistance of your secondary winding, if you were so inclined to do that... I'd guess it should be in the 100 to 300 ohm ballpark.
     

  16. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    One reason I was guessing 370V is that other folks who've used this PT have ended up there. But we'll see.

    I measured the resistance of the high voltage secondary on my Classictone 40-18016. I got 109 Ω .
     

  17. RLee77

    RLee77 Friend of Leo's

    May 15, 2016
    Silicon Valley
    Thanks for measuring it, good to know. It's useful for anyone trying to mimic the power supply source resistance of vintage amps to duplicate the sag response of the PS.
     

  18. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Sure! One of the many, many things I don't know is how to ballpark voltages and the like. Even though it is, as you say, a moving target, how do people normally guesstimate this stuff based on PT specs and so forth? Let's say I have 122V at the line and am using the stock 250Ω cathode resistor to the pair of 6V6s, along with a vintage 5Y3 (not new-production Sovtek)? What other data does one need to ballpark the voltages?
     

  19. King Fan

    King Fan Friend of Leo's Ad Free Member

    Jan 1, 2013
    Salt Lake City
    Sorry, RL, I got to thinking about this again for some reason. I'd forgotten that the Weber copper cap simulates tube drop. But then I get to wondering -- does it sag like a tube? I wouldn't put that past Ted at all -- but as little as I know about amps, and as much as people act like sag is a bad thing, I gotta think of it as a virtue in a tweed, especially the lovely old 5e3... Anyhow, let us know when you start your build!!!
     

  20. Wyatt

    Wyatt Tele-Holic

    856
    Nov 3, 2004
    The resistance added to drop the voltage also creates sag, it's the whole idea behind "sag resistors." The copper cap is pretty much an inrush current limiter (for slow ramp up), SS diode rectifier network, and sag resistor(s) in one casing.

    Ted used to have a whitepaper online with the whole breakdown (Ted was an "open source" kind of guy), but I wouldn't know where to find it today, even on the Internet Archive.
     
    Last edited: Jan 23, 2018
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