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What are these sections of this power supply?

Discussion in 'Power Electronics' started by j4cobgarby, Sep 18, 2018.

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  1. Ylli

    Ylli

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  2. VenomBallistics

    VenomBallistics

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    excellent.
    Now , lets look at the amp you have at hand.
    What you have here seems to be an early Fender Champ clone.
    this statement includes two terms you might want to evaluate.
    "Early" as in the front end tube is not exactly plentiful.
    and "Clone" as in not necessarily accurate. In fact it's use of an NFB loop makes this a sort of attempt at a HiFi amp ... in as much as a single ender can be.
    Given the expense of some of your components, I kinda take a buy once, cry once approach to this.
    Your can save a great deal of cash over say, a Marshall JVM 410 at it's low low price of $3000, But you're not getting through this under a few hundred bucks no matter how you try.
    Power and output transformers as well as a power supply choke coil will run up a bit of a bill even if everything else is relatively cheap.
    That said, I'm going to encourage you to look at your schematic as a means to gain an understanding of how things talk to each other in the circuit ....
    Then I'm going to pull a Guitar Center and upsell you on this one.
    I built a few of them, they are stuff of legend and the closest thing to magic left in this world.
    https://ampspecs.com/454/

    and further research ... a fairly large collection of the Fisher designs, outlining some of the variation he put into them
    http://www.freeinfosociety.com/electronics/schematics/audio/trainwreckexpress.pdf

    Since you're going to spend on this anyhow. Spend a little more and build a Ferrari instead of a Toyota
     
  3. j4cobgarby

    j4cobgarby

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    Sep 18, 2018
    Seems like good advice, thanks!

    Unfortunately, the schematic you linked to looks far too complicated for me to comprehend -- there are even some components which I don't recognize at all. That said, I'm sure you're right about it being a better schematic, so I will probably try to first understand it and then build it! But where to start? The power supply looks simple enough, but the amplifier circuit itself looks crazy. Maybe in a few months I'll understand some of it...
     
  4. VenomBallistics

    VenomBallistics

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    The "Crazy" portion is probably the tone stack. You'll see things ranging from similar to far worse spread across all the various designs .
    Let me introduce you to the 12AX7.
    This is a high gain DUAL triode. That is, one tube, two triodes. Thus, the halved segments in the schematics are exactly that ... one element of the two in the tube.
    There are actually three used in the trainwreck, and often times the first tube is paralleled to offer a little more current to drive through the tone stack. immediately after it.
    From the first B+5 junction to the 1M volume pot is the tone stack. In theory, you could replace all of it with a .047μF Mylar to block the DC and permit the signal.
    You will want tone control so at least look up the tone control from the Marshal 18. It's simple enough for a noob.
    If you go the slacker route, commit the tone section to its own board so that you can swap it out for a more serious iteration later.

    The next two sections step up the signal from the tone stack. Sum total, they can amplify to glorious excess which can sequentially overload the tubes from the output to the third 12AX7 element in order.
    this amp is worth the pain.
    It can go from a clean zero to full rock hero with a clairvoyant response. Stomp box ... don't need em.

    heres a demo that really showcases its "clairvoyance".
     
    hevans1944 likes this.
  5. j4cobgarby

    j4cobgarby

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    Thanks again for another detailed response.

    I'm not sure I quite understand the need for a "tone stack", or, really, what one is.
     
  6. VenomBallistics

    VenomBallistics

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    A tone stack is the electronic circuit that makes up your tone controls, bass, treble and midrange.
    Without it you're either cracking teeth, or pumpin' mud.
    at the very least you should have a tone control.

    At the bottom of this page is a free calculator that lets you design and tweak these circuit sections.
    In your case, it'll show you an isolated schematic of said circuit. You'll spot it right away.
    http://www.duncanamps.com/software.html
     
    hevans1944 and j4cobgarby like this.
  7. Sanu

    Sanu

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    Sadly, the schemes you relate to look far too difficult to understand some of the components are even unfamiliar to me. Which means, I'm sure you're right that I'll actually try to understand and construct it first! The electricity supply seems easy enough, but the amplification device is nuts. I'm going to understand some of it perhaps in a few months.
     
  8. VenomBallistics

    VenomBallistics

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    You really just have to break them down section by section.
    Just ignore the tone controls at first, consider the whole network a single capacitor and study the active sections.
    You'll see how the input stage kinda repeats itself a few times ... easy enough
    The output stage and phase splitter can be confusing. As they are typically drawn, they are kind of "folded in half" to establish the class A push pull arrangement.
    Grapple with that next.
    The last thing to understand is the tone stack.
    All its doing is restricting certain frequencies, grounding others, sending the rest on along to another portion to restrict ground and send until it hits the next tube where whats left of the signal is resuscitated and applied to the art and science of loud.
    Don't bother with understanding it until everything else is understood. It is quite the snarled network and must be dissected slowly
     
  9. davenn

    davenn Moderator

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    there's no circuit
     
  10. bertus

    bertus Moderator

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    hevans1944 likes this.
  11. VenomBallistics

    VenomBallistics

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    there is. it's embedded in the software.
    Just checked out the new version.
    They've added a quite a few types since I last used it.
    Looks like it'll better support effects peddle design now.
     
    Last edited: Mar 11, 2020
    hevans1944 likes this.
  12. hevans1944

    hevans1944 Hop - AC8NS

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    I downloaded the app and found that it works just fine in Windows 10. Now, all I need is some way to link it between the microphone input and the sound card output of my laptop so I can actually hear what the different tone control stacks actually DO to guitar string sounds. We have three electric guitars, imported here to Florida when our kids abandoned them in Ohio before we moved here. All they need is replacement of a missing string and someone who knows how to strum them... do people still strum guitars?
     
  13. VenomBallistics

    VenomBallistics

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    You can simulate them with a parametric EQ in most audio workstations.
    The purpose of the software is to allow a simulation to show how changes to the values in the circuit will impact the curve.
     
  14. hevans1944

    hevans1944 Hop - AC8NS

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    Yeah, I know what the simulation is for. As you probably know, there is a huge difference between seeing an audio response curve and actually hearing the difference. I guess a parametirc EQ might work, but each point would need to be entered manually. Not a really quick method for evaluating tone stacks or the effect of adjustments made on them. Oh, well... could be the start of yet another project, but it looks more software intensive than hardware intensive, and I hate trying to write software programs. Maybe looking around the World Wide Web will turn up something...
     
  15. VenomBallistics

    VenomBallistics

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    I suppose amp sims could give you test drives of each. At least good enough to drill down some direction on a real life project.
    I've seen that many home recording studios, as well as a few pro studios use them.
    I don't believe they'll ever give the feel of a proper tube amp, but they do their job where the style is black and white.
    So its still worth it to build an amp.
     
  16. hevans1944

    hevans1944 Hop - AC8NS

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    I love the "sound" tube amps are capable of producing, but that seems to have been all but forgotten by solid-state designs, both analog and digital. Of course tubes never really died, and the old circuits became classics that are now carried on by a new generation of builders. So what if the tubes are made in Russia, or Brazil, or China, or wherever? What works, works. I am somewhat amazed at the prices well-heeled customers are willing to pay for tube amps. When those prices begin to exceed a thousand bux per watt (honest, sine wave power) it might be time for me to start bending sheet metal and warm up the ol' soldering pencil. I still have my (mostly) updated Sylvania tube manual, so it would be interesting to see what tube types have survived into the 21st Century. I am pretty sure the old standby dual-triodes (12AX7, 12AU7, 6SN7, et. al.) and various pentodes, including beam power-pentodes, are still available. Audio output and line-power transformers might be hard to source unless willing to accept a one-off e-bay product source. And I probably would not want to use a vacuum tube rectifier since silicon diodes are so cheap and work so much better.

    A few years ago I was solicited by a Japanese company (ELP) who wanted to sell me a turntable that used a laser-tracking optical sensor instead of the usual tone-arm. I had long had the idea of building something similar, but was stymied by my lack of machine shop facilities needed to fabricate a custom optical tracking mechanism. The turntable is rather pricey, so I didn't order one.

    I don't think (without ever trying it) that it would be very difficult to move a radial linear optical head to maintain an inward spiraling position over an LP vinyl record turning at 33-1/3 rpm. Might need to image two or more adjacent grooves to achieve enough redundancy to maintain tracking during quiet cuts on the record, and during the transition between cuts for records made that way.

    BTW, good to see you back here posting again, @VenomBallistics.
     
    Last edited: Mar 15, 2020
  17. VenomBallistics

    VenomBallistics

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    Thanks for the welcome back. I've been heavy on the aerodynamic quests of late.
    Both tubes and solid state have merit in audio.
    solid state can track with far greater accuracy so it's better for audio reproduction.
    The quirks and non linearities of tubes work well in various segments of audio production.
    That is to say there's a distinction between production and reproduction of audio, though there is some cross pollination.
    I find solid state rather annoying when overloaded, as is commonly done in guitar. The only stomp boxes I retain in my peddle board capable of such function is an overdrive that I use with the gain full down and the level cranked up for a clean signal boost to drive a tube amp into overload more aggressively. that and a VT-999 Tube fired distortion which focuses on overloading a 12AX7 within a clean solid state nest of preamp, tone stack and buffer. Otherwise that low end grunt gets lost in solid state at the gain goes up. Tubes seem to hold onto it with both hands and a foot. I don't count delays reverbs, chorus and similar as these are not overloaded.
    In audio reproduction, I sometimes like what tubes add, but understand it's a deviation. As I try to add more of that tube warmth, the deviation grows to the point of annoyance. It works better in instrumental than vocal, so it's far from universal.
     
  18. hevans1944

    hevans1944 Hop - AC8NS

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    Years ago I bought a Conn organ off the showroom floor, probably paying waaay more than it was worth. I think it was a Conn Model 552 Theatrette Organ. See images below. I installed it in our smallish living room and (probably) proceeded to annoy the neighbors as well as my family with my feeble efforts to learn how to play it (loudly).

    [​IMG]

    [​IMG]
    This was a vacuum-tube based organ, consisting of several groups of twelve independent oscillators making up the chromatic musical scale. Various wave-shaping circuits controlled the timbre or "voices" of the organ. The two keyboards were a maze of wiring and tiny neon lamps that directed notes from the wave-form oscillators to various wave-shaping circuits. The organ even had a rotating Leslie speaker as well as a tremelo circuit. Lots of knobs and levers and one-and-a-half octave foot pedals (including a volume control), which may have been excessive "window dressing" considering its intended use inside a home.

    But, what the hey, back then I was raking in the big bux as an electrical engineer working on highly classified "stuff" for the guv'mint, so I could afford the indulgence. I never did learn how to play the organ, or any other musical instrument for that matter, although I continued to try to learn with MIDI synths and MIDI piano keyboards until finally giving it all up. I may try again later this year with the guitars the grandchildren left behind. They were sensible enough to acquire (somehow) tube-type guitar amps for their garage band, before disbanding and going their separate ways sometime in the last century... leaving the amps and stomp boxes behind for me to ponder over.

    I agree one hundred per-cent with your distinction between production and reproduction of audio. Reproduction fidelity is a "given" in the professional music industry today, although I haven't kept up with the "latest and greatest" loudspeaker and enclosure developments. I doubt I ever had "Golden Ears," but surely today they are definitely rusted and otherwise corroded. I now "enjoy" almost anything loud and boomy, pretty much as I did in my youth. Wife bought a portable Bluetooth JBL stereo speaker the last time we were in the Sprint store. I like this a LOT, especially after I bought a Bluetooth USB dongle for my H-P Pavilion g6 laptop. I have a lot of tunes ripped years ago from CDs. I've kept the CDs too, but prefer the convenience of having content readily accessible on my hard disk drive or on the shared network storage drive. One of these days, "real soon now," I will revive my turntable and try to save some tracks from my vinyl record collection. I think most of this stuff is now available for download in "re-mastered" form on my Amazon unlimited music subscription, so it may be a total waste of time trying to recover anything from vinyl records
    .
     
  19. VenomBallistics

    VenomBallistics

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    I really like mp3 in the car where the speakers are not what you'd call studio monitors. It is convenient, and if you can render the interface down to a tactile system, it's perfect.
    Guitar isn't that hard, you have 5 basic chord shapes. learn them and the intervals that form them.
    from there you can work out how to modify the chord shapes to form any voicing ... minor, sus2 sus4 add9 dim ect ect.
    any chord shape can be slid up the neck to address the whole of the chromatic scale.
    Everything repeats after the 12th fret.
    the knowledge required can be absorbed inside a half hour to form a rather sophisticated and robust system.
    But .. thats the brain portion of the game. it's these inherently lazy slabs of meat we call hands that are the portion of the equation that takes the most conditioning. Just because your fingers won't do it, does not mean your brain doesn't have it. That part defeats many noobs as they fail to make distinctions between the metal, mental and meat.
    Given the implied age of the instruments, the "chosen one" should be restrung, I recommend an 008 set for beginners ... the less effort you have to put into fretting the faster you can condition your hands to the task.
    Theres nothing quite so wonderfully visceral as a tube fired amp driving a 4x12 stack ... welcome tot he science of loud
     
  20. hevans1944

    hevans1944 Hop - AC8NS

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    I suppose I need to develop calluses on my left finger tips to properly press the strings against the frets. And I reckon a 4x12 stack means four 12-inch speakers in a cabinet (cab?) driven to perhaps thirty to fifty watts by a vacuum tube power amplifier? I do love "the science of loud," believing that music should be felt, not just heard.

    Sitting near a full orchestra in a theater with superb acoustics comes close to ideal, but listening to an amplified stage performance can be even better, no matter what instruments are used. So-called "live" performances are today enhanced with pre-recorded and heavily mixed sound tracks, but I see nothing wrong with that. Lip-sync performances can be somewhat disconcerting, but at least the vocal artist is presented (via a recording) in the same manner for every performance. An artist thirty or forty years past their prime can belt out, with lip-sync, the same songs that made them popular way back when. You don't like lip-sync performances? Then just close your eyes and listen to the music.
     
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