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Tweed Component Selection Help & Speaker Question

Discussion in 'Shock Brother's DIY Amps' started by timewaster1700, Apr 10, 2018.

  1. Smokingheadstocks

    Smokingheadstocks TDPRI Member

    38
    Mar 18, 2018
    Blue Planet
    Alright... Easy there. First off... @timewaster1700 If I was critisizing I really wasn't referring about you. Second, i believe that the forums, youtube, etc... Is quite a good place to start scratching the surface of this fascinating field. But I am also 100% possitive that if you keep studiing and deepening your knowledge about electronics you will soon find that all what you've read, etc until now is really just that: scratching the surface, and thats completely fine cause everyone need to start by the beginning right? No one can start by being an expert.

    What I was trying to address is the false advice that people gave you about the supposed "fact" that it is all the same with the different components as long as the "specs and stuff" are the right ones. Specs meaning here the basic specs like resistance, capacitance, max current handling, input voltage, output voltage, etc etc

    As I said you can build pretty good sounding amplifiers with "surface scratched knowledge". But that's just that, the surface. Once you start getting deeper, you will see that electronics start becoming something quite more complicated than those mere "specs" and that there is a whole load of variables and aspects that come into play as well, but for that you need to dig in (I am thinking in transformers or tubes here for example, or even caps)

    Now, regarding @JuneauMike comment, i believe that those old amplifiers that sat the standard for good sound were really not THAT special, i think though that Leo, specially Leo, took a lot of care finetuning their sound, hearing and tweaking until he would find the desired tone, and that he had a heck of a good taste and some friends that were some truly excellent guitar players that knew how an electric guitar should sound. The difference is that at that time the best and most brilliant minds in the world were very busy developing components and they were also really excited about what they were doing, hence they built really good stuff, quality stuff.
     
    Last edited: Apr 16, 2018
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  2. SngleCoil

    SngleCoil Tele-Meister

    450
    Apr 13, 2010
    Charlotte, NC
    Just curious what, in your opinion, makes them junk?
     

  3. jimgchord

    jimgchord Tele-Meister

    Age:
    44
    128
    Apr 3, 2018
    victor,ny
    Maybe I shouldn't have stated it like that. What I should have said is I think they are junk when it comes to using them in a Tweed amp. To my ears they are a bit strident or sterile sounding. They do have Thier applications I suppose, maybe junk was a poor word choice.
     
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  4. SngleCoil

    SngleCoil Tele-Meister

    450
    Apr 13, 2010
    Charlotte, NC
    Thanks. I’ve personally never used them in an amp build. There are all sorts of opinions on polyester vs. polypropylene and it seems to come down to the context of the amp and personal preference. I can see where a little softer sound that a lot of people describe from Mallory 150- styled polyester caps would work better in a tweed circuit.
    My preference is based on something much more important....Mallorys just look better than vs those big Orange Drops sticking up everywhere :D
     
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  5. jimgchord

    jimgchord Tele-Meister

    Age:
    44
    128
    Apr 3, 2018
    victor,ny
    Softer is exactly how I would describe it
     

  6. Smokingheadstocks

    Smokingheadstocks TDPRI Member

    38
    Mar 18, 2018
    Blue Planet
    Check put the jupiter vintage they look even better ;)
     

  7. jimgchord

    jimgchord Tele-Meister

    Age:
    44
    128
    Apr 3, 2018
    victor,ny
    Or the sozo blue.
     
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  8. Nickfl

    Nickfl Tele-Holic

    873
    May 24, 2016
    Florida
    You are close, but not quote on the right track for figuring this stuff out. The tube datasheets are an important resource, but max dissipation, current etc are only maximums and don't necessarily have anything to do with what you will see in a specific application. In practice a 12ax7 triode will draw less than 1ma.

    To figure this out you have to use some voltage readings and work backwards, since the original 5e3 documents notoriously lack voltage readings, lets use the 5f11 vibrolux layout:

    V1a cathode - 1.3v
    V1a cathode resistor - 1.5K

    So v1a current = 1.3/1500 = .000867 amps, or 0.86ma

    The plate voltage is the plate to cathode voltage, 160v-1.3v, so the plate dissipation is 158.7*0.000867 = 0.1376 watts. Way less than the tube's 1 watt max.

    For the v1a plate dissipation, look at the voltage being dropped across that resistor.

    B+3 = 260v
    v1a plate = 160v
    plate resistor = 100K

    So, the resistor voltage drop is 100v, current is 100v/100000ohm = 0.001amp or 1ma

    Power dissipation across that resistor is then .001amp*100v = 0.1watt. You want at least 2 to 3x that rating for your component, so 1/2 watt will work and 1 watt is very robust for this position.

    All this works backwards and forwards and you can figure out your whole power supply from a little starting information and some estimates this way.

    Another example:

    You know your B+ 3 node voltage is 260v, your v1a triode draws 0.9ma, and your v1a plate resistor is 100k, so what will your v1a plate voltage be?

    100000*0.0009 = 90v gives you 170v at the v1a plate.

    As you can see the numbers on the old fender layouts are ballpark with some rounding/measurement errors (remember that they specified +/- 20% component variation) but they will give you the info you need.

    Hope this helps, it took me a long time to learn this and how to apply it. Amp forums seem to often have more vague insunuation than practical help.
     

  9. JuneauMike

    JuneauMike Tele-Afflicted

    May 5, 2015
    Alaska
    Yep, they do. That's usually because we're stumbling through it ourselves. But every once in a while someone likes you comes along and shines some light on the subject. And we're all smarter for it.

    Thanks Nickfl. This is another post to print out and keep.
     
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  10. timewaster1700

    timewaster1700 Tele-Meister

    170
    Feb 17, 2016
    Utah
    Sorry for my late response. This week has been insane! Responsibility totally getting in the way of my amp research ;P

    I apologize for getting defensive. Thanks for clarifying. I agree this is just scratching the surface. I think building one will teach me a lot too.

    Thank you SO much! I feel like a complete idiot. How did I not think to use the voltages off the schematic and Ohm's law to estimate the current. That should have been common sense for me
     
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