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Doll Houses for Guitar Geeks

Discussion in 'Amp Input - Normal or Bright' started by GunMonkeyINTL, Nov 4, 2017.

  1. GunMonkeyINTL

    GunMonkeyINTL Strat-O-Master

    771
    Feb 5, 2015
    NC
    Saved up my lawn-mowing money and got the 20w Push-Pull Playset....with enough left over for the Tube Rectifier Action Pack.

    You know you’ve all been looking for an excuse to play with a doll house on a cold rainy day.

    Found it!


    602A7478-28D5-47ED-893B-43BC84AD59AF.jpeg
    3F317271-2C37-46AB-A33C-2D404E8A4B0C.jpeg
    7A6DA6D0-3D0C-450A-B358-393894E69549.jpeg
     

  2. Robins

    Robins Dr. Stratster Strat-Talk Supporter

    Dec 22, 2010
    Germany
    Now we run into some trouble.
    It is a very clever idea to come up with some good planning for an amp build.
    Better be safe than be sorry later.

    By the way the power transformer is "shooting" into the output transformer that way but most probably there seems to be enough room for the magnetic field(induction-hum) between them.

    You know the headphone trick?
    put both transformers on the chassis and connect a headphone to the output transformer. Connect the power transformer to the power outlet (take care and both transformers isolated wires etc.).
    Now move the transformers (move, rotate, whatever it needs) to where you get the least hum in the headphones. That´s the best place for the transformers.

    You have to make sure the output transformer doesn´t shoot into the preamp tubes and the power transformer is farthest away from the preamp tubes.
    The rectifier isn´t critical at all because it just needs voltage and not current, it can´t be harmed by the transformers.
    The power tubes aren´t as critical as the preamp tubes because they have a way higher signal(and because of other reasons but not to be discussed here).

    The "shooting" axis is the side(s) you can "look" into the winding (virtually).

    Sorry for the long read.

    All the best,
    Robin
     
    Last edited: Nov 5, 2017
    jvin248, mad axe man, mshivy and 8 others like this.

  3. GunMonkeyINTL

    GunMonkeyINTL Strat-O-Master

    771
    Feb 5, 2015
    NC
    No. I did not know the headphone trick, but, now that you point it out, it makes brilliant sense. Should I wait until I have the actual blank chassis fabricated? Will the cardboard mockup suffice, or should I be testing the positioning on a conductive chassis?

    Also, the PT is set up to be mounted through the chassis. Once I sort out the layout, I’d prefer to mount it that way, but can do standoffs to put it all above the chassis, if necessary. Is there an advantage/disadvantage either way, other than space?



    I’m reading Morgan Jones’ book on amp building, and it discusses the concepts of best lay-out practices for noise reduction, heat dissipation etc. That’s why I started the mock-up- to be able to visualize what he is describing and see how I could work with it within my dimension restraints.

    Jones describes the concept of deconflicting the transformer fields, but I have not ID’d the orientation of the fields of my transformers yet. Your headphone trick will make that more certain, and I’m going to try it as soon as I get home (on a business trip). I bet I could also hook my audio probe up to it and listen through an amp, no?


    Don’t apologize for the long or detailed answers. Your responses and emails have been invaluable, and I’m counting on the continuation of your generosity in sharing what you know and saving me headaches. So, thanks.
     
    T Guitar Floyd likes this.

  4. Robins

    Robins Dr. Stratster Strat-Talk Supporter

    Dec 22, 2010
    Germany
    Well, the headphone trick is just a good method to find the best spot for each transformer inducing no hum into each other. Using a headphone is the best to not adding any fancy other equipment which can add hum into the setting.
    It is always the power transformer shooting into the output transformer.
    Also you have to make sure not placing anything power related into the near of the preamp. Be it transformers or any wires carrying high voltages(or components like caps-filtering caps ie).
    Components in the preamp not too close to each other will help as well. Short cables from the output transformer to the power tubes and keeping signal cables away from high voltage cables and esp. the heater cables.
    Not running them in parallel (signal cables and power related cables) or close to each other but in a 90° angle if you have to.
    Putting the OT in the near of the preamp tubes is a bad idea, placing the power tubes close to the power transformer will heat the power transformer in addition and some other things - placing the board too close to the input/pots.
    I don´t want to confuse you with those things and for sure a good concept for the grounding and heater wire placing is the best start keeping an amp quiet.

    (I think the pic below is more confusing than helping but you get the idea)
    [​IMG]

    All the best,
    Robin
     
    Last edited: Nov 7, 2017
    GunMonkeyINTL and mshivy like this.

  5. Robins

    Robins Dr. Stratster Strat-Talk Supporter

    Dec 22, 2010
    Germany
    Pink Taco original transformers and tubes layout

    Pink Taco PT20 Guts (19) (1280x719).jpg

    All the best,
    Robin
     
    GunMonkeyINTL likes this.

  6. GunMonkeyINTL

    GunMonkeyINTL Strat-O-Master

    771
    Feb 5, 2015
    NC
    So, I finally got home and was able to run the headphone test. The image below is what I came up with.

    Surprisingly, the orientation shown on the actual Friedman (and most other amps I’ve seen) was not the quietest with my transformers.

    What I did was:
    1- Position the PT in the most convenient place and orientation.

    2- Put the OT too close to the PT, and found the loudest orientation (turned out to be 90deg), and quietest orientation (as pictured).

    3- Set the OT to the loudest orientation and moved it away from the PT until the sound almost disappeared.

    4- Turned the OT to the quieter orientation and confirmed that it went from almost silent to dead silent.

    5- Moved the OT another 1” away.


    I think I know the answer to this already, but I’ll ask before committing to a layout:

    Should I trust the results of my own headphone test, or second guess it because it appears to be the opposite of the original?

    Here is what I have for a gross layout right now:
    C2B0A611-C36C-40EE-9829-FB73488B9FAD.jpeg
     
    Robins likes this.

  7. Robins

    Robins Dr. Stratster Strat-Talk Supporter

    Dec 22, 2010
    Germany
    It is so great you are keep on reading and learning and not doing the normal "tell me how and I do it".
    It really keeps me happy when people build amps and they are willing to learn and keep on pushing and I get such great feedback. It is constructive and positive for both.

    It was my intention showing you the Friedman original setup/layout is not the quietest possible. I told you the Taco is not quiet and noise free and you found one reason why. Great job!

    You found the absolute best setup for your transformer set but take care for the preamp tubes. They are too close (in the near) of the OT. This will get you trouble later. The PI tube is not the problem. Move the OT closer to the middle so both preamp tubes are clear away from the OT. I don´t think that will induce hum putting it closer to the power transformer.

    All the best,
    Robin
     
    GunMonkeyINTL likes this.

  8. GunMonkeyINTL

    GunMonkeyINTL Strat-O-Master

    771
    Feb 5, 2015
    NC
    Thanks, again.

    Oddly, I did end up moving the OT closer to the PT when I started working on the layout doc- but not because I was smart enough to realize I needed to get the OT further away from the pre-amp tubes.

    I ended up moving the OT almost to the middle because I wanted to shorten up the runs from the output tubes to the OT and the OT to the output jack.

    I knew I had a margin left in the quietness since I set the distance by the loudest orientation and added some.
     
    Robins likes this.

  9. Sarnodude

    Sarnodude Senior Stratmaster

    Sep 26, 2015
    Mukilteo
    I like your use of CAD (cardboard aided design).
     
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