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Am I destroying my Pignose with this mod?

Discussion in 'Amp Tech Center' started by LesQuire, Jan 27, 2021.

  1. LesQuire

    LesQuire TDPRI Member

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    Hey gang, so I have a Pignose 7-100 amp that I modded recently. I made a video about it with the intention of uploading it to YouTube but after reading on some other forum that the part I removed was used to control the temperature of the transistors, I started thinking about if this would be unethical to post. (Details about the mod at the bottom of the post) I mean, I wrote disclaimers in the beginning, middle and end of the video but if someone else would do this mod and their amp is damaged, that would really suck. So I guess my question is twofold:

    1. For those of you that know more about these things than me, do you think this will cause the amp issues? Overheating or other problems..?

    2. What do you think of the ethical aspect?

    If everything seems ok to you I would like to post it since I have seen several people complaining about that strange distortion haze over the clean sound and this mod really helped to lessen it.

    So the mod:

    Desoldering one of the legs of the D1 Diode, 1N4148, effectively taking it out of the circuit. Simple as that. I have attached the schematic (that I think is correct) below, hope it’s visible to you. Otherwise there are some to be found on google.

    [​IMG]

    And here is my video if you're interested, for now set to unlisted:
     
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  2. Boreas

    Boreas Friend of Leo's Silver Supporter

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    Ethics? Here?? I don't really understand the mod, but your disclaimers should be fine. It is YouTube after all...
     
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  3. LesQuire

    LesQuire TDPRI Member

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    Ethics, why not here?! :D
    Well, removing the diode makes the amp clean up better with the guitars volume knob, it can be heard in the cleaner examples. Normally there is a distortion sound happening that won't go away no matter how low you turn down, this made me look at the diode, I figured diodes are sometimes used for clipping and distortion.
     
    Last edited: Jan 27, 2021
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  4. Boreas

    Boreas Friend of Leo's Silver Supporter

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    I know what you mean, but that is the signature Pig sound and it was designed to be there at all volume levels. Not everybody likes it. If you want clean, I would recommend one of these if you can find one:

    https://www.amazon.com/dp/B0002OP7VQ/?tag=tdpri-20
     
  5. LesQuire

    LesQuire TDPRI Member

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    I'm actually really happy with the pignose now after my mod, heck even before it, my question is still if this will damage the amp in the long run..
    Those tiny fenders sounds like old telephones, right?
     
  6. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The 820 and 220 resistors form a voltage divider. The voltage out without the diode is about 1.9V with a 9V source in. If the diode is *on* it will drop an additional max of 0.7V.

    Worst case scenario with a 9 volt supply is 1.9 volts which is well within spec for the TIP41C transistors. Heck even a 12 volt supply would only provide 2.54 volts. So yes, I would think it is safe to remove the diode from the circuit.
     
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  7. Boreas

    Boreas Friend of Leo's Silver Supporter

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    Well, I use my Fender more than the Pig. I don't sit down and play with either as I have better amps, but I use them on my bench for testing controls and setups on my guitars. It helps to have a clean tone for that.
     
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  8. NTC

    NTC Tele-Meister

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    Removing the diode resets the bias point. The output transistors were biased at or below cutoff with the diode in, so there would be lots of distortion. Normally you would have two or three diodes in series to bias the transistors just above cutoff. The base to emitter junction is a diode just like the 1N4148, so the voltage drops match. The transistors won't turn on until the base voltage is 0.7V above the emitter voltage. With the resistor on the emitters, the signal has to be more than 0.7V to turn on the transistors.

    This circuit is actually very much like a tube amp.
     
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  9. Jon Snell

    Jon Snell Tele-Holic

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    Your batteries will be exhausted sooner as it now has quiescent current flowing.
    As long as the output transistors do not run burning hot, it should be fine but it will no longer sound like a Pig Nose.
     
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  10. LesQuire

    LesQuire TDPRI Member

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    Awesome, thanks for sharing that info!
    What parts are the most sensitive to temperature? Transistors and capacitors?

    So basically it cleans up because the output transistors gets a higher voltage?
    Thanks for the info!

    That's a good point, I'll make sure to include that info and also check the transistors. Thanks!
    At full gas there wasn't really any difference in tone, still sounds like the "legendary" piggy, it just has a more useful clean up!
     
  11. radiocaster

    radiocaster Poster Extraordinaire

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    Have no idea if it harms anything, but to be honest I didn't hear a huge difference with it "clean" either. There were still those overtones.

    I'd be more curious to hear it through a big speaker cab.
     
  12. LesQuire

    LesQuire TDPRI Member

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    Yeah, it wasn't the best recording, I might make a better one. I run it into other amps often and via an Electro Harmonix Magnum 44 power amp through a 4x12 sometimes, sounds massive and can be much louder of course than if I were to put a speaker out jack in it. If you want to hear that you can check out this video:

     
  13. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    To answer the question directly... both. hah.

    I am not sure how long the 7-100 line was produced. Electrolytic caps only last so long before they should be replaced IMO. The caps dry out. An analogy with tires on an old car is often used. Heat on the caps shorten the life. The electrolytic caps on the schematic have a 16V rating which is enough as long as you are not using higher voltages to power the amp. Most e-caps are rated for a max temperature of 65C to 85C.

    The transistors should last... so long as their max ratings are not exceeded. As far as temperature, the datasheet says a max of 150 degree centigrade. Whew that is hot.

    My brother had one of the early 7-100 amps. Bought it when they first came out. I never worked on it. I have the big Pigs. The G40V and the G60VR.
     
  14. Chiogtr4x

    Chiogtr4x Poster Extraordinaire

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    Hey Pignose owners,

    Am I hearing correctly in this video, that using the Line Out in a Pignose ( assuming new and stock) does NOT cut out the volume of the Pignose speaker?

    I like that idea to run line out into another amp's input to get dual ( yet still small) amps.
    The dry, dirty Pignose, with a little Reverb/ bigger speaker/low-end from a larger amp. Thanks!
     
  15. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I just listened to the sound-clip/video. I don't hear a lot of difference with the diode *in* or *out*. There is a volume change.

    Perhaps the answer to *why the diode is in the circuit?* has to do with the battery power. As the batteries lose power, at some point the diode will not conduct. This would essentially prop up the signal voltage when the battery power declines. The amp would not change sound dramatically as the batteries wear down.

    The above is just a thought. The designer may have had a different reason to include the diode.
     
    Last edited: Jan 28, 2021
  16. fraser

    fraser Tele-Afflicted

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    correct, the jack out on the pignose does not cut out the speaker, its always on.
    I used to do what you are saying.
    Run the pignose into another amp, and mic both amps, splitting the signal.
    You can get some great sounds that way.
     
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  17. stepvan

    stepvan Tele-Holic Silver Supporter

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    I saw your video and with the disclaimer I would post it. Honestly I don't think you would really have an issue with heat unless you were busking on some hot sunny street outside a mall and had it closed up and directly on the asphalt or concrete.just my 1.25's worth.
     
  18. Chiogtr4x

    Chiogtr4x Poster Extraordinaire

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    Thanks!

    You have no idea how much more attractive that makes the idea of getting a Pignose.

    Granted I'd like one as I dig small, good sounding amps ( even 'trashy' can sound good to me), and the Pignose is a '70's pop culture icon.

    But the fact that I could use it in this manner, for small gigs- 2 amps, yet still keep things portable/light, is a real bonus
     
  19. Pasta Player

    Pasta Player Tele-Meister

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    Aren’t even the latest produced (today) Pignoses… 7-100’s?
    I’ve a pair of the early ’73 Pignoses (Germanium transistors)
    that are still driving me crazy here trying to resurrect.

    But yes @Chiogtr4x you can run multiple Pignoses together
    & still have all individual speakers working (using line-out jack).
    AND Pignoses - plus other similar amps work equally as well.
    *Some even used as a preamp with much larger amps too.

    Built a 25% larger cab with 6” Jensen here trying to improve
    a Pignose to compete with a Dwarf’s performance & found
    that it required 12 or 18 volts to push the larger 6” speaker.
    *Sorry Pignose, closer, but no cigar.
    (Rumor has it that Zappa used 18 volts with his Pig.)

    BP&D1.png
    (As if I haven't posted this image here enough already.)

    So if you’re all feelin’ f-risky, try to up the voltage to 12
    and check the improved performance overall. AND no,
    I’ve yet to bake a 7-100 Pignose pushing it with 18 volts.

    The old Dwarf amps (1974) are much more bang for the buck
    and they’ll push a 10” or a 12” external cab surprisingly well
    via their extension speaker out jack.

    VPA1.png

    Even an old Pygmy amp (from PAiA) if you can find one…
    beats a Pignose. (Sold as a DIY kit for $39.00 back in 1974).

    Always up for a Pignose mod ‘round here and I just might try
    the “minus diode” route. Thank ya.;)
     
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  20. Chiogtr4x

    Chiogtr4x Poster Extraordinaire

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    So just to be clear if I have a Pignose ( I don't) it's OK to run an instrument cable from its line OUT into the Input of another guitar amp, and guitar is plugged into the Pignose amp.

    Basically it's almost like a Pignose is being used as an ' OD pedal with a speaker' Right? Thanks
     
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