Volume pedal between output and speaker?

Discussion in 'The Tone Zone' started by BLG, Aug 9, 2020.

  1. BLG

    BLG New Member

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    This may be a terrible idea, but I had it nonetheless. I originally put a volume pedal in my effects loop thinking that would allow me to crank the volume to achieve a good amp sound while still playing at bedroom levels, but soon realized that I was barely engaging the output stage at all in doing so, so idea not fully realized. I still don't understand why this doesn't help me drive the pre-amp at a higher level and get a better sound. If anyone wants to address that I'd appreciate it. But the main point of this question is what if I put the volume pedal between the amp output and the speaker? Would I potentially just blow/damage the amp because the impedance doesn't match? Or could this work?

    Probably a bad idea but I thought I'd just ask for the heck of it.

    This is for a DSL40C for the record.
     
  2. IOSEPHVS

    IOSEPHVS Well-Known Member

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    You would need a very robust circuit in the pedal, one that is capable of handling the signal level from the power stage - think power soak in a variable foot pedal. Most aren't designed to operate in that capacity.
     
  3. South Park

    South Park Well-Known Member

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    Bad idea you want a balanced signal from The out put to the speaker . Cutting power to the speaker will not let the tubes work right . The only you can do is the power soak
     
  4. anitoli

    anitoli Well-Known Member Gold Supporting Member

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    You need a Rockcrusher. It has a studio/load box setting that allows you to fully dime the amp then bring up the volume with a pot. It works but the tone may not be what you are looking for.
     
  5. Trelwheen

    Trelwheen Well-Known Member Double Platinum Supporting Member

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    Design and build a sturdy, overbuilt attenuator that doesn't suck tone, make the db reduction controllable with a footswitch, then call me. I'll be your first customer.
     
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  6. JohnH

    JohnH Well-Known Member

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    If the aim is to achieve volume reduction with cranked tone, then job done. You can buy an attenuator or build a better one for less as shown in the Workbench thread.

    https://www.marshallforum.com/threads/simple-attenuators-design-and-testing.98285/

    Just look at post 1.

    Attenuation with foot control brings in a few other issues though. If you need a smooth volume pedal then its an order of magnitude more difficult to get it right. The issue is finding a very high power pot that can also be geared to a pedal. Its unlikely. So for this scenario it may need a reactive load box, normal volume pedal then feeding into another amp for re-amping. Anyway this is done its big $.

    In between, is the scenario with a footswitch to engage a fixed or preset attenuation. Some commercial units have this. The issue with this is transient and current issues if you then want to switch on the fly while playing at power. If it means going from reduced power up to full power then there is likely to be a nasty switching moment when the signal is either short circuited or open circuit, both potentially bad, and high currents are involved.

    But, if you just need a foot-switched lead boost, between two attenuated settings, then its doable. The designs we are building have a first stage at -7db, ie a 40W amp is down to 8W, which is still loud. Provided tthat this first stage is always on, so the amp is loaded consistently, then a footswitch could be wired in to bring the volume down lower, in various ways, and its handling much less current.

    Do any of those ideas address your needs?
     
    Last edited: Aug 9, 2020
  7. Bloodrock

    Bloodrock Well-Known Member

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    No. You’ll kill your amp. You can put the volume pedal in the loop tho. It may not have your desired tone affect but it won’t blow up your transformer.
     
  8. pedecamp

    pedecamp Well-Known Member

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    Depends on how much gain you want. I run a JHS volume box in my loop, amp dimed, set JHS to home volume, I get a respectable ACDC Zep crunch I am very happy with. Your volume pedal should get the same result, and if you need a heavier tone put a boost or OD out front. :yesway:

    You have a DSL any way, it gets its gain from the preamp, it has a master volume, so you dont need to do anything but plug and play! You don't need any of this extra pedal stuff! :shrug:
     
    Last edited: Aug 9, 2020
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  9. junk notes

    junk notes Well-Known Member

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    You are describing something that @ampmadscientist* help me out with an idea of mine. (*unfortunately he is not hanging out as of late.)
    I put together (several) 9 volt 1 watt 8Ω 1x12 combos, out of a Marshall MS-2 9v headphone amp. I achieved whisper tones with the circuit dimed. I was pushing it hard, setting the wall transformer up to 12 volts, even getting feedback ;-) (sound clip was posted). The combo turned up all the way, gets louder than bedroom levels, and records decent.
    There is a seller on ebay that sells an external pedal designed to go between the amp and speaker. I notice from feedback that his marketing is surprisingly working.
    Looks like he uses a bright cap helping the highs at lower volumes. (good idea - like a guitar treble bleed?) I know nothing of this seller only that of surfing ebay. He builds these pedals for designated amps and has a disclosure, so to be taken with a grain of salt.

    I tried to keep value of the L-pad pot close to the amp's spec when making that decision. - 8Ω speaker/2 watts /0-12 volts
    I am guessing this is how the ebay seller is spec'ing out his pedals? They are looking all the same?
    Here is how I incorporated it in my combo. I had posted the wiring diagram in the other thread.

    The seller on ebay sells similar in an external box. Perhaps something that would interest you?

    [​IMG]
     
  10. TXOldRedRocker

    TXOldRedRocker Well-Known Member Gold Supporting Member

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    For me, tube amps and volume controls in the loop aren't a good mix. What's the point of having the tubes if you're not going to let them do their thing? I mean, when playing clean fine, but otherwise, no. I have a JHS Little Black Amp Box I have used in the loop of non-tube amps, when I used to own any. But with a non-MV tube amp, an attenuator is the only way to go. That's what I have on my SV20H. Maxed out crunch with bedroom volume when I need it.
     

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