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Replace master volume pot to achieve lower minimum volume?

Discussion in 'Amps and Cabs [BG]' started by CatSquare, Jan 2, 2016.


  1. CatSquare

    CatSquare

    Mar 7, 2014
    So I've got an Orange Terror Bass 500w amp head - I love love love the preamp, but boy is that power amp brutal. With the volume knob just barely at 1, the amp is already way louder than I'd like for just playing by myself, especially when I start diving the preamp in pursuit of a nice overdriven sound.
    So here's what I'm thinking: I'll replace the master volume pot with something of the same value, but a multi-turn instead of a single turn. The idea is that I'll get finer control on the low end of the knob but ultimately have the same range.
    Any reason this wouldn't work? Is there any kind of minimum power for class D amps or anything like that?
     
  2. 5544

    5544

    Dec 1, 2015
    Why not use the volume pot on your bass?
     
    Aqualung60 and 2behead like this.
  3. CatSquare

    CatSquare

    Mar 7, 2014
    because I need to hit the amp's pre with a certain level of signal to get it to start driving, so I don't want to change what's coming in on the preamp side.
     
  4. I don't see why the multi-turn pot would not work. My only concern is that there may be a time when you need to make a quick volume change on the amp. I've seen some cool knobs, mostly on high end test equipment, that include a turns counter. There would be the usual 0 to 10 around the knob, but it also would include an inset number that counts 0 to 10 full turns of the pot. The inset is a X 10 display. If you like running somewhere between 1 and 2 full turns, the inset would show 1 (X 10) and set the outside dial to, say 5. Then you would be running at 15 on a scale of 0 to 100. This makes it easy to reset to a known volume when needed.
    These types of knobs are not cheap, nor is a ten-turn pot. I'd suggest you look at electronic surplus sites for the knob and even the pot. I often frequent Surplus Sales of Nebraska, because they are right here in town. If you don't find what you need on line at SS of NE, call or email and ask for Bob, the owner. Tell him "Zed" sent you. It won't get you a discount and (and I don't think he'll charge extra).:smug: I don't get a cut either. My only connection is that we are both Ham Radio operators, I am a cheapskate, and love rummaging through the surplus parts stores. There are other good surplus places on line as well.
     
    CatSquare likes this.
  5. dincz

    dincz

    Sep 25, 2010
    Czech Republic
    Have you tried the active/passive switch? Otherwise an attenuator in the effects loop would help.
     
    CatSquare likes this.
  6. /\/\3phist0

    /\/\3phist0 ( ͡° ͜ʖ ͡°) mmm Woody! Supporting Member

    If you are going to mid the head why not have a tech install an effects loop, or at minimum a preamp out, that way you could feed a lower power amp.
    OR get a practice amp
    Or say, a 16ohm cabinet (say a single 110 loaded with a Faital, designed for Genz Benz like Avatar cabs is selling) or a 32 ohm 2x10 , with the same speakers in series)
     
    MattZilla likes this.
  7. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Why not just use a log taper pot, which will probably already do what you want?
     
  8. BassmanPaul

    BassmanPaul Inactive

    I would have thought that a an audio/log taper pot would what’s in there now Charlie.
     
  9. CatSquare

    CatSquare

    Mar 7, 2014
    Me too, surplus electronics places are the best.
    I had considered needing the quick volume adjustment, but I think having the lower volume would be of more value to me. I agree with you about putting the counter on there to know where I have my volume set, but I don't know if I want to ugly up the amp that bad.
    I'm using the active switch, but that's still before the pre i believe. An attenuator in the effects loop is an interesting thought. Maybe I'll give that a shot before I take a hot iron to this puppy.
    It's got one, and I could do that, but I don't need/want more amp gear, I want to be able to turn down without having to toggle between too loud and off on my existing gear.
     
  10. CatSquare

    CatSquare

    Mar 7, 2014
    I haven't cracked it yet to check, but I'm assuming there's a log pot in there already
     
  11. Yeah! You've got the effects loop, then yeah! That is a x10 better idea than mine.
    To build on a great idea... How about a variable attenuator?
     
    CatSquare likes this.
  12. /\/\3phist0

    /\/\3phist0 ( ͡° ͜ʖ ͡°) mmm Woody! Supporting Member

  13. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    I kind of doubt it, given the symptom. Lots of people use linear pots with a following wiper-to-ground resistor to set the pot law, which is often my favored approach for my own builds. In any case, I'd look at that before resorting to an expensive and maybe inconvenient solution like a 10 turn pot.
     
    Last edited: Jan 2, 2016
  14. CatSquare

    CatSquare

    Mar 7, 2014
    I'll take a look see what they used. The amp is a bit banged up and I got a decent price, so it's entirely possible that's what's going on, although I've heard other Terror Bass folks complain about it being abnormally loud.
    What do you think about switching a resistor into circuit with the volume pot for a bit of attenuation?
     
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    A well qualified tech who understands the circuit could fine tune it to your needs. I would check the pot taper first.
     
    JackANSI and Passinwind like this.
  16. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    What Andy (agedhorse) said. I've never seen the schematic, but if you can scare one up it would take things in the right direction at least. BTW, have you looked at how the pot is mounted yet? Subbing in another one isn't always the most straightforward process, especially if you need to add resistors inline or in parallel.
     
    CatSquare likes this.
  17. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Some amps have the master as an attenuator after the pre-amp, others have the master after the phase inverter. I recall one Orange amp that had a 500K linear dual gang pot in the power amp. So it might not be as simple to modify the circuit as you imagine.

    A pot in the effects sent (or preamp out) and the effects return (or power amp in) might be an easy thing to try.

    Often a linear taper pot is used but you can try a log taper.


    volume box mod.jpg
     
    Last edited: Jan 3, 2016
  18. MattZilla

    MattZilla

    Jun 26, 2013
    CNY
    what I read: "how can I make my broadsword more usable for filleting small fish? I really don't want to have two cutting implements."

    just get a practice amp dude.
     
  19. CatSquare

    CatSquare

    Mar 7, 2014
    If I had the money and the space for more gear, then yeah. The obvious thing had occurred to me.
     
  20. What you want and/or need already exists, and is standard on many ham radios. The turning control changes the amount of change based upon the speed you spin it. For example, on a scale of 1 - 1000, if you rotate the dial slowly it will move from 1 to 2 to 3, etc. If you rotate it a little faster it will move 10 to 20 to 30, etc. If you just spin it as fast as it can go it will move 100 to 200 to 300, etc. Two problems here, one being the control has to be connected to another part which controls the spread of the movement, and two it is large, heavy, and expensive. It would not work as a foot pedal but as a finger device you have to reach over to it and give it a spin. So you couldn't do it while playing. Not a bad idea though. Any other ham radio operators on TB that might know how to rig this up? Icom IC-7851: Ham & Amateur Radios - Equipment, Parts and Supply | AES On the shown example, see the large dial on the face. That is the dial you want and need.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Mar 3, 2021

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