Building a Single Ended 5 watt amp - Can anyone help me install a Master Volume?

Discussion in 'The Workbench' started by Yamariv, Jul 28, 2020.

  1. Yamariv

    Yamariv Well-Known Member

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    Hey Guys, I want to build my own version of this little amp but have never added a Master Volume on a single ended Cathode Biased amp like this. Is it possible to put in a good sounding MV, if so, where and how :S

    I know it's not a Marshall but I've posted on another forum and have gotten nothing so far so I thought I'd turn to you guys!

    I've attached the schematic below. Thanks for any help!

    5 WattSchematic.jpg
     
  2. thetragichero

    thetragichero Well-Known Member

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    doubt you'll need a master volume for this type of amp. waste of components
    keep it simple
     
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  3. Yamariv

    Yamariv Well-Known Member

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    I thought that too but 5 watts is still very very loud in a living room and I want to get full saturation from the amp. Ideally, I'd like to have this amp be one watt but that's above my design capabilities right now so I thought I'd just do this with a master volume.
     
  4. thetragichero

    thetragichero Well-Known Member

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    get a different ot and steal this output stage (again I'd leave out the master volume... keep it simple stupid)

    [​IMG]

    could use 12ax7 if you don't have 12au7
     
    Last edited: Jul 28, 2020
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  5. Yamariv

    Yamariv Well-Known Member

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    Fully understand what your saying but I already have all the parts and transformers so your build is not possible. Looking to see how to do a Master Volume on my original Schematic above

    From what I've read, Single Ended amps are difficult to add MV's for some reason, is that true?
     
  6. thetragichero

    thetragichero Well-Known Member

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    you can replace the grid-to-ground resistor with a pot but then you're messing with the previous stage's loading. these are super simple circuits so messing with one thing effects other things
    I'm a non-master volume player myself
     
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  7. Yamariv

    Yamariv Well-Known Member

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    Yeah, that's what I've found so far, it's hard to add a MV to these which sucks.. So your saying replace the 220k resistor to ground before the EL84 Grid? What kind of consequences would I hear by doing that?
     
  8. Gene Ballzz

    Gene Ballzz Well-Known Member

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    One of the problems of a Master Volume on an amp this simple, is that much of the overdrive, distortion and "saturation" achieved with an amp like this comes from overdriving the power tube, as well as the preamp. When you lessen the amount of signal driving that power tube, you also lessen the "saturation!"

    I think a better solution for your situation would be a GOOD attenuator. Given that you're already tackling the task of "building" an amp, you likely have the skills to build a stripped down version of this:

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

    When I say "stripped down" I'm referring to fewer stages and possibly lower wattage resistors, as you will have much less power to shed. This attenuator design messes with tone and dynamics much, MUCH less than any master volume would!

    And no, a Master Volume is not HARD to add, but one that doesn't sound terrible is another story!

    And in reference to the design @thetragichero suggested, it's my opinion that triode power sections are generally lackluster, lifeless and short on dynamics. The final sound is much like you get when you take a nice sounding amp design using tetrodes or pentodes for the power tubes and switch them to triode mode for dropping wattage/power. They're fine if all of your sound and character is getting fully developed in the preamp and the power amp is simply used in a clean manner to operated the speaker. Triode power sections usually sound pretty "wimpy" when driven hard.

    Just My $:2c:,
    Gene
     
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  9. Micky

    Micky Well-Known Member VIP Member

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    I use an attenuator on my Champ.

    A MV will essentially remove the 'character' of saturating the power tube.
    I use a Bugera PS-1 and it works great.

    You may want to look into a 1W amp...
     
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  10. Im247frogs

    Im247frogs Well-Known Member

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    might be worth putting a switch on the 6.8k r to ground which will give you a nice wooly mids boost at lower volume
     
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  11. danman

    danman Active Member

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    With only two gain stages in your circuit, a MV is pointless because the preamp will not develop enough gain to overdrive. Most of the overdriven tone from this amp will only come from the power tube so an attenuator is really the only choice to get a driven sound at lower volumes. Most amps that use a MV will have multiple preamp stages to achieve enough gain to make the MV usable.
     
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  12. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Consider a Weber Mini Mass for attenuation, not too pricey, will handle a 5 watt amp with no problem.
     
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  13. RLW59

    RLW59 Well-Known Member

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    I've had two single ended master volume amps. Both were single 12AX7 driving an octal tube.

    You can get a significant bit of distortion out of a single 12AX7 but it's fizzy and crappy sounding.

    Master does work pretty well if you're just looking for fatter cleans or light crunch at low/moderate volume. But that's all -- it won't give you "cranked up amp" tone because that really needs the power tube to be pushed.
     
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  14. South Park

    South Park Well-Known Member

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    If you want preamp gain you need a cascade gain stage in the preamp . If want to a single ended amp this is the one I built .
     

    Attached Files:

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  15. neikeel

    neikeel Well-Known Member

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    Funnily enoug I built an 18w IIb lite with very similar preamp to the one South Park postée and I put a pre pi MV in (two gain stages ->tone stack->pi and two EL84s. I can saturate the preamp even with this and play at whisper levels. Turn the master up and plug into a 4x12 with G12Hs and it sounds huge.
     
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  16. Yamariv

    Yamariv Well-Known Member

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    Thanks guys! This is why I came to this forum, all of your comments make perfect sense why the MV won't work. Sadly (pure sarcasm..) it looks like I have another project on my list now, a good attenuator! :naughty:

    So I started to read the hugely long link above and before I dig into another 10 pages of it this aft, is there a final tried and true design with layout that everyone agrees on is a great sounding attenuator to build at home? If I'm going to build one, I'd definitely go all out and want to make one that will last and can handle my TSL60 all the way down to this 5 watter.. I'm open to all suggestions :fingersx:
     
  17. Gene Ballzz

    Gene Ballzz Well-Known Member

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    Yes there is! The thread gets updated regularly and the design you want is in the very first post of the thread. It's called the M-lite.Build it for 16 ohm or 8 ohm amp output. I highly suggest that if you have a 16 ohm tap on your amp, build it for that, as the 16 ohm versions don't care whether the speaker is 8 or 16 ohm, but the 8 ohm version needs extra circuitry to work well with a 16 ohm speaker. If you need to handle more than 50 watts, simply double the wattage rating of all resistors for up to 100 watt amp. FWIW though, if you source the resistors thru e bay, you'll find it is simple and inexpensive enough to simply build one dedicated for each amp you own and install it there!

    The rest of the thread is very imformative though and fairly easy to figure out how to just skim through the chaff. Also the designer @JohnH is very gracious and timely about answering questions and pointing you to the correct area of thread if needed!

    Have fun!
    Gene
     
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  18. ibmorjamn

    ibmorjamn Well-Known Member

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    Look up the November from AX84 !
     
  19. Yamariv

    Yamariv Well-Known Member

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    Thanks for your help Gene, ok "M Lite" version it is but I have a few questions I'm hoping you or other can help me out with.

    - All of my cabs are 8 ohm except for my Vox AC30 which is 16ohm. If I build the 16ohm version, what would happen when I want to use my 8 ohm cabs, any drawbacks?

    - I am totally new to those Inductor Coils so forgive me.. I was looking for all the parts on Mouser and there are so many options I have no idea if I'm even finding the right coils I need. Any chance someone has a link to the induction coils I need? Can we get them on The Bay or is Mouser a good source?

    - I think for cost savings I'll do the 50 watt version as the biggest amp I have is the 60watt TSL. If I was going to build the 100 watt version of the M Lite, what are you guys doing for the big 200 watt resistor? I can't seem to find 200 watts easily..
     
  20. Gene Ballzz

    Gene Ballzz Well-Known Member

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    None that have been reported, other than I believe the attenuation ends up being about -1db or so more when using an 8 ohm speaker on the 16 ohm attenuator. You would still come out the 16 ohm tap/setting on your amp. If you ask the same question in the attenuator thread, @JohnH will likely be able to direct to the post with testing results for the most precise answer.

    Here's a good source for inductor coils and they ship to Canada:

    https://www.madisoundspeakerstore.com


    Simply use two 100 watt, 60 ohm resistors in parallel or 15 ohm in series. Search ebay for resistors. You'll save boatloads over Mouser/DigiKey prices!

    Happy Strippin', Drillin', Screwin' & Solderin'! :ca: :cheers:
    Gene
     
    Last edited: Jul 30, 2020
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