Modding the 5150 III EL34 50w amp into an absolute beast
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Thread: Modding the 5150 III EL34 50w amp into an absolute beast

  1. #1


    Join Date: Sep 2008
    Location: Arizona
    ME: Ibanez
    Rig: Mesa JP-2C

    iTrader: 0

    Modding the 5150 III EL34 50w amp into an absolute beast

    So I did a couple of mods to the 5150 III recently that really make the amp quite a bit better. First off, I have yet to hear anyone that likes the stock blue channel on this amp, which is an absolute shame because all the other 5150 III heads have an amazing blue channel. It's come to light more and more over the past year or so that simply snipping out a small capacitor fixes this.

    This is the easiest mod you can make to this amp and it totally kills. Just snip out capacitor 137 and the blue channel comes to life, making it just as great as the blue channel on the other 5150 III amps.

    Modding the 5150 III EL34 50w amp into an absolute beast-innards-jpg

    Now for the second level of experimentation. Now that the blue channel rocks, let's make some changes to the red channel. This will be easier, as it's just tube preference.
    Modding the 5150 III EL34 50w amp into an absolute beast-tubes-jpg

    I went into this morning wanting to mess with preamp tubes to make two changes to the red channel of the 50w EL34 amp:

    1) make the gain knob more of a usable sweep, and
    2) get rid of the squeaky midrange the red channel can have.

    I wound up with this configuration that accomplished both:

    V1: Mesa SPAX7-A (a decently high-end 12AX7)

    Red channel specific tubes:
    V2: JJ12AU7 (much lower gain)
    V3: Sovtek 12AX7LPS
    V4: Mesa 12AX7

    This worked! I highly suggest replacing V1 and V4 with higher-quality tubes than the amp ships with. The 12AU7 reduces the gain of the red channel, making the gain knob useable throughout instead of topping off at 10 o'clock. The Sovtek LPS gets rid of the mid honk, making the amp sound much more balanced. If I had any spare Tung Sols lying around they would've gone in V1, V4, and V5, but the Mesa tubes will do just fine for now. All-in-all I recommend experimenting with the tubes in this amp and had success with this today, for sure.
    Attached Thumbnails Attached Thumbnails Modding the 5150 III EL34 50w amp into an absolute beast-innards-jpg   Modding the 5150 III EL34 50w amp into an absolute beast-tubes-jpg  


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  3. #2


    Join Date: Oct 2008
    Location: Cambridgeshire, UK
    ME: Charvel San Dimas
    MB: Charvel 3b
    Rig: Marshall JVM210H (modded)

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    Nice. I see that capacitor-snip done all the time on these amps, but I've never got the bottom of what the actual complaint is about the blue channel?

    The JVMs suffer the same issue as the EVH red channels - Way too much fucking gain, making the gain dial redundant by the time you're around noon. There are mods to compensate for this (changing the value of some of the grid resistors), but I feel they neuter the amp in a way that's unpleasant to my ears (takes away quite a bit of low end) so I just leave it as it is. Preamp valves will be my next experimentation point.
    www.numbskullaudio.com
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  4. #3


    Join Date: Sep 2008
    Location: The B.L., WA.
    ME: Ibanez PGM100
    MA: Washburn
    Rig: 5150III

    iTrader: 22 (100%)

    Nice! Guess I'll be tearing into mine tonight and try the blue channel mod.

    Also, if you get a chance, try the EL34 to E34L swap I think I mentioned in one of our conversations. Supposed to give a bit more headroom but the main thing I noticed is this thing growls so good now. And the low end tightened up quite a bit.

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  6. #4


    Join Date: Sep 2008
    Location: Arizona
    ME: Ibanez
    Rig: Mesa JP-2C

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    Quote Originally Posted by Mattayus View Post
    Nice. I see that capacitor-snip done all the time on these amps, but I've never got the bottom of what the actual complaint is about the blue channel?
    It just isn't good. They tried to make a vintage sound, but it just sounds like mud IMO and never has enough gain even boosted. The EVH blue channel is iconic and many bands use it as their main heavy tone. Snipping out this capacitor fixes it in the 50w EL34 amp, which is the only amp they tried this.

    Quote Originally Posted by DonBot View Post
    Nice! Guess I'll be tearing into mine tonight and try the blue channel mod.

    Also, if you get a chance, try the EL34 to E34L swap I think I mentioned in one of our conversations. Supposed to give a bit more headroom but the main thing I noticed is this thing growls so good now. And the low end tightened up quite a bit.
    I need to do this! I've just never biased an amp before and need to learn how to use my multimeter before I try this! Soon!

  7. #5


    Join Date: Sep 2008
    Location: The B.L., WA.
    ME: Ibanez PGM100
    MA: Washburn
    Rig: 5150III

    iTrader: 22 (100%)

    Quote Originally Posted by Vince View Post
    I need to do this! I've just never biased an amp before and need to learn how to use my multimeter before I try this! Soon!
    No re-bias needed for this swap. That's the best part!

  8. #6


    Join Date: Sep 2008
    Location: Woodbridge, VA
    ME: KxK ProtoVii-7
    MA: Martin D-28
    Rig: Mesa/Boobies Stiletto

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    Quote Originally Posted by DonBot View Post
    Also, if you get a chance, try the EL34 to E34L swap I think I mentioned in one of our conversations. Supposed to give a bit more headroom but the main thing I noticed is this thing growls so good now. And the low end tightened up quite a bit.
    +1 since I did this to my Stiletto Deuce. Tighter bottom end and a fierce lower midrange.

  9. #7


    Join Date: Sep 2008
    Location: The B.L., WA.
    ME: Ibanez PGM100
    MA: Washburn
    Rig: 5150III

    iTrader: 22 (100%)

    Quote Originally Posted by noodles View Post
    +1 since I did this to my Stiletto Deuce. Tighter bottom end and a fierce lower midrange.
    I was shocked with the obvious difference in tone.

  10. #8


    Join Date: Sep 2008
    Location: Arizona
    ME: Ibanez
    Rig: Mesa JP-2C

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    Quote Originally Posted by DonBot View Post
    I was shocked with the obvious difference in tone.
    Alright you sold me, two E34Ls inbound

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