Lyle Caldwell mods for AC30C2?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Outlier52, Jun 12, 2016.


  1. Outlier52

    Outlier52 Member

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    Do the CC2 mods work the same way for the C2 series?
     
  2. WillLane

    WillLane Member

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    The best way to find out is to be handy with the schematics, and to actually have the schematics. Sadly, the schematics are not just handed out, you have to be an authorized service center.

    From what I am seeing here: http://www.ac30-guide.com/?page_id=524 , the circuits are not similar enough to be able to follow that guide exactly with an AC30C2. For instance, The bright cap is labeled C13 in the CC2, but C15 on the C2. They share the same value and location, though.
     
    Last edited: Jun 13, 2016
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  3. Kelsey

    Kelsey Member

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    Why don't you just contact Lyle?
     
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  4. jay42

    jay42 Member

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    It's not helpful as I am on the wrong computer. I have the C2 schematic somewhere. The point of the mods is that Vox was playing pretty loose with the CC line schematic and you just put it back to stock mostly. The C2 is closer to stock, but not a clone either. I will try to find them, though it won't be today.

    [Edit] I did pull it off of MEF, which used to be Ampage. Contact me if you need this still.
     
    Last edited: Jun 20, 2016
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  5. Outlier52

    Outlier52 Member

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    So I pulled off the bright cap mod and it fixed the issue I was having with a fizzy top boost channel, especially with pedals. For anyone wondering, the bright cap on the AC30C2 is C15, just underneath the top boost volume pot.
     
  6. TMcB

    TMcB Member

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    Just thought I'd post this for posterity. The AC30cc2 and AC30C2 Preamps are almost exactly the same, apart from the the C2 series doesn't have the switches and have chosen far more sensible values for the treble bleed caps etc.
    So yeah, theoretically they'll work. The problem is mapping them to the new board..which I've done :D The CC2/Lyle Caldwell mods references are on the left, the C2 on the right

    Plate resistor mod:
    R6 & R7 = R14 & R12 respectively. However, R14 is already 220k so all you have to do is change R12 from 100k to 220K

    Normal channel gain increase:
    R49 = R13 – jumper this for more gain. The treble bleed cap on the normal channel is C8, stock is 120pf if you wish to muck around with that. (Mod changes this cap to 100pf, and has a "brilliance" switch that puts a 68pf cap in parallel with the 100pf)

    Top Boost treble cap:
    C13 = C15 (stock 120pf) tweak to taste (68pf?) or remove

    Tone stack tweak
    C16 = C23 (stock 56pf) -> 47pf

    Removal of Top Boost Cathode Bypass cap
    This is the U2 mod - the Edge's amp doesn't have this cap and it makes for tighter bass, more headroom/lower gain on the TB channel.
    C9 = C18 (kinda nice to put on a switch)

    Coupling caps - change them out to Mallorys/Sozos for corksniffery good times
    C11 = C7 (.047uf)
    C14 = C38 (.022uf)
    C15 = C28 (.022uf)
    C17 = C45 (.1uf)
    C18 = C48 (.1uf)
    C19 = C51 (.1uf)
    C20 = C50 (.1uf)
    C23 = C80 (.0047uf)

    If you liked the Custom/Normal switch you could lift the leg of R47 that connects to the bass pot. Then you'd put a switch between the bass pot and R47 - the custom setting on the AC30cc2 disconnected the bass pot from being connected to ground, the normal connected it to ground.

    This is currently all theoretical and I'm just some guy on the internet so poke your own amp with the hot thing at your own risk
     
    Last edited: Feb 17, 2017
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  7. WillLane

    WillLane Member

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    Thought I would mention this:

    I decided to perform the bright cap mod on the C2, which the cap for the TB channel is C15. It was surprisingly more difficult than I imagined since C15 is almost underneath the top ledge of the control panel. I wanted to just lift the leg out one of the PCB holes so I could easily reverse it but the leg ended up snapping. Oh well- The bloody thing seems brighter!

    Maybe I am just used to hearing the amp through the layers of a warm mic, cabling and routing through my Church building's sound system. I am sure the amp is not actually brighter, but it definitely feels as such and I changed some settings to compensate. My ears are ringing a bit. I was hoping it would help take away some of the hard-compression, dense OD sounds and make it more akin to the TBX series- I do not think it did. As far as the main purpose of clipping the bright cap - taking pedals better - it seems to but without A/B'ing signals I cannot really tell for sure. It is not something I feel like I should have to go back and restore. We will see in a band mix and through the system if it was more beneficial than the trouble I went through.
     
  8. TMcB

    TMcB Member

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    Thought I might just mention - those mods I listed earlier are now verified in my own AC30C2

    I also replaced the top boost, normal, and master volume pots with push pull pots - the normal to switch between normal and brilliant, the top boost to take the cathode bypass cap in and out, and the Master Volume to take the master vol out of the system
     
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  9. WillLane

    WillLane Member

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    Make some sound clips for us? I am particularly curious about the MV bypass.
     
  10. doctorx

    doctorx Member

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    Dunno about the C2, but my CC2 was a total PITA to get at the board to do the LC mods.
     
  11. TMcB

    TMcB Member

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    The PCB is easier to get to than the AC30CC2 series with the trade-off that the mods aren't as night and day as the CC2 is
     
  12. doctorx

    doctorx Member

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    Does the MV bypass really make a difference? I thought when it is maxed it is out of the circuit.
     
  13. TMcB

    TMcB Member

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    In all honesty, it's fairly subtle. There's a tad more high end/harmonic content because it's not getting knocked off the top by the 500k pot, as well as a slight bump in volume.

    It felt a bit more alive to me but whether that's psychological because I needed to be more careful of pick attack with it defeated I'm not sure.

    It was very simple to do - you're just making or breaking the connection between pad 1 on the pcb and lug 1 on the pot.
     
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  14. Gene02

    Gene02 Member

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    TMcB
    I have the vox ac30c2x Mercury power and output transformers Weber Alnico Blue Dog and Alnico Silver Bell speakers tubed right with a custom made Birch cabinet. I like what you listed in your Coupling Caps replacements.
    looking to replace with Sozo caps. what I need to know what caps you used and how dose your Amp sound.
     
  15. Gene02

    Gene02 Member

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    I tried contacting Lyle 3 times no return calls to me back.
    TMcB Listed the right things to do
     
    Last edited: Mar 23, 2017
  16. Gene02

    Gene02 Member

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    TMcB
    I'M GOING TO USE THE 220K 1W 1% METAL FILM RESISTOR IN R12 NOT THE 220K 1/2W CARBON COMP IN R12 THAT YOU USED.
     
    Last edited: Mar 25, 2017
  17. Gene02

    Gene02 Member

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    TMcB
    waiting for the C23 47pf 500v 1%. I have all the 8 Sozo, R12 resistor then I will have it all installed. can't wait to hear how it sounds
     
  18. Gene02

    Gene02 Member

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    TMcB
    I CHANGE MY MINE GOING WITH THE 220K 1/2W CARBON COMP RESISTOR LIKE YOU DID. YOU ARE RIGHT.
     
  19. WillLane

    WillLane Member

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    Can you make some sound clips of the mods you have done?
     
  20. Gene02

    Gene02 Member

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    WillLane
    Going to get installed R14 1-220k 2W 1% 500V Carbon Film Resistor, R12 1- 220k 2W 1% 500V Carbon Comp Resistor went with the 2W not 1/2W, C7, C38, C28, C45, C48, C51, C50, C80 8-Sozo Coupling Caps, C23 1- 47pf 1% 500v Black Silver Mica Cap, C8 1- 100pf 1% 500v Black Silver Mica Cap. .
     
    Last edited: Apr 27, 2017
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