JCM800 2205 effects loop

Discussion in 'The Workbench' started by StraightToTheBar, Oct 13, 2021.

  1. Pete Farrington

    Pete Farrington Well-Known Member

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    I can’t read the schematic values for R22 and C24, it’s too pixilated.
     
  2. StraightToTheBar

    StraightToTheBar Active Member

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  3. Deftone

    Deftone Well-Known Member

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    I think can do that. When I get home from work.

    Plug a cable in to the "SEND" and put a meter to the tip and the barrel?
     
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  4. StraightToTheBar

    StraightToTheBar Active Member

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    Yes, with the amp and bypass on, so you hear the sound, strumming hard on the clean channel. (DMM can be on lowest AC voltage setting.)
     
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  5. hako

    hako New Member

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    Actually yes, the "Y" point is where R30 and C25 meet.
    Sorry, no Tube Town loop in the 2210 :D!
     
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  6. Pete Farrington

    Pete Farrington Well-Known Member

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    After the master vol there’s a potential divider, which is also used as a passive mixer for the wet / dry signals.
    The dry signal level is cut down significantly, about 1/50 of its level at the master vol.
    Taking the send output from R22, or shorting out C24 (and hence R32), bypasses or disables the potential divider. But the reverb effect will be buggered.
    Dunno what to suggest to fix things, other than add an fx loop board somehow.
     
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  7. StraightToTheBar

    StraightToTheBar Active Member

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    You're simply amazing Pete, reverb was indeed gone with C24 shorted. I'll look into a 3rd party loop solution.

    Thx so much.
     
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  8. Pete Farrington

    Pete Farrington Well-Known Member

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    Ok, I’ll try to sketch up a good insert point for it.
    Probably before the master vol.
     
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  9. XTRXTR

    XTRXTR Well-Known Member

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    If you think about it, at least I don't think it makes sense to send reverb to an external FX loop. Everybody has there own opinion. For me it makes sense to apply whatever tones, compression, sustain, distortion, overdrive...then send that to a delay, reverb, phase, LFO and return to the PI input.

    With that in mind taking the reverb out of the 2205 circuit makes sense. Perhaps a redesign more like a 2204 with a FX loop added between the tone stack and the PI, the FX unit in the loop providing the reverb or delay. Its just an idea but you do have the same iron as the 2204 and 5 12AX7 tube sockets already wired. You could remove V4, use 1,2,3 as the preamp and tube buffered loop and the V5 is still the PI.
     
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  10. Deftone

    Deftone Well-Known Member

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    I must be doing something wrong but I get 0.00, sorry not of help at all.

    Fucking love that amp though! Sounds amazing. Mine was converted to EL34's by a previous owner.
     

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