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EF86 with morph control in PP gigging amp

Discussion in 'Shock Brother's DIY Amps' started by tubeswell, Jun 22, 2011.

  1. tubeswell

    tubeswell Friend of Leo's

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    So much did I enjoy the EF86/morph control in the SE amp that I built a couple of months back, that I thought I'd take the same concept into more powerful gigging amp.

    Finished the (Ef86 concept) version of this amp tonight. Didn't get a chance to really blast it yet, but it sounds very promising.

    Happy to say no buzzes or rattles or hums. Tone is EF86tastic! (Need to do some soundbytes). Tone controls need tweaking to get the scoop/hump concept improved upon.

    (Corrected/edited) schematic of as-built version with measured idle voltages attached below. I think it needs a voltage tweak in the power rail. I'll chuck a 5AR4 in and see how that goes (or maybe drop the first supply resistor to 4k7).
     

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    Last edited: Jun 23, 2011
  2. laird

    laird Tele-Holic

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    Most excellent! I don't think I've seen that kind of morph control before... I've tried the traditional squish, but what does the addition of the .047u from the EF86 plate to the pot do to the behavior?

    I experimented with a couple of tone/scoop control variations on my AC15-like EF86 channel but I didn't have the benefit of a following stage to recover the lost gain. If I did I probably wouldn't have given up. :D When I get home I'll see if I can dig up any notes I took.

    I love the use of the 12DW7 and the voltage-divider network out of the second triode instead of using a 12AU7, lets that last triode overdrive some instead of dumping a giant clean signal onto the PI, especially with the smaller tail. I might have to try that sometime!

    A little more voltage in the preamp could help. Keeping the EF86 down around 200v is great for getting some richness on a mostly clean signal, but it leaves very little headroom. In my EF86 experiments I liked the B+ around 240-260v the best when a squish control was present - the squish seemed to behave nicer in that operating range.

    ... And bias-vary tremolo to boot. That thing has got to have some serious mojo!

    -Laird
     
  3. tjalla

    tjalla Friend of Leo's

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    tubeswell - very nice!! By 'NZ' is there any chance your location is New Zealand? That's looking very much like something I'd love to take out on gigs!
     
  4. tubeswell

    tubeswell Friend of Leo's

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    Thanks tjalla. Yup, kywee
     
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