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Putting some teeth into a Yamaha Electone D-85 (with a channel-select effects loop)

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  • Putting some teeth into a Yamaha Electone D-85 (with a channel-select effects loop)

    First post (so be gentle...)

    Recently acquired a D-85 in excellent, full working cond. Jumped on a Kijiji offer for CAD$100 without realizing that this model has some minor-league cult status, but have spent the past week discovering why.

    As a 'flagship model' that dates from a major technological inflection point, it's a curious (but surprisingly well-integrated) blend of mature (analog) and emerging (digital) tech. Standing back from the guts, though, it also reflects consumer appetites and cultural aesthetics that were becoming unsettled. (When you consider that thousands of D-85s were being shipped to dealers while Devo's Whip It was climbing the charts, the DX-7 looks more inevitable than innovative... Still, Yamaha deserves credit for finding ways to leverage new means of achieving the familiar while also expanding the familiar to include the new.)

    But, as a child of the '80s, I naturally can't abide by a sonic palette crafted for my Granny's living room. I want to coax more 60s, 70s and 90s out of this thing. Inspired by this easy-peasy substitution of an effects pedal for the reverb tank, my head started swimming with all kinds of external processing possibilities. And then I cracked open my copy...

    No reverb tank sitting just so under the lower manual. No plug 'n' play RCA leads. What I found was a dingy, single-spring, open air reverb loitering beneath the Leslie enclosure. It is fed by a pre-amp (as I've learned all spring reverbs must be) that takes the final 'centre channel' mix (i.e., solo synth, upper/lower drawbars and presets w/ chorus/tremolo, but not rhythm and pedal) to approximately Walkman-level headphone output (couldn't resist). The 'wet' return from reverb is mixed with the parallel 'dry' signal by a slider (wiper, pot?).

    But, man, could some fun be had if I could insinuate a multi-effect pedal or box into this well-heeled beast...especially since last-gen units that can emulate eighty different patches and chain handfuls of them at a time are going for $50! Between just these two casual purchases, the range of sonic possibilities is absurd. (I know the same $150 will get you a quad-core tablet and DAW freeware, but where's the fun in that?!?)

    Here are my thoughts/hopes/questions:
    1. Level- & impedance-matching. There is a blurry distinction between 'instrument level' effects units designed to see/handle input from things like guitar pickups and 'line level' gear designed for the effects loop send/receive on guitar amps, mixers, etc.. The distinction is blurry because modern equipment can be designed to tolerate wide ranges of input levels, but (a) this isn't always advertised and (b) satisfactory results are, to some extent, in the ear of the beholder. Bottom line is that stuff rarely blows up, so long as you creep volume into new setups. So it's not all that surprising that a decent-quality multi-effect pedal (Boss ME-5) was easily swapped into the path. But if it's that easy...

    2. Signal separation. With all of the ways that the D-85 can slice, dice and combine signals (solo synth coupled to pedal, choral preset mixed to lower manual; banjo mixed with upper; symphonic chorus and delay independently set for all three, etc.) it seems a shame to lose that selectivity at the point of effect looping. It does make perfect faux-acoustic sense to put all of the upper-register stuff through a reverb--all those pipes and strings are in the same church, right? (I'm sure the drums would get ugly-muddy and pedals would overwhelm a 10" single spring, so they're exempted.) In contrast to that kind of piety, though, I'd like the purview to, say, single out the just the flutes and maybe the tuba for abuse. So I'm imagining a series of 'taps' that reach further back in the signal path than the reverb circuit to capture at least five distinct signals: e.g., solo synth, upper keys, lower keys, pedal, rhythm. I think I want to syphon these off after 'celeste' and 'symphonic chorus' treatment but, ideally, before sustain and the anemic reverb. (We are conditioned to hear time-domain effects happen to originating sources, not the reverse.) The tremolo is physical, so that switching logic diverts a final mix of certain signals toward amplification for that speaker. Likewise, there are two 'symphonic' (not to be confused with 'symphonic chorus') channels that play through dedicated speakers on the right and left sides of the cabinet with middling impact. This project would be pretty easy if I'd settle for two things: (a) using the channels as they are separated/mixed for piping to an external amp/tone cabinet and (b) using an external amp or tone cabinet.

    3. Returning signal to onboard amplification. However, since I (a) want more control and (b) have neither the room nor spousal-approval headroom for more big, wooden, noise-making boxes what I'd really like to pull off is a nifty panel of six or eight toggle switches that can throw any of the isolated streams out and back through a pair of 1/4" jacks. (Heck, while it's up on the lift, why not just make 'em three-way switches and have 'A' and 'B' loops?) The idea is for these signals to rejoin the regularly scheduled D-85 broadcast already in progress, so to speak. (So it's also not really desirable to just buffer the headphone signal, process it and play it back through the AUX In (or EXP In) jack with the jack-switched muting gate defeated so the speakers are live.)

    4. Latency. So long as they aren't passing through something as doughy as a computer half as old as the organ, there shouldn't be any latency problems, right? (Consumer-grade USB audio interfaces have achieved sub-10ms, which is in home theatre surround territory. I assume pedals and rack gear are practically zero.)

    5. Wiring. So I see that the run between the reverb pre/post amps and the unit proper gets shielded, but is that a special case or do all of these signals need shielding for any length of run?

    6. Levels (again). There is an assortment of resistors upstream of, for example, the main channel mixing pre-amp. I assume they are for balance and so it would be advisable to pick up signals between these and the pre-amp (if that's the right spot). The difference is between snipping wires and disconnecting/unmounting/desoldering/jumpering/remounting a vintage circuit board. (Maybe this is the kind of situation where those mysterious 'trim pots' come into play--put one into each path so levels can be...leveled...by trial and error instead of legitimate engineering?)

    7. Never use a switch when you can use a dial? Is a loop/bypass binary switch a lost opportunity to implement a wet/dry mix on each channel, similar to the current reverb level slider? Or is this an uninformed slide toward a half-assed homebrew mixing board that would be more sensibly implemented by means of the Real Thing? Not that I'm personally opposed to the Real Thing, but I know someone unlikely to endorse a rainbow of patch cables sprouting from YAT (Yet Another Toy)...

    This would be utter folly for someone of my enough-to-be-dangerous skill level without the schematic: block diagram for D-85 effects mixing, AUX in/out and amplification. (File is 1.4MB PDF of 50"x30" reasonably well-scanned image--I have the rest of the manual if anyone is interested. Hope that link works in lieu of attachment.)

    I won't belabour this already-long post further with my hunches about appropriate ambush sites. I think the best spots would be just before the Mixing Amps on board MA (coord. K 2-5), but that means jumping off from the PCB. It would be nice to nab them on their way to the board, but that gets them ahead of the pre-amping that the preset tones/voices apparently need and, more importantly, would return them before the Celeste and Symphonic Chorus IC fandango. I can't imagine those artfully digesting a stomped on signal, but as a prelude to stomping? Lovely.

    Thanks, in advance, for any insights. A singular Line Out seems de rigueur in Hammond circles (with a tone cab habit like theirs to feed, who can blame them?), but Yamaha has always chosen the over-engineered path to nirvana. Making this more complicated and futzy than it needs to be just feels like the right way to honour the instrument.

    p.s. On the subject of risk-level, I'm trying to skate between preserving the fun we're having with it (intact) and the excitement of tinkering and wringing even more fun out of it, as well as between the impulse to preserve the integrity of a piece worth preserving and the fact that I'm only into this for a hundred bucks and a six-pack worth of moving help. So, I'm willing to be intrepid, but not reckless. My goal is to not do anything I can't back out of without too much trouble.

  • #2
    gubbeen,

    That is a wonderful first post ! It sounds like an interesting project for sure. I have no advice to offer, but will be watching this thread as you go forth with it.

    Also, I love your writing style - fun to read.
    Regards, Larry

    At Home : Yamaha Electones : EX-42 ( X 3 !!! ), E-5AR, FX-1 ( X 2 !! ), US-1, EL-25 ( Chopped ). Allen 601D, ADC 6000D. Lowrey CH32-1. At Churches I play for : Allen Q325 ( with Vista ), Allen L123 ( with Navigator ). Rodgers 755. 1919 Wangerin 2/7 pipe organ.

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    • #3
      Welcome to the madhouse, gubbeen.

      The D85 is a forum favourite. We’ll be following your adventures with enthusiasm. You may find this long-running thread of interest.

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