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Hello all. Well, we wanted to remove the speaker in M3me's M3 and be able to use it as you would any console type Hammond. So, after searching Hammond-Wiki (there is some REALLY DANGED POOR advice in there .. be VERY careful with the methods described in that collection of .. uh .. info. Steaming pile of info, that is), and after looking into a good many "methods" of obtaining a line out from an M3, we elected to utilize The Admiral's suggested (and long proven) design. We did it our own way, but the general "scheme" is the same.</P>
Our M3 is an old one that uses a Field Coil speaker. These types of speakers use an electromagnet (a magnet that needs an electrical supply to be a magnet) instead of the modern permanent magnet type. So there are some "higher" voltage leads as well as the audio leads going to the speaker. A quick verification of The Admiral's info proved spot on. The brown and grey wires are the Field Coil wires, and the Green and Black wires are the audio signal wires. Do NOT confuse the two sets! This would be expensive, and perhaps dangerous. The idea is to remove the old speaker and still provide the power section of the onboard amp a "load" to work against. We also need to provide the audio output section of the amp a small load to keep it happy as well. </P>
You can see what we did here in this prototype. For the reduced outputaudio output section, Admiral suggested an 8ohm x 10 watt resistor for this, which we easily located. And for the Field Coil transistor dummy load, The Admiral suggested a 700ohm x 20 watt (or larger) resistor for this application. We located a 750 ohm x 25 watt finned resistor mounted in a heat sink for this....</P>
</P>As you can see, Field Coil wires come in on the left side of the pic and terminate directly there at the large 25 watt resistor. You're done with that part of the mod. The wires coming in in the middle are the speaker leads that used to be connected to the speaker. They go straight to a "switching jack" that's stereo. What this gives me is an "amplifier out" that will drive any 8 ohm-ish speaker load. When there is nothing plugged into it, the signal autoamtically goes to the other jack in the front of the box where the 10 watt load resistor is connected by default. As soon as you plug a speaker cord into the jack on the side, the signal isautomatically rerouted directly out of that side jack and on to a speaker. This way there is no time that the amplifier is left without a load attached to it. The rear-most jack is going to be for an onboard speaker that we will install later. So if you want to use the M3 like stock, you simply plug a short jumper from the rearmost jack to the other side jack which connects the power smp to the onboard speaker. The audio signal still only goes through the "speaker out" even if there is something pluggted into the "line out". The line out isn't made available until the "speaker out" is empty. Cool?</P>
So, in summary ... want to use the onboard speaker with the onboard amp? Run a jumper from side jack to side jack. Want to use the onboard amp to drive an outboard speaker? Run a speaker cord from the "Speaker out" kack to the speaker of choice. Want line out? Plug into the front jack and be sure to remove anything plugged into the "Speaker Out" jack on the side.</P>
Here's detail on the line out resistor ...</P>
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And here's detail on the switching "Speaker Out" jack. It's a switchcraft #14B....</P>
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And the Field Coil resistor....</P>
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Here it is being used to connect my Leslie 251 (which has no amplifier in it at all). I used it this way to use the onboard M3 amplifier to drive the 251. It sounded pretty darned good like this!. It's screwed down very solidly to the main wooden chassis, too. Nice clean installation. *Mystery Custom Box* look about it .. [:)]</P>
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Here it is connected to the "line out" jack. I've yet to build-in my own votage reduction circuit so for now I am using a very custom tweaked passive transformered DI. It works wonderfully.</P>
</P>Ok so here's a couple-few MP3s of it. I don't think I did too awfully bad for not having played keys in over 8 years. So forgive the awful technique and try (if you can) to listen to the tones. You'll hear chords drawn out too long ... I was tweaking something or writing notes whilst doing these demos, so ... And I've never in my life used a mic to record with so this is an ongoing education. Unfortunately y'all get to be punished until I get my mic recording act together. Enough excuses.</P>
On all the recordings, I used this condenser mic (MXL 990) approx 3 feet away from the Leslie, it's axiswas aligned pretty much right on with the upper rotor...</P>
</P>With this mic-preamp (btw, the mic pictured above came FREE with the below pictured preamp .. it was some special that Musician's Friend was offering for a short time .. so the pair was under $125.00 w/free shipping)...</P>
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The clip below is the 1958 (?) M3 with the above listed mods, using the stock M3 amp to drive my Leslie 251.</P>
www.farndurk.com/demos/m3-farnlineout-stockm3amp-drivingleslie.mp3</P>
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In the clip below I went out of the "line out" jack into the passive DI, and into this specially modded amplifier of mine that I modded just for my Hammonds (extra heavy duty transformers, less brilliance, a post-eq FX loop, and a post-phase-inverter master volume, as well as a few othyer little tricks ... NOT FOR SALE! ... EVER! [:)] ), and then straight into my Leslie 251....</P>
www.farndurk.com/demos/m3-farnlineout-farnamp-drivingleslie.mp3</P>
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And this last clip, linked below, we go out from the line out jack (no DI used), then on into a <U>TREK II OBL-2 Line Output Box</U>.That thingwas WAY hot, I had the knob nearly at minimum just to get it to clean up a bit. But other than that, it worked fine. A teensy bit "less bright" than my tweaked DI method...</P>
www.farndurk.com/demos/m3-trekiilineout-farnamp-drivingleslie.mp3</P>
So, you choose for yourself as far as which signal reduction method you use and end the myth and mystery. To me they all sound pretty close to one another. Even mine seems to sound no better than any of them (I think it's because we're dealing with such a "lo-fi" circuit to begin with that subtle changes in reduction circuits are nearly indiscernable). The DI costs less than $30, the Trek II is more than $75.Everwhat. In defense of the TrekII, it has 'gator clips to easily "undo" your connections, it has 4 screwholes to mount it underyour TG shelf, and it's built fairly well. Should live as long as the Hammond it serves. On the other hand, "transformer" style signal reduction ensures proper impedence levels all the time, and are generally nicer to your gear in the general sense of things. The Farndurk system will be transformer style, you can bet on that. No "second best ideas" here, goodfolks! Compromise sux.</P>
Most importantly, The Admiral's suggestions work FAMOUSLY!!!!!!!!!!!!!!!!!!!!!!! Thanks TONS, kind sir! The only thing about it .. is that the little sucker gets pretty hot. That large resistor could be a bit larger wattage, and it could/should be mounted outboard/in air flow. Thee entire box gets almost the exact same outter temp as the amp chassis does. You can hold your hand on it, but it's kinda uncomfortable doing so. The large aluminum box serves well as a good heat sink, even better had I used Heat Sink Compound between the resistor and the aluminum enclosure.</P>
Hope this exercise was of some help to someone other than me! I was most certainly surprised at how well the stock M3 amp (old AO-29) drove the Leslie speakers. Pretty sweet! Audio-interface clipping notwithstanding! (Sorry .. I'm such a novice at all this).</P>
Numb-In-The-Head ... Farny ...</P>
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