Hammond M3- wiring out a line jack

[frenzy1971]

So I bought a 1959 Hammond M3 in great condition. I pick it up today. I've be researching them, and I know about locking down the tone generator before moving it. One thing I'd like to know though, is how to wire out a line jack. I found instructions on http://www.dairiki.org/hammondWiki

for two different methods, but both seem pretty darn complicated and have no pics.

 

Does anyone know where I can find pics detailing the process, and some more detail on the procedure?

Also is it better to wire out from the speaker or the phono input jack?

[coyote]

The line-out shown there is the most effective way to get the real character of the sound out to an amp. And it's not a complex circuit at all; if you follow that diagram you'll have exactly what you need. Any photo would likely be less clear than that diagram:

http://www.dairiki.org/hammond/pics/m3-line-out.gif

[Prague]

That looks like a good way to do it. You'll find that many headphone jacks on amplifiers are done in the same manner.

 

Use a high-quality 20k potentiometer. Match the line out level with another keyboard like a synth or something.

[Tedly Nightshade]

You will find the line out signal to be despicably dirty, noisy, nasty, and generally unpleasant to work with. We did this on our A100. It's amazing how all that hack sounds wonderful through a Leslie or a Hammond tone cabinet, or through the speaker in the organ. What do you want to do with it?

 

When we hooked up a Leslie to the M3 we used the speaker output.

[frenzy1971]

I don't have a leslie and don't see affording the 147 any time in the near future.

I have a tube driven Kettner & Hughes Rotosphere that is a pretty good stereo leslie simulator with speed and brake control.

I want to run into it from my M3 and from there to a keyboard amp with DI to the PA. It requires a 1/4" connection.

I'm pretty sure the only jack I have is an input jack, and from what i've read it isn't good to rewire it as output.

[jabney]

I have a difficult time accepting a speaker-level output as the only solution. To me, that is not line-level.

 

I have an M3 and a Motion Sound Pro 3T and we need to add an organ part to a song. Since I can't find a schematic for an honest-to-goodness line-level out put (I mean at pre-amp level, before the 6V6s, tranny, etc.) I think I may wind up recording the M3 and then re-amping through the Pro 3T.

 

What I would eventually like is to break the circuit somewhere between the output of the expression pedal and the grid of the final 12AU7 inverter tube; take the full signal out to the Pro 3T and then bring the L channel/mono lows signal from the Pro 3T back into the M3. Then a simple jumper from the new out to the new in would still allow the M3 to work on its own. Seems like it should be the best of both worlds.

 

Problem is, there are around four capacitors, four resistors, and a 12AX7 between those points, and I'm darned if I know the exact best spot to tap.

[S_Gould]

From what I've read, the best way is to take the signal right off of the expression pedal, and pad it with a resistor (sorry, can't remember the value right now). I've been meaning to try this with my M2, but somehow never got around to it after picking up a mint A100 (where I tap the preamp signal to go to my Motion Sound).

 

Scott

[Tedly Nightshade]

The great thing about using the speaker output is that you get all the nice vintage Hammond tube amp sound. I guarantee you it sounds "Hammondier" that whatever's in that Hughes and Kettner or whatever's in a Motionsound. You can just hook up directly to the speaker or crossover network in the Leslie or would-be Leslie.

[paully]

That 'phono-out/in' seems the logical place to tap the summed signal in the preamp, although I read somewhere that it is a better input than output, and therefor not recommended. It is a nearly direct connection (a cap sits in the path) to the grid of tube V4B (pin 7). It probably would work, if you don't mind the organ's internal speaker still playing at the same time as your Rotosphere. There is a workaround that allows the signal to be sent out, while breaking the path to the internal amp, allowing just the external to be heard. TREK II can supply a plug-in tube socket adapter, which breaks out the grid at pin 2, goes to a reverb, then returns the signal to the grid. You can get JUST the adapter W/O the reverb. It's around $35. It inserts between the tube and it's socket; neat and easy. A 1/4" jack could then be wired so that the signal path is normalled back to the tube when the Rotosphere is not used, allowing the internal amp to work. When a 1/4" cable is inserted, the signal is re-directed to the Rotosphere (as you want), and the signal return to the internal amp is broken (no internal amp sound). Switchcraft makes such a jack. Any good shop can figure out how to normal the jack. You can download a copy of the M3 schematic at:

 

http://www.captain-foldback.com/Hammond_sub/schematics/M3_early.zip

 

I've done this mod, so if you want to try it, PM me and I'll give you the wiring. Good luck, Paul

[frenzy1971]

Originally posted by paully:

That 'phono-out/in' seems the logical place to tap the summed signal in the preamp, although I read somewhere that it is a better input than output, and therefor not recommended. It is a nearly direct connection (a cap sits in the path) to the grid of tube V4B (pin 7). It probably would work, if you don't mind the organ's internal speaker still playing at the same time as your Rotosphere. There is a workaround that allows the signal to be sent out, while breaking the path to the internal amp, allowing just the external to be heard. TREK II can supply a plug-in tube socket adapter, which breaks out the grid, goes to a reverb, then returns the signal to the grid. You can get JUST the adapter W/O the reverb. It's around $35. It inserts between the tube and it's socket; neat and easy. A 1/4" jack could then be wired so that the signal path is normalled back to the tube when the Rotosphere is not used, allowing the internal amp to work. When a 1/4" cable is inserted, the signal is re-directed to the Rotosphere (as you want), and the signal return to the internal amp is broken (no internal amp sound). Switchcraft makes such a jack. Any good shop can figure out how to normal the jack. You can download a copy of the M3 schematic at:

 

http://www.captain-foldback.com/Hammond_sub/schematics/M3_early.zip

 

I've done this mod, so if you want to try it, PM me and I'll give you the wiring. Good luck, Paul

NICE! When I get courage to mod it, I'm sure you'll hear from me.

[frenzy1971]

Ok, so I've built the circuit, and am now ready to hook it in. The speaker has 4 wires coming off of it. What I have made from the above diagram has 2. It almost looks like the speaker has an a & b load with a- hot & grd, and b- hot & grd.

The wires are brown, grey, then green, black. I've hpt them stripped back and the brown and grey when I turned the organ on sparked together like a bat and grd touched would do. Should I try running the grey and green to the hot side and the grey and black to the ground?

[frenzy1971]

update- ok ran the green/brn and the green/blk. I am getting sound, but a low very noticble hum is coming out with the organ sound.

[Ricochet]

You've got a "field coil" speaker, which uses an electromagnet energized by the current drawn by the rectifier tube to supply the high voltage for the amplifier. It also acts as a choke to help smooth out the pulsations in that direct current. It makes a little bit of hum, naturally. That ripple voltage in the field coil is going to be picked up to some extent by the voice coil (which is close and parallel to it) and amplified by your second amp if you tap it straight off the speaker this way. You've GOT to make sure not to get the speaker wires mixed up. I don't know the color codes off the top of my head, but the field coil is the big one on the back of the speaker with the iron core.

 

If the hum bothers you, you're either going to have to do a conversion to a permanent magnet speaker (with a large 700 or 1000 ohm resistor, depending on which speaker you had originally, in place of the field coil), or use one of the other methods of tapping off a line-out instead of the speaker output. Have you tried the phono input? Many have found it to be a satisfactory output. And it sure is easy to do, with just a 1/4" to phono plug adapter that you can probably find for $2 at the Radio Shack.

[frenzy1971]

do i have to run both the field and voice coils? The secondary hum i get sounds like one of the pedals is held down

[alfonso]

Guitarists use devices capable of being proper loads for the speaker outputs of their amps that provide line level outputs, together with the possibility of hooking the speakers to them to have the full amp sound at reasonable levels. There are several, they must be matching the Ohms of the speaker...that would be the most natural and good sounding solution.

 

This one is said to be pretty good:

http://www.thdelectronics.com/products/hotplate.htm

 

Naturally your speaker must have a compatibile load, you have to investigate on device specs and your organ specs.

[Ricochet]

Originally posted by frenzy1971:

do i have to run both the field and voice coils? The secondary hum i get sounds like one of the pedals is held down

Yes, you have to run both the field and voice coils, else you must replace the voice coil with an equivalent resistance or your amp will be getting too much voltage and soon it'll short out its filter capacitors and go up in smoke or out with a bang, literally, as the overheated caps explode. The earlier Hammond field coil speakers had a 1000 ohm field coil resistance, but I think yours has a 700 ohm one. The DC current through it is 140 mA, and the voltage drop through it is 100V.

 

Personally I wouldn't do the speaker exchange, but lots of folks have done it. (I'm a fanatic for keeping irreplaceable antiques original, as far as possible.) At least, keep the original parts with it for future restoration.

[frenzy1971]

Hmm, I don't have a phono in jack, anywhere on the thing. I think I may hook t he speaker back up and attempt to mike it for now, until I can find someone who has actually sucessfully done the line out, and I will beg/pay/blackmail/threaten them to do it for me uless i can find a pre-made kit i can just hook the wires to. I don't have a leslie out either. Will miking it work? Do you get the dirt (distorted) sound just by tromping on the pedal volume?

[Ricochet]

There's a screwdriver-adjustable gain control on the amp that you can crank all the way up if you want a little extra "dirt."

 

Might experiment with miking the speaker from the back. It'll keep the mic out of your way as you play, and having it inside the cabinet may help shield it a bit from extraneous stage noise. (You may pick up a little bit of noise from the tone generator, if it's not a quiet running one.)

[coyote]

Once you build the circuit, it's no longer speaker-level. The circuit converts it to (approximately) line-level.

Originally posted by jabney:

I have a difficult time accepting a speaker-level output as the only solution. To me, that is not line-level.

[jabney]

Thanks Tedly, Coyote, Paully, etc.

 

I called Trek II and asked about buying the tube breakout. The gentleman I spoke with explained that because the tube they use in the M-3 is in a feedback loop, that I would not get the results I'm after. I was impressed by their integrity, and though I didn't buy anything today, said I hoped to be able to do business with them in the future (they have some nice stuff).

 

He did say that it should be OK to use a switch to choose using the speaker OR the resistor. So I started trying to figure out how many poles and decks would need to be in the switch itself.

 

Then it struck me: I could simply set-up a two-position toggle switch just ahead of the PM speaker. One position could send the signal to the speaker, the other position to a beefy 8 ohm resistor. Then I could build two iterations of the rest of the circuit that Coyote posted and have two outputs. One for when the internal speaker was wanted, and one for when it was not.

 

Can anybody think of any problems doing it that way? If not, then I think I'll try it. It's probably cheaper than trying to order a custom rotary switch, don't you think?

 

best,

 

John

[JMcS]

This might be what you are looking for:

The Hammond Tap Off Kit (5th item down)

 

http://www.speakeasyvintagemusic.com/cgi-bin/parts.cgi?page=hammondparts.html

 

Good Luck

[frenzy1971]

that kit looks like the way to go. When i get home i need to write down the serial and research my instrument. I think it may be older than 59. It's a M-3, model A-1. I had also thought about building a small padded box within the guts of the organ in the empty space to the right of the amp. In theory I would detach the big 15 speaker and mount it inside the box, and mount a mike directly across from it, pointing right at it, then padding the outside, so that I hear very little from the speaker. I would ideally hear more of the miked sound, going to my leslie sim, etc.

[coyote]

If I recall correctly, that kit conects to the speaker leads.

Originally posted by JMcS:

This might be what you are looking for:

The Hammond Tap Off Kit (5th item down)

http://www.speakeasyvintagemusic.com/cgi-bin/parts.cgi?page=hammondparts.html

Good Luck

[Tedly Nightshade]

Be careful switching speaker loads. It's very demanding and tricky to do, but it can be done.

 

Our M3 hookup had a 3 position switch- Leslie, Both, Internal speaker. Mostly we just kept it on Leslie.

[jabney]

Thanks Tedly,

 

I always forget whether it's tube amps that hate an open and don't mind a short or solid state amps. I am pretty sure the two types of amps behave in an opposite manner. I suppose if it's an open that tubes hate, then a make-before-break switch is the way to go, but those retro looking 'knife' switches look so cool :-)

[Ricochet]

Tube amps hate open output circuits and don't mind a short. Transistors are the other way around.

[jabney]

Thanks Ricochet,

 

I do plan on patching with the M-3 turned off, but you know what they say about plans :-) I'm starting to like the idea of using duplicate line-outs from the M-3. I will try to use a make-before-break switch if I can find one.

 

Any idea if the components other than the 20k audio taper pot ought to be of 'ultra' high quality? Any advantage in trying to use paper or polystyrene caps or is Radio Shack good enough?