Linn LM-1 Drum Machine

via this auction

"Linn LM-1 drum machine, serial # 365. These are relatively rare, as only approximately 500+ were ever built. This model was the first commercially-available EPROM-based digital drum machine with 8-bit sampled sounds. Designed by Roger Linn in the late 1970’s, this drum machine holds a place in history, basically laying the foundation for sample-based sounds within popular music. The concept and execution was so popular that it spawned a large number of imitators by Oberheim, Prophet, EMU, Alesis, Kawai, Korg, Roland, et al.

While this is a digital drum machine that uses 8-bit EPROM based samples run through companding DACs, nothing really sounds like the LM-1. I have an Oberheim DX and DMX, Sequential Drumtraks, Emu Drumulator and SP-12, and a Linn LM-2 Linndrum, and in my opinion, none of them can mimic the LM-1. The snare and bass have a very solid fat sound, and the hi-hat is very unique: the hat sample is constantly running, and the difference between the open and closed sounds is merely a long or short analog envelope applied to the sample output, respectively. So even with metronomic triggering, the hi-hat has some ‘feel’ since the envelope is applied at varying points in the playing of the sample. Finally, there’s actually some analog processing inside to smooth out some of the ‘rounder’ sounds: the toms and the bass get processed by a classic CEM 3320 VCF chip.

Here are the basics:
- 9 voices:
- Bass (2 volume levels)
- Snare (2 volume levels)
- Hi-hat (2 volume levels and an open hat)
- Toms (2 tuning levels)
- Congas (2 tuning levels)
- Cowbell (1 volume level)
- Tambourine (2 volume levels)
- Cabasa (2 volume levels)
- Claps (1 volume level).
- Individual ¼” outs for each drum sound
- Left/right mix ¼” out for the all voices (though both outs are same mono mix)
- Start/stop foot switch input ¼” jack
- Internal clock output ¼” jack (48ppq in HiRes setting)
- Tape sync to/from ¼” jacks for sync’ing with recorded tracks
- Tape storage to/from ¼” jacks for drum pattern data storage
- External Clock In ¼” jack (48 ppq)

So what’s different about this particular LM-1? Well, one of the terrific features of the Linn LM-1 was the external tunability of the voices, each with its own knob. However, this tunability wasn’t apparently conceived as a performance feature, but rather as set-the-tuning-per-song, so the tuning pots were located on the back. Not only were they very difficult to reach from the front, it was difficult to guess at which voice you were tuning.

A fellow named Tom M. came up with the idea to replace the limited, hard panning switches on the front panel (all-to-the-left OR all-to-the-right OR center, nothing in-between) with the tuning pots for each voice. That’s a terrific idea and one I’ve seen on a few LM-1’s.

So I adopted that here. This LM-1 has tuning pots on the front panel, right above the label of the drum, so there’s no confusion about which drum tuning you’re adjusting (see the pics). The last “tuning” pot, which sits above the Click, is actually the open Hi-Hat decay adjustment. I used Kilo knobs that match the very nice original Alco knobs that are used for Tempo and Volume. This modification makes the LM-1 a lot more fun to play in real-time.

This tuning mod is possible, because those 3-position panning switches were OFF in the center position. So not having the switches connected means all voices are tuned to the center of the left-right pan. But the LM-1 has individual outs, so the need to use the native stereo mix from the LM-1 seems almost unnecessary today. If you want a mono mix, you can now get it at the Left or Right output at the rear of the machine. And serious LM-1 users will choose to bring individual drums through their individual outs to an external mixer, for compression, EQ, etc.

I put hole plugs over the now vacant holes in the back of the chassis where the old tuning pots used to be, as well as replaced the old chrome hole plugs that were in some of the abandoned holes in the back. So now the rear panel has a clean look (see the pics).

Here’s a video demo of this LM-1:

Linn LM-1 with Front Panel Tuning

YouTube via rolandsh1000

What else is different here?
- I replaced ALL the sliders with newly-manufactured versions of the same design. The old design were CTS sliders, the kind also used on ARP synthesizers, and tended to age notoriously badly. These new ones are much better, and lubricated with silicone grease. They are supplied these days for ARP synthesizer refurbs by synthrestore.uk.

- I’ve replaced all the electrolytic capacitors on the voice and processor boards with new ones, with equivalent or higher voltage ratings.

- I replaced all the electrolytics on the power supply, again with new ones of equal or higher voltage ratings. I also adjusted the power supply to provide the correct voltages to the circuitry.

- I’ve replaced the internal NiCd batteries with new ones of similar capacity (see the pics), as well as replaced the battery holder which had corroded.

- I’ve replaced the power switch with the closest modern approximation to the old design; it’s dimensionally identical to the old one.

- I replaced the 3-prong IEC power jack, which was corroded and near breakage. In doing so, I also rewired the connections to the power supply and fuse from the 120VAC jack and power switch.

- I repaired the volume pot with newer dual audio 10k potentiometer modules: the originals were Allen-Bradley units, which Clarostat took over some years ago. I used more recent Clarostat equivalents, which operate smoothly with no scratchiness.

- I replaced various nuts and bolts around the unit which had either corroded, stripped, or otherwise.

- I opened up and cleaned all the front panel drum and control buttons as gently as I could, since these buttons are pretty much irreplaceable. They all trigger consistently now.

- I restored the External Clock In jack with a Switchcraft ¼” jack, normally-closed mono, per the original schematic. Any 48ppq input can now run the LM-1.

All buttons work well with no double-triggering. All sliders work cleanly and clearly, with no scratchiness. I’ve checked out almost all of the functions per the user manual (available for download on the Yahoo Linndrum group) and everything seems correct."

via Brandt

Update via thegoodbutcher in the comments: "Just to correct the mistake in that listing:

the guy who runs the iSatellite website is the fellow who first had the concept for moving the pitch pots to the front panel. He prototyped it using 808 pitch knobs on his LM-1.

Tom M. was the guy who did the first full blown version of the mod, after conversations with a mutual friend of iSatellite."