The Inpulse One is a surprisingly rare drum machine featuring 8 velocity sensitive pads, playable with hands or sticks, plus an insanely easy to use drum sequencer, crude MIDI, SMPTE timcode implementation and 256KB RAM. Sadly only 140 or less were made before production ended, and finding parts, extra sounds or information is next to impossible.

Back in 2002-2004 this page was put online to try and find the machines in the wild, track down tapes and document an often overlooked bit of musical technology history, since when Allen & Heath have put their own pages in place for the Inpulse One:

The current page, with original brochure and user's handbook can be found here.

And their historic "Veterans" page is here - though their serial numbers are incorrect - they actually started at 1000-1089 with a further batch of "around 20" made following MIDI improvements, which were retrofitted to many of the older units.

Since acquiring this some time ago, I've had contact with perhaps 3, maybe 4, owners and the designer - not one of the other owners I have spoken to has a working machine.

In 2004 my retrozone article appeared in the August 2004 Sound On Sound. In has not been possible to correct some small errors in there, but they are corrected on this page and will continue to be as more information is gathered.

The article is incorrect in that the Simon at Livingston Studios would have been Simon Bohanon, not Simon Jones (which could be a subconscious attempt by H2G2 to break out of my head in print).

Since this page was originally created in 2004, a few new bits of information have come up.

Contributors to the history, creation and understanding of the Inpulse One and in some cases information contained on this page include:

Allen & Heath Brenell people:

Glenn Rogers, MD
Alan Robinson - designer
Steve Bell - the mysterious "045" of Allen & Heath fame - the engineer that assembled the machines, hence the 045 stickers you'll find
Mike Clarke of Allen & Heath, who arranged permission for the media to be shared and tried very hard to track down more information and technical documentation

Livingstone Studios people:

Nick Kinsey, owner of Livingstone Studios at the time
Simon Bohanon - who has clarified some more about the means of getting samples into the Inpulse One
Robert Henrit - sound engineer/consultant, and has also provided a great deal of insight into the system

(quick plug: Robert's got a book out - Banging On!)

Barry (Clempson?) - one of the consultants recording sound, who sent sample tapes to another person involved - Andy

Sounds were sampled for the Inpulse One using a combination of an Apple //e computer and an AMS DMX 15-80 - a studio grade delay unit with a fifteen bit sampling circuit. The memory of the AMS was read using a dummy memory card, by the Apple //e. Chances of me recreating this are slim, the AMS is still an expensive and rare device.

Users of the Inpulse One:

It is fair to say that verified accounts of musicians using the Inpulse One are as rare as the machine itself. Naturally Robert Henrit is one user, as he created many of the samples for it. Bill Nelson is known to have used one on the iconic 1986 album "Getting The Holy Ghost Across ", now released on CD for the first time. He discusses it in an interview with Sound on Sound in 1986 and hints at the long gestation and time taken for the machine to reach the market. At some point in history, I found a reference on usenet or a forum somewhere that suggested Ed Vargo of T.H.D used one, though can't contact or verify that. 1045 I am fairly sure I bought from Mark Jenkins, an electronic/prog music producer in the UK. None of my recordings have been released.

Experience the Inpulse One's Sound now!

The Inpulse One is now approaching 30 years old and it remains overlooked. For owners of the Teenage Engineering OP-1, I have produced a couple of drumkits ready to use with the sounds I have currently. These are clean recordings from a working Inpulse One, and are ready to go - compare them to the kits available from other machines of the era!

You can download the kits here, along with a list of instrument/sample names and keymapping.

Please note: I do not own the copyright for any materials other than my own presentation and articles - the sound files and data are the original works of Allen & Heath or the team at Livingstone Studios and related consultants and suppliers to the Inpulse One. I have been given permission to redistribute these for the purposes of helping Inpulse One owners find new sounds, and keeping the history of this unusual drum computer alive. Whilst I'm sure no issues will arise of any fair use of these creations, do not copy and resell them in commercial sample libraries. Will we track you down? It's unlikely, but I do regularly search for new information, forum posts and mentions of the system.

If you want to share this with other drum machine enthusiasts, please link to this page so the full story is told. That's all I ask.

Sound Tapes and Samples

In 2002 Mike Clarke, Technical support of Allen & Heath was assisting me in finding tapes/data - and did find a copy brochure and manual, which Allen & Heath still host on their website. He gave me permission to redistribute tapes for Inpulse One users, so I am trying to find as many as I can.

Where available, the table below will have both the sound sample in AIFF form and the data from the tape - the data files for this website are not recorded from the tapes, but have been loaded into my Inpulse One, then resaved as a single set of data. At the moment these are large AIFF files - if smaller formats preserve the data's ability to load over the tape interface they'll be used in future.

Tape Loading is fun, and involves a lot of tweaking of levels to get it right. If you can find one in good order, an old home computer tape recorder with a speaker that works during playback even when an earphone lead is connected will make all the difference.

Inside the AHB Inpulse One

Allen & Heath make mixers that are designed for serious, long-term service. The Inpulse One did not attempt to break away from that format. Remove the screws holding the two control panels, and you will be faced with this:

To the best of my knowledge, there are no custom chips in the system.

Replacement ROMs could be available through AHB; if they are, or they give me permission to dump the ROMs in my own system, I will provide images and details here of how to blow your own to avoid bit-rot. That white battery almost directly in the centre is apparently the cause of death for many Inpulse Ones, btw - I intend to have mine replaced ASAP as a preventative measure. The Inpulse One is built like a tank, so the soldered battery is not really drama.

To replace the battery:

Your Inpulse One has a 3.6V NiCD battery nearing 30 years old Here are the batteries of 1045 and 1058 respectively... and this is several years ago.

Unplug the Inpulse One. The PSU electronics are exposed, so it's not just for protection of the machine.
Undo the four screws on the side of the control panel. Lift the panel to one side, the earth cable on the left (machine facing you) limits movement so be careful.
Undo the six screws on the side of the drum pad panel and depending on the state of your machine, either the three screws on the top or the three screws under the shield at the back, near the output ports.

The image below shows why you want to lift the output board AND the top panel together, even though the three black screws are partially obscured. This is the output board in place, with four ribbons linking the pad boards to the output board and the earth wire linking it to the chassis. These ribbons are also on the least reinforced areas on the machine.

Also, see that capacitor? Don't touch the contacts. Seriously.

If you have undone the three visible screws on the top, be very careful, slide the panel towards you just enough to reach the three black screws securing the output board. Slide it back, and refit the three screws securing the output panel to the drum pad panel.

The top panel is now attached to the drum machine by one earth wire and two ribbon cables. The ribbon cables can be detached by pushing the two clips outwards - they may be stiff, but be cautious and steady. The pins will lift straight out if you do this correctly. I usually disconnect the ribbon cable at the output board in both cases.

Whilst in there, check the condition of the pins on the connectors - 1058's were badly corroded.

Now remove the MIDI board. Two screws go through plastic standoffs, then a small locknut secures it on the lower right corner. Unto the ribbon cable from the port on the PCB, noting orientation if it's not already marked, detach the ports (they should be labelled In and Out) and take it away. Remove the short plastic standoff from the stud as it gets in the way of detaching the ribbon cables, but don't forget to refit it.

Now you have the MIDI PCB out of the way you can detach the power cable - mine has a bent pin that looks like a factory mod to disconnect part of the board or avoid issues with an unused pin. Orientation is VERY important on this!

Detach the two ribbon cables from the computer board linking it to the DMX board - the larger one can be very stiff.

Finally, remove the black screws securing the computer PCB to the chassis. The battery is a commonly available 3.6V Mempack, for which Varta and others make direct replacements. It's easy to solder as the board is straightforward, and unless you're incredibly unlucky leakage won't have hurt the machine, and any damage in that area can be repaired.

Reassembly is the reverse, with the caveat that you need to watch those ribbon cables, and remember to put the screws through the MIDI board and slide the longer 2 standoffs on before refitting. I take pictures at every stage.

Still having trouble?

This is not an exhaustive repair guide, but some erratic behaviours I have seen include:

Entire front panel flashing, refusing to boot: Poor connections to power, battery coming up to operating charge, and 100mA 20mm Fuse on Power Supply PCB.

Drums not working, but everything else looks good: -5V fuse (400mA 20mm, on rear of machine) blown.

Patterns not programmable: Refer to the manual - after erratic junk gets into the memory, it can play up - delete patterns. You can only step-sequence a pattern of 4 bars or less.

Unusual pitch behaviour: This should not happen, but the corrupt memory as the battery fails can also cause MIDI mapping issues and similar. Press HOLD and 0, then tap a pad - the key range assigned will be displayed. Press "RES" to reset, then press FROM - on your MIDI keyboard/controller, press the key you want to start a range from. Then press TO on the front panel, and the corresponding end of range note on the MIDI controller.

Pressing Pat and the two pitch keys will enable pitch changes from MIDI. It's a bit odd, but kinda works.