My Completed Sequentix P3


The Sequentix P3 is a step sequencer with analog pots for entering notes and other data. It was originally sold both as a kit and assembled, but recently (most likely due to RoHS legislation) it is now only available wholly assembled.

The About P3 section of the Sequentix site states begins:

The P3 Sequencer is an 8 track, hardware MIDI sequencer, with a user interface comprised of knobs, keys and LEDs. A sixteen character by two line PLED display provides confirmation of pattern data and access to advanced features and configuration options.
P3 allows real-time control of track mutes and simple pattern or pattern chain selection across multiple tracks, plus analogue-style editing of patterns. Each of its 384 patterns has independent values for note, velocity, tie, gate, length, gate delay, and a combination of up to four MIDI controllers, extra notes, or 'auxiliary events', per step.

I've never really cared for sequencing music by clicking around in a computer so I figured that a hardware sequencer would be especially useful for me. With my recent building of (all too) many MIDI-controlled synthesizers I was also needing something other than a keyboard for triggering them, so when I had the unexpected chance to purchase the parts for a P3 and built it myself, I jumped at the chance. In the end it cost a bit more than I'd originally planned, but it seems worthwhile thus far.

P3 End of Life

On September 5th, 2006 Colin Fraser posted a message on the Sequentix Music Systems News Release page stating that the P3 will soon be out of production. The release states:

It's been just over a year since the P3 Sequencer was launched as a production unit.
We have sold well over 100 units in that time, and the response from users has been excellent.

However, due to a number of factors, we have decided to cease production of P3 after the current run is sold out.

The main reason for this is that a thorough review of the numbers shows P3 is simply too expensive to produce.
All units built so far have been assembled in-house.
The amount of effort this requires has meant we have been unable concentrate on developing future products.
Fully out-sourcing production of P3 in its current form would mean a significant increase in the final price - it just wasn't designed to be cheap to manufacture, with a large number of separate circuit boards, internal wiring, and a complex case design.

Ceasing production will give us the opportunity to take the lessons learned from P3 and develop a replacement product that can be made and sold at a viable price.

In the meantime, we expect the remaining stocks of P3 to move quickly.

They will be available until stocks are exhausted, direct from Sequentix, from our US dealer Analogue Haven, and our German dealer Schneiders Buero.

Later, on September 7th a new post was made stating:

All remaining units are now spoken for.
There is a reserve list in case anyone decides not to follow through on an order, so there is a small chance if you are quick...

So, it sounds as if they are all gone.

According to a recent posting by Colin Fraser on the analogue-sequencer Yahoo! Group, after the final Sequentix P3 is shipped there will have been 137 production units made. An additional 24 pre-production P3s were made and there were a total of 86 kits sold. Assuming that all kits were assembled, there are only 247 (at most) P3s in the world. So not only is this an interesting, fairly unique sequencer, it's somewhat rare, too.

Rackmount Sequentix P3


Around April 2006 a few remaining sets of P3 PCBs surfaced and were made available for purchase through analoguehanven for US$249. I purchased one of these and let it sit in my basement for a few months.

After directly contacting Colin Fraser, the creator of the P3, I was able to purchase one of the pre-made enclosures for the P3 from him. This enclosure kit also included Cherry keyswitches and keycaps which were custom-labeled for the P3. While the price of US$339.55 plus $77.62 postage (after exchange from GBP) seemed a bit high at first, when I took into account the time it would take to design my own enclosure, locating the switches, and the cost of having a custom front panel made, and the price seemed pretty reasonable.

With another US$200 or so in parts from Mouser, Digi-Key, and Jameco I had everything needed to assemble the P3.

Assembly went very smoothly, and except for an issue with the clearance of the top pot board (which turned out to be a known assembly issue) there weren't any problems. The PCBs are fairly simple and assembly was easy with the most difficult part being the making of jigs for the keyswitches on the step board and keypad board. This is definitely one of the easier kits I've assembled.

There are various photos of the construction of my P3 available, all of which can be seen in the Gallery album entitled Sequentix P3. Specifically, there are separate albums showing some of the parts used, various photos of the assembly in progress, and a few of the completed Sequentix P3.

On November 15th, 2006 the wooden end cheeks for the Sequentix P3 arrived. These took a few minutes to install and have really polished off the look of the P3. Images of the completed Sequentix P3 have been added to the latter half of the completed Sequentix P3 photos. While the rackmount version is nice, I greatly prefer the smooth, finished look when the wooden end cheeks are fitted.

Bill of Materials

This bill of materials details all parts which I purchased from US suppliers and used for the assembly of my P3 with the v1.6 PCB set. As of the time when I started this project there was no coheasive BOM for the v1.6 of the P3 PCB set, so hopefully others will find this useful. This was initially based on the v1.52 BOM posted to the Sequentix P3 Yahoo! Group by Colin, but since many of the parts are no longer available I'd made some changes.

Most parts are from Mouser. Digi-Key was used for a few harder to find ICs and the switching slim wall wart-type power supply was purchased from Jameco. The PLED display is from Crystalfontz. Listed part numbers link to the product pages at the various vendor's sites.

Note that not all parts are RoHS compliant, so anyone ordering components from the EU may want to pay attention to what is being ordered.

In my assembly I did not have the proper length LED standoffs available to me when assembling the Function Switch Board, so I stacked two shorter standoffs. The specified .32" standoffs should be the appropriate length, but it is suggested that you order a few similar sizes and see what fits best.

When doing the final assembly on my P3, I found that the case wouldn't close. It turned out that the top Main Pot Board hit the back of the case, keeping it from closing. I found that if one bends the top board back against the housings and makes the connecting cable a slight bit longer (maybe another 5mm) everything fits great. In some email sent with a great degree of synchronicity, Colin confirmed that this needs to be done on some P3s, depending on which pots are used. Keep this in mind when building a P3. In order to make connecting cables easier, you may also wish to mount the 16 Pin header on the opposite side of the PCB.

Main Board

Main Board

 Part Name on PCB   Value   Part Number   Quantity 
C1, C2 33pF 81-RPE5C1H330J2P1Z03 2
C4 150pF 81-RPE5C1H151J2P1A03 1
C6, C8-C12, C14 100nF 80-C322C104K5R 7
C5 10nF 140-PF2A103G 1
C3, C7, C15 10uF 140-L16V10-RC 3
C13 1000uF 140-XRL25V1000-RC 1
VR1 10KΩ 531-PT10V-10K 1
R10-R13 100Ω 271-100-RC 4
R18, R21, R25, R26 10KΩ 271-10K-RC 4
R19, R27 10Ω 271-10-RC 2
R-9 150Ω 271-150-RC 4
R1, R32-R36 220Ω 271-220-RC 6
R23,R24 22Ω 271-22-RC 2
R14-R17 4.7KΩ 271-4.7K-RC 4
R2 510Ω 271-510-RC 1
D1 5.6V Zener 512-1N5232B 1
D2 1N4148 512-1N4148 1
D6 1N4001 512-1N4001 1
U1 AT89C51ED2 Ships w/ PCBs 1
U2, U3 62256 428-1782-ND 2
U4 74HC573 512-MM74HC573N_Q 1
U5,U8 74HC138 512-MM74HC138N 2
U6 DS1210+ DS1210+-ND 1
U7, U10, U11, U15 74HC574 595-SN74HC574N 4
U9 74HC245 595-SN74HC245N 1
U12,U13 74HC241 296-8271-5-ND 2
U14 ADC0804 ADC0804LCN-ND 1
U16 4051B 595-CD4051BE 1
U17 6N139 512-6N139 1
U18 7805 511-L7805ACV 1
U19 PIC 12F629 Ships w/ PCBs 1
U20 74HC04 511-M74HC04 1
Q2 BC547B 512-BC547BTAR 1
F1 500ma FUSE 652-MFR050-LF 1
J1 3 Pin Vertical Header 538-70543-0002 1
J6 4 Pin Vertical Header 538-70543-0003 2
J2-J5 16 Pin Box Header 517-30316-6002 4
XTAL1 24 MHZ 520-HCU2400-S 1
VB CR2032 525-E-CR2032BP 1
VB PCB Cell Holder 534-103 1
L1, L2 Ferrite 81-BL01RN1A1D2B 2
U6, U17, U19 8 Pin DIP Socket 575-193308 3
U20 14 Pin DIP Socket 575-193314 1
U5, U8, U16 16 Pin DIP Socket 575-193316 3
U4, U7, U9-U15 20 Pin DIP Socket 575-193320 9
U2, U3 28 Pin DIP Socket 575-193628 2
U1 40 Pin DIP Socket 575-193640 1
U18 TO220 Heatsink 532-504102B00 1
U18 TO220 Mounting Kit 532-4880 1

Step Board

Step Board

 Part Name on PCB   Value   Part Number   Quantity 
D1-D16 1N4148 512-1N4148 16
D17-D32 Dual-Color LED 604-WP59EGW 16
D17-D32 LED Standoff 593-STD250B 16
J1 16 Pin Box Header 517-30316-6002 1
S1-S9 Keyswitch Ships w/ Enclosure 9
S1-S9 Keycap Ships w/ Enclosure 9

Keypad Board

Keypad Board

 Part Name on PCB   Value   Part Number   Quantity 
D1-D9 1N4148 512-1N4148 9
J1 16 Pin Box Header 517-30316-6002 1
S1-S9 Keyswitch Ships w/ Enclosure 9
S1-S9 Keycap Ships w/ Enclosure 9

Function Switch Board

Function Switch Board

NOTE: Square pad on LED pads is anode. This is commonly the longer lead on the non-flat side of an LED.

 Part Name on PCB   Value   Part Number   Quantity 
D1-D4 Green LED 604-WP7104PGD 4
D5-D8 Red LED 604-WP7104ID 4
D9,D10 1N4148 512-1N4148 2
S1, S2 Keyswitch Ships w/ Enclosure 2
S1, S2 Keycap Ships w/ Enclosure 2
J1 16 Pin Box Header 517-30316-6002 1
J2 2 Vertical Header 538-70543-0001 1
D1-D8 LED Standoff 593-ST320B 8

Main Pot Board

Main Pot Board

NOTE: There are two Pot Boards, Upper and Lower. Part names are duplicated on each.

 Part Name on PCB   Value   Part Number   Quantity 
VR1-VR16 10K Linear 31CA401F 32
C1, C2 100nF 80-C322C104K5R 4
U1, U2 4051B 595-CD4051BE 4
U1, U2 16 Pin DIP Socket 575-193316 4
J1 16 Pin Box Header 517-30316-6002 2
VR1-VR4, VR9-VR12 White Knob 550-67005 16
VR5-VR8, VR13-VR16 Gray Knob 550-67003 16

I/O Board

I/O Board

 Part Name on PCB   Value   Part Number   Quantity 
MIDI IN, OUT 1-4, SYNC 5 PIN DIN Socket 161-0504 6
J1 16 Pin Box Header 517-30316-6002 1
R1-R5 220R 271-220-RC 5
F1-F10 RFI Filter 81-DSS306Y5S102M100 10

Data / Tempo Pot Board

Data / Tempo Pot Board

 Part Name on PCB   Value   Part Number   Quantity 
TEMPO, DATA 10K Linear Pot 31CA401F 2
DATA White Knob 550-67005 1
TEMPO Gray Knob 550-67003 1


 Part Name on PCB   Value   Part Number   Quantity 
  PLED Module CFAP1602A-Y-JCV 1
A1 16 Pin R/A Box Header 517-30316-5002 1
A2 PCB Header 517-6111TG 1

Power Input

 Value   Part Number   Quantity 
Power Switch 103-R13-112A-02 1
2.1 mm Power Socket 163-4302-EX 1
9VDC Power Supply 252751 1


 Value   Part Number   Quantity 
16 Pin IDC Plug 517-8916 11
Crimp Terminal 538-16-02-0097 17
16 Place Ribbon Cable 517-3365/16FT 2
2 Pin Single Row Plug 538-50-57-9402 1
3 Pin Single Row Plug 538-50-57-9403 1
4 Pin Single Row Plug 538-50-57-9404 3

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