Tuesday 14 December 2021


 My prototype Moog 901B in 8hp of eurorack. 2 PCBs, all thro' hole. The rear PCB holds the oscillator, the front PCB holds the sockets, pitch control, range switch and range caps (plus an op-amp as I've added a PWM input).Two Molex connectors on the rear are for the "bus" from the 901A controller, plus one with all of the outputs on it.

The extra pot and wiring in the pictures is because there is (as yet) no 901A controller - the design for the 901A is ready, but no point in proceeding with it until I had a working oscillator!

The output:

(any glitches visible on the triangle and sine are because I don't yet have all of the range caps installed - these are also used for filtering the triangle waveform).

While the prototype uses thonkiconn jacks, I'm swapping it (and the 901A) to use PJ3410's, as the Alpha rotary switch sits higher on the PCB than I had originally envisaged. I could also do with using a longer shaft pot for the pitch control.

Friday 19 November 2021


Some of our front panels are currently in short supply.

We are therefore providing complete files for  "Front Panel Designer" to allow customers to order panels directly from Schaeffer AG.


Please note:

  • We have no affiliation with Schaeffer AG.
  • While these files utilise the same FPD files and print graphics that we use for our own panels, we have not necessarily ordered these specific panels ourselves from Schaeffer AG.
  • For personnal, non-commercial, use only.


Currently available: 


100m-ish LFO

Silver Ano panel with Black graphics  

Black Ano panel with white graphics    


100m-ish Audio Delay

Black Ano panel with white graphics    

(We have plenty of stock of silver ano panels with black graphics)  


100m-ish VCO Driver

Silver Ano panel with Black graphics 

Black Ano panel with white graphics   

Polymoog Resonator 

Silver Ano panel with Black graphics

Black Ano panel with white graphics

(While "Moog" is a registered trademark, in the UK "polymoog" has not been regiistered for a number of years.)                          

Black Ano panel with white graphics 

To match Behringer System 55.    

Saturday 18 September 2021

Behringer 904A filter with the AMSynths daughter board installed - this swaps out the Behringer capacitors for matched lower value polyester capacitors as used in the late 60's Moogs. 

Took about an hour to convert - most  of that time was spent removing the original Behringer capacitors (they are thru-hole, the rest of the Behringer circuit is surface-mount). Just used solder sucker and braid - no fancy desoldering station needed.

This now sounds very very nice!

Thursday 16 September 2021

 Just arrived - my first two "Moog" PCBs to complement the Behringer System 55 modules.

The left hand PCB is the "control voltages" section of the Moog CP3/992 modules - this can be used as part of a Eurorack CP-style module, or for a 992 Control Voltages module to drive the 904 series filters. Note that my PCB differs from the Behringer CP3-O and 993 modules:

1. There are no front panel inputs or outputs - the PCB is designed to support "Trunk Lines" as in the original Moog Modular, but using Molex connectors on the back of the PCB.

2. The "Ext Input" is an attenuverter  (or "Reversing Attenuator" in Moog-speak): Moog and Behringer have an attenuverter on the 992, but only an attenuator on the CP3-O. I've also added the option to normalise the Ext. Input to +6V - useful for switching in pre-set transpositions etc.

On the right is a dual purpose Mixer PCB that can be configured as either the CP3 (transistor based), or as the CP3A (op-amp based). The PCB supports the "click filter" for the CP3 option (missing on the Behringer CP3A-M module!), and optionally a performance control (SW2 on the PCB) to mute channels 1&2 or channels 3&4. I will be combining both of these PCBs behind a panel to make "CP3" modules, but the Mixer PCB can also be rotated 90 degrees to form a stand alone (16HP) mixer module

Wednesday 18 August 2021

 I recently purchased a Behringer 914 (Moog modular in Eurorack format) Fixed Filter Bank module, for a price so low that I couldn't build it for the price. I subsequently bought the Behringer 960  Sequential Controller, a 921 VCO, a 904A low pass filter, and I'm waiting for a 902 VCA to be delivered.

I just completed assembly of the (excellent!) AMSynths AM984 Four Channel Mixer PCB, this is now waiting for a panel.

Note that, as designed, the Mixer draws approx. 60mA per power rail (Rob of AMSynths has confirmed this) and hence the 79L06 regulator runs "warm" - use of a TO92 clip-on heatsink is recommended.

I'm planning on developing the following DIY modules to match the Behringer "Moog" series:

  • 995 Attenutators (panel only) - the Behringer module is overpriced IMO.
  • 994 Mults - ditto
  • 993 Filters, I have a small stock of vintage "tropical fish" capacitors. This will be DIY (PCB, panel) only, as AMSynths already sells an assembled version of this module.
  • 992 control voltages - as the Behringer module, but without the front panel jacks for "behind the scenes" CV buses.
  • 901B Oscillator and 901A Oscillator Driver. This is the original Moog modular VCO, which has a number of "quirks". It needs rare parts - I already have my personal stock of CA3019's waiting.

Prototype for a 10HP CV to MIDI (not MIDI to CV !) converter. Driven by an Arduino NANO, the software will be open source in the true sprit of "DIY" - if you don't like it, change it.

Five front panel CV inputs, plus an optional one on the PCB. All of the panel controls (including "attenuverters") are software controlled, so can be re-assigned to other functions if required.

The 26-pin connector is for a "Waveblaster" compatible MIDI sound generator card (available commercially, a DIY version is under development).

The module is also designed as a general purpose Arduino based development platform, so has optional sound input, PWM sound output (MOZZI compatible), MIDI input.

Tuesday 30 March 2021

Got a couple of surface mount components in the wrong size, which enables an interesting comparison:

                                               (L-R: UK penny, US cent, Euro cent)

Note that the Imperial 0603 and 0402 size designations are also valid Metric ones (but two sizes too small).

Tuesday 19 January 2021

 TR-EX panels in Stock

I now have stock of 1.6 mm Aluminium panels (white on gloss black print) for the TR-EX expansion module for the Fitzgreyve Transient or dAhDShR modules.

Panel price GBP 10.00 each. (PCBs GBP 5.00 each) 

See "euro" pages.

 Overdrive Engine (Valvecaster) PCB restock.

I have restocked the Overdrive Engine PCB. The latest PCB version (V2) corrects a couple of minor issues with the original. the latest build manual is on the "Euro" pages.