AMSynths Newsletter - AM8019 Athena VCA & AM8328 Mirage VCF

"Newsletter March 2014
Latest News: Spring has at last arrived in the UK with the first few days of sunshine after many months of rain and floods. Over the last few weeks we have been developing new exciting modules, as well as refining some of the existing range, and shipping modules to customers! The new AM8105 Super JX VCF & VCA will be available in April, providing a really nice sounding 4-pole VCF with smooth oscillation and a VCA, all in one EuroRack module. It uses the IR3R05 Roland chip that appeared in the legendary MKS80 and MKS70.

Updated AM8012 and AM8075 filters will be shipping in April, with new vertical jacks and revised electronics, along with the new AM8125 Analog VCO which has 3 waveforms and sync.This month we are shipping AM8019 VCA's, AM8109 VCF's and a final run of AM8319 Diode Array Filters. The AM8019 is in stock now, the others will appear over the next 2 weeks, along with some AM8140 Dual ADSR's.

In the workshop we are continuing to develop the amazing Athena synthesizer, a PCB and panel project for Synthesizer DIY, as well as testing dual VCO EuroRack modules and a new LFO module based on the Jupiter 8 with variable delay and five waveforms.

This year we plan to continue to bring new modules to market and to increase the production volumes from the 115 we shipped in 2013.

Best Wishes and thanks to all our customers.

Rob Keeble
Owner and Designer, AMSynths"

http://www.amsynths.co.uk

"The AM8019 is a replica of the ARP 2600 Voltage Controlled Amplifier, which is a transistor VCA dating back to the ARP2500 and 1970. This EuroRack module makes use of matched transistor arrays and a high quality buffer Op Amp at the output stage. The VCA is designed to be used with the Athena VCO and VCF's, enabling a replica of the 2600P or Odyssey in a rack format to be achieved.

This 16HP wide module has have enhanced from the original 1970 ARP design with high quality components and additional control inputs, the circuit has been adjusted to provide a better HF response than the original design. The VCA is based on a Wilson Current mirror, and the AMSynths version uses matched transistor arrays to replace the discrete transistors. There are two signal inputs with level controls, one inverted and both pass through a 470nF capacitor which acts as a high pass filter at 10 Hz, thereby blocking any DC offsets.
The ARP 2600 VCO's have a DC offset which is effectively removed via this input (post VCF mixer) and thereby eliminates ADSR thumps. This means the AM8019 is not designed to be used as a ring modulator - see the AM1005 for this application. There are 2x linear control inputs and 2x exponential control inputs, all adjustable by front panel slider potentiometers. There is also a GAIN slider pot on the upper right hand panel, with an amber LED output signal level indicator. The slide potentiometers have been especially manufactured for AMSynths and we have used coloured plastic caps to give the VCA that vintage look and feel.

The discrete transistor VCA is a product of the 1960's before integrated circuits were affordable and the use of the CA3080 OTA chip. This modern and updated version takes the design into the modern era and provides a versatile and clean VCA. The Wilson current mirror and discrete VCA is used in a number of other AMSynths modules such as the AM8047 Multi-Mode Filter."