Retroaktiv MPG-70

Finally! After a long time I have managed to do a rather late article about the MPG-70, a fabulous design by Rob at Retroaktiv Synthesizers. This was the second product from Rob of it’s kind after the PG800mini and now has spawned many other control products for other synths. The PG800mini has since been replaced by the MPG-8.

This post is long overdue after finally completing the construction with a new front panel and production standard main board. It is a beautiful piece of work: A sea of knobs and solid construction.

Professional Application

This beautiful video shows the MPG 70 being employed creatively by Jim Daneker, who uses his JX10 in professional music projects.

Jim Daneker is a composer, producer and arranger working across a vast range of styles and fields.

History

Initially, when Rob was talking about the MPG-70 idea in the SuperJX community, it was only intended to be a limited production run. It was considered adventurous as it supported the SuperJX PWM modification by Fred Vecoven with a limited user base. However the success of the PWM modification continues to grow and the need to control it to it’s maximum potential has led to a huge amount of success.

Creative Freedom Inspired

Getting the best out of the SuperJX is easy with the MPG-70 as it also has the additional parameters for the Vecoven PWM upgrade. With Vecoven firmware, adding an MPG 70 to the set-up, makes the SuperJX a very straightforward and powerful sound generation tool.

It can control more than one SuperJX at once through it’s auxiliary functions, thus PG800 and Sysex can operate simultaneously or have 2 channels of sysex.

There are performance features too, provided through the assign and Expression pedal features, the control possibilities are seemingly limitless, allowing multiple parameters to be manipulated by a single control or expression.

Other instruments can be controlled from the MPG-70. Controls can be mapped to generate other messages for other instruments simultaneously.

Once this is installed in place with an MKS70 or JX10 there is little need to touch their user interfaces. Remember though to use System Exclusive connections rather than PG800 port to control it and get the most out of the features as well as front panel. PG800 interface doesn’t support many of the features.

Killer Feature – Random Patch Generator

The MPG has as killer feature, the random Patch Generator. It has it’s own dedicated button and pressing enter generates a new patch that is loaded into the SuperJX.

Upon trying this, I was smitten. It can be configured and steered to generate different types of patches. Simply press Enter to try again, after a day doing it over and over, I still don’t get bored.

Display

The MPG-70 contains a small but effective OLED display to help access other functions. As every SuperJX control is now at one’s disposal, this display is focused on configuration.

Rack or Tabletop

It can be table top mounted and connections arrive out of the top of the panel yet don’t interfere with other units if installed in a rack.

Development

Software

Rob has coded everything in the MPG-70 and drew on a few SuperJX enthusiasts in the community to support testing of the software. This area of the product is a lovely piece of work and is the basis of all his new and exciting products.

The arrangement has a boot-loader allowing updates of software through normal sysex dumps and Rob continues to add features since it shares the same code base as his other products.

Electronics

Rob undertook all the electronic design and I was privileged to be involved in it’s development. Rob took on my idea for the Assign feature, made it his own and improved on it and allowed me to influence the circuit design too.

Below is a picture of my set up during early electrical testing of one of the prototypes.

The power circuit is taken from the Super Synth Projects VFD Display project to ensure high efficiency. To keep current consumption as low as possible, high value potentiometers were employed, this can cause issues, so to counteract errors and noise, ratio-metric measurement circuits are implemented.

Measurements are extremely stable with no twitching or mis-representation of values. This is a vital feature when considering the numbers of parameters. Parameters can be set with high precision but users can also use a nudge feature if they wish, by pressing an up/down button.

MPG-70 has astonishingly low power consumption of only 35mA. It can be powered from the SuperJX with negligible impact on it’s internal power supply.

This is in sharp contrast to the Roland PG800 that consumes much more power and doesn’t have very stable control readings.

Conclusion

If you have a desire for getting the very best out of the Roland SuperJX with a PWM modification, the MPG-70 is a perfect choice if tactility is remotely desired. Not only that, it can control other instruments, but if you are blessed with both MKS-70 and a JX10 like myself, it makes for a remarkable set up for sound generation using analogue synthesis.

Check out his other interesting products for other Synthesizers in a similar vein, they breathe new life into vintage instruments.

Guy Wilkinson