I sold the last kit from the latest build six months back. I do not market it aggressively so sales are slow.
My current issue is that I ran out of circuit boards and have to order more, along with sourcing components. Covid and sanctions on China disrupted the supply chain (also made my last 2 component orders difficult and expensive).
I can’t get the quality of circuit boards I need and the price has gone up 5x plus we have to pay a 25% tariff on top of this for orders from China.
The worldwide shortage of chips/components is serious for all makers and for me has got to the point where critical items like the DAC used are no longer available.
I created a board design using newer components but those components are also in short supply. It is going to take a while to resolve this as I can’t source the quality and price I need to make it viable at the current price.
Tag Archives: MIDI
Opto-Key Project is here, and the builds started
Kevin’s Opto-Key build environment has transferred from Synthfool to This Old Synth. The components, software, circuit boards etc. arrived on Wednesday afternoon. Two days of work later I have 
partially completed 5 units. Time to get a components order submitted so I can complete them! I did purchase the very last of unit built by Kevin and have begun testing using it in my MiniMoog; exciting times!
CHD MIDI Upgrade for the Roland TR-808
When writing about the MTG TurboCPU upgrade I promised to put a blog entry up for a really nice and non-intrusive MIDI mod for the Roland TR-808, and here it is. The thing I really like about this implementation is the degree to which they went to make in non-intrusive (i.e. drilling holes!).
It comes complete with a printed manual of step-by-step instructions, and supporting CD.
For the MIDI connector the existing Din-Sync connector is removed, along with its In/Out switch. A new connector that includes MIDI In/Out is fitted (a special adapter cable is supplied. The switch is replaced by a 3 way one, In/MIDI/Out.
The “umbilical cord” for triggers and power is socketed at the controller end, so for service it can be unplugged and the TR-808 will still work (so this is not a CPU upgrade/replacement like TurboCPU).
Only one hole needs to be drilled, and it is for a MIDI active Led and sits in the Start/Stop switch, under the yellow label. Awkwardness here is that they specify a metric drill, and for accuracy a 
woodworking one is probably best. I’m sure you could get by with a slightly larger US drill and use a band of shrink-wrap tubing or some-such to tighten the fit. Of course you could ignore this step and just know that center switch is MIDI on!
Be sure to keep the parts removed such that the TR-808 can be put back to standard if need be. Here is a link to the CHD TR-808 MIDI kit. I may well contact CHD and offer to distribute this in the USA.
This Old Synth acquires the exclusive rights to Synthfools Opto-key for MiniMoog project
As a tech I’m increasingly frustrated with the chore of trying to restore the (oxidized) key contacts on the MiniMoog to full operation, and unless it is frequently played the issue of “squirelly keys” comes back. I have been installing Opto-key for my customers which removes the key cleaning cycle, AND adds simple note-on/off MIDI.
I was concerned and saddened to hear that Kevin Lightner at Synthfool could not continue the Opto-key project as it addresses the biggest reliability/playability issue with the MiniMoog, and have negotiated with him to transfer ownership here.
Once the on-hand materials such as circuit cards arrive I will commence building the product to Kevin’s spec and make it available for sale.
As I’m also a software developer with experience in embedded systems I plan to enhance and support Opto-key moving forward. I’m really excited by this!
MTG Turbo CPU + MIDI + CV
Turbo CPU
I’m generally against modifications. I have seen too many vintage synths spoiled by badly drilled holes that hold fragile switches, connected through an “umbilical cord” to undocumented perf-board based mods made decades ago, and then more wires soldered to the circuit boards. Working on the gear becomes difficult as these wires are holding the case to the cards, and of course wires fatigue and come away, and you have a challenge as to where they once went, and how the mod is supposed to work.
I do see the benefits of a good MIDI implementation, and I have come across a couple of MIDI kits where the designers have come up with good clean designs that can be unplugged for service. In this entry I talk about the Turbo CPU upgrade kit from MTG (Music Technologies Group). Grant runs the MTG and I have found him responsive, friendly, and helpful so recommend doing business with him.
In a different post I will talk about a nice MIDI solution for the Roland TR-808 from another vendor.
All of the instructions are available to download from MTG (http://www.musictechnologiesgroup.com/index.html), so you can see what is involved. I’m on the list of experienced installers and would be happy to implement this for you, but note that I am not a reseller so you have to purchase the kit from MTG. Turbo CPU a simple removal of the CPU and install of the Turbo CPU module.
I think most folks would be interested in the MIDI interface which for a solid installation does mean drilling the base of case to mount the MIDI interface card, and the back of the case for the MIDI connectors.
I prefer the look of the MIDI connectors squeezed between the lettering, and made some identification labels for the 
MIDI ports. Both customers for this kit wanted the MIDI interface, plus the “DIY” CV interface which adds a tiny MCP4728 chip to the v2.00 MIDI board (I was fortunate that the MCP4728 was pre-installed on one unit, but had to order it from Mouser for the other.
Fine soldering skills are required to install this chip as it is surface mounted, so ask Grant if you can have a card with the MCP4728 pre-installed when you order :-). The DIY CV interface gives you MIDI control over 4 CV wires and is a great addition that requires no trace cutting or case butchering, so I like it!
For my implementation of DIY CV I installed a connector at the MIDI interface card for the 4 wires so it could be disconnected for service.
