hardware interface

Building the mini disc titler interface has two parts. Firstly constructing and testing the electronic circuit which should take no more than two hours work assuming you take your time and get it right first off. Secondly a suitable connector needs to be constructed/sourced to fit the remote control input socket of the mini disc recorder. Please note that the below circuit is not my own design, if you would like further details/information please visit the D.I.Y. interface page at the Mironics website.

		parts

All resistors are either 1/8 or 1/4 watt with at least 5% tolerance.

		schematic

As you can see from the diagram there is not much to the circuit. Basically it consists of a set of resistor networks which are controlled via signals sent via parallel port wires. As with the standard in-line Sony Mini-Disc remote control, the circuit adjusts the values of resistance on the Mini-Disc recorders remote control wires to send key presses. Of special note are the 1500 & 1000 ohm resistors in parallel at the bottom left hand corner of the circuit, which help to compensate for resistance the circuit places on the remote control input wires.

Due to the importance of the interface to accurately adjust output resistance, the usage of 5% tolerance or better resistors is considered vital. Power to run the interface is derived from the parallel port, which drives the CD4051 IC at the heart of the circuit and avoids the need for an external power source.

		construction

Fairly simple to construct, either on a piece of veroboard as I did or if you have the facilities you could make up a printed circuit board. With the large number of resistors that make up the circuit it is not a bad idea to keep a multimeter handy to check the resistor values as you put them in place. Also check, check and check once more to make sure the components are put in the right place as it is much harder to troubleshoot a faulty interface than to get it right first time. Once the circuit is constructed, wire up the printer plug to a length of multi-core cable. I actually used 6 core cable and installed the four diodes within the printer plug to lessen the number of wires required.

The final step is to construct a suitable plug to insert into the mini-disc recorder. If your not confident in constructing a plug for the task, you could always hack your current Sony mini-disc remote control plug or purchase a second remote control for the task. For a D.I.Y. plug you could either use a piece of veroboard, the end off an edge connecter from a PCI/VESA PC expansion card as I did or, if you have the facilities you could etch one yourself.

If you take the veroboard/edge connector option you will need to remove the extra copper strips from the board to match the spacings of the Sony remote plug using a sharp knife of something similar. Ensure you get the right two contacts to emulate a plug by checking the resistance of two contacts from your current Sony inline remote control in sequence until you find the contacts that alter resistance with remote key depresses. The final thickness of the plug needs to also be considered - too think and it will be tight in the mini-disc recorders socket and may possibly cause damage. I found the final thickness to be just under 1mm, thinner than most circuit boards, so a little work with file and sandpaper will most likely be required.

	With the plug built to size its just a matter of wiring it up to a length of cable and onto the circuit. Case the interface in a suitable enclosure and you should be done!

		testing

Before connecting your mini disc recorder to the interface it is a good idea to check the functionality of the circuit by monitoring the output resistance on the remote control wires to ensure they are within the required specifications. This can be achieved through the use of a multimeter and interface testing application available for download on the software page.

With the testing software installed, connect the interface to the parallel port. Run the application and select the correct parallel port, then click each of the control buttons in turn, measuring the resistance across the remote control wires using a multimeter. The resistances read back for each remote function should be fairly close to that of the table above, but will not be exact due to the 1500 & 1000 ohm correction resistors. With resistances verified for each control option, connect the mini disc recorder and re-check.

What if it doesn't work? If one or more of the resistances are wildly outside that of the resistance table, you may have an incorrectly wired resistor(s) in the circuit. If no resistance/activity is present at all check the voltage on pins 8 & 16 on the CD4051 with the interface connected to the parallel port and the interface tester running, it should be around 4.5 - 5 volts. Failing this re-check you wiring on both the circuit and parallel port plug for possible errors.

With a hopefully working interface in your possession, you are now ready to get recording with my winamp titler software utility.

		final notes

I have found one slight problem with the interface unable to function correctly when the MZ-R700 recorder is being powered/charged via the supplied power pack adaptor. Remote control keypresses are not recognized correctly by the minidisc recorder and unpredictable behaviour starts to occur. I think the problem is related to the fact that the interface is being powered by one power source (computer parallel port) and the minidisc player another (plug pack) which could cause the resistance changes due to multiple grounding points. A possible solution would be to power the interface and minidisc player from the same power source - most likely the Sony power pack.

To overcome this problem at present I use battery power to record by fully recharging the minidisc battery before recording. The Sony manual claims a fully charged battery can record for a little over 5 hours, in reality I can record a full 2.5 hours of audio to minidisc and use the player for listening for around another 4-5 hours before another recharge which is great for a single AA battery.

The Mironics interface shown above is not the only option available either. Lionel Pawlowski has at his MDCOM website plans for an alternative Sony minidisc interface. Whilst I have not built nor tested Lionel's interface I have attempted to include support for MDCOM into my software package which should work fine. If someone does try my winamp titler utility with Lionel's interface without success, please e-mail it through along with the problems present and I will try my best to correct it.

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last updated : 2002-03-19