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MIDIbox SID V2

User Manual --- Hardware Options

MIDIbox SID V2 can be extended successively from the minimal configuration to the complete control surface with up to 8 SIDs. The overall hardware costs mainly depend on the quality of components, and on the availability of the SID chip. Costs can be reduced by organizing group orders in the MIDIbox Forum!

Minimal Setup

The picture above shows the minimum hardware requirements to get the SID synthesizer running. In this low-cost configuration, the sound parameters are only accessible via SysEx (*). With an additional BankStick, 128 patches can be stored and recalled via Program Change (up to 7 BankSticks are supported for patch storage).

The estimated price for this setup is ca. 30..50 EUR (price mainly depends on the availability of the SID chip).

(*) at this time, MIDIbox SID V2 is in beta stage, and a SysEx editor is not available yet. It is planned to provide a platform independent, Java based editor like known from MIDIbox SID V1

Stereo Setup

With MIDIbox SID V2, two SID chips can be controlled from a single core. The firmware provides many features which simplify the creation of stereo effects. If you have the choice between building two separate MIDIbox SIDs, or just to control the two SIDs from a single core, I would strongly recomment to go for the stereo setup.

In following demo, some preset patches are played with a stereo setup - except for a limiter, no additional external effects have been used:
mbsidv2_stereo_demo.mp3

The same sequences have been recorded again with a Mono setup - direct download (e.g. for comparison with headphones): Stereo Mono

Another advantage of the stereo setup: in multi mode 6 polyphonic voices/instruments can be played from a single core:
mbsidv2_multi.mp3

In following demo, one core controls two basslines - more infos can be found in this forum posting.
Warning: >8 MB, very repetive stuff!
mbsidv2_bassline_demo2.mp3

Multi SID Setup

If you like the SID sound so much (like me), and if you are planning to play multiple patches in a song without the need for overdubbing (recording the sequences separately with a single synth), especially for finetuning the sounds so that they fit together, then you could consider to build multiple MIDIbox SID V2.

It is possible to control up to 3 additional synths from the same frontpanel. The first core, which also manages the control surface, will act as a "master", and the remaining cores are handled as "slaves". Communication is realized over a fast CAN interface, this approach is called MBNet.

MBNet is a separate communication channel, which works much faster than MIDI and allows bidirectional data exchange over a single wire. The CAN protocol is normaly used in automotive and industrial applications, where reliability does matter. So, it is not just a "tinkering solution", it's a professional approach.

This schematic shows, how the cores have to be connected together. Each core module needs a unique MIOS device ID in the network. This ID is burned into the "PIC ID header" together with the Bootloader. The master should get the ID 00, the slaves ID 01, 02 and 03. If you bought a preburned PIC, e.g. from SmashTV or Mike, and forgot to specify the right MIOS Device IDs, you can change them later with the "change_id" application, which can be downloaded from this page. There are prepared .hex files (device_id_01.hex .. device_id_03.hex), which you can use without rebuilding the application.

As uploading an application requires a bidirectional MIDI connection to the slaves, you temporary need to attach the MIDI Out port of your MIDIbox SID to the slave MIDI outs. Alternatively you can plug the PIC18F4685s which should work as slave temporary into the master socket and upload (and especially test!) the applications from there.

Once MIOS and the MIDIbox SID V2 application has been installed, you don't need to repeat this time consuming procedure for firmware updates anymore, as a "cloning" mechanism is available, which allows you to transfer the firmware of a master to all slaves via MBNet. This should be done after every firmware update - just press the MENU button during power-on, until the Cloning message appears on screen.

SID chip selection

There are two different SID derivatives: the 6581 (first version, initially used by C64 in the "brown breadbox case"), and the 8580 (later version, used by C64 in the flat gray case). There is also a 6582, which was sold as replacement for defective 8580s, and which sounds very similar (or identical?).

Main difference between the two derivatives is the supply voltage and filter caps. 6581 has to be supplied with 12V and requires 470pF caps, 8580 and 6582 with 9V and requires 22nF caps. This has to be considered when building the MBHP_SID module.

But there are also sound differences. It is difficult to say, which one sounds better, as both have their advantages... the filter of 6581 sounds more moody and dirty, whereas the filter of 8580/6582 sounds more precisely. Resonance has nearly no effect on the 6581, some mixed waveforms are not working, and it has a much higher background noise (see also demo samples in the Lead Engine chapter), therefore the 8580/6582 is normaly the preferred choice, especially for filtered basslines.

Power Supply Unit (PSU)

Two different voltages are required for the digital and analog domain. All digital chips require 5V, whereas the SID requires 12V (6581) or 9V (8580/6582) in addition.

For a minimal setup a single AC or DC PSU which delivers ca. 12V for CORE/SID module with 8580, or 15V for CORE/SID module with 6581 works fine. It should deliver up to 500 mA. Although normaly 6-9V are recommended for supplying the core module in order to avoid that the 7805 regulator gets too hot, it can be supplied from the same PSU like the SID due to the low power consumption.

Once you add a LCD with backlight, the power consumption increases so much that this solution doesn't work anymore. The 7805 gets much hotter, and you will propably also hear a silent 50Hz/60Hz buzz at the Audio Out. A separate PSU for the SID module helps here, or the "optimized C64 PSU circuit.

I did some experiments with different PSU and regulation circuits, and finally found out that re-using the power supply which came with the C64 is the best solution. Not only that most users already own such a PSU if they canibalized the SID from an old C64... the main reason which qualifies this PSU is, that it already contains a 5V regulator for higher currents (so that the 7805s of the core modules can be removed), and that it provides a separate AC output which can be used to provite an unregulated voltage for the SID module:
mbhp_8xsid_c64_psu_optimized.pdf

Be careful when working with a C64 PSU which has no special fuse socket. The internal fuse could burn on a short circuit, and it is nearly impossible to open the case (and especially to close the case once it has been somehow opened). I for myself fortunately never came to such situation (although I shortened the PSU outputs multiple times by fault), but other users reported such issues in the past.

Control Voltage outputs (CV/AOUT)

MIDIbox SID V2 can control up to 8 analog outputs by connecting an MBHP_AOUT module, or up to 4 MBHP_AOUT_LC modules to the core.

There are so many possibilities, that a special chapter has been spent - see CV Options.

Analog Control Inputs

MIDIbox SID V2 provides 8 analog inputs (5 currently used, 3 reserved for future features). They can be used to connect additional pots/faders or joysticks for direct sound control, but they could also be driven from analog signal generators. More info can be found in the Frontpanel chapter.

SID Audio Input

The SID chip provides an audio input, which can be used to route external signals through the filter. So long no external source drives the audio input (J4 of the SID module), use a jumper to connect it to ground instead, otherwise you will notice some additional background noise!

An inventive guy called AlphA found out, that by forwarding the Audio Out to the Audio In through a resistor the sonic characteristics of the SID can be dramatically changed (Link to the website.

See also this forum article for additional infos.

Control Surface

...is discussed in detail in the Frontpanel chapter.

Detented and/or Non-Detented Encoders?

It is recommended, to use a detented rotary encoder as menu controller (datawheel), and non-detented encoders for remaining parameters if a complete control surface is build.

The detented encoder allows more exact control, whereas non-detented encoders are better for fast parameter sweeps. Note that the detents can be easily removed (see also this Wiki page and this forum posting).

Modulation Matrix with transistor drivers

The modulation matrix consists of 8x7 (optionally 8x8) LEDs, which are driven by a 74HC595. As this output current of this shift register is limited to 20 mA, low-current LEDs should be used, which are mostly not much more expensive than low-cost LEDs.

Alternatively transistor drivers can be added to the 74HC595, which is used as common line driver. The DEFAULT_SRM_USE_SINKDRIVERS switch in your setup_*.asm file has to be enabled in this case, so that the outputs are inverted. See Wilba's Wiki page for a schematic.

BankSticks

Both, 24LC256 (32k) and 24LC512 (64k) are supported BankSticks, but 24LC512 are recommended, as it can store 128 patches.

Up to 7 BankSticks can be used for storing patches, each needs a unique device address (CS=0..CS=7).

The 8th BankStick at CS#7 (E0/E1/E2 pin of BankStick connected to Vd (5V)) will be used to store ensembles. It doesn't matter of you are using a 24LC256 or 24LC512 here, in both cases 128 ensembles will be stored in the lower 32k range.

Note that your MIDIbox SID will also work without BankSticks, but in this case only a single patch and a single ensemble can be stored within the internal EEPROM, which isn't a really useful setup and therefore not recommended.

Hardware costs

Premade PCBs can be purchased at www.mikes-elektronikseite.de or http://mbhp.coinoptech.com. They also purchase complete kits for the modules and some of the other parts (like rotary encoders).

Prices and ordering numbers are from Reichelt if not specified. A list of alternative electronic shops outside germany can be found in the Wiki

Note: The PIC18F4685 is a quite new microcontroller, which is unfortunately hard to find in common webshops yet.
SmashTV did a batch order and provides the PIC with preburned Bootloader and MIOS for an extremely fair price to the community ($9.95 !!! Compare it with stock listings under findchips.com and you won't find cheaper offerings for single parts!)
Doc is doing the distribution for Europe for those guys who want to save shipping costs - just contact him in the MIDIbox Forum

Complete PCB

The modular approach used in MBHP has the high advantage of improved exchangeability and testability. On the other hand, MIDIbox SID V2 has reached a level, where up to 20 modules are involved, which doesn't make it easy to bring everything into a case. Not for forget, that a single PCB saves costs and makes the hardware more robust.

Wilba has created a customized PCB for his MB-6582, that he has introduced in the Wiki. A batch order of these PCBs has been started for those people who are interested in an all-in-one solution - details can be found in the Wiki.

Update: Wilba has created another project called "sammichSID", details in the Wiki

Resources

• Firmware: see this forum article
• Connection diagram for buttons & encoders: mbsid_v2_din_default.pdf
• Connection diagram for LEDs: mbsid_v2_dout_default.pdf
• Connection diagram for the power wiring: mbhp_8xsid_c64_psu_optimized.pdf
• Interconnection diagram for MBNet and MIDI interconnections: mbsid_v2_communication.pdf
• More Photos: midibox_sid_photos/
• Frontpanel template: mbsidv2_front.fpd - can be edited with Frontpanel Designer, available at Schaeffer Apparatebau (*)

Copyright © 1998-2023, Thorsten Klose. All rights reserved.