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        <h2>Stereo SIDs on the Commodore 64</h2>
        <span class="little">(last updated 2019-04-18)</span></td>
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<table><tr>
  <td style="padding: 12px; white-space: nowrap"><p style="line-height: 150%">
    <a href="#history">History</a><br>
    <a href="#stereo-mod">The Stereo Mod</a><br>
    <a href="#cartridges">Stereo SID Cartridges</a><br>
    <a href="#playing">Playing Stereo SIDs</a><br>
    <a href="#editor">The Stereo Editor</a><br>
    <a href="#textfiles">Text Files from Q-Link</a><br>
    <a href="#resources">Resources</a></td>

  <td style="padding: 12px">
    <p>This page contains information about the stereo mod for the
    Commodore 64, including history, hardware pictures (most can be
    clicked on for a larger view), screenshots, and downloads. Much of
    the history came from an
    e-mail <a href="dickenson-interview.html">interview</a> I did with
    Mark Dickenson in July 2006. If you have any comments or
    corrections, you can mail me
    (cenbe&nbsp;<i>at</i>&nbsp;protonmail&nbsp;<i>dot</i>&nbsp;com).

    <p><b>Want to hear a stereo SID right now?</b> Here's an MP3 of
    the late great Jerry Roth's version of
    <a href="drj5-johnny-b-goode.mp3">Johnny B. Goode</a> (the one
    that started it all). And here's another
    one, <a href="drj5-wild-weekend.mp3">Wild Weekend</a>. I made
    these by running StereoPlayer in the VICE emulator, taking a .WAV
    capture, and converting them to MP3.
  </td>
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    <p style="text-align: center"><a href="../index.html"><span 
       class="little">(back to main Commodore page)</span></a></p>
    <hr>

    <h3><a id="history">History</a></h3>

    <div style="float: right; margin: 12px">
      <img src="enhcover.gif" alt="Enhanced Sidplayer cover" 
           style="border: 1px solid"/>
    </div>

    <p>The Commodore 64 was blessed with a great little sound chip
    called the 6581 SID (Sound Interface Device), designed by Bob
    Yannes (here's
    an <a href="http://web.archive.org/web/20070222065716/http://stud1.tuwien.ac.at/~e9426444/yannes.html">interview</a>
    with him). It has three independently controlled voices and is
    capable of a wide range of sounds, including ring modulation, low
    frequency oscillation, and high-, low-, and band-pass
    filters. Later versions of the chip included the 6582 (which ran
    at 9V rather than 12V), and the 8580, which had improved filters
    but broke a popular way of playing back digitized samples. See the
    excellent <a href="http://en.wikipedia.org/wiki/MOS_Technology_SID">Wikipedia
    article</a> for more information. There are also some
    microphotographs of the SID chip circuits available
<!-- dead link
<a href="http://www.digital-circuits.org/sid/CSG%20Micrographs">here</a> and 
-->
    <a href="http://mail.lipsia.de/~enigma/neu/6581.html">here</a>,
    which are beautiful to look at even if you don't understand them.

    <p>However, the limited memory available to the machine made it
    impossible to include sound commands in the BASIC interpreter, and
    setting the hardware registers
<!-- dead link
<a href="http://stud1.tuwien.ac.at/~e9426444/sidtech2.html">registers</a>
-->
    manually with POKE commands or machine language was very
    time-consuming. So many software packages for writing and playing
    music on the Commodore were created, and as usual, one rose to the
    top (at least here in America). It was a program written by Craig
    Chamberlain, released in 1985 as a book and disk combination by
    the publishers of Compute! magazine and popularly known as "the
    Sidplayer". It was followed by another version in 1986 that added
    new commands and was known as "the Enhanced Sidplayer" (see
    photo). Here is a <a href="enhanced-sid.d64">D64 image</a> of the
    disk that came with the book. More information on the original
    Sidplayer can be found on
    Craig's <a href="http://sidplayer.org/">Sidplayer site</a>.

    <p><a id="video">Raymond Day</a> sent me
    a <a href="../video/craig-chamberlain.mkv">video</a> of a talk by
    Craig at the 1999 Chicago Commodore Expo (<i>caution: the file is
    over 300M</i>). Here's how the show was described in a post on
    comp.sys.cbm:
    
    <p style="margin-left: 24px; margin-right: 24px; font-size:
    smaller"><code>On September 25 the Chicago Commodore Expo will be
    held at the Day's Inn in Lansing, Illinois, and it looks to be
    bigger and better than last year's show.  I'm sorry that I'm going
    to miss it.  What a line-up of C= luminaries!  Maurice Randall
    (Wheels 64/128, GeoShell), Fender and Judi Tucker (Loadstar), Jim
    Butterfield (programmer/writer), Raymond Day (hardware/software
    hacker), Tim Lewis (president of the Lansing Area Commodore Club,
    Michigan), Craig Chamberlain (Enhanced SID Player), Maurine
    Gutowski (newsletter editor for the Muskegon Commodore Club), and
    Steve Judd, Jason and Katherine Compton, Mark Seelye, Robin
    Harbron, and Darren Foulds (programmers).</code>

    <p>The Sidplayer still had a fairly steep learning curve, but one
    of the reasons it became the de facto standard for writing SIDs
    (as music files became known here in America) was the fact that
    huge libraries of them were available on the online services, like
    GEnie and QuantumLink (also affectionately known as "Q-Link", an
    early Commodore-only dialup network that went on to become America
    Online). See the <a href="#resources">resources</a> section to
    download these collections.

    <p style="text-align: center"><span 
       class="little"><a href="#top">back to top</a></span>
    <br style="line-height: 50%"><hr>


    <h3><a id="stereo-mod">The Stereo Mod</a></h3>

    <div style="float: right; margin: 12px">
      <img src="drj5.jpg" alt="Jerry Roth picture" style="border: 0">
      <p class="little" style="line-height: 50%; text-align: center">the 
         late Jerry Roth (DrJ5)</p>
    </div>

    <p>Although people were having a lot of fun making SIDs and
    playing them back, many were feeling the limitations of the SID
    chip. For example, there was only a single master volume control
    rather than one for each voice, making it difficult to balance
    softer waveforms. In addition, three voices are really not enough
    for more sophisticated efforts. Enter Mark Dickenson, who, as he
    puts it, "noticed the hardware addressing had open areas that were
    perfect for adding a second SID chip." In early 1987, Mark came up
    with a way of adding the second chip (here is a copy of
    his <a href="qlink/stereo-schematic.txt">original instructions</a>
    as uploaded to Q-Link), as well as a player that would read two
    SID files at a time and play them simultaneously, one through each
    chip (see <a href="#playing">below</a> for more information on the
    player). He suggested the idea of stereo SIDs to a couple of the
    better-known SID writers on Q-Link, and Jerry Roth (a.k.a. DrJ5),
    whose rock 'n' roll SIDs are still considered some of the most
    imaginative and technically advanced, took him up on it. The
    resulting stereo version of "Johnny B. Goode"
    (<a href="drj5-johnny-b-goode.mp3">MP3</a>) was demonstrated at a
    SIDfest in Columbus in June 1987. It caused a sensation, and many
    people either modified their machines themselves or had someone do
    it for them (Raymond Day did quite a few). Here's
    a <a href="drj5.d64">D64 image</a> of a whole bunch of Dr J's
    SIDs, both mono and stereo.</p>

    <div style="clear: both"></div>

    <div style="float: right; width: 340px; margin: 0px 12px 12px 24px">
      <a href="stereo-circuit.jpg"><img src="stereo-circuit-340x213.jpg" 
         alt="stereo circuit" style="border: 0"></a>
      <p class="little" style="line-height: 150%; text-align: center;">
      This is a schematic of the stereo mod (created on a Commodore
      64) that Jerry posted to Q-Link. Note the typo: 7/29/78 should
      be 7/29/87.</p>
    </div>

    <p>Below are some pictures
    that <a href="http://portcommodore.com/">Larry Anderson</a> sent
    me of the "piggyback mod", as it came to be known (because the
    second SID chip was mounted directly on top of the first
    one). This version adds two RCA outputs on the left side of the
    computer case and a switch controlling the I/O address of the
    second SID chip ($DE00 or $DF00) on the right. Click for larger
    views.</p>

    <table style="margin-left: auto; margin-right: auto">
      <tr>
        <td style="width: 260px; padding: 6px"><a href="dualsid64-1.jpg">
          <img src="dualsid64-1-240x180.jpg" alt="Larry Anderson dual SID #1" 
               style="border: 0"></a></td>
        <td style="width: 260px; padding: 6px"><a href="dualsid64-2.jpg">
          <img src="dualsid64-2-240x180.jpg" alt="Larry Anderson dual SID #2"
               style="border: 0"></a></td>
      </tr>
      <tr>
        <td style="vertical-align: top; padding: 6px">
          <p class="little" style="text-align: center">
             entire board, showing wires to jacks and switch</p></td>
        <td style="vertical-align: top; padding: 6px">
          <p class="little" style="text-align: center">
              closeup of the "piggyback" mod itself</p></td>
      </tr>
    </table>

    <table>
      <tr>
        <td>
          <p>Here are a few more pictures of the piggyback mod; these
          were posted during a discussion in IRC. You can see that
          although the basic principles are the same, implementations
          varied widely. The quest for the perfect stereo mod
          continues to this day; several people are currently working
          on alternate designs.</p></td>
        <td>
          <a href="second-sid-dopple.jpg">
            <img src="second-sid-dopple-240x180.jpg" alt="Dopple dual SID"
            height="180" style="margin: 12px; border: 0">
          </a>
        </td>
        <td>
          <a href="second-sid-mech.jpg">
            <img src="second-sid-mech-240x180.jpg" alt="Mech dual SID"
            style="margin: 6px; border: 0">
          </a>
        </td>
      </tr>
      <tr>
        <td>&nbsp;</td>
        <td class="little" style="text-align: center">Dopple's mod</td>
        <td class="little" style="text-align: center">Mech's mod</td>
      </tr>
    </table>

    <table>
      <tr>
        <td style="padding: 6px">
          <a href="sid2sid.jpg">
            <img src="sid2sid-200x283.jpg" alt="SID2SID board" 
                 style="border: 0">
          </a>
        </td>
        <td><p>A slightly less painful option is
          the <a href="http://www.8bitventures.com/sid2sid/">SID2SID</a>,
          which is a circuit board designed for use with the Prophet64
          cartridge, now known
          as <a href="http://www.8bitventures.com/mssiah/">MSSIAH</a>. It
          fits inside the Commodore 64 (or 128), and although it
          requires just as much work, the instructions and parts lists
          are very clear and detailed. You must provide the second SID
          chip, as well as sockets, resistors and so forth.</td>
        <td>
          <a href="sid2sid-assembled.jpg">
            <img src="sid2sid-assembled-200x174.jpg" height="151"
                 alt="SID2SID assembled" style="border: 0">
          </a>
        </td>
        <td>
          <a href="sid2sid-installed.jpg">
            <img src="sid2sid-installed-200x151.jpg" alt="SID2SID installed" 
                 style="border: 0">
          </a>
        </td>
      </tr>
    </table>

    <div style="clear: both; text-align: center"><a href="#top"><span 
       class="little">back to top</span></a></div>
    <br><hr>
    

    <h3><a id="cartridges">Stereo SID Cartridges</a></h3>
    
    <div style="float: right; margin: 0px 18px 18px 18px">
      <a href="md-stereo-404x600.jpg">
        <img src="md-stereo-172x256.jpg" alt="Mark Dickenson stereo cart"
             style="border: 0; display: block; margin-left: auto; 
                    margin-right: auto">
      </a>
      <p class="little">one of Mark's hand-made cartridges</p>
    </div>

    <p>Although a lot of people were modifying their machines to add a
    second SID chip, many more were squeamish at the thought of
    opening the machine and taking a soldering iron to it (I still
    haven't done it to any of my machines, even after 30
    years). Eventually, Mark Dickenson came up with another hardware
    hack: putting the second chip in a plug-in cartridge that would
    avoid the need for surgery. He built a run of hand-made cartridges
    (few of which survive today), and sold them on Q-Link. The
    cartridge had a defeat switch, an RCA plug for the audio output,
    and a plug-in clip lead that had to be attached to one of the pins
    of the SID chip inside the machine (which meant that some
    disassembly was still required). Here are scans of
    pages <a href="dickenson-1a.jpg">one</a>, <a href="dickenson-2a.jpg">two</a>,
    and <a href="dickenson-3a.jpg">three</a> of the instructions that
    came with.

    <div style="float: left; margin: 0px 18px 18px 18px">
      <a href="SID-Symphony.jpg">
        <img src="SID-Symphony-172x194.jpg" alt="SID Symphony"
         style="border: 0; display: block; margin-left: auto; 
                margin-right: auto"></a>
      <p class="little">the SID Symphony cartridge</p>
    </div>

    <p>Kent Sullivan, with his imaginatively-named company Dr. Evil
    Laboratories, improved on the design, replacing the 6581 chip with
    a 6582, which required 9V rather than 12V (<i>note that these two
    chips are not interchangeable!</i>). This made it possible to use
    a 9V battery for power, which rested inside the cartridge case
    itself. To replace the battery, you would gently pry apart the two
    halves of the cartridge casing to expose the power leads (see
    pictures below). Here is the <a href="qlink/sidcart.txt">original
    Q-Link post</a> from Kent Sullivan announcing the cartridge, and
    here is a recent
    a <a href="https://www.commodoreserver.com/BlogEntryView.asp?EID=C42BCFDCF09E4E748A0F4DEF0BC4F4D9">blog
    post</a> about its history. The picture on the left is of the
    final version (eventually sold by CMD), which did not require a
    battery. At last, you could just plug in a cartridge and start
    playing stereo SIDs. When they appear on eBay (which is rare),
    it's not unusual to see them go for over $100.

    <table style="clear: both; margin-left: auto; margin-right: auto">
      <tr>
        <td style="padding: 6px">
          <a href="sid-symphony1.jpg">
            <img src="sid-symphony1-200x150.jpg" alt="SID Symphony inside #1" 
                 style="border: 0">
          </a>
        </td>
        <td>
          <a href="sid-symphony2.jpg">
            <img src="sid-symphony2-200x150.jpg" alt="SID Symphony inside #2" 
                 style="border: 0">
          </a>
        </td>
        <td>
          <a href="sid-symphony3.jpg">
            <img src="sid-symphony3-200x150.jpg" alt="SID Symphony inside #3" 
                 style="border: 0">
          </a>
        </td>
        <td>
          <a href="sid-symphony4.jpg">
            <img src="sid-symphony4-200x150.jpg" alt="SID Symphony inside #4" 
                 style="border: 0">
          </a>
        </td>
      </tr>
      <tr>
        <td colspan="4" style="text-align: center"><p class="little"
          style="text-align: center">first version of the SID Symphony
          cartridge, opened up to show its construction (click for
          larger views)</p></td>
      </tr>
    </table>

    <br>
    <div style="float: left; margin: 0px 12px 12px 0px">
      <a href="fotios-board-1024x768.jpg">
        <img src="fotios-board-240x180.jpg" alt="Fotios stereo SID #1" 
             style="border: 0">
      </a>
    </div>

    <p style="font-weight: bold">Pictures of
    <!--
    <a href="http://www.cbm8bit.com/fotios/fbss.php">
    --> Mangelore's stereo cartridge <a id="fotios">(click for
    bigger images)</a></p>

    <p>In the late 2000s, someone finally came out with a new stereo
    cartridge. Fotios Kotsiopoulos ("Mangelore") came up with
    a device that lets you map the second SID chip into I/O space at
    any one of sixteen different addresses from $DE00 to $DFE0 (via
    jumpers and a DIP switch). It also has a pass-thru port that will
    accept a Prophet64 cartridge.</p>

    <div style="float: right; margin: 0px 12px 12px 12px">
      <a href="fotios-1024x768.jpg">
        <img src="fotios-240x180.jpg" alt="Fotios stereo SID #2" 
             style="border: 0; margin-right: 6px">
      </a>
      <a href="fotios-prophet64-1024x768.jpg">
        <img src="fotios-prophet64-240x180.jpg" alt="Fotios stereo SID #3" 
         style="border: 0">
      </a>
    </div>
   
    <p>The only catch is that you must provide your own SID chip; the
    board comes in 12-volt (6581) and 9-volt (8580) versions. Also,
    the board has not been made for quite some time, so if you want
    one, keep an eye on eBay!

    <div style="clear: both; text-align: center"><a href="#top"><span 
       class="little"><br>back to top</span></a></div>
    <br><hr>


    <div style="float: right; margin: 12px">
<!--
      <img src="stereoplayer-400x242.jpg" alt="StereoPlayer title screen"
           border="0"><br>
      <p class="little" style="line-height: 50%; text-align: center">the 
        StereoPlayer's title screen</p>
-->
      <p><img src="stereoplaying-400x283.jpg" alt="StereoPlayer screen shot"
              style="border: 0">
      <p class="little" style="line-height: 50%; text-align: center">playing 
        Jerry Roth's Johnny B. Goode</p>
    </div>

    <h3><a id="playing">Playing Stereo SIDs</a></h3><p>Have a stereo
    SID setup of some kind but don't know how to try it out? Here's a
    .D64 of Mark
    Dickenson's <a href="stereoplayer-10_3.d64">StereoPlayer&nbsp;10.3</a>,
    which I believe is the last version released.  I don't have the
    docs for it, but here's a .D64
    of <a href="stereoplayer-10_2.d64">StereoPlayer&nbsp;10.2</a>,
    which does include lots of docs (as well as the "Star Wars"
    extended .WDS/.ANI demo).

    <p>Since there's some room on the .D64 of version 10.3, I put some
    of my favorite stereo SIDs on it as well so you can get started
    right away. Here are some quick configuration tips:<ul>
      <li>hit the Commodore key to get to the second menu</li>
      <li>use 'A' to set the second SID's I/O address (usually $DE00)</li>
      <li>hit Space on a mono SID to set which voices play in which 
          channels</li>
      <li>use 'M' to simulate stereo mode for mono SIDs</li>
      <li>use 'E' to control the delay between the two mono channels in stereo
          mode</li>
      <li>the MIDI options don't work (they were never implemented)</li></ul>

    <div style="text-align: center"><a href="#top"><span 
       class="little"><br>back to top</span></a></div>

    <div style="clear: both"><hr></div>
    
    <div style="float: right; width: 406px; margin: 12px">
      <img src="stereoeditor-400x283.jpg" alt="Stereo Editor screenshot">
      <p class="little" style="line-height: 150%; text-align: center">The 
         stereo editor, showing the opening commands of Jerry Roth's<br> 
         arrangement of "Johnny B. Goode"</p>
    </div>

    <h3><a id="editor">The Stereo Editor</a></h3>
    <p>Stereo SIDs had become wildly popular, but the process of
    creating them was still very labor-intensive. Each channel of
    three voices had to be edited as a separate file, then tested
    using StereoPlayer. If errors were found, it was back to square
    one to repeat the cycle. In 1988, Robert Stoerrle created a stereo
    editor that allowed the editing and playback of all six voices at
    once. At this point, we had the full stack: hardware support (the
    second chip), a way to create stereo SIDs (the editor), and a way
    to play them back (the StereoPlayer). The Commodore stereo
    revolution was born!

    <p>Here is a .D64 of the <a href="stereoeditor.d64">stereo
    editor</a>, which can be extracted to a Commodore floppy disk or
    used in an emulator. There are help files on the disk, and the
    program has a text file viewer for them.

    <div style="text-align: center"><a href="#top"><span 
       class="little">back to top</span></a></div>
    <br style="clear: both; line-height: 50%"><hr>

    <h3><a id="textfiles">Text Files from Q-Link</a></h3>

    <p>These are some text files downloaded from Q-Link back in the
    Olden Times.

    <p style="line-height: 150%">
    <a href="qlink/SIDfile-format.txt">Format of SID files</a> (Dick
      Thornton)<br>
    <a href="qlink/stereo-document.txt">Stereo Sid-Player docs</a> for
      version 7.0 (Mark Dickenson)<br>
    <a href="qlink/SIDnews-four-one.txt">Sidplayer News #4 part one</a> (April 1986)<br>
    <a href="qlink/SIDnews-four-two.txt">Sidplayer News #4 part two</a><br>
    <a href="qlink/sidnews8.txt"> Sidplayer News #8</a> (February 1987)<br>
    <a href="qlink/11_08-SID-class.txt">SID class transcript 11/08/????</a><br>
    <a href="qlink/11_15-SID-class.txt">SID class transcript 11/15/????</a><br>
    <a href="qlink/11_22-SID-class.txt">SID class transcript 11/22/????</a><br>
    <a href="qlink/half-moon-lake-patches-v1.txt">SID patches</a> (ADSR settings) from Half Moon Lake BBS<br>
    <div style="text-align: center"><a href="#top"><span 
       class="little">back to top</span></a></div>
    <br style="clear: both"><hr>

    <h3><a id="resources">Resources</a></h3>
    <ul>

    <li><p>A <a href="drj5.d64">D64 image</a> of some SIDs by Jerry
    Roth (DrJ5)</li>

    <li><p><a href="http://www.c64music.co.uk/">Compute's Gazette SID
    Collection</a></li>

    <li><p>The <a href="http://www.hvsc.de/">High Voltage SID
    Collection</a></li>

    <li><p><a href="http://sidplayer.org">sidplayer.org</a> (history
    of Craig Chamberlain's original Sidplayer)</li>

    <li><p><a href="dickenson-interview.html">e-mail interview with
    Mark Dickenson</a> (Mark agreed to be interviewed for a
    presentation on stereo SIDs I gave at CommVEx 2006)</li>

    <li><p><a href="http://sid.kubarth.com">SID in-depth information
    site</a> (includes SID chip die pictures)</li>

<!-- dead link
    <li><p>Here are some more pictures of
    the <a href="http://www.digital-circuits.org/sid/CSG%20Micrographs/6581R4/">SID
    chip dies.</a></li>
-->

    <li><p>This is a large picture of a <a href="MOS_6581_R3.jpg">6581
    R3</a> die.</li>

    </ul>

    <p style="text-align: center"><a href="../index.html">back to main Commodore
    page</a><br>
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