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socrates

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  1. My long due MB6582 Build

    in MIDIbox SID

    Posted

    So I acquired all the parts for my MB6582 years ago. Very slowly I assembled the base plate and then got into some problems during the checks I believe. Now after years of collecting dust I want to finish it off and get that awesome sound out of it :happy:. So this thread will probably be a debug/build/progress but also at some times a cry for help thread :P.

    So lets get to it. This is how I found it. Directly did the testing described in the MB6582 build guide.

    • No Shorts between GND and Voltages

    • SID's pin 25 are all connected to 5V and all pin 14 to GND

    • Core's pin 11 are all connected to 5V and all pin 12 to GND

    • 6N138 is connected to 5V and GND

    And now the trouble starts:

    On the 74HCxxx all pin 8 got to GND so that is good.

    But there are 3 problems on the pin 16 to 5v though. Looking at the picture you would already have guessed it, they are at U3_SID1, U4_SID2 and U23. So it is time to heat up the soldering iron and resolder those pins I guess.

    Comments are welcome and hope show you more progress soon.

     

    IMG_5525_small.jpg

    IMG_5526_small.jpg

    • Like 1

  4. MIDIBox Mixer - A PGAx311 Audio Mixer

    in MIDIbox User Projects

    Posted

    lost posts:

    lylehaze

    Posted 28 October 2009 - 16:24

    I managed to build 8-channel 3-band Butterworth filter to feed each channel to a single PGA.

    If you're happy with the circuit, I hope you'll share it

    I'll connect the three per-band outputs together (hoping there are no big time differences between the bands,

    using an osciloscope there is a difference but it seems to be the same for all bands) and employ the 4th PGA input

    to be used for per-channel master gain control.

    That works, but leaves you without pan/balance control.

    waiting for a SOIC ZIF socket to test everything (two channels for start) on a breadboard or

    vectorboard.

    I used "Schmartboards" successfully to prototype the circuit. They worked very well.

    there is no problem for employing several cores to drive multiple stages for this design if necessary, so

    single-stage is not a strict requirement.

    My desire for less stages is about sound quality more than core count.. I don't know of any quality problems with

    multiple stages, but I have never tried, either.

    The software is a bit over-commented.. some find that annoying, but it is the lesser of two evils.

    Put simply, incoming MIDI messages that affect the mix are stored in a big array, and any channels that may

    change as a result are flagged for re-calculation.

    Then the "math" part processes each flagged channel, combining volume, expression, master volume, pan/balance,

    effects levels, and effects flags into a single gain setting for each PGA gate. Finally, after all calculations are current

    with the MIDI data table, the gain settings are written out as a big block to the PGA chips.

    Of course there are other minor routines.. save and restore bank settings, display channel names and gain settings,

    responding to MIDI requests for the current state of the MIDI table.

    After explaining all that.. consider this: instead of a 3 band EQ followed by a single gain control.. how about adding

    to the end of the "math" part above by taking the final gain result for a given channel, then multiplying it by each of

    "Bass" "Mid" and "Treble" levels for that channel.. NOW you'll have achieved the same as if you had a separate level

    control after the EQ, but you'll have used one less PGA channel to do it. Those three PGA channels give you all the

    control after the EQ, but you'll have used one less PGA channel to do it. Those three PGA channels give you all the

    control you asked for.. but with less hardware.. And less hardware usually means better sound quality.

    I'm not sure I'm explaining myself properly.. I'll try a different way..

    Please see the attached crude graphics..

    (http://midibox.org/forums/index.php?

    app=core&module=attach&section=attach&attach_rel_module=post&attach_id=5571)

    (http://midibox.org/forums/index.php?

    app=core&module=attach&section=attach&attach_rel_module=post&attach_id=5572)

    You're using six gates, but each signal is only being "processed" ONCE..

    You still have ALL the controls you had before, but a shorter signal path.

    The software will combine volume, expression, balance, master volume, and EQ settings into six levels, for those six

    PGA Level controls.

    You also get the (probably not useful) option of having a separate EQ settings for left and right.

    One last thing.. if you went to a 4 band EQ, there would be one PGA chip for each audio channel,

    much easier to divide up as you build.. (though I think the software could handle it either way)

    I have written enough for now.. I'd love to see some discussion on this when I get back from work tonight.

    LyleHaze

  5. MIDIBox Mixer - A PGAx311 Audio Mixer

    in MIDIbox User Projects

    Posted

    Lost posts:

    freddy

    Posted 28 October 2009 - 12:34

    First, I must apologize for the slow reply.

    After a long period of unemployment, I'm now working, and I managed to put in 66 hours this week, so I have not

    had much time for web surfing.

    No problem at all, everyone has other things to do. Just keep your job!

    So the EQ.. take the incoming line level audio feed into four parallel bandpass filters.. the result is four

    separate audio signals, Bass , lo-mid, hi-mid, and high. Now we feed each of those into one of four PGA channels,

    this is where we get "control" of the EQ.. after those, they all re-combine into a single audio signal that has been

    tone-conditioned.

    Now comes the choices.. we can either.. take that "toned" signal into the existing PGA design, and use 2 more

    channels of PGA for volume control.. OR.. we can make TWO of those 4 band EQs, and have each one dumping

    directly to the output busses (left and right)

    Meanwhile I managed to build 8-channel 3-band Butterworth filter to feed each channel to a single PGA. I'll

    connect the three per-band outputs together (hoping there are no big time differences between the bands, using an

    osciloscope there is a difference but it seems to be the same for all bands) and employ the 4th PGA input to be used

    for per-channel master gain control. I've received 4 PGAs yesterday, expecting another 5 free TI samples arriving

    today, waiting for a SOIC ZIF socket to test everything (two channels for start) on a breadboard or vectorboard.

    I'd like to make output section configurable therefore would like to build a patch-panel to mix individual channels

    to resulting output buses, I need to test this as well since I'm unsure how many outputs can drive how many inputs.

    I'm still unsure how many PGAs will be needed for 4 buses (2x L, 2x R) with individual per-channel pan control. If

    there would be no pan one PGA (4 inputs would suffice). I didn't peek into sources yet so I don't know how was

    your pan implemented (whether two opposite-bound channels to lower left while raising right and vice-versa), but

    I'd say there is a better solution for sure.

    Option 1 requires a total of SIX pga channels(there are 4 per chip) for a stereo feed (non-effects) and the

    audio passes through two gain stages before reaching the output..

    OR

    Option 2 requires a total of EIGHT pga channels, but the signal is only processed through ONE gain stage.

    Hm, there is no problem for employing several cores to drive multiple stages for this design if necessary, so singlestage

    is not a strict requirement.

    Either way could work..

    I have not built either yet.

    I intend to make an EQ after I'm done with the meter bridge transmitter, but I have not made it yet.

    I DO NOT want anyone to wait for me.. I am busy, and the software is "open" in hopes that others will contribute

    things like EQ and stuff.. SO this is just my concept of how it might work.. Others are invited to contribute in any

    way they wish.. (more on that later)

    MIDIbox 28-10-09 21:16

    http://midibox.org/forums/index.php?app=forums&module=forums&section=printtopic&client=printer&f=39&t=6776 Pagina 57 van 58

    way they wish.. (more on that later)

  15. Reloop or Korg Spare parts

    in Parts Questions

    Posted

    I want to make a midibox in white like te reloop Ltd. series. So I'm searching for white knobs en fader caps. I have searched for site's with reloop spare parts specially foor the Ltd. series, but I found nothing. Then I saw the Korg KM-402 and KM-202 mixers, they got also white knobs aand caps, but I didn't find any spare parts for it..

    So does someone know where you can find those Korg or Reloop spare parts or otherwise nice white caps and knobs.

    Or have a other solution.

  17. LC Ansteuerung mit mehr als 8 Fadern?

    in Deutsch

    Posted

    Hallo,

    das hast Du richtig erkannt.

    Für jede einzelne LC-Box (also für jeweils 8 Kanäle) brauchst Du eine eigenständige LC.

    Für jede LC wiederum benötigst Du eine eigenständige MIDI-IN/OUT Verbindung.

    Es geht nicht per MIDI-THRU !

    Ist der Master einbegriffen bei die 8 Kanäle?

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