d2k Posted November 3, 2004 Report Share Posted November 3, 2004 HeyheyGot hold of this old casio synth which came out in '87. It has a pretty basic (but rugged) sound and def worthy of some tinkering...;)As it's so old it's MIDI control implementation is standard to say the least - just note, pitch n mod up for grabs and none of the juicy stuff - which I was hoping to change...I gave casio a bell and manage to get a service manual - £10 later and they sent a photocopy version through the post. I've just scanned n PDF'ed it for those who'd like to peep...It seems theres a cpu which control the main 'music lsi' chip. But things like the vcf are a sep IC/circuit - mebbe I could add c/v control here?Anyway - any ideas would be great :)BestD Quote Link to comment Share on other sites More sharing options...
moebius Posted November 3, 2004 Report Share Posted November 3, 2004 Hi,I haven't realized that those old Casios were that hot beasts.. even a nice (?) analog chorus there ;) Well, only one vcf per part, but anyway...Looking at schematics and functional description - I would insert additional filter frequency (thru resistor) control voltage at point (b) as seen on page 19. (That's pin7 at LA6358-2, for melody part and pin1 at LA6358-3 for chord part, page 3)..Original voltages are scaled between 0,8v <-> 2,6v.. and additional voltages should be scaled the same (?!).For resonance control, lift the side of the 220k resistor that connects to uC side. Add an non-inverting unity gain buffer circuit between lifted resistor leg and uC. (We don't want to know what that processor thinks about seeing external voltages on it's output pins.. ;)) Then insert resonance CV at buffer output (lifted resistor leg).. It's scaled between 0,5v and 2.2v but I think that you can go at least bit higher than that ;)But study circuits yourself and see if I make any sense here ;))Bye, Moebius Quote Link to comment Share on other sites More sharing options...
d2k Posted November 3, 2004 Author Report Share Posted November 3, 2004 ahhh, i thought u'd have a few ideas moebius - great stuff :)even a nice (?) analog chorus therewell, i think this is where some noise comes from so thought I'd bypass it neways...I'll redraw the specific parts of the ckt that I'll cut to and post back!Cheers Quote Link to comment Share on other sites More sharing options...
d2k Posted November 5, 2004 Author Report Share Posted November 5, 2004 This on the right track (roughly) for adding the res c/v for instance?:Cheers! Quote Link to comment Share on other sites More sharing options...
moebius Posted November 5, 2004 Report Share Posted November 5, 2004 Well,Opamp feedback (from output) goes to the - terminal (pin2, in this case). And leave the pot out.. (and opamp of course is powered +/- something ;)) And ext. cv must have Ground connection..Otherwise it looks good. You could use two inverting opamps to scale ext. cv to 0,5-2,2v inside the machine so it would accept 0-5v modulation or whatever you like, with biasing it can also be used with bipolar modulation, or use 2,5v as point with no external modulation.So, it's going nice, Moebiusp.s. No wonder Chorus is noisy, there is no "compander" noise reduction.. By the way, if your going to bypass that, can I have the chips ;) Quote Link to comment Share on other sites More sharing options...
d2k Posted November 5, 2004 Author Report Share Posted November 5, 2004 fffs just typed a load and clicked reset instead of post!!new ckt:No wonder Chorus is noisy, there is no "compander" noise reduction..Can u direct me to a compander circuit i can use? - If i can improve that too then I guess I'll leave it in...Thanks Quote Link to comment Share on other sites More sharing options...
moebius Posted November 5, 2004 Report Share Posted November 5, 2004 Yup,The upper section in the pic looks right ;)And for the companders - Take a look at http://www.generalguitargadgets.com/index.php?option=content&task=view&id=140&Itemid=156Circuit around SA571 (or 570) is compressor after input and expander before output buffer. Should be easy to adept to HT-3000 chorus.. Compressor before LPF part of the BBD input and Expander after the LPF part at the BBD output..Bye, Moebius Quote Link to comment Share on other sites More sharing options...
d2k Posted November 6, 2004 Author Report Share Posted November 6, 2004 Hey MoebiusThe upper section in the pic looks rightgreat :) the lower one was an attempt to in regards to when u said:You could use two inverting opamps to scale ext. cv to 0,5-2,2v inside the machine so it would accept 0-5v modulation or whatever you like, with biasing it can also be used with bipolar modulation, or use 2,5v as point with no external modulation.However, I am confused by all these dif voltage ranges tho - I take it this is in relation to what the input c/v is? So i need to make an aout module with 0-5V range? (assuming i use 2 opamps for these cv mods to the HT cutoff and res)...And for the companders...Thanks, but i'll leave all that for the minute till I get this cutoff/res c/v sorted - too much of a headscratch for me now!*Cheers* Actually, just checked that link u posted - seems I can reuse those chips for nice analog delay box ;) rather have that then a chorus! Quote Link to comment Share on other sites More sharing options...
moebius Posted November 6, 2004 Report Share Posted November 6, 2004 Hi,I guess that accuraty isn't that important here, so I think you can use voltages from AOUT directly - just omit resistors R_y and R_p and replace resistor R_x with wire link will give you output voltages from 0 to 2,048v. (Yes, it's the same buffer circuit ;))I think using AOUT_balanced for CVs is smart thing to do - midpoint would then give zero external modulation ect..Bye, Moebiusp.s. Hmm.. basic analog delay.. well, voltage controlled ones are way cooler ;D Quote Link to comment Share on other sites More sharing options...
d2k Posted November 6, 2004 Author Report Share Posted November 6, 2004 (Yes, it's the same buffer circuit )same ckt as what? as the one we've been dicussing since the starts of the thread?? why not just say to use the aout module 'as is' in the 1st place lol...mebbe Im missing summin???I think using AOUT_balanced for CVs is smart thing to do - midpoint would then give zero external modulation ect..aout balanced??? as in balanced audio connex (+/-)?midpoint?? zero external modulation??o dear, it's got all messy now :/p.s. Hmm.. basic analog delay.. well, voltage controlled ones are way coolerif i can control it great, but a smillie wont do nefin to me gettin it implemented!thanks neways, but this is all lookin a bit long now :( Quote Link to comment Share on other sites More sharing options...
moebius Posted November 7, 2004 Report Share Posted November 7, 2004 Sorry for confusing you.. Nope. You build that buffer circuit as you had it in your picture. But, you probably don't have to do additional scaling to ext. cv voltages, if you MODIFY AOUT, by omitting those R_y, R_p resistor in AOUT board and putting wirelink in place of R_x (then it equals the buffer you made in HT-3000, that's what I meant) - It will give you 'bout 0-2,048v out.Then (There's only reference to this at forum, sooo..) adding http://www.ucapps.de/mbhp/mbhp_aout_balanced_cv.pdf you simply make external cv to be 'bout 0v at CC64, -1,024v at CC0 and +1,024v at CC127...This would mean, that when ext. control is in mid. point it doesn't affect HT-3000, and lower values make resonance go down and higher values make it go up..Bye, Moebius Quote Link to comment Share on other sites More sharing options...
herr_prof Posted November 7, 2004 Report Share Posted November 7, 2004 wow! i have an ht and was going to remove the speakers and use the space for my midibox control projects...do you think you can repost that service manual, or upload it via ftp to my space? Quote Link to comment Share on other sites More sharing options...
d2k Posted November 7, 2004 Author Report Share Posted November 7, 2004 Sorry for confusing youNo need to apologise - i'm easily confused! :oYou build that buffer circuit as you had it in your picture...Coo, I've made some changes to it:The ckts within the dashed lines are the additional mods. So, for 1 res c/v input (to control both chord + melody). The 741 there is to boost the res signal some more (ok?). For cutoff, both freq and env has c/v - ok again?you simply make external cv to be 'bout 0v at CC64, -1,024v at CC0 and +1,024v at CC127..."simply" eh :o how do I do that? with the 500R trimmer ye?Thanks for ur patience ;)BTW Herr Prof - pdf shud still b there Quote Link to comment Share on other sites More sharing options...
moebius Posted November 7, 2004 Report Share Posted November 7, 2004 Ahemm.. ;)Leave 741s, no need for those.. (And actually with THAT circuit you would be inserting max -10v to resonance input that originally swinged between +0,8 and +2,2v :D)Then: use separate resonance controls for melody / chords VCF. (To external cv ins)And there's no need to insert many external CV's to frequency controls, just put one per vcf and insert it to the place (b) as seen in the manual..And making CV balanced.. yeah.. Kind of like that ;) Making that mbhp_aout_balanced_cv.pdf circuit creates an offset voltage. And then it's connected to the AOUT board. (replacing one "jumper" with resistor).. Be sure that you have most recent AOUT schematics so you see how it's connected.Bye, Moebius Quote Link to comment Share on other sites More sharing options...
d2k Posted November 7, 2004 Author Report Share Posted November 7, 2004 And actually with THAT circuit you would be inserting max...arrgh, well it was a stab in the dark ;p Is there no way to give the resonance some more ooompth then? even at max it still sounds pretty tame......and insert it to the place (b) as seen in the manualah ok, it's just it says point c 'controls cut freq' whilst b said 'vcf env'...thought both could perhaps be used for slight variations...taBTW, Do u think it'd be possible to get 'inside' the DP935G in order to control other params which are normally only accessible from a the moody data dial pot...? I guess it'd be like controlling the SID chip in that sense...but without specific info it'd be too hard right? unless there's some way to decipher the digital signals...??? Quote Link to comment Share on other sites More sharing options...
moebius Posted November 8, 2004 Report Share Posted November 8, 2004 Is there no way to give the resonance some more ooompth then? even at max it still sounds pretty tame...Hmm.. *Whisling*... It MIGHT be just a feature vcf chip (New Japan Radio doesn't even remember to have manufactured this part, no datasheet) - or just lame design by Casio not to make home keyboardist scared :PYou can try boosting resonance voltage.. You can modify that buffer (uC -> resonance) to be a low gain non-inverting opamp circuit or use two inverting opamp circuits in series.. (with adjustable, but low gain) use something like: http://www.vwlowen.demon.co.uk/java/opamp.htmBTW, Do u think it'd be possible to get 'inside' the DP935G... unless there's some way to decipher the digital signals...???Yes, but it's too hard ;) (Must have pro gear like datalogging logic analyzer)Bye, Moebius Quote Link to comment Share on other sites More sharing options...
d2k Posted November 8, 2004 Author Report Share Posted November 8, 2004 You can try boosting resonance voltage.. You can modify that buffer (uC -> resonance) to be a low gain non-inverting opamp circuit or use two inverting opamp circuits in series..So like what I put in that last ckt then! (that extra 741 for increased res like i said in the post too) but just not as much gain - change Ra and Rf to what? use something like: http://www.vwlowen.demon.co.uk/java/opamp.htmSee above - need 'elp inputting the right values...;pYes, but it's too hard (Must have pro gear like datalogging logic analyzer)We'll leave that for now then ;p. Mebbe just a MIOS controlled digipot in place of the data dial (standard 50k pot)....was thinking tho - as each param is on a specific value (from the 0-127 range) of the pot, cudnt a lookup table be made so that when, ie, a mios button is pushed it calls that value up on the digipot (or mebbe relay pot) so I'm then ready to access the params much quicker instead of turning the pot all the time!! that make sense lol??CheersD Quote Link to comment Share on other sites More sharing options...
d2k Posted November 8, 2004 Author Report Share Posted November 8, 2004 Hey...How about this:http://kitsrus.com/projects/k24.pdf..for catching the music lsi chip logic...? Quote Link to comment Share on other sites More sharing options...
moebius Posted November 8, 2004 Report Share Posted November 8, 2004 So like what I put in that last ckt then! (that extra 741 for increased res like i said in the post too) but just not as much gain - change Ra and Rf to what? That was a single INVERTING opamp, outputting negative voltages..If you use single non invering opamp: Use 1kOhm for Rf and 1kOhm (restricts gain to 2) + 100Kohm trimmer in series for Ra. Then you can adjust gain from very little boost to BIG boost.. (I hope vcf survives - Don't blame me)We'll leave that for now then ;p. Mebbe just a MIOS controlled digipot in place of the data dial (standard 50k pot).... ;Dthat make sense lol??And why not? I don't know how often uC scans that dial ect. But I think you could make it even so, that it has own pot for each parameter - when some parameter is changed, first midibox checks if "datawheel" is on that parameter, if not changes to that parameter, and then enters to data mode (?) and uses pot value to update parameter... (of course midibox could also read what's the value on display ;)) this kind of application would have many uses for other equipment also..Bye, Moebiusp.s. That logic probe is more like of a toy..useful one of course but to see how uC controls that Music LSI you'll need (probably) MHz capable device, that can log bus wide data. Quote Link to comment Share on other sites More sharing options...
d2k Posted November 8, 2004 Author Report Share Posted November 8, 2004 If you use single non invering opamp: Use 1kOhm for Rf and 1kOhm (restricts gain to 2) + 100Kohm trimmer in series for Ra. Then you can adjust gain from very little boost to BIG boost.. (I hope vcf survives - Don't blame me)eheh okay, 'owz this now:And why not? I don't know how often uC scans that dial ect. But I think you could make it even socool! i'll get that goin (attempt to neways ;p) after these c/v bits are done :)Best Quote Link to comment Share on other sites More sharing options...
moebius Posted November 8, 2004 Report Share Posted November 8, 2004 Hi,Looking good, expect: res buffer, connect the other end going to ground to wiper instead. (In curret configuration it acts like voltage diviner, not variable resistor..) (and if you like, you can leave ot IC2.For frequency buffer, just put ext. cv thru 47K resistor and insert it in vcf side of that resistor following that opamp.Bye ya, Moebius Quote Link to comment Share on other sites More sharing options...
d2k Posted November 8, 2004 Author Report Share Posted November 8, 2004 right then, this time I musta got it?? :o ::)Thanks! Quote Link to comment Share on other sites More sharing options...
moebius Posted November 8, 2004 Report Share Posted November 8, 2004 Looks like it, yeah!Now go and blow up your Casio, Moebius ;Dp.s. Of course your going to connect CV input wires from the TIP of the plug, right? Quote Link to comment Share on other sites More sharing options...
d2k Posted November 8, 2004 Author Report Share Posted November 8, 2004 Now go and blow up your Casio, Moebius  p.s. Of course your going to connect CV input wires from the TIP of the plug, right?eheh, i've already got the main pcbs out and ousted a  few parts - still workin :)CV would be tip ye - shows it coming of 'T' (for tip ;p) in the ckt there...Cheers!BTW, I assume i can use a single TL072 for both chord and melody res buffers right? Quote Link to comment Share on other sites More sharing options...
moebius Posted November 8, 2004 Report Share Posted November 8, 2004 Ups, didn't check the lettering and the symbol is confusing ;DYeah, TL072 should be just okay for this task.Bye, Moebius Quote Link to comment Share on other sites More sharing options...
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