IC 555 instead of IC 50240

[MP1]

Yes, fatman would give you some flexibility. Also, you mentioned programming. I was wondering if you knew that microcontrollers can be programmed with basic. The PIC can use PicBasic and AVR microcontrollers have Bascom AVR. Even if you do not use it for the heart of your project, it makes for a nice LCD interface, etc.
What are you using for a keyboard? I did not notice if you mentioned this.

MP

 

[Reptilian Feline]

The "keyboard" is made from rotary switches.

On the harp there is 4 knobs on the front, and a 5th knob on the top side. If I use one knob (the 5th) for volume control, I have 4 knobs for my keyboard. My latest idea on how to use those knobs is based on a couple of circuits I found on a synth-site.

If I understand it correctly a frequenzy multiplier works as a harmony generator - input one frequenzy and get 3 (1+5+8). There are 12 half-notes in a cromatic octave. If I divide the 12 half-notes between 3 knobs with rotary switches, I have a spare knob. That knob (rotary switch) will control which one of the harmonic knobs are used (1, 2, 3 or OFF). That way I can set up three "chords" and just turn the selector-knob to the chord I want to play. While that chord is playing, I can select another chord on one of the other knobs if need be. That way I can play continous sounding chords with one hand, and play the strings on the harp with the other. When I don't change chords, I can get half-notes by turning the bottom string-knob (not electronic) if I need to.

I know there are some electric guitar pedals that produces harmony based on the note that is played, so it's not unheard off. I also found a circuit for a keypad harmony synth module that seems promising. I'll do some more reading and then post some links.

 

[audioguru2]

Hi RF,
A major chord is C,E, G and C for example. A minor chord is C, E flat, G and C. Then there are other kinds of chords. C, F, A and C sounds nice but I can't remember what the chord is called.

The phase-locked-loop circuit you found can "follow" the root key "C" in this example and will make both Cs, the E and the G to play a major chord. You would need another PLL circuit to make an E flat to play a minor chord. You would need two more PLL circuits to play C, F, A and C.

You could add ocillators to make vibrato and tremolo if you want.

Instead of a PLL are you thinking of making 12 oscillators then combining them to make your own chords? A 50240 IC did it with digital dividers so the frequencies were always in tune with each other, but it is very complicated to make one.

 

[Reptilian Feline]

Audioguru - imagine you're playing the piano and singing at the same time. Your voice is "playing" the melody. Your left hand is playing the base on the piano, and your right hand is filling in the chords. Your left hand can play one note, or maybe the octave as well, and your right hand playes the 3rd, 5th, and maybe 7th note in a rythmic fasion or arpeggio style. To fatten it a bit you add the 5th to your left hand as well, so in your left hand you play 1st, 5th and 8th note (in C that would be C-G-C).

On the harp, the electronics will be the "left hand", and the strings the "right hand".

In the diagram on http://home1.gte.net/res0658s/fatman/4046pll.html there is referens to 3F in the "Harmonic generator mixer"-box. That is what I want to use. If the input from the VCO is C I get G and C, and if the input is F I get C and F, and if the input is D I get A and D.

 

[audioguru2]

Hi RF,
I realise now the PLL circuit produces a chord with only C, G and C without the E. If you want a complete major or minor chord or any other kind of chord then more PLL circuits are needed.

Have you considered allowing the PLL to listen to the harp then track its frequency?
Do you sing? The PLL can also track the frequency of your voice.

 

[MP1]

FYI:
PLL will not give you a sine wave. A VCO with AR generator and filters will allow you to duplicate many different instrument sounds.

MP

 

[Reptilian Feline]

Audioguru - the idea to have it follow the harp is nice. I haven't thought of that possibility. It should add some interesting effects  And yes, I do sing. My voice is my main instrument.

MP - I'm beginning to understand the different parts in this. The PLL is a small part of a larger circuit when put to use.

So... what have I been up to today... well... I downloaded ExpressPCB and the PAiA Fatman manual, and I'm working on reprodusing the scematics for the analog part of the Fatman from the PDF-manual. It takes a while, but is a good excercise. I will download the mods from the same place as the harmonics generator, and see how they fit in, and then put together the harmonics generator in ExpressPCB as well. Once that is done, I'll ask you about the circuits and how it can be modified to fit into what I want. The Fatman seems like a good small synth, and with less knobs on the front I think I can fit the parts into the harp. That's one of the reasons I'm working in ExpressPCB.

 

[MP1]

RF,
I don't think you can print out your finished board with ExpressPCB. The manufacturer gives it away so that you will send them the file and pay them for boards. No one else can read their files.
You can get a free copy of Eagle on the links section of this site. It will work much better for you. You can print the files to use for etching a board or send them to any board house, etc. With ExpressPCB, you are stuck with using their services.

MP

 

[Reptilian Feline]

ExpressPSB wasn't what I expected. I wanted it to put together a netlist based on the circuit diagram, but it didn't. I first drew the diagram in the part called ExpressSCH, but when I tried to import it into the PCB-part,all it could do was to show me where the parts were linked. I had to manually import and name all the footprints. *sigh*!!! It was a good exercise, putting together the schematics, but having to do the footprint part as well with all those resistors and capasitors to keep track of... *ble*!!!

I'll try Eagle next. I liked the tutorial from FreePCB, and if I could make a proper netlist for the fatman, I'd use that.

Back to the Fatman... I'm confused... The midi part and the analog part are sharing ICs! The parts are separated in the manual, but I don't know what parts I can remove from the analog part of the schematics. The manual can be found here: http://www.paia.com/manuals/docs/9308-fatman-manual.pdf Could you help me? Also the ground symbol comes in two versions, and I don't know if there is a difference in how they'r wired. The empty triangle and the "three-line-triangle" both mean ground, right?

 

[MP1]

You don't need a lot of separation between digital and analog parts. This is why they have different ground routings. Treat the two ground symbols as two different connections, then connect them together at one single point at the chassis. The triangle symbol is normally used as a digital ground and the symbol with the lines signifies chassis cround. I have seen many agencies use these differently. Ampeg used the triangle to denote the 1/2 VCC reference on some of their designs whereas the ground with lines was the actual ground. Of course, yours are both grounds and need to be connected at one point.

MP

 

[Reptilian Feline]

OK. Thanks! It was a bit confusing. I'll try and "untangle" the schematic and see if I can find the places to "cut" away the digital parts.

 

[purelypygmalion]

Hi RF,

Told you I was bored. If you're still looking for a 50240, Organ Service Corp. has a generic replacement. Check it out at http://www.organservice.com/crm/topdividers.htm#Fig5. The order # is KS-83, price 39.95 US. A little pricey but maybe cheaper and definitely easier than trying to puzzle out an alternative.