Adding CV to 808 accent circuit

creatorlars · Posted: Wed May 06, 2009 8:11 am Post subject:

Did some more jamming with the new accent circuit last night and just want to double-confirm it works quite well.

Also to note -- I am using Thomas Henry's trigger conditioner circuit at all the trigger inputs in the 808 clone, including Accent.

Sebo -- for your application, I guess you'd just need to connect ax/bx/cx pins to +5V and ay/by/cy pins to your +5-15V accent level.

gabbagabi · Posted: Wed Jul 15, 2009 1:21 pm Post subject:

edit: i was wrong

gabbagabi · Posted: Wed Jul 15, 2009 1:30 pm Post subject:

edit: i was wrong

fonik · Posted: Thu Jul 16, 2009 4:04 am Post subject:

hi lars,

i believe you mixed the 4053's pins 11 & 10 on your schematic. pin 10 is the control input for channel A on the CD4053. pin 11 is the control input for channel C.

as i understand it, the accent (pin 14 - 'A') is connected to +5V (pin 12 - 'AX')by default. as long as a trigger pulse sets the control input high (pin 10), the accent gets connected to your accent CV input (pin 13 - 'AY'). smart.

creatorlars · Posted: Thu Jul 16, 2009 7:39 am Post subject:

Hey Fonik, yes it looks like you're right -- thanks for noticing that.

g.gabba, you can get the eagle schematics for Schmitt and Noise on the MB808 site here: http://www.eight-oh-eight.org

yes, i used the 40106-based schmitt trigger, works great!

i'm not sure how you're getting CV-controlled accent by changing the pulse-length of the 505 triggers... could you explain in more detail how your circuit works?

I need to take some videos of my in-progress 808 clone soon! Smile

Here's a pic:
http://www.synthesizers.com/mok2009/IMG_9051_m.jpg

creekree · Posted: Thu Jul 16, 2009 1:30 pm Post subject:

creatorlars · Posted: Thu Jul 16, 2009 1:51 pm Post subject:

thanks! yeah i was pretty excited about how bright that orange silkscreen came out.

wow, i didn't know dirk lindhof was doing an 808 clone too, this is awesome!!!

vcfool · Joined: Jun 19, 2008 Posts: 23 Location: Barcelona

Thanks for sharing this! I have used it on my clone and it works perfect.
I omitted 2 resistors and the diode and added a trimpot to get the 5V. I also used one of the 4053 switches to drive a LED.

But I have a little problem:
I am using one attenuator pot (B100K) for each of the voices so each voice can have different amount of accent, or none at all. I first thought of an independent accent trigger/circuit for each voice but finally I decided to go for attenuators. I thought I could use the pots wired connecting one leg to 5V (instead of GND, like a normal attenuator), the other leg to the Accent output and the wiper going to the voice accent input. Well, ok, the pots are acting really strange. When the pot is on full accent everything is ok. When I begin turning the pot I get the attenuation right but then the sound is almost lost on most of the pot traveling and then gets back with no accent when the pot reaches the end, at 5V. So I get the attenuation say from 10 to 8, then no sound till 0 when it gets back with no accent. So in fact the pots work but not as good as I expected.
I don't know if I am making myself clear. I guess this is a simple question but my electronic knowledge is really limited.

I attach the adapted schematic I have used. As you can see on the outputs I have the 5V along with the Accent to go to the attenuators.

Thanks again!

808acc_02_sch.png

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808 Accent Circuit

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creatorlars · Posted: Tue Nov 03, 2009 8:45 am Post subject:

Awesome! It's about time for me to finally work on my 808 clone some more now that I just rebuilt my Midibox sequencer!

What's happening with your pots is that you aren't attenuating the signal at all, going to +5V like that.

Another option may be using a dual gang pot, attenuating +5V on one side and the accent signal on the other, then summing them.

Probably the best way to do this would be a an op-amp buffer with an offset. send 0-10V from the accent circuit instead of 5-15V... and then have an op-amp buffer at the accent input of each circuit which is an attenuator (like you have ,but to GND) followed by an op-amp buffer that adds +5V to the signal. That way it's always 5-15V going into the circuit.

Let me know if that makes sense, I could draw up a schematic.

vcfool · Joined: Jun 19, 2008 Posts: 23 Location: Barcelona

Thanks for the answer.

I do understand. But that would take 2x12 op-amps, and there's no much space left inside my case, specially with all the wire mess. 24 op-amps would be 6 quad op-amps. That would be maybe as complicated as adding an independent accent circuit for each voice using a 4053 switch for each one, that would be just 4 IC... without buffers or CV. I'll think about it some more, but for now I'll just enjoy my 808 clone as it is for some time!!!

BTW, here it is:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Thanks again!

creatorlars · Posted: Wed Nov 04, 2009 10:05 am Post subject:

looks great!!! did you use the microlarge layouts?

vcfool · Joined: Jun 19, 2008 Posts: 23 Location: Barcelona

Yes, I used the 3 bigger layouts containing several voices, not the modular ones.

Sebo · Joined: Apr 27, 2007 Posts: 564 Location: Argentina

Hi vcfool:
Nice work you did!!!
I'm building my 808 from that same 3 PCB from microLARGE site, did you find
any errors/problems that I have to be aware of?
Did you implement all the mods?
Hopefully I will be finishing it before the end of the year, I have to do all
the wiring, and build the MIDI interface.