I’m an idiot… I misunderstood the op amp without the half moon indentation. It was in backwards. I’m so sorry I’m usually more thorough before I ask for help - but I’m going through the links you shared and making notes! Appreciate it x
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Happens to the best of us (and worse, if it’s a CEM3340 instead of a TL074)!
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I’m very glad I didn’t fry the expensive bit! 
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and I see you already taped over the extra socket , a couple of us have had issues with that 
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I don’t trust myself
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I’ve already tried at least twice to put a power cable here
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I have built my first VCO!
Everything is working after looking over the layout again and fixing some things, it works!
One thing I have noticed is that the pulse and ramp waves are both substantially louder then the triangle wave I understand that they are louder because of the nature of the wave type but is it common to be that noticeable of a volume jump?
Just wondering, cheers everyone
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That’s because of the design of the 3340 chip, see
and
and the 3340 datasheet.
The pulse wave in particular has a larger maximum level than some modules expect — the peak to peak difference is fairly OK, but it’s 0 to 10.5 V rather than centered on zero — so might need attenuation going into them.
There are 3340 VCO designs out there that add gain/offset stages to make all waveforms the same amplitude, and remove the DC level, so they’re all ±5 V. But the 1222 isn’t one of them.
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So this is normal for the design? And isn’t that much of an issue if you know how to gain stage later on with other modules? I looked at both the links you directed me to but it is kind of a whole lot of nothing in my brain, is this going to dramatically effect tuning? Do I need to buffer the triangle wave?
I think this is all a lot for me where all I just want to make cool sounds and hook it up to midi I don’t overly care if it is 100% actually in tune.
I really appreciate the help but i just don’t know nearly enough, do you think it will still serve my purpose?
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I don’t have any issues just running it through a mixer stage. If you don’t have one, look up simple mixer. I made a thread about it.
Gain won’t affect tuning exactly. It’s frequency, not amplitude that changes pitch. Obviously there’s some caveats but in general loudness is a separate issue to pitch.
TLDR; its probably fine to not stress about it.
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All the waveforms are buffered in the 1222, so that’s not an issue. Tuning shouldn’t be affected. (Though note the 1222 is subject to tuning shift with PWM, that’s discussed elsewhere here.) I think it’s easier to work with consistent, zero-centered ±5 V waveforms, but as long as you’re aware they have a DC offset and different amplitudes, and how to gain shift and offset them if it becomes relevant, you’re okay.
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About tuning…
- my module is working but i think not to it’s full potential.
- i watched sam’s video about tuning and read many good posts like this one right here in this thread and the other thread with 3340 tuning advice
- during the built i deviated only once form the BOM 2.0 and replaced the LM4040AIZ-4.1 with a DIZ-5.1. i read here that going above the 4.1 could be regulated down
- i used a 20K resistor for my AS-Chip (as hinted by sam)
- i got 4 volts on the reference point and 0 to 4 volts in increments of 1 on the pins of the rotary switch
- the tuning display is recognizing notes (sometimes)
- i have audible sound on all wave forms
- BUT i think i’m missing the upper part of the spectrum and the trk-pot is at its end (clock-wise)… great base lines but where is Whitney Houston?
- only 2 (adjacent) positions of the rotary switch can have “good” sound, the rest is above or below the sweet spot…
any hints?
(edit: bad link)
Check all control voltages:
Also check the connections and component values going into pin 13. R4 should be 1.5M and should connect to +12 V. R2 should be 470R and connect to ground.
If all those connections and voltages are good then it’s a matter of getting the scaling right. R3 (connected to pin 1) should be 24k, R5 (pin 2) should be 5.6k, RV1 (TRK trimmer, between R3 and R5) should be 10k.
For tuning, it’s best to have a scope, frequency counter, or an instrument tuner that tells you frequency. Lacking those you can do your best with any tuner. Set both the TRK and HFT trimmers to the middles of their ranges. Put 0 V and 2 V alternately on the V/Oct CV. These should be accurate voltages or at least have an accurate difference of 2.000 V. The resulting pitches should differ by 2 octaves; in frequency terms, the ratio of the two frequencies should be 2.000. If not, change the TRK trimmer and check both voltages again. (Both frequencies will change, but it’s just the ratio you need to pay attention to.) If the frequency ratio is going in the wrong direction, change TRK back the other way. Keep repeating until the frequency ratio is 2.000 (or the tuner says it’s as close to 2 octaves as you can get).
Then put 3 V and 5 V in and do the same thing, but this time use the HFT trimmer to get the frequency ratio to 2.000. After that go back to 0 V and 2 V and do it all again from there, with the TRK trimmer, then 3 V and 5 V with the HFT. It might take two or three times through the whole routine before everything’s set.
If you hit the limit on either trimmer and can’t get to 2.000 ratio then there’s probably a bad connection or incorrect component value. Check those again.
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Also be sure that resistors on the rotary switch are all the exact same value
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0 to +12V on center trimmer
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0 to 1V on fine tune pot
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4.0x V on TP1
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very close to 1V increments on the octave pins, with self measured precision resistors
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checked the components highlighted by @analogoutput, they should be up to spec
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relowed (hopefully) all solder connections
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tried an other AS3340
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rewatched sam’s tuning video to raincheck myself
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read post #47 and a few adjacent posts form the linked therad. not sure if i “got” it
BUT not the result i was hoping for… it’s sound like a diesel car. when things are about to get interesting (slightly pitched) the signal breaks up.
also the whole module gets touch sensitive on higher pitched settings… i must have made a mistake somewhere or overlooked a bad solder connection. i’ll probably order a second one to help me debuging…
it’s about the journey and learning something isn’t it? if i whanted just working modules i could have gone with a more readyly available synth format
THX anyway and CU out there
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I built three and the third one was just chugging away like an engine. I had a bit of a dodgy molex connection on the octave selector. Probably not your issue if you’ve verified the voltages but I know a few people have had issues there
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I second the molex connector issue, it was sneaky really as it still showed all the correct voltages but when i replaced it for just normal cable soldered directly it then worked fine
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I’ll third that. I’ve seen poor connections to the octave switch cause issues that sound similar.
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- Thank you @BoneMusic @TylerTheFolf & @ChristianBloch, i fiddled around with the rotary connection, i don’t THINK it is my problem
- Thank you @lookmumnocomputer for your tip with removing the arduino (in the Q-Jam), it didn’t help either. THANK YOU AGAIN! it was an honor talking to you!
wild speculation from a layman following…
- from what i read here i got the impression that the pitch of the output (also?) depends on the amount of pover the as3340 is fed or can consume (being extra vague here). myabe a bad connection is strawfeeding mine… how would i measure that?
- i measured (insitu) the resistors around pin 1-3 and the trk-trimmer. i got values i expected (as on the schematic)
anyway…THX
i’ll keep on tryin and enjoy the base underway
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You may have already tried this, but I might try testing this module alone. Unplug all other modules. It doesn’t sound like power sag, but worth testing.
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