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2VCO Problems
Moderators: Altitude, adafruit_support_bill, adafruit, phono, mome rath

Re: 2VCO Problems

by altitude on Sat Apr 07, 2012 6:44 am

No, its just an opamp. There is nothing special about it other than its rare, expensive, and should be left for devices that actually need it. Judge for yourself, look at BCbox's post in this thread and see if you can hear a difference: viewtopic.php?f=12&t=17694&p=98926#p98926 . Those two samples have a loop going that switches between a 6110 and 662a

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Re: 2VCO Problems

by izze on Sat Apr 07, 2012 9:54 am

Ok.. well i guess my x0xb0x already sounds really 303ish.. i dont think i can get any nearer, thanks for saving me the bucks altitude! :)
So i will be happy with my acid dripping silver beast :D
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Re: 2VCO Problems

by izze on Thu Apr 12, 2012 12:22 pm

Another quick question regarding the Click problem.
I now got almost no click with the OSCs off, but the click occurs when the oscillators are on. its louder than last time i checked. I have the Reserve Diode inserted.
The click seems to change with the patterns, so its not really the click i had before (with OSCs off).
Any way to fix that ? maybe the capacitor on Q1 is not the right one ? I read that the reverse diode can make things worse if you choose the wrong capacitor.

Altitude, you said you used a 150 nF.. from where did your capacitor run exactly again ?

Thanks
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Re: 2VCO Problems

by aminoacid on Thu Apr 12, 2012 3:08 pm

i think when i made the mod (linked by guest) i tried with 10nf together with a resistor, but that cap was not enough.

i think i landed on 33nf, although slightly lower would probobly be even better becase higher values gives a higher "envelope attack" to the cv input of the vca chip. this cap filters out the fastest transients from the cv input of the 6110.

the resistor must be there in case of a cap being inserted to ground, otherwise it will sound crackly. the resistor will tame the snappyness of the sound, which i think is the biggest difference between 662 and 6110. it limits the cv signal and will take down those super punchy accents which are not present in the 622. i am using 82kohm to match the accents from a clone i have with a 622, but slightly lower resistance is okey.

i used a polyester cap by the way!
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Re: 2VCO Problems

by altitude on Thu Apr 12, 2012 3:56 pm

izze wrote:Another quick question regarding the Click problem.
I now got almost no click with the OSCs off, but the click occurs when the oscillators are on. its louder than last time i checked. I have the Reserve Diode inserted.
The click seems to change with the patterns, so its not really the click i had before (with OSCs off).
Any way to fix that ? maybe the capacitor on Q1 is not the right one ? I read that the reverse diode can make things worse if you choose the wrong capacitor.

Altitude, you said you used a 150 nF.. from where did your capacitor run exactly again ?

Thanks

That sounds like the free running OSC click. It comes from the env firing halfway through a wave giving a click as a result. Try changing the tune and see if the pattern of clicks changes as well.

I do use a 150 nf (or 0.15 uF)

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Re: 2VCO Problems

by izze on Fri Apr 13, 2012 7:27 pm

@Altitude
Ok thanks i will try that soon

@aminoacid

Did you put the resistor between ground and the capacitor ? And where did you connect the capacitor to ?
I heard of different ways so it would be interesting to hear what you did exactly and where you did it.

Thanks again guys
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Re: 2VCO Problems

by aminoacid on Fri Apr 13, 2012 9:36 pm

sorry for not having a camera... but ill try explain it.

on the bottom side of the pcb, i cut the trace between middle pin of q1 and the pin of ba6110 which it goes to.

then i put the resistor between thoose two points instead. also bottom side of the pcb but i wire it so it takes the way on the other side of the ba6110 so i can use a ground point from one of the holes that ba662 should sit in.

the cap should have one leg to that ground point (which ground point is prob not important) and the other solderd to the resistors leg that is tied to q1.

try with 15 or 22nf and something between 70-80kohm.


what was the thing about dc offset by the way? input voltage offset being different then the ba662?
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Re: 2VCO Problems

by guest on Sun Apr 15, 2012 7:33 am

i didnt realize you also used a capacitor with that mod
i thought it was only the resistor
that makes more sense now
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Re: 2VCO Problems

by altitude on Sun Apr 15, 2012 7:42 am

aminoacid wrote:..


what was the thing about dc offset by the way? input voltage offset being different then the ba662?



Not different, BA662a has the same thing. In fact, the SH101 has the same circuit on the board but its not populated (pretty sure thats where Brian got the idea from). It just allows you to trim out the pop that comes from the tiny changes in the parts. IIRC the dotted 662a were selected for low dc offset so the trim circuit was not needed

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Re: 2VCO Problems

by izze on Sun Apr 15, 2012 7:47 am

I tried the thing with the resistor and the cap (is it some sort of filter?) It is a little better, but far away from beeing silent. Should i remove the reverse diode and just use the Resistor and cap ?
I just wonder why this noise came out of nowhere, i used to have the VCA Click, that you could hear really good when the OSCs where off, but now its something different, the VCA Click with OSCs off is barely there, but the other clicky noise pattern which goes along with the OSC is there, drives me insane :(

Thanks
Patrick
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Re: 2VCO Problems

by altitude on Sun Apr 15, 2012 7:59 am

The click pattern thing is inherent to the design, its not something you can fix. The only real way to get rid of it is to add some kind of osc sync circuit but that is changing the design of the synth. One of the software clones actually has a toggle to do just that. That being said, it sounds like you may have done something to make it more prevalent

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Re: 2VCO Problems

by aminoacid on Sun Apr 15, 2012 9:50 am

what values did you use for the cap and resistor? i have only done this with one xox so it may not be working all the time.

i dont think it should do any difference if you remove the other mod...

when you say that this click came from nowhere, i think about that it could be something else... loose solder joint or something broke from the vca and down the line..?
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Re: 2VCO Problems

by izze on Sun Apr 15, 2012 10:04 am

The solder is fine everyhwere, i also resoldered, checked all the cables. I used the same values as you.
I may be taking things too serious, i made a quick recording to test my modded distortion, you can hear the clicking at the beginning.
http://k003.kiwi6.com/hotlink/c6706e3mk ... on_x0x.mp3
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Re: 2VCO Problems

by aminoacid on Sun Apr 15, 2012 5:10 pm

im sorry to say but that sounds just perfect to me! was that recording done with or without the mods?
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Re: 2VCO Problems

by izze on Mon Apr 16, 2012 12:09 am

That recording was with the mods already. Ok if you say it sounds right, then i can live with it 8) Thanks for the help

By the way, this is my modded boss distortion.
Image
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