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professional manufactured SSM2044 VCF PCBs are AVAILABLE!!
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EdisonRex
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PostPosted: Tue Nov 27, 2007 6:27 am    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
ok so i would add an 87k resistor to the 100k in parallel to get 47k. BUT i havent built the board yet so couldnt i just use a 47k to start with?

thanks


I was thinking more about how to turn 150k into 75k, but yes, you are right, just use a 47k where indicated...

And you can always just buy a 75k resistor too.

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loss1234



Joined: Jul 24, 2007
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PostPosted: Tue Nov 27, 2007 7:04 am    Post subject: Reply with quote  Mark this post and the followings unread

now i am confused.

i thought you had said the mod was meant to turn r23 into the value of 100k and x in parallel?

so i can put a 47k in place of the 100k for r23??

thanks

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EdisonRex
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PostPosted: Tue Nov 27, 2007 7:48 am    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
now i am confused.

i thought you had said the mod was meant to turn r23 into the value of 100k and x in parallel?

so i can put a 47k in place of the 100k for r23??

thanks


Slow down and read it again.

r23, when modified, becomes 75k. It is something else when unmodified.

The Fc pot's bottom, normally connected to ground, gets disconnected from that, tied to a 47k resistor (which doesn't have a designation on the schematic) and the other side goes to -V.

When I talk about putting a resistor in parallel for r23, it was because I was too lazy to desolder the one that was there, and had just the right one to bring the equivalence to the right number. Let's not make things too complex.

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loss1234



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PostPosted: Sat Dec 15, 2007 3:56 pm    Post subject: did i do the mods right????? Reply with quote  Mark this post and the followings unread

BUILT THE FILTER..... have a few questions....

DO THE SQUARES MEAN HOT?? in other words, on any of the solder pads going to the jacks or the pots, there is one with a square and one with a circle. I need to MAKE sure that the square is going to the positive side....I am assuming it is but for the cutoff mod this would make a real difference. As it is, i made the cutoff mod, by taking the third wire of the pot and running it to a 47k resistor and then to -15...

do i need to cut a trace for this mod??

ALSO i cant get the cutoff to have a bright high end at 100 percent and no sound at 0. in other words, i dont want the cutoff to be messing with the sound when its all the way at 10. but when i bring it down to zero i want there to be nothing or almost nothing there...i was under the impression that the mod did this but either i did it wrong or there is no way to get nothing at 0 AND no change at 10. (i did mess with the trim pots...)

also, i used a 1000pf polysty for the 820 mica (i didnt have an 820 mica-only a 500) and a 22 mica for the 15 mica. is this ok? would i have been better off with the 500 mica? i will change these once i get some with the right value)

thanks


THANKS

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EdisonRex
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PostPosted: Sat Dec 15, 2007 4:52 pm    Post subject: Re: did i do the mods right????? Reply with quote  Mark this post and the followings unread

loss1234 wrote:
BUILT THE FILTER..... have a few questions....

DO THE SQUARES MEAN HOT??



No. Look at the board's traces. Trace a ground or hot. The squares are an indexing aid.

Quote:

As it is, i made the cutoff mod, by taking the third wire of the pot and running it to a 47k resistor and then to -15...


Good job!

Quote:


do i need to cut a trace for this mod??



I didn't. I just stopped using the ground side of the pcb end, and stuck the wire in series with a 47k to the -15 holes available down by the power connector. Whichever power connector you choose, there's a spare.

Quote:

ALSO i cant get the cutoff to have a bright high end at 100 percent and no sound at 0. in other words, i dont want the cutoff to be messing with the sound when its all the way at 10. but when i bring it down to zero i want there to be nothing or almost nothing there...i was under the impression that the mod did this but either i did it wrong or there is no way to get nothing at 0 AND no change at 10. (i did mess with the trim pots...)


Check your trimpots some more. You might have the wrong resistor in the VC circuit too.

Quote:

also, i used a 1000pf polysty for the 820 mica (i didnt have an 820 mica-only a 500) and a 22 mica for the 15 mica. is this ok? would i have been better off with the 500 mica? i will change these once i get some with the right value)


I used a 1000pf instead of an 820 too on that same circuit. Mine is working fine. I did use a 15 on the other one since I had one.

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loss1234



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PostPosted: Sat Dec 15, 2007 5:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

you mentioned that the squares are just for reference. so i am worried that maybe just maybe i tied the WRONG side of the cutoff pot to -15....would this really matter though or would it just reverse the pots response?

thanks

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EdisonRex
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PostPosted: Sat Dec 15, 2007 5:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
you mentioned that the squares are just for reference. so i am worried that maybe just maybe i tied the WRONG side of the cutoff pot to -15....would this really matter though or would it just reverse the pots response?

thanks


You'd notice some really wacky behavior. I just cut P2's right hand wire, the one going to ground, if you are looking at the board upwards (ie the words are all readable without cocking your head around), and took the wire to a 47k resistor and then to to -15v input. Depending on which way you have your pot wired, it is possible to get it in the wrong direction, but that's kind of obvious, as things go the other way round when you turn the knob.

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loss1234



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PostPosted: Sat Dec 15, 2007 7:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

hmmmm...i am definitely having some weird issues...first, does the ssm run a little bit warm? definitely feel some warmth on the chip...maybe thats natural.

BUT what is bothering me is that i am definitely getting some filtering even when i have the cutoff at 10. i was under the impression that like most filters, at 10, i will get no filtering. now i am getting resonance and cv control,etc. the main problem is i just cant get the right range. i DID try disconnecting the freq pot to make sure it wasnt miswired...no issues there.

trying to figure out what i could be doing wrong.

thanks all

my offset trim is at about 20k right now.

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fonik



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PostPosted: Mon Dec 17, 2007 12:31 am    Post subject: Reply with quote  Mark this post and the followings unread

so the filter actually works? i will have a look at the range of mine again this week, so hold on.

BTW apply a signal to the filter, set your cutoff pot to 10 and then see what you can do with the offset trimmer. does it change?

sorry for my late reply. i am a little busy these days...

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loss1234



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PostPosted: Mon Dec 17, 2007 4:52 am    Post subject: Reply with quote  Mark this post and the followings unread

the filter does work and quite well but i suppose i was under the impression that it would go from very high to no sound. its a great sounding filter though and i will check the trimmer today again. i am not too worried anymore..it sounds so silky

wow


thanks again

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loss1234



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PostPosted: Mon Dec 17, 2007 11:26 am    Post subject: Reply with quote  Mark this post and the followings unread

no the offest doesnt change with the trimmer when cutoff is on 10. i got the filter to a point where i love it. this thing is so smooth sounding


awesome pcb artwork too...i tried getting my wife to admit that it looked like art but....where do you get your pcbs done? nice boards, good colors, and the boards seem very thick.

thanks alot

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Luka



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PostPosted: Tue Dec 18, 2007 3:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

got my 2044 finally
incase people are looking for them chipforbrains has another 5 up on ebay Wink
they are about US$5

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