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Yusynth ladder sounding super low volume
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MapacheRaper



Joined: Feb 15, 2018
Posts: 90
Location: Spain

PostPosted: Wed Oct 03, 2018 12:18 am    Post subject: Yusynth ladder sounding super low volume Reply with quote  Mark this post and the followings unread

Hi,

Finally I debugged the moog ladder... I was using some 2n3906 trannies instead of BC547C (facepalm, I mixed it while matching pairs for other builds)

Now the filter sounds, but the output is quite low volume... So I guess it has some residual bug.

I must confess that the new BC547C aren´t matched...

Is there any hack to get it sounding louder? I understand that the matched trannies are about the "quality" of the sound, but the loudness factor should be related probably to the end amp stage, isn´t? Probably the resistor located between the tl072 out and -inverted in?

Yeah, I know I should match the trannies it but I was diying to hear it first!!

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g.gabba



Joined: Nov 29, 2008
Posts: 420
Location: berlin
Audio files: 23

PostPosted: Thu Oct 04, 2018 4:02 am    Post subject: Reply with quote  Mark this post and the followings unread

ok, ok
Filter fully open, resonance off

what is the amplitude of the signal ur feeding in?
what is amplitude of the signal ur getting out?
R31 is 56K? what value ur using for R32?
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MapacheRaper



Joined: Feb 15, 2018
Posts: 90
Location: Spain

PostPosted: Wed Oct 10, 2018 1:40 am    Post subject: Reply with quote  Mark this post and the followings unread

The signal is 10vpp. The output 2.5vpp. Now im using a buffer amplifier to get it to 10V

Im using a yusynth PCB with the suggested components, so if I hadn´t messed it R31 is 56K and R32 120K

http://yusynth.net/Modular/Commun/MOOGVCF/Moogfilter-sch.jpg

So I should do R32 470K or 24K, isnt? (Not sure if I have to multiply or divide Smile
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g.gabba



Joined: Nov 29, 2008
Posts: 420
Location: berlin
Audio files: 23

PostPosted: Wed Oct 10, 2018 5:12 am    Post subject: Reply with quote  Mark this post and the followings unread

let me give u a picture that i use to make it easy to remember,
in german we use to call this a " Bridge for the Donkey" Smile

if you would consider this as the most common way how we are drawing the basic opamp circuit
and then refer to the geographical position of the resistors as top and bottom or high and low or em cima e em baixo - whatever

u already have there position in the calculation

so 470k seem to be not a bad idea Smile


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MapacheRaper



Joined: Feb 15, 2018
Posts: 90
Location: Spain

PostPosted: Wed Oct 10, 2018 11:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

That´s crystal clear and perfect, again. Definitively I own you a hackaton of beers...

Cheers!! party time!
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MapacheRaper



Joined: Feb 15, 2018
Posts: 90
Location: Spain

PostPosted: Fri Oct 12, 2018 1:55 am    Post subject: Reply with quote  Mark this post and the followings unread

So, it happens that the PCB and the part list does not match. R32 in the official page is R33 in the silkjcreen of the PCB... T1 and T3 are messed too. Nothing of this is noted in the web nor in the site where I bought it...

So after a bit of following paths, I changed the 120K for 470K and it sounds pure CREAM. Not only the voltage and volume is correct but qualitatively the sound is monster.

Why in the part list and PCB it appears as 120K when should be 470K is something I dont understand... Whatever... It works!!!

So, note to future yusynth ladder builders. Use 470K for R32 in the silkscreen instead of the 120K printed.
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g.gabba



Joined: Nov 29, 2008
Posts: 420
Location: berlin
Audio files: 23

PostPosted: Fri Oct 12, 2018 3:53 am    Post subject: Reply with quote  Mark this post and the followings unread

**


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MapacheRaper



Joined: Feb 15, 2018
Posts: 90
Location: Spain

PostPosted: Fri Oct 12, 2018 4:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, ok, is slightly noted in the corder of a JPG that you have to open in a separate window, and decipher that is 470k instead of 120K after solder, read voltages, study OPAMPS, desolder and solder again...

I think it should be listed in the BOM as *use 470K here for eurorack levels...

Whatever... I have magic smoked one of my most precious babies (the CV-12 that you were to buy but let it to me) and Im angry... GRRRR

By the way, before friying it (by connecting the power lines in the wrong way), the module was working flawlessly. Totally my fault...

I have contanted Robert again and he says he is reestocking in a few days. I´ll be buying another one and I recommend you one. Such a bang for the buck and a breezy built
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g.gabba



Joined: Nov 29, 2008
Posts: 420
Location: berlin
Audio files: 23

PostPosted: Sat Oct 13, 2018 2:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Sir Yves has done more then enough for the comunity, there is no way to blame him for a single resistor value. Depending of the price u have paid for the PCB´s you could blame the the PCB-guy.

sorry to hear about your loss, may you only need to swop the chips and it will work again? I guess the processor was available seperatly.


if u would be ready to solder again, u could add a high-pass funktion to the filter relatively easy. one OPAMP, 3 Resistors and a trimmer, what do u think?
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MapacheRaper



Joined: Feb 15, 2018
Posts: 90
Location: Spain

PostPosted: Sat Oct 13, 2018 3:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, you are right. Also Yves is my hero. Maybe I should just mail him with this for him to change it in the site instead of whinning... Wink

Regarding the high pass version, yeah, I would love to add it. Where do you have to sign? Very Happy
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MapacheRaper



Joined: Feb 15, 2018
Posts: 90
Location: Spain

PostPosted: Mon Oct 15, 2018 12:46 am    Post subject: Reply with quote  Mark this post and the followings unread

I have been looking for the mod, and I have found this:

https://www.youtube.com/watch?v=SKcGhaduvfs

Basically:
original signal - lowpass of original signal = highpass of original signal

So you need an attenuverting mixer, that is probably what you said, one opamp and three resistors. Is that?

The nice thing is that you can use this mod with all the filters. And make notch from bandpasses, for example. So, I guess Im going to build a dual or triple one... Wink
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g.gabba



Joined: Nov 29, 2008
Posts: 420
Location: berlin
Audio files: 23

PostPosted: Tue Oct 16, 2018 3:00 am    Post subject: Reply with quote  Mark this post and the followings unread

yeah the theory is
if u are subtracting the output-signal of a filter from its original - u get the "inverse" filter funktion

this works with 24dB Filters, with other Filters u get problems cos of the phaseshift

i would suggest a two opamp subtractor, the opamp with the trimmer is the input for the "louder" signal, the amplitudes wich are going in the second stage should be as equal as possible

good luck mate,
gabi


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