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 Forum index » DIY Hardware and Software » Thomas Henry designs
Mankato VCF - Audio input switches?
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vtl5c3



Joined: Sep 08, 2006
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PostPosted: Sat Jul 04, 2009 5:13 pm    Post subject: Mankato VCF - Audio input switches? Reply with quote  Mark this post and the followings unread

How many of you built yours with the switches on the audio inputs? I'm debating whether it's worth it (or not). To be honest, I'm not sure I see the point - If you want to process audio, just run audio into the inputs. If you want to process CV, run CV into the inputs.

Just thinking out loud, I guess, but I'd be interested in your thoughts.

Romeo
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aerogramma



Joined: Feb 27, 2008
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PostPosted: Sun Jul 05, 2009 2:54 am    Post subject: Reply with quote  Mark this post and the followings unread

hello romeo, i quickly run through the mankato building docs but haven't quite found what you are referring to, can you be more specific?

anyway.. i've built my mankato with 2 audio inputs and 2 CV (FM) inputs


works beautifully

Wink

aero
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Tim Servo



Joined: Jul 16, 2006
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PostPosted: Sun Jul 05, 2009 7:51 pm    Post subject: Mankato VCF - Audio input switches? Reply with quote  Mark this post and the followings unread

Hey Guys,

The DC coupling caps (C101, 102, 103) are used to remove any DC offset from the audio waves. A DC offset or bias can cause pops or clicks when a signal is changed in amplitude very quickly (like when run through a VCA, or a VCF and you rapidly change the CV). Most modular VCOs have their waveforms centered around 0 volts, and so there is little or no DC bias. I'd say the switches and caps aren't that necessary if you're only using modular synth VCOs as tone sources. Of course, you want to take the caps out of the path if you're using the Mankato to process control voltages. You're more likely to see a bias if you're processing signals like a guitar, microphone or recordings. I've set up my Mankato without the switches, and simply configured two of the inputs without the caps, and one input with.

If you want the coupling caps but don't want to use the panel switches, just put the caps on the PCB and leave the switches off. If the switch is open (or not there) the signal will go through the cap.

If you don't want the caps in the signal path, just put a jumper in place of the caps OR (if the caps are already in place on the board) just put a jumper wire in place of the switches.

Tim (enjoying a three day weekend) Servo
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vtl5c3



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PostPosted: Mon Jul 06, 2009 10:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Tim, that's a great explanation.

I've gone ahead and built it without the switches.

This is one cool unit! I think I'll forever be confused as to whether to think of it as a VCO or a VCF. It works well in both capacities!
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