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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Voltage Controlled Echo feedback loop mod
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agustindead



Joined: Jul 22, 2015
Posts: 33
Location: Big City, bright lights
Audio files: 1

PostPosted: Mon Apr 02, 2018 12:24 pm    Post subject: Voltage Controlled Echo feedback loop mod
Subject description: having trouble inserting send and return for a feedback loop
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Hi! I'm trying to make a feedback loop in the VC echo but I'm having some trouble...

The obvious point to insert the send/return jacks seemed to me where both feedback and dry signal meet (through R4 and R21 respectively). As shown in the schematic attached, I cut the trace there but it's not working at all... Of course it's alright when normalized or self patched, but as soon as I put something in between, no delayed signal comes through (even with something as simple as an active attenuator).

Can someone help me telling me what's wrong? Should I put a resistance in series with the return input or something??

Could I insert the loop somewhere else?

Thanks!


vc echo feedback.png
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agustindead



Joined: Jul 22, 2015
Posts: 33
Location: Big City, bright lights
Audio files: 1

PostPosted: Mon Apr 02, 2018 3:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

I was checking the point that I chose for the send/return points and I saw that the signal has an offset and it's pretty attenuated... I'm asuming the later is to not clip the PT2399 or LM13700 inputs...

so... would my send/return connections need amplifying/attenuating? Still not sure about that offset...

Guess those two jacks on the front will remain unconnected Laughing
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matinnin



Joined: Oct 13, 2016
Posts: 29
Location: the Big D
Audio files: 1

PostPosted: Sun Jun 24, 2018 7:28 am    Post subject: MFOS ECHO Reply with quote  Mark this post and the followings unread

HI,
i dont see too many messages about this build. i just completed one last night and plugged it up , and it works fine, but... its way too noisy! a huge amount of hiss , its practically unusable at this point. i'm wondering if anyone is using 15v , i dont see that Ray addressed it on the page for it. might be i need to change some values for 15v or my pt2399 is not right. im going to poke around on it a little .
it works fine but i think the levels are generally way to hot, this may be related to the noise and the voltage difference.

thanks,
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micromusic



Joined: May 05, 2014
Posts: 61
Location: england

PostPosted: Mon Aug 27, 2018 11:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi

I was using mine over the weekend and have the same issue with noise, the echo level pot at over half way starts to inject noise and by full travel its a white noise generator, all the circuit works fine apart from this and all components are to the specified
This noise is present with the PT2399 pulled out of circuit so its not the culprit
I strapped a 220uf capacitor across the output jack to ground and its gets rid of almost all of the noise, but not being an expert I don't know why this works or if its the right thing to do ?
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