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Opamp question
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kxspxr



Joined: Nov 20, 2008
Posts: 35
Location: Denmark

PostPosted: Sat Jan 31, 2009 7:19 am    Post subject: Opamp question
Subject description: 555 Modifier from Armageddon Processor
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I have a few questions about the 555 Modifier found in Beavis Audio's Armageddon Processor: http://www.beavisaudio.com/projects/ArmageddonProcessor/

I would like to substitute the LM386 for an opamp and add a small LFO section to control pin 5 on the 555. If I use a dual opamp where the first acts as buffer for the input signal and the next as a non inverting amp with a variable gain from 20 to 200, would it still (at least in theory) work? I'm thinking of using a TL072. I've had one two many projects failing to work properly lately, that's why I'm asking..

-Kasper


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JovianPyx



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PostPosted: Sat Jan 31, 2009 9:19 am    Post subject: Reply with quote  Mark this post and the followings unread

My own guess as someone who has used 555s in analog synth circuits is "yes".

My suggestion is this: The circuit is simple enough to breadboard on solderless breadboard or stripboard or vector board or whatever you use.

Just try it and see.

One thing I would do - use a 7555 timer, not a 555. Pinout is identical, but the device is CMOS and won't nail your power supply with a huge current spike each time it resets as a bipolar 555 timer will. This spike is the source of the VCOs in a FatMan wanting to lock together (soft synch) when the VCO pitches are close together. I've used part number ICM7555.

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kxspxr



Joined: Nov 20, 2008
Posts: 35
Location: Denmark

PostPosted: Sun Feb 01, 2009 5:05 am    Post subject: Reply with quote  Mark this post and the followings unread

ScottG wrote:

My suggestion is this: The circuit is simple enough to breadboard on solderless breadboard or stripboard or vector board or whatever you use.

Just try it and see.

One thing I would do - use a 7555 timer, not a 555. Pinout is identical, but the device is CMOS and won't nail your power supply with a huge current spike each time it resets as a bipolar 555 timer will. This spike is the source of the VCOs in a FatMan wanting to lock together (soft synch) when the VCO pitches are close together. I've used part number ICM7555.


I will build the original circuit first, then my new version with an opamp and a IMC7556 -got a few of them lying around. I can use the remaining 555 for the LFO. Thanks for the help and advice! If anyone's interested, I can upload the layout for (both the original and my own opamp version) vero once I've verified it.

-Kasper

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kxspxr



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Location: Denmark

PostPosted: Mon Feb 02, 2009 10:30 am    Post subject: Reply with quote  Mark this post and the followings unread

The 555 Modifier sounds great with the LM386. - so I built the PWM Fuzz from the Armageddon too. Sounds awesome! Two nice and easy builds both with their own (very) unique fuzz sound!

-Kasper

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