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 Forum index » DIY Hardware and Software » The layout factory
[veroboard] 3 in and 3 out matrix mixer with buffered inputs
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kaputtpanzer



Joined: Nov 02, 2009
Posts: 139
Location: Cologne
Audio files: 15

PostPosted: Sun Sep 23, 2018 5:42 am    Post subject:  [veroboard] 3 in and 3 out matrix mixer with buffered inputs Reply with quote  Mark this post and the followings unread

Somehow I am fascinated by some of the matrix mixer clips on youtube, so i decided to build one myself. I am really pleased with this little device and I made a veroboard layout, that i would like to share with you guys... Wink


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artilect99



Joined: Oct 01, 2018
Posts: 49
Location: USA

PostPosted: Tue May 28, 2019 5:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm curious as to why you didn't just run the op-amps at 12v? Or just use a 9v adapter instead of regulating down from 12?

What exactly is the 4.5v rail for?
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Sven



Joined: Mar 10, 2017
Posts: 48
Location: Norway

PostPosted: Wed May 29, 2019 1:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Its the virtual ground. It's needed when you use a single power supply with dual supply opamps.
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kaputtpanzer



Joined: Nov 02, 2009
Posts: 139
Location: Cologne
Audio files: 15

PostPosted: Thu May 30, 2019 9:11 am    Post subject: Reply with quote  Mark this post and the followings unread

artilect99 wrote:
I'm curious as to why you didn't just run the op-amps at 12v? Or just use a 9v adapter instead of regulating down from 12?

What exactly is the 4.5v rail for?


Well it is just a bad habit, to put regulators in every box Razz
No, actually it has some use. Mainly it is to get a nice regulated power source. It removes a little bit of the noise and ripple that comes out of these cheap dc wall warts and is it also quite useful when you need to distribute power to more than one consumer in your circuit. Sure you lose some voltage, which in the worst case means you lose some of your signals resolution or headroom. But I realized I can not hear much of a difference when I use a 3V higher voltage source, but I can very much hear the noise that comes with a cheap wall wart. So I use regulators and filtering in all of my circuits, to get the a nice, stable and clean power. And also this thinking about headroom is not really necessary, because in this circuit there are just buffers and the signal is most likely not oscillating from opamps rail to rail. In this circuit you lose a little bit of volume, but not much of the high or low frequencies.

In the attachement you find a part of my standard power supply, that i use in most of my circuits. It is just my habit, probably it is not always worth the effort.

And the 4.5V is just the bias voltage for the opamp application. Opamps need for most applications (beside the use as a comparator or so) 3 reference voltage sources. The 4.5V is the bias voltage where those signals oscillates around.


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R_Gol



Joined: Oct 17, 2019
Posts: 34
Location: World

PostPosted: Sat Apr 18, 2020 3:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for posting that schematic. I'm actually interesting in building one my self and I've got a question regarding the buffered 4.5v. How you create it ? What I mean is that in order to make this "virtual ground" you don't need to use some capacitors and resistors? like in here: https://www.tangentsoft.com/elec/vgrounds.html

or is enough just to refer to a point between the 9v and the gnd and then the original gnd become as the minus voltage reference and the new middle point becomes the gnd ?

Thanks for any clarifications
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