M450b as a buffer amp

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Brian Houle

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Dec 18, 2018, 12:28:56 PM12/18/18
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I own 10 m450bs and a card cage for them.

I'm a live audio engineer.
I use a software console called SAC (software audio console).
The interfaces I use are the Behringer ADA8200.
The analog output of the ada8200 has a maximum output of +18 with minimal current capability to drive long snake lines.
I'd like to use the m450bs as a line driver but I'd also like to use them to buffer the ada8200s so that the output of the m450b would be +24, or essentially add 6db of gain to my outputs. How would I go about doing this with the m450b?

Thanks for your guys time!
Brian Houle

Anthony Kuzub

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Dec 18, 2018, 11:17:20 PM12/18/18
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what is the problem you're trying to solve?

if your amps can't handle +24 what's the point?
Why are your amps needing more gain on the front end?





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Charles Beauregard

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Dec 18, 2018, 11:18:08 PM12/18/18
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Hi Brian,

I think it will works good. You'd have to connect it as a program amplifier. Minimum gain is 24 but you can add an attenuator in the middle of the circuit (in red in the attached modified M450b diagram). I did that on two M450B I installed into a M460 rack for a summing amp purposes and my client is satisfied with the results. You don't have to break any traces, just lift a resistor and connect wires on some unused pins of the edac connector. Easily reversible if needed.

Cheers!


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Charles Beauregard

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Dec 18, 2018, 11:53:21 PM12/18/18
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Anthony is right, if it's for driving power amp you probably won't need +24dbu. You're going to attenuate it anyway.

Brian Houle

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Dec 19, 2018, 6:43:43 AM12/19/18
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A lot of pro live audio gear is +24 in and out these days. Most serious consoles are as well as most processing gear.
I mostly want the gain and current to drive longer lines. Some of my hopes are that these amps will have a warmer sound than my all digital gear, and lastly I'd like to not be mixing "into" my console so hard to drive the PA processing gear.
Charles, your first post did not include an attachment so I could see where in the circuit you were adding the pot.

Thanks for your replies gentleman!

Brian Houle

Charles Beauregard

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Dec 19, 2018, 9:21:36 AM12/19/18
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Oups sorry, here it is.

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450b_modded.jpg

Anthony Kuzub

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Dec 19, 2018, 11:04:02 AM12/19/18
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Anthony Kuzub

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Dec 19, 2018, 11:06:14 AM12/19/18
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Here is the M450  
It uses the fairchild739 chip

it has more analogue MOJO = slower slew rate 
 M450 - P13 - Schematic.jpg


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