ada8000 DC/gain modification for silent way

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smrl
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ada8000 DC/gain modification for silent way

Post by smrl » Sun Feb 12, 2012 8:36 pm

Well, I managed to figure out the modifications necessary for DC-coupling the Behringer ADA8000, and getting the voltage at the output from the 3.528v measured one one channel up to 10.88v.

Image

I looked at the schematics that had been redrawn by Marcelo Johann, but to my chagrin Behringer has changed the design in the meantime - it now uses a single ADC/DAC chip per 2 channels, the CS4270. In some ways it has made it easier to modify, as the output of this chip is single-ended rather than differential. In the end, I was able to modify the output schematic somewhat elegantly, but it involves desoldering the op amps and swapping in a few resistors. It also requires a small circuit to produce a voltage reference to bias the signal back to 0v.

Before:
Image


After:
Image

Notes on my very quick schematics:

The op-amps were TL072, I subbed them for TL082 for better output offset performance. You could re-use the 072's. MCP6002 was used because it runs off of a single supply. I powered it & the voltage divider in front of it with the 5v supply for the ADC chip -- IC3 according to Marcelo's notes. Trim until the output measures 0v. I desoldered the IC's and bent up the appropriate pins (5&10 I believe) then bridged them. I made 2 voltage sources, one connected to the first 4 channels, the other connected to the other. Probably not necessary but I had an extra op-amp available. If you really wanted to get fancy you could probably make voltage sources for each one to trim them each to 0v. I haven't measured the difference between channels yet.

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lukas412
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Post by lukas412 » Sun Feb 12, 2012 9:00 pm

wow nice work man!

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os
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Post by os » Mon Feb 13, 2012 11:37 am

Cool! I was about to post the link to Johann's schematics, but I see you found them.

I imagine Behringer had to chang the design because the Wavefront DACs they used to use went obsolete.

bafonso
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Post by bafonso » Fri Jul 10, 2015 3:19 pm

Hi guys,

Has anyone looked at the possibility of doing this to the ADA8200 ? I have it and would like to convert its outputs and inputs to DC coupled.

pd2018
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Post by pd2018 » Fri Jul 13, 2018 4:58 pm

bafonso wrote:Hi guys,

Has anyone looked at the possibility of doing this to the ADA8200 ? I have it and would like to convert its outputs and inputs to DC coupled.
Would also like to know if this is possible. Can the ADA8200's 8 outputs be used to control anything without major surgery?

gotama
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Re: ada8000 DC/gain modification for silent way

Post by gotama » Thu Feb 27, 2020 9:17 am

Sorry to dig up this old thread, but I recently acquired an ADA8000 and have been looking in to mods. Do you by chance have the photos that tinypic seems to have killed?

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