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Old 28th August 2012, 01:45 PM   #11
Pano is offline Pano  United States
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No, not that I can tell. The problem isn't the ADC, it's the analog circuitry in front of it and to some extent, the power supply. It may be worth your while to replace that. I have, with great results. No need for an outboard ADC.

Hacking the DCX is easy, I've not yet done the inputs of the DEQ (just outputs) but they are very similar.

Also, for whatever reason, the DEQ is happiest when fed AES from another Behringer product such as the DEQ or SRC.
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Old 21st October 2012, 11:16 AM   #12
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Hi Pano,
I have DEQ and DCX 2496. I was wondering if you would share how you have them connected and what mods you feel are worthy to do, my unit are stock at this time but fixin' to get the iron out on them soon ,lol.
I grew up a little south of you in Greenville ,Sc. small world,sometimes !
Thanks alot,
No Smoking
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Old 21st October 2012, 12:16 PM   #13
Tenson is offline Tenson  United Kingdom
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Quote:
Originally Posted by Pano View Post

Also, for whatever reason, the DEQ is happiest when fed AES from another Behringer product such as the DEQ or SRC.
Do you mean the DCX is happiest fed from the DEQ or SRC? I think that's because the DCX digital input needs a minimum of 200mV input and many bits of kit these days don't deliver it. I've no idea why, since the standard for SPDIF is 500mV.
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Old 21st October 2012, 12:41 PM   #14
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Originally Posted by Tenson View Post
The SRC has the same basic input circuit as the DEQ and DCX. The ADC in all is superb, it is an AKM AK5393. However as you said, the analog circuit is rather poor and introduces excessive IMD.

IMO the best thing to do is replace the analog circuit.
How do you measure IMD of this combo? And can you put some numbers to "excessive"?

Andrew
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Old 21st October 2012, 04:53 PM   #15
Tenson is offline Tenson  United Kingdom
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Hi,

I can't put absolute numbers to it as I have to use a DAC to test it. However, here is a comparison showing a DacMagic recorded into a standard DEQ analog input vs the same into my M-Audio Fast Track Ultra analog input. The Fast Track Ultra is a good quality USB audio interface. With the DEQ analog input circuitry replaced it can do even better than the Fast Track.

There are a few things to consider when replacing the circuit though; the ADC likes to have a 2.5V DC bias, and the switched capacitor filters on the ADC input can easily de-stabilise op-amps.

Click the image to open in full size.

Last edited by Tenson; 21st October 2012 at 04:55 PM.
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Old 21st October 2012, 06:08 PM   #16
Davey is offline Davey  United States
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That amount of IMD seems excessive to me. I don't remember mine (DEQ) exhibiting that much distortion, but it's been years since I tested it.

Did you take a look at distortion content of your input signal?

Dave.
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Old 21st October 2012, 06:18 PM   #17
Tenson is offline Tenson  United Kingdom
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I assume if the M-Audio records much less IMD it is not on the input signal. I've measured a lot of DEQ over the years, this is typical performance.
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Old 21st October 2012, 07:14 PM   #18
Davey is offline Davey  United States
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I wasn't clear if you used exactly the same input signal for both evaluations. I guess you did.

I can't see the top of your plot. Is the 8/9khz level at 0db?

Dave.
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Old 21st October 2012, 09:47 PM   #19
Tenson is offline Tenson  United Kingdom
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It's at about -3dB. You shouldn't put much faith in the absolute levels though.

I'm making a website to sell my DEQ and DCX mods for analog inputs and outputs at the moment, so I will have some more direct comparisons soon.
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Old 21st October 2012, 11:20 PM   #20
Davey is offline Davey  United States
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I wasn't concerned with absolute levels, but since your graph didn't show the upper part even relative levels couldn't be viewed.

I'm considering modification to my DCX/DEQ so will be interested in your mods. Are you using an OPA1632 (or similar) for the input stages?

Cheers,

Dave.
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