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TOPIC: DDRC-24 THD is bad above 1V input

DDRC-24 THD is bad above 1V input 2 weeks 4 days ago #33487

  • Robspak
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I'm sorry if this topic has been approached before, but I'm a little perplexed between the technical specs of the DDRC-24 and reality. I need a clean 1.6v to be fed to my amplifier for propper gain and full output capability. However, though the specs say 2.0v output on the DDRC-24; the measured THD output becomes completely unacceptable at anything above about 1v input, thus the output is below even that.

Have I got a faulty device, or is the spec sheet very misleading?

Thank You
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DDRC-24 THD is bad above 1V input 2 weeks 4 days ago #33488

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Let me make a correction after further review. The THD alone does double + above 1v input. But it stays in a borderline acceptable range. I was initially testing THD+N it seems to be the noise the really jumps above 1v. It seems to me that the 1V threshold or thereabouts engages some additional circuitry that really increases the noise. The noise jumps dramatically. I thought maybe it was the weakness of the wallwort power supply, but I tried 3 different power supplies, including a non switching PS. It's definitely internal circuitry.

So, above 1V input, THD alone doubles and THD + N is about 130% above 1V
Last Edit: 2 weeks 4 days ago by Robspak.
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DDRC-24 THD is bad above 1V input 2 weeks 4 days ago #33489

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I don't know if anyone really cares about this type of thing, or maybe this info is already known. But based on my testing, best Sound quality for analog Inputs (that's all I've tested so far) will come from the following setup.

Volume maxed out on DDRC itself, considerable noise is added when you turn the volume down on the DDRC, I'm guessing this circuit is just a filter of some kind, thus the noise.

The sad part is, you are best to use your source for volume control. Set your amp, AVR, receiver at a default level and control volume at the input to DDRC if possible. As mentioned above, below 1v input had about half the THD and more than half the THD+N. Depending on your system, 1V may be louder than you ever play it, so you will always be in the higher quality 1v and under circuitry. If you do crank it up, chances are it will be so loud that the SQ decrease will not be noticed.

FYI, I did no testing above 1.8v input. My goal was a clean 1.6v for my particular amp.

I was able to test with both channels input being driven and thankfully that seemed to have zero effect on anything. It did not even appear to create noise via crosstalk, however my source was the same, so I'm not positive that crosstalk would be noticable.

Final thought, keep and eye on your preamp voltage output if you use one. I found that my B&K was nuetering the output. It did not want to push much more than 1v out cleanly. While my Denon and NAD had no issues pushing to my 1.6v cleanly. The B&K would not even output the entire input, seemed odd to me. Thanks
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