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QuantAsylum QA400 and QA401
QuantAsylum QA400 and QA401
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Old 10th February 2019, 04:32 AM   #2561
agdr is offline agdr  United States
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QuantAsylum QA400 and QA401
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Originally Posted by QAMAtt View Post
Outstanding blog post, Matt! So very helpful.
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Old 10th February 2019, 04:41 PM   #2562
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Originally Posted by chris719 View Post
Nice article! Does the distortion rise significantly with the 10k source impedance compared to OPA1612?
I had to measure to be certain about THD, but the answer is "not much" for THD. Degradation is about under a dB for THD. THDN is about 1.7 dB for 2156 and 5 dB for 1612.

In the plots, you can see the output is -17 dBV, and the measured in is -17.86, which is the 10K source forming a divider with the 100K input.

As an aside, on the QA website Demian correctly observed the hash seemed a bit worse with the 2156. That seems true to me too. When using an external 10K at the end of a BNC cable more stuff seems to be picked up by the cmos versus bipolar. But this is sample size of 1, room temp, nominal voltage etc, so I don't know what to make of it at this point.
Attached Images
File Type: png Right OPA1612 10K Source Z.png (74.6 KB, 589 views)
File Type: jpg Left OPA2156 10K Source Z.jpg (335.6 KB, 534 views)
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Old 10th February 2019, 04:45 PM   #2563
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Thank you for writing it.
The learning is always fun for me and I'm glad it is useful to folks! Do you think the OPA2156 could get a SON package option in the next year?
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Old 10th February 2019, 06:41 PM   #2564
31697B is offline 31697B  Thailand
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Originally Posted by QAMAtt View Post
I had to measure to be certain about THD, but the answer is "not much" for THD. Degradation is about under a dB for THD. THDN is about 1.7 dB for 2156 and 5 dB for 1612.

In the plots, you can see the output is -17 dBV, and the measured in is -17.86, which is the 10K source forming a divider with the 100K input.

As an aside, on the QA website Demian correctly observed the hash seemed a bit worse with the 2156. That seems true to me too. When using an external 10K at the end of a BNC cable more stuff seems to be picked up by the cmos versus bipolar. But this is sample size of 1, room temp, nominal voltage etc, so I don't know what to make of it at this point.
To reduce noise pickup, the 10K in series with input MUST be placed at the input and not remote at a cable/probe tip.
At a distance from input, the cable line Z is increased to 10k making EMI/RFI pickup a certainty.

I am wondering about changing one input to OPA2156 cmos. That way, I can choose which QA401 input to use for optimum app. Comment?

THx-RNMarsh

Last edited by 31697B; 10th February 2019 at 07:09 PM.
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Old 17th February 2019, 02:04 AM   #2565
johnc124 is online now johnc124  United States
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The learning is always fun for me and I'm glad it is useful to folks! Do you think the OPA2156 could get a SON package option in the next year?
Should be on the market around June
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Old 19th February 2019, 05:41 AM   #2566
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Should be on the market around June
Thanks, John, the investments you folks are making in audio continues to impress.
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Old 19th February 2019, 05:42 AM   #2567
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Originally Posted by RNMarsh View Post
That way, I can choose which QA401 input to use for optimum app. Comment?
Definitely doable by a DIYer. The SOIC package is easy to swap back and forth many times if you are careful.
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Old 19th February 2019, 05:34 PM   #2568
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Release 1.709 was released yesterday, and it has a new plug-in for quickly generating graphs of gain and distortion versus input level. This plug-in is mostly useful for folks that are working on musical effects. It is interesting to see how a guitar distortion pedal introduces 2H and 3H distortion based on amplitude of input.

Quantifying Fuzz

-Matt



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Old 23rd February 2019, 04:23 AM   #2569
agdr is offline agdr  United States
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Quantifying Fuzz

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Another awesome blog post, Matt!
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Old 6th March 2019, 07:42 PM   #2570
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This blog post went up earlier this week. It covers release 1.71 which has two new plug-ins for DAC evaluation and you can see how quickly a DAC can be evaluated in the link below. The entire plug-in and graphing portion is getting redone in the near future, and it will be much easier to save and compare traces from the sweeps, stack them, do statistical analysis on them, etc.

Rapid USB DAC Evaluation – QuantAsylum

Thanks, Matt

PS. Unless you are really wanting to do DAC evaluation immediately, I'd hold off on the release and wait until the graphing changes are done.
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