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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

What is the difference between pre-amplifier and input attenuator?
What is the difference between pre-amplifier and input attenuator?
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Old 3rd November 2019, 05:20 AM   #11
CowCat is offline CowCat
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Quote:
Originally Posted by PRR View Post
If the source and preamp happen to deliver 0.2V, this is all we can get out of a passive volume control full-up. (If they deliver 2V, we must turn-down.
I received a unit of SMSL M100 DAC from aliexpress.com. On specification, it outputs 2V. My aliexpress.com chinese no-name TPA3251/TPA3255 amplifiers also accept 2V as input. TPA3251 and TPA3255 accept 2V as input.

I discovered that if the right channel volume of M100 is 0dB, when the sound is loud, the right speaker emits a lot of crackles. If the right channel volume of M100 is -1dB or -2dB, the crackles stop.
I made sure to play the same audio data on the left and the right channels by editing and playing audio data in audacity.

I swapped RCA cables on my amplifier, and the crackles appear on the left speaker.
If I swap RCA cables on my amplifier and M100 DAC, the crackles appear on the right speaker. Thus, I concluded that the right channel of M100 DAC is abnormally higher than the left channel of M100 and that there is no problem with RCA cables and my amplifiers.

I filed a dispute to request a full refund with video evidences showing my discovery. The seller says my videos are not a professional test and thus I didn't prove that the product I received is a defective unit. I will have to escalate the dispute so that aliexpress.com intervenes.

Did I receive a defective DAC if the right channel of DAC actually produces crackles or clippings on the right speaker? My onboard soundcard doesn't have nearly as much channel imbalance as this.

Last edited by CowCat; 3rd November 2019 at 05:40 AM.
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Old 3rd November 2019, 08:46 AM   #12
analog_sa is offline analog_sa  Europe
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What is the difference between pre-amplifier and input attenuator?
Why is this dramatic story of pain, suffering and Chinese torture in this thread?
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Old 3rd November 2019, 09:00 AM   #13
CowCat is offline CowCat
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Originally Posted by analog_sa View Post
Why is this dramatic story of pain, suffering and Chinese torture in this thread?
Good point. I'll make another thread.
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